期刊文献+
共找到39,181篇文章
< 1 2 250 >
每页显示 20 50 100
Multiple factors correlating with wing malformations in the population of Parnassius apollo (Lepidoptera: Papilionidae) restituted from a low number of individuals: A mini review
1
作者 Karolina Pierzynowska Marta Skowron Volponi Grzegorz Wegrzyn 《昆虫科学:英文版》 SCIE CAS CSCD 2019年第3期380-387,共8页
The Apollo butterfly, Parnassius apollo (Linnaeus), was common in Europe over 100 years ago, but currently it is considered as near threatened. Different conservation programs have promoted the persistence of this spe... The Apollo butterfly, Parnassius apollo (Linnaeus), was common in Europe over 100 years ago, but currently it is considered as near threatened. Different conservation programs have promoted the persistence of this species;however, it is still endangered. An example of such programs was the action devoted to reestablish the Apollo butterfly population in Pieniny National Park (Poland) from only 20-30 individuals which had survived till the last decade of the 20th century. This reintroduction has been successful;however, unexpected developmental problems appeared. Butterflies with deformed or reduced wings became frequent in the population living in the natural habitat, and particularly among those reared under seminatural conditions (in the same environment, but fenced by a net). Until recently, reasons for these malformations remained unknown. However, reports published during last months indicated that there are genetic, biochemical, and microbiological factors contributing to this phenomenon. In the malformed individuals, lesions in the wingless gene and dysfunctions of laccase 1 and 2 were found to be significantly more frequent than in normal insects. A large fraction of butterflies with deformed or reduced wings was devoid of the prokaryotic symbiont Wolbachia, which was present in most normal individuals. Moreover, Yersinia pseudotuberculosis (Pfeiffer) Smith and Thai, and Serratia sp., bacteria pathogenic to insects, were detected in the biological material from both normal and malformed butterflies from this population. These findings are summarized and discussed in this review, in the light of conservation of insects and restitution of their populations from a low number of individuals. 展开更多
关键词 Apollo butterfly LACCASES malformed wings POPULATION RECONSTITUTION WINGLESS gene Wolbachia
不同产地忽地笑的叶绿体基因psbA-trn H序列分析
2
作者 全妙华 赵丽娟 +3 位作者 贺安娜 佘朝文 向小亮 蒋向辉 《中草药》 CAS CSCD 北大核心 2019年第2期491-501,共11页
目的通过叶绿体基因psbA-trn H序列分析,探讨我国忽地笑种质资源的系统进化关系及分子鉴定方法。方法分别提取15省(市)52个忽地笑居群的DNA,经PCR扩增叶绿体基因psbA-trn H序列及测序,并用Mega5.0等软件对测序结果进行分析。结果 52条ps... 目的通过叶绿体基因psbA-trn H序列分析,探讨我国忽地笑种质资源的系统进化关系及分子鉴定方法。方法分别提取15省(市)52个忽地笑居群的DNA,经PCR扩增叶绿体基因psbA-trn H序列及测序,并用Mega5.0等软件对测序结果进行分析。结果 52条psbA-trn H序列长度为544~656 bp,GC含量为35.8%~37.0%,遗传距离为0.000 00~0.009 47;核苷酸变异(多态性)位点数共33个,其中简约信息位点9个,单一突变位点18个,插入/缺失片段6个;单倍型数量(H)10个,单倍型多态性水平(Hd)0.749,核苷酸多态性(π)0.002 63,收集的忽地笑资源具有较高的遗传多样性。最大简约法(maximum parsimony,MP)系统树中52个居群聚为4类,并且该聚类结果与其地理分布基本一致。结论不同产地忽地笑居群的遗传变异较大,psb A-trn H序列可作为忽地笑种源分子鉴定的依据;我国忽地笑种质资源在进化上具有明显的地域性特征。 展开更多
关键词 忽地笑 居群 psbA-trnH序列 核苷酸多态性 系统聚类
基于多源数据的福建省人口数据空间化研究 预览
3
作者 杨晓荣 陈楠 《贵州大学学报:自然科学版》 2019年第2期79-84,95共7页
