首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   152篇
  免费   4篇
  国内免费   30篇
  2020年   5篇
  2018年   3篇
  2017年   10篇
  2016年   4篇
  2015年   6篇
  2014年   9篇
  2013年   3篇
  2012年   5篇
  2011年   3篇
  2010年   5篇
  2009年   9篇
  2008年   18篇
  2007年   7篇
  2006年   8篇
  2005年   15篇
  2004年   14篇
  2003年   5篇
  2002年   8篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   3篇
  1996年   3篇
  1995年   4篇
  1994年   2篇
  1993年   3篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1985年   3篇
  1984年   2篇
  1981年   1篇
  1980年   2篇
  1978年   6篇
  1977年   1篇
  1976年   1篇
  1973年   2篇
排序方式: 共有186条查询结果,搜索用时 15 毫秒
81.
茶园节肢动物类群多样性和稳定性研究   总被引:11,自引:4,他引:7  
对常年用人工或除草剂除草的茶园和地面种植长节耳草(Hedyotis uncinella)的茶园茶树生境节肢动物类群的多样性和稳定性进行了分析和比较.结果表明,复合茶园节肢动物类群主要特征的丰富度值除一次低于4外,其他都在4~8之间,最高达7.7403.单一园丰富度值大部分在4~6之间,最高的为6.7810;复合园丰富度值平均值为5.4672±0.3483,高于单一园相应值4.8809±0.3175.复合园节肢动物Shannon-Weiner多样性指数平均值为3.8535±0.1232,比单一园相应值3.4654±0.1856高.复合园均匀度指数平均值0.8781±0.012,高于单一园均匀度值0.8261±0.038.相反,复合园节肢动物优势集中度平均值(0.0992±0.009)低于单一园值(0.1636±0.038).复合园稳定性指标Ss/Si和Sn/Sp比单一园的高,而复合园多样性变异系数ds/dm值(0.1107)比单一园相应值(0.1855)低.研究表明,复合茶园生态系统有比单一茶园生态系统更丰富的生物多样性和更高的系统稳定性.  相似文献   
82.
桃园节肢动物群落的多样性、均匀度和相对稳定性季节动态   总被引:10,自引:0,他引:10  
对桃园节肢动物群落进行了系统调查,并对数据进行了数学分析.结果表明,群落与植食动物亚群落的多样性指数相关系数为0.9480,两者极显著相关;群落与捕食动物亚群落的多样性指数相关系数为0.7855,两者极显著相关;两个亚群落的多样性均与群落多样性有关,两个亚群落多样性指数间相关系数为0.6741,两者显著相关;群落多样性指数与群落均匀度指数问相关系数为0.7870,两者极显著相关;群落多样性指数与两个亚群落均匀度指数之间均不相关.群落多样性指数(H’),与捕食性动物个体数(Sd)和植食性动物个体数(Sz)之比值(Sd/Sz)相关系数为0.8112,两者极显著相关;与群落物种数(Sz)和个体数(Si)之比值(Sz/Si)相关系数为0.9188,两者极显著相关;与捕食动物类群(科)数(Spl)和植食动物类群(科)数(Szl)之比值(Spl/Szl)不相关。  相似文献   
83.
吡虫啉对烟田节肢动物群落的影响研究   总被引:12,自引:8,他引:4  
利用群落参数分析了吡虫啉对烟田节肢动物群落及其各亚群落的影响。结果表明,施药后对烟田节肢动物群落、害虫亚群落的物种数有一定的影响,对天敌昆虫和蜘蛛亚群落物种数的影响不明显。5月23日施药后至6月13日施药区(Ⅱ)和对照区节肢动物群落、害虫亚群落个体数均下降,下降程度施药区大于对照区。6月14日施药后施药区节肢动物群落、害虫亚群落个体数下降,对照区显著上升。两次施药对天敌昆虫和蜘蛛亚群落个体数的影响不明显,施药后一段时间内优势种烟蚜种群个体数量显著下降,使节肢动物群落和害虫亚群落优势集中性下降,多样性指数和稳定性增加。  相似文献   
84.
双季稻区两类生境稻田节肢动物群落结构比较   总被引:4,自引:0,他引:4  
刘雨芳  古德祥 《生态科学》2004,23(3):196-199,203
用吸虫器采样法,对双季稻区中处于多样化生境及单一生境中的两类稻田中的节肢动物群落结构特征进行了比较研究。结果表明:在早稻生长发育初期和晚稻生长全期,多样化生境稻田中捕食性节肢动物的物种数和个体数量都显著高于单一化生境稻田。同时,多样化生境中稻田植食性昆虫的物种丰富度高于单一化生境稻田,但其个体数量较低。非稻田生境主要作为稻田捕食性节肢动物群落的种库,能促进稻田捕食性节肢动物群落的重建。  相似文献   
85.