针对人口统计数据无法精细直观反映人口真实的空间分布状况的问题,该文以福建省为例,对其2015年的人口数据进行空间化。以多源数据为基础数据,在县级尺度上采用了空间回归模型构建福建省2015年福建省500m人口空间分布数据,在乡镇尺度上... 针对人口统计数据无法精细直观反映人口真实的空间分布状况的问题,该文以福建省为例,对其2015年的人口数据进行空间化。以多源数据为基础数据,在县级尺度上采用了空间回归模型构建福建省2015年福建省500m人口空间分布数据,在乡镇尺度上对其空间化结果进行精度验证并与WorldPop、中国公里网格人口分布数据集比较。结果表明:NPP/VIIRS夜间灯光、路网、DEM、土地利用数据与人口具有较强的相关性,有足够能力模拟人口的空间分布;对于2015年福建省人口数据空间化,空间误差模型比空间滞后模型的回归拟合效果更好;人口数据空间化结果精度比较高,在空间上能精细展现2015年福建省的人口分布状况;人口高值区主要集中在县城所在地,人口呈现出主城区高、四周低的空间分布格局。 展开更多
关键词 人口 影响因素 空间回归 空间化
在线阅读 下载PDF
城市创新力与人口发展协调性的考量研究——基于北京、上海、深圳、杭州四大城市的多维指标比较
4
作者 周悦 张铭哲 杨艳东 《科技和产业》 2019年第3期23-28,共6页
在创新已成为核心竞争能力的当下,人口要素在城市创新力提升中扮演着重要角色。为深入诠释人口对城市创新发展的重要意义,以人口发展潜力对城市创新力的支撑作用为核心评价依据,建构人口视角下的城市创新力分析框架,从人口的发展、经济... 在创新已成为核心竞争能力的当下,人口要素在城市创新力提升中扮演着重要角色。为深入诠释人口对城市创新发展的重要意义,以人口发展潜力对城市创新力的支撑作用为核心评价依据,建构人口视角下的城市创新力分析框架,从人口的发展、经济及创新潜力等三个层面构建评价指标体系。通过对北京、上海、深圳、杭州四大城市各指标的比较,分析四个城市保持创新力的优势和劣势,为不断增进人口与城市经济、产业、科技等要素创新发展的协调性提出思路启示。 展开更多
关键词 城市 创新力 人口 发展 协调性
在线阅读 免费下载
Monitoring of brown stink bug (Hemiptera: Pentatomidae) population dynamics in corn to predict its abundanee using weather data
5
作者 Xinzhi Ni Ted E. Cottrell +3 位作者 G. David Buntin Xianchun Li Wei Wang Hong Zhuang 《昆虫科学:英文版》 SCIE CAS CSCD 2019年第3期536-544,共9页
The brown stink bug (BSB), Euschistus servus (Say)(Hemiptera: Pentatomidae), is a serious economic pest of corn production in the southeastern United States. The BSB population dynamics was mon itored for 17 weeks fro... The brown stink bug (BSB), Euschistus servus (Say)(Hemiptera: Pentatomidae), is a serious economic pest of corn production in the southeastern United States. The BSB population dynamics was mon itored for 17 weeks from tasseling to preharvest of corn plants (i.e., late May to mid-September) using pheromone traps in three corn fields from 2005 to 2009. The trap data showed two peaks in early June and mid-August, respectively. The relationship between trap catch and pregrowing season weather data was examined using correlation and stepwise multiple factor regression analyses. Weather indices used for the analyses were accumulated growing degree day (AGDD), number of days with minimum temperature below 0℃(Subz), accumulated daily maximum (AMaxT) and minimum temperatures (AMinT) and rainfall (ARain). The weather indices were calculated with lower (10℃) and upper (35℃) as biological thresholds. The parameters used in regression analysis were seasonal abundance (or overall mean of BSB adult catch)(BSBm), number of BSB adults caught at a peak (PeakBSB), and peak week (Peakwk). The BSBm was negatively related to high temperature (AmaxT or AGDD) consistently, whereas IstPeakBSB was positively correlated to both ARain and Subz, irrespective of weather data durations (the first 4, 4.5, and 5 months). In contrast, the 7-month weather data (AGDD7) were negatively correlated to the BSBm only, but not correlated to the second PeakBSB. The 5-year monitoring study demonstrated that weather data can be used to predict the BSB abundance at its first peak in tasseling corn fields in the southeastern U.S. states. 展开更多
关键词 Euschistus servus first TRAP CATCH peak PHEROMONE TRAP CATCH population dynamics STEPWISE regression modeling weekly mean
Did maize domestication and early spread mediate the population genetics of corn leafhopper?
6
作者 Julio S. Bernal Amanda M. Davila-Flores +3 位作者 Raul F. Medina Yolanda H. Chen Kyle E. Harrison Kimberly A. Berrier 《昆虫科学:英文版》 SCIE CAS CSCD 2019年第3期569-586,共18页
Investigating how crop domestication and early farming mediated crop attributes, distributions, and interactions with antagonists may shed light on today's agricultural pest problems. Crop domestication generally ... Investigating how crop domestication and early farming mediated crop attributes, distributions, and interactions with antagonists may shed light on today's agricultural pest problems. Crop domestication generally involved artificial selection for traits desirable to early farmers, for example, in creased productivity or yield, and enhanced qualities, though invariably it altered the interactions between crops and insects, and expanded the geographical ranges of crops. Thus, some studies suggest that with crop domestication and spread, insect populations on wild crop ancestors gave rise to pestiferous insect populations on crops. Here, we addressed whether the emergence of corn leafhopper (Dalbulus ma id is) as an agricultural pest may be associated with domestication and early spread of maize (Zea mays mays). We used AFLP markers and mitochondrial COI sequences to assess population genetic structuring and haplotype relationships among corn leafhopper samples from maize and its wild relative Zea diploperennis from multiple locations in Mexico and Argentina. We uncovered seven corn leafhopper haplotypes contained within two haplogroups, one haplogroup containing haplotypes associated with maize and the other containing haplotypes associated with Z. diploperennis in a mountainous habitat. Within the first haplogroup, one haplotype was predominant across Mexican locations, and another across Argentinean locations;both were considered pestiferous. We suggested that the divergence times of the maize-associated haplogroup and of the "pestiferous" haplotypes are correlated with the chronology of maize spread following its domestication. Overall, our results support a hypothesis positing that maize domestication favored corn leafhopper genotypes preadapted for exploiting maize so that they became pestiferous, and that with the geographical expansi on of maize farming, corn leafhopper colonized Z. diploperennis, a host exclusive to secluded habitats that serves as a refuge for archaic corn leafhopper genotypic diversity. B 展开更多
关键词 Dalbulus maidis HAPLOTYPE network analysis PERENNIAL TEOSINTE population genetic structuring ZEA diploperennis ZEA mays mays
城市经济承载力评价与政策选择研究--以贵州省为例
7
作者 肖良武 《贵阳学院学报:社会科学版》 2019年第2期53-60,共8页