应用随机扩增多态性DNA(RAPD)技术,对9个不同地理种群美国白蛾进行了遗传多样性和UPMGA聚类分析.结果表明:25个RAPD引物共扩增191个位点,片段大小在200~2000 bp,其中158个是多态位点,多态百分率为82.72%,遗传距离指数在0.2043~0.5108,遗传相似性系数在0.4892~0.7957;9个不同地理种群的美国白蛾可以分成3类:辽宁省和山东类群、北京和天津类群、美国类群,表明美国白蛾不同地理种群间的遗传分化与地理位置相关.  相似文献   
86.
The decay time of the fluorescence of excited molecules, called fluorescence lifetime, can provide information about the cuticle composition additionally to widely used spectral characteristics. We compared autofluorescence lifetimes of different cuticle regions in the copulatory organ of females of the bedbug, Cimex lectularius. After two-photon excitation at 720 nm, regions recently characterised as being rich in resilin showed a longer bimodal distribution of the mean autofluorescence lifetime τm (tau-m) at 0.4 ns and 1.0–1.5 ns, while resilin-poor sites exhibited a unimodal pattern with a peak around 0.8 ns. The mean lifetime, and particularly its second component, can be useful to distinguish resilin-rich from resilin-poor parts of the cuticle. The few existing literature data suggest that chitin is unlikely responsible for the main autofluorescent component observed in the resilin-poor areas in our study and that melanin requires further scrutiny. Autofluorescence lifetime measurements can help to characterise properties of the arthropod cuticle, especially when coupled with multiphoton excitation to allow for deeper tissue penetration.  相似文献   
87.
A megacheiran arthropod, Enalikter aphson, was recently described by Siveter et al. (2014) from the mid‐Silurian (late Wenlock) of Herefordshire. Previously, megacheirans had only been recognized from the Cambrian. Struck et al. (2015) considered the body plan of Enalikter to be incompatible with this affinity, arguing that many of the arthropod features were either not present or misinterpreted. Instead, they compared Enalikter to polychaete annelids, identifying characters from numerous polychaete lineages which they considered to be present in Enalikter. A reply to this critique by Siveter et al. (2015) reaffirmed arthropod affinities for Enalikter by presenting additional evidence for key arthropod features, such as arthropodized appendages. Here, we augment Siveter et al. by critically addressing the putative annelid characters of Enalikter presented by Struck et al. and additionally explore the morphological and phylogenetic implications of their hypothesis. We conclude that similarities between Enalikter and polychaetes are superficial and that character combinations proposed by Struck et al. are not present in any annelid, living or extinct. This taxon highlights the importance of using a phylogenetic framework for interpreting fossils that present unusual morphologies, such that proposed shared characters are hypotheses of homology rather than merely phenotypic similarities. Crucially, we argue that autapomorphic characters of subgroups of large taxa (like families or classes within phyla) should not be used to diagnose problematic fossils.  相似文献   
88.
徐光辉 《古生物学报》2004,43(3):325-331
描述3块新的标本,分别是节肢动物Pisinnocaris sp.,Tanglangia longicaudata Luo et Hu,1999和Pygmaclypeatus daziensis Zhang,Han et Shu,2000。新的标本进一步增进我们对其形态结构特征的了解。通过与相关属种的比较,简要讨论其系统位置问题。  相似文献   
89.
The influence of arthropod availability on the formation of male little bustard breeding territories in central Spain was studied in two consecutive years. Arthropods (68,217 individuals) were sampled using pitfall trapping and male territories estimated by means of kernel functions. Hymenopterans (ants), beetles, mites and spiders were the main taxa found in the samples, while the highest contributions in terms of biomass came from hymenopterans, beetles and orthopterans. The only group that exhibited significant biomass differences between territory and non-territory locations was that of the beetles; this pattern was consistent between years. Carabidae was the main beetle family in terms of biomass, followed by other large beetles such as Tenebrionidae, Cleridae, Scarabeidae and Elateridae. The biomass of Carabidae that were larger than 15 mm was significantly higher within territories than outside them. The biomass of Cleridae was greater in fallows, while Elateridae were more abundant in arable fields. The total biomass of beetles that were larger than 15 mm was higher in arable fields than in fallows. Family richness differed between years, while diversity showed differences between agricultural fields (it was highest in fallows), although these variables did not differ between territory and non-territory locations. Results indicate that large beetles (particularly carabids) seem to be a valuable food resource that is defended by little bustard males during the highly energy-demanding breeding season, which is discussed here in relation to habitat selection, the mating system and its implications for the conservation of the species.  相似文献   
90.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号