城市经济社会发展的重大问题是维持城市生态经济系统的稳定,达到生态环境保护与经济建设之间的均衡。随着工业经济的快速发展,城镇化进程的快速推进,城市的生态系统遭受破坏,城市各种"病"逐渐显现,城市还能否继续增长?为此,... 城市经济社会发展的重大问题是维持城市生态经济系统的稳定,达到生态环境保护与经济建设之间的均衡。随着工业经济的快速发展,城镇化进程的快速推进,城市的生态系统遭受破坏,城市各种"病"逐渐显现,城市还能否继续增长?为此,需要对城市经济承载力进行测算,以测算结果为基础,分析出城市经济承载力的变化轨迹,剖析引起城市经济承载力变化的主要因素,探寻城市经济承载力提升的路径,并提出相应的建议。 展开更多
关键词 生态环境 经济承载力 人口 城市增长
在线阅读 免费下载
近年来乌梁素海疣天鹅种群数量变化及原因分析
8
作者 赵格日乐图 灵燕 高敏 《动物学杂志》 CAS CSCD 北大核心 2019年第1期8-14,共7页
为查清内蒙古乌梁素海湖泊湿地疣鼻天鹅(Cygnus olor)繁殖期和秋季迁徙前期种群数量,2014至2017年采用路线统计法和样点统计法对其进行精确计数统计,结合近十余年来的文献数据和监测记录,探讨了种群数量的变化及原因。结果显示,2015至2... 为查清内蒙古乌梁素海湖泊湿地疣鼻天鹅(Cygnus olor)繁殖期和秋季迁徙前期种群数量,2014至2017年采用路线统计法和样点统计法对其进行精确计数统计,结合近十余年来的文献数据和监测记录,探讨了种群数量的变化及原因。结果显示,2015至2017年春季繁殖成鸟数量依次为84只、92只、80只,基本稳定;2014至2017年,秋季种群数量依次为411只、302只、281只、153只,逐年减少;近几年适宜繁殖地和觅食地面积不断缩小、天敌偷袭、捡蛋和投毒等因素影响亚成鸟和幼鸟的生存。根据文献和保护区监测数据,1996至2004年种群数量逐年增多,与自然保护区的建立、严禁捡蛋和没收猎枪有关,而2005至2013年因干旱缺水、水域被开发利用、芦苇(Phragmites australis)和宽叶香蒲(Typha latifolia)面积扩增、水质恶化、富营养化加重等原因种群数量下降。研究表明,近几年乌梁素海被过度开发利用,人为干扰频繁,影响疣鼻天鹅正常繁殖栖息;栖息地的科学管理和严禁捡蛋及投毒行为,对该种群的生存及增长至关重要。 展开更多
关键词 疣鼻天鹅 种群数量 动态变化 乌梁素海
泉州湾河口湿地互花米草种群的季节动态研究
9
作者 高苏蕊 李元跃 +5 位作者 陈融斌 潘文 赵秋毅 熊章静 唐业勋 黎中宝 《集美大学学报:自然科学版》 CAS 2019年第2期94-99,共6页
迄今为止,互花米草(Sporobolus alterniflorus(Loisel.)P.M.Peterson & Saarela)虽被列入外来入侵植物,但就其生态环境效应仍在学界颇有争议。以福建省泉州湾洛阳江河口湿地的互花米草种群为研究对象,分别于2017年6月(夏)、9月(秋)... 迄今为止,互花米草(Sporobolus alterniflorus(Loisel.)P.M.Peterson & Saarela)虽被列入外来入侵植物,但就其生态环境效应仍在学界颇有争议。以福建省泉州湾洛阳江河口湿地的互花米草种群为研究对象,分别于2017年6月(夏)、9月(秋)、12月(冬)和2018年3月(春)进行采样,测定互花米草在不同潮位的密度、株高、丛径、鲜重和干重等指标。研究结果表明:季节变化对互花米草的密度、株高、丛径、鲜重与干重差异均有显著影响(P<0.05)。三个潮区互花米草密度都呈现夏季>秋季>春季>冬季,且不同潮区四个季节之间互花米草密度差异显著;株高在四个季度中呈现秋季>夏季>冬季>春季,秋季显著高于其他季节;丛径随季节变化差异均显著,在夏季达到最大值;鲜重与干重在四个季度中均呈现秋季>夏季>冬季>春季,且鲜重随季节变化差异均显著,干重表现为秋季和夏季显著高于冬季和春季。 展开更多
关键词 河口湿地 互花米草 种群 季节动态 泉州湾
在线阅读 免费下载
内蒙古高原有蹄类动物资源的分布与历史变迁 预览
10
作者 萨如拉 张荣 高润宏 《林业资源管理》 北大核心 2019年第1期12-18,共7页
内蒙古高原有蹄类动物有4科10属13种,其中西伯利亚狍和马鹿是林草交错区分布的动物,以林为主,但也渗透到草原;藏原羚、岩羊、盘羊和北山羊栖息于高原的一些山地和丘陵,不进入高平原区;普氏原羚、蒙原羚、塔里木鹅喉羚、赛加羚、野骆驼... 内蒙古高原有蹄类动物有4科10属13种,其中西伯利亚狍和马鹿是林草交错区分布的动物,以林为主,但也渗透到草原;藏原羚、岩羊、盘羊和北山羊栖息于高原的一些山地和丘陵,不进入高平原区;普氏原羚、蒙原羚、塔里木鹅喉羚、赛加羚、野骆驼、蒙古野驴和普氏野马是典型的高原物种,其中蒙原羚和塔里木鹅喉羚是北方草原和荒漠的代表种。但是,近现代以来,这些物种的分布发生了剧烈的变化,普氏野马、藏原羚、普氏原羚和赛加羚近代已从内蒙古高原消失,野骆驼疑似在阿拉善的马鬃山有分布,而盘羊、岩羊和北山羊挤压到草原和荒漠的几个山地孤岛上,大范围分布的蒙原羚和和普氏原羚种群呈线性下降。造成这些动物的种群减少和消失主要原因是人为干扰的结果,这些干扰表现为:垦殖行为、围栏割裂行为、水资源过度消耗行为。为保护这些动物建议建立国家公园体系,同时预留生态空间。 展开更多
关键词 内蒙古高原 有蹄类动物 种群 栖息地 变迁
在线阅读 下载PDF
Dynamical control of population and entanglement for open Λ-type atoms by engineering the environment
11
作者 王晓岚 任玉坤 曾浩生 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第3期97-102,共6页
The exactly analytical solution for the dynamics of the dissipative Λ-type atom in the zero-temperature Lorentzian environment is presented. On this basis, we study the evolution of the population and entanglement. W... The exactly analytical solution for the dynamics of the dissipative Λ-type atom in the zero-temperature Lorentzian environment is presented. On this basis, we study the evolution of the population and entanglement. We find that the stable populations on the two lower levels of the Λ-type atom can be effectively adjusted by the combination of the relative decay rate and the environmental spectral frequency. However, for the initial Werner-like state, the stable entanglement between the two Λ-type atoms has very little tunability. Furthermore, the stable entanglement for the bilateral environment case is larger than that of the unilateral environmental case. A nonintuitive relation between the stable entanglement and stable population is found. 展开更多
关键词 OPEN quantum systems POPULATION ENTANGLEMENT
The current status of hormone treatment for prostate cancer patients in Korean real-world practice:a multi-institutional observational study
12
作者 Jung Kwon Kim Jung Jun Kim +12 位作者 Taek Won Gang Tae Kyun Kwon Hong Sup Kim Seung Chui Park Jae-Shin Park Jong-Yeon Park Seok Joong Yoon Youn-Soo Jeon Jin Seon Cho Kwan Joong Joo Sung-Hoo Hong Seok-Soo Byun the Korean Urological Oncology Society 《亚洲男性学杂志:英文版》 SCIE CAS CSCD 2019年第2期115-120,共6页
We aimed to evaluate the current nationwide trend,efficacy,safety,and quality of life(QoL)profiles of hormone treatment in real-world practice settings for prostate cancer(PCa)patients in Korea.A total of 292 men with... We aimed to evaluate the current nationwide trend,efficacy,safety,and quality of life(QoL)profiles of hormone treatment in real-world practice settings for prostate cancer(PCa)patients in Korea.A total of 292 men with any biopsy-proven PCa(TanyNanyMany)from 12 institutions in Korea were included in this multi-institutional,observational study of prospectively collected data.All luteinizing hormone-releasing hormone(LHRH)agonists were allowed to be investigational drugs.Efficacy was defined as(1)the rate of castration(serum testosterone≤50 ng dl^-1)at 4-week visit and(2)breakthrough(serum testosterone>50 ng dl^-1 after castration).Safety assessments included routine examinations for potential adverse events,laboratory tests,blood pressure,body weight,and bone min era I density(BMD,at baseli ne and at the last follow-up visit).QoL was assessed using the Expa nded Prostate Cancer Index Composite-26(EPIC-26).The most comm on initial therapeutic regimen was LHRH agonist with an ti-androge n(78.0%),and the most commonly used LHRH agonist for combination and mono therapy was leuprolide(64.0%for combi natio n and 58.0%for monotherapy).The castration and breakthrough rates were 78.4%and 6.6%,respectively.The laboratory results related to dyslipidemia worsened after 4 weeks of hormone treatment.In addition,the mean BMD T-score was significantly lower at the last follow-up(mean:-1.950)compared to baseline(mean:-0.195).The mean total EPIC-26 score decreased from 84.8(standard deviation[s.d.]:12.2)to 78.3(s.d.:8.1),with significant deterioration only in the urinary domain(mean:23.5 at baseli ne and 21.9 at the 4-week visit).These findi ngs dem on strate the n ationwide trend of current practice setti ngs in hormone treatment for PCa in Korea. 展开更多
关键词 EFFICACY HORMONAL treatment KOREAN population PROSTATE cancer safety TREND
濒危植物五小叶槭(Acer pentaphyllum Diels)天然种群遗传多样性的ISSR标记分析
13
作者 郝云庆 罗晓波 王晓玲 《四川大学学报:自然科学版》 CAS CSCD 北大核心 2019年第1期161-166,共6页
五小叶槭(Acer pentaphyllum Diels)是中国四川特有野生珍稀濒危植物,仅分布于雅砻江中上游干旱河谷地带;探索其遗传多样性特征可以为其遗传资源的保护和利用提供理论依据.本文采用ISSR技术对五小叶槭的5个野生种群的44份材料进行遗传... 五小叶槭(Acer pentaphyllum Diels)是中国四川特有野生珍稀濒危植物,仅分布于雅砻江中上游干旱河谷地带;探索其遗传多样性特征可以为其遗传资源的保护和利用提供理论依据.本文采用ISSR技术对五小叶槭的5个野生种群的44份材料进行遗传多样性分析,8条引物总共检测到38个位点,其中多态性位点35个,多态位点百分率(PPL)平均为90.21%.应用分析软件Popgen32分析得出:在物种水平上,五小叶槭的香农多样性指数(I)为0.3924,Nei氏基因多样性指数(H e)为0.2498;种群间基因分化系数(G st)为0.3722,种群间的基因流(N m)为0.8433,这表明五小叶槭的遗传变异主要存在于种群内.在种群水平上,香农多样性指数(I)为0.2125,Nei氏基因多样性指数(H e)为0.1456.结果表明木里、九龙三垭宫和康定这3个种群的遗传多样性水平较高,而雅江和九龙洛莫种群遗传多样性较低.通过Mantel检测,种群间遗传距离和地理距离之间没有显著相关性. 展开更多
关键词 五小叶槭 ISSR 遗传多样性 种群
在线阅读 免费下载
Conservation implications of population genetic structure in a threatened orchid Cypripedium tibeticum
14
作者 Jian-Ling Guo Wen-Juan Cao +2 位作者 Zhi-Min Li Yong-Hong Zhang Sergei Volis 《植物多样性:英文版》 CAS CSCD 2019年第1期13-18,共6页
Cypripedium tibeticum is a threatened orchid which efficient conservation requires knowledge of its extent and structure of genetic variation. Using two chloroplast DNA fragments(rps16 and trnL-F), we analyzed 157 ind... Cypripedium tibeticum is a threatened orchid which efficient conservation requires knowledge of its extent and structure of genetic variation. Using two chloroplast DNA fragments(rps16 and trnL-F), we analyzed 157 individuals from 9 populations representing the species range in China. Seven haplotypes were identified. C. tibeticum had high total genetic diversity(H_T=0.80) with major contribution to this diversity made by among-population component(GST=0.64,ФST= 0.86). However, despite high population differentiation there was no clear phylogeographic structure. The populations CY and DC made the greatest contribution to the total gene diversity as well as allelic richness. The possible mechanisms and implications of these findings for conservation of the species are discussed. 展开更多
关键词 CYPRIPEDIUM tibeticum ORCHID genetic diversity Population differentiation East Himalaya-Hengduan MOUNTAINS CONSERVATION strategy
Assessment by microsatellite analysis of genetic diversity and population structure of Enhalus acoroides from the coast of Khanh Hoa Province, Vietnam 预览
15
作者 Xuan-Vy Nguyen Papenbrock Jutta 《海洋学报:英文版》 SCIE CAS CSCD 2019年第1期144-150,共7页
Seagrass beds degraded significantly since the last century on both, global and local scale. The seagrass species Enhalus acoroides (Linnaeus f.) Royle is a common species found in almost all marine ecosystems includi... Seagrass beds degraded significantly since the last century on both, global and local scale. The seagrass species Enhalus acoroides (Linnaeus f.) Royle is a common species found in almost all marine ecosystems including bays, lagoons and around offshore islands in tropical regions of the West Pacific. It was shown that genetic diversity is an essential indicator of the conditions of ecosystems. In the present study, microsatellite markers were used to assess the genetic diversity and population structure of six distinct seagrass beds along the coast of the Khanh Hoa Province, Vietnam. The results indicate that the genetic diversity of the populations in the open sea is higher than in the lagoon. Seagrass beds occurring in disturbed sites show reduced genetic diversity. The fixing index value (FST) depicts a relatively high genetic structure among populations. Structure analysis clusters the populations into open sea and lagoon populations and cluster analysis and AMOVA indicate a significant difference between the two groups. There are low but non-significant positive correlations between geographic and genetic distances. The different habitats of the open sea and the lagoon are probably responsible for forming two groups. 展开更多
关键词 Enhalus acoroides GENETIC DIVERSITY LAGOON open sea POPULATION structure
在线阅读 下载PDF
新疆地区人口-经济-土地系统城镇化耦合协调演化研究 预览
16
作者 陈笑利 陈俊科 +1 位作者 余国新 聂春霞 《天津农业科学》 CAS 2019年第1期48-52,共5页
为探讨新疆地区2006-2016年人口-经济-土地系统城镇化耦合协调的演化趋势,本研究选取2007-2017年《新疆统计年鉴》数据,构建人口-经济-土地系统城镇化协调度模型,测算耦合度和协调度。结果表明,2006-2016年,新疆地区城镇化人口-经济、人... 为探讨新疆地区2006-2016年人口-经济-土地系统城镇化耦合协调的演化趋势,本研究选取2007-2017年《新疆统计年鉴》数据,构建人口-经济-土地系统城镇化协调度模型,测算耦合度和协调度。结果表明,2006-2016年,新疆地区城镇化人口-经济、人口-土地、经济-土地等二系统以及人口-经济-土地三系统的综合评价指数均呈波动上升趋势;二系统耦合度较三系统高,其中二系统处于“颉顽”向“磨合优化”的过渡阶段,三系统则处于“颉顽”初水平阶段;系统间协调度均呈波动上升趋势,由最初的严重失调过渡到初级或中级协调。综合而言,新疆地区2006-2016年城镇化发展较慢,系统间的耦合度和协调度整体水平均较低,有待进一步提升。 展开更多
关键词 新疆 人口 经济 土地 城镇化
在线阅读 下载PDF
Molecular phylogeny and ultrastructure of a new population of Urostyla grandis(Ciliophora,Hypotrichida)from Harbin,China 预览
17
作者 CAI Xinglong CHEN Ying +5 位作者 ZHAO Xiaolu GAO Jing Saleh A.AL-FARRAJ YU Lijie PAN Xuming QIU Zijian 《海洋湖沼学报(英文)》 SCIE CAS CSCD 2019年第1期256-265,共10页
A new population of Urostyla grandis,collected from a freshwater pond of northeastern China was investigated by living observation,silver impregnation,and molecular phylogeny based on small subunit ribosomal rRNA(SSU ... A new population of Urostyla grandis,collected from a freshwater pond of northeastern China was investigated by living observation,silver impregnation,and molecular phylogeny based on small subunit ribosomal rRNA(SSU rRNA).Besides,its ultrastructural characteristics were investigated carefully by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)methods.Complementary descriptions of some inner ultrastructures were provided and some new organelles were also found.Especially,the oral inner microtubule system was illustrated by SEM and TEM for the fi rst time and a new type extrusome was reported.These results may supply complement taxonomic data and ingestion mechanism on ciliates in genus Urostyla. 展开更多
关键词 Urostyla grandis PHYLOGENY ULTRASTRUCTURE NEW POPULATION
在线阅读 下载PDF
5个新疆野生黄花苜蓿居群表型变异性 预览
18
作者 李倩 若扎·扎尔汗 +2 位作者 李陈建 王玉祥 张博 《草业科学》 CAS CSCD 2019年第2期414-421,共8页
以5个新疆野生黄花苜蓿(Medicago falcata)居群为材料,通过对其叶、花、茎节等20个表型性状及分布地区进行相关性、主成分及变异性等分析,探究原始居群表型性状的遗传多样性规律,以期为进一步开展新疆黄花苜蓿遗传变异及种质创新研究提... 以5个新疆野生黄花苜蓿(Medicago falcata)居群为材料,通过对其叶、花、茎节等20个表型性状及分布地区进行相关性、主成分及变异性等分析,探究原始居群表型性状的遗传多样性规律,以期为进一步开展新疆黄花苜蓿遗传变异及种质创新研究提供基础数据。结果表明,1)5个居群20个性状差异明显,除叶长差异和叶柄长差异达到显著水平(P<0.05)外,其余18个性状差异均达到极显著水平(P<0.01);2)黄花苜蓿具有丰富的多态性,表型性状在居群内平均变异系数为20.19%,居群间为27.66%,且居群间差异大于居群内,表明黄花苜蓿不同居群表型差异主要来源于居群间;3)20个表型性状间均存在不同程度的相关性,经纬度与分枝数、海拔与株高均呈现负相关关系;4)20个表型性状可归为6个主成分因子,累计贡献率达71.75%,居群间表型性状变异主要来自叶片、节间及花部特性。 展开更多
关键词 黄花苜蓿 表型 居群 变异性
在线阅读 下载PDF
长江经济带城镇化对能源消费的经济门槛效应
19
作者 严翔 成长春 +1 位作者 易高峰 柏建成 《经济地理》 CSSCI CSCD 北大核心 2019年第1期73-81,共9页
在文献回顾的基础上,从与经济发展相关的产业、空间与人口三层面梳理、构建城镇化对能源消费影响的融合传导机制,并基于Hansen面板门槛回归模型,利用长江经济带11省市2005—2015年的面板数据,实证分析流域城镇化与能源消费间非线性发展... 在文献回顾的基础上,从与经济发展相关的产业、空间与人口三层面梳理、构建城镇化对能源消费影响的融合传导机制,并基于Hansen面板门槛回归模型,利用长江经济带11省市2005—2015年的面板数据,实证分析流域城镇化与能源消费间非线性发展关系。研究表明:城镇化进程中的经济发展水平决定了生产与生活能耗模式,对能源消费的影响具有显著的经济门槛效应。经济落后与经济发达地区的城镇化进程对传统能耗依赖较小,而经济处于快速发展中的区域城镇化对能源消费的促进作用明显。进一步指出,虽然城镇化进程中的产业结构调整与技术进步对能源消费抑制作用明显,但在人口压力及资源约束加剧的新城镇化背景下,更应坚持以人为本,不仅要促进量的转移,更要注重质的提升,关注居民消费引导与空间紧凑布局对能源消费的影响,继续发挥规模经济的削减作用,努力实现共享经济的集约效能;各省市间则应建立互动协调机制,根据自身城镇化对能耗的影响路径因地制宜地采取相应策略,这也是全流域可持续发展的关键。 展开更多
关键词 城镇化 能源消费 经济门槛效应 绿色发展 节能降耗 人口 长江经济带
基于互联网的中高危心血管病危险人群管理的效果分析 预览
20
作者 柴敬杰 韩丽莹 +4 位作者 陶晓莉 沈吴箴 于占文 沈亚萍 李梅 《全科医学临床与教育》 2019年第4期296-298,共3页
目的探讨基于互联网的中高危心血管病危险人群管理模式的效果。方法将346例具有中高危心血管病风险人群随机分为观察组和对照组。观察组采用基于互联网的管理模式,对照组采用传统慢病管理模式。2年后比较两组人群死亡率、心血管病发生... 目的探讨基于互联网的中高危心血管病危险人群管理模式的效果。方法将346例具有中高危心血管病风险人群随机分为观察组和对照组。观察组采用基于互联网的管理模式,对照组采用传统慢病管理模式。2年后比较两组人群死亡率、心血管病发生率以及心血管病发病风险。结果健康管理后,观察组收缩压、血清总胆固醇水平和吸烟率均低于对照组,差异均有统计学意义(t分别=7.22、8.00,χ^2=2.14,P均<0.05)。观察组的高危心血管病危险人群占比低于对照组,低危心血管病危险人群占比高于对照组,差异均有统计学意义(χ^2分别=15.37、3.57,P均<0.05)。结论移动互联网技术在社区慢病管理中具有重要的作用,可以降低心血管病发病危险,降低收缩压、血清总胆固醇水平和吸烟率。 展开更多
关键词 互联网 中高危 心血管病 人群 管理 效果
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