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   588篇
  免费   51篇
  国内免费   95篇
  2024年   5篇
  2023年   8篇
  2022年   17篇
  2021年   11篇
  2020年   9篇
  2019年   11篇
  2018年   20篇
  2017年   12篇
  2016年   7篇
  2015年   17篇
  2014年   25篇
  2013年   26篇
  2012年   34篇
  2011年   49篇
  2010年   48篇
  2009年   44篇
  2008年   31篇
  2007年   40篇
  2006年   39篇
  2005年   44篇
  2004年   35篇
  2003年   30篇
  2002年   30篇
  2001年   14篇
  2000年   7篇
  1999年   13篇
  1998年   12篇
  1997年   9篇
  1996年   7篇
  1995年   6篇
  1994年   3篇
  1993年   2篇
  1992年   4篇
  1990年   3篇
  1989年   4篇
  1988年   3篇
  1987年   6篇
  1985年   3篇
  1984年   2篇
  1980年   2篇
  1979年   6篇
  1978年   3篇
  1975年   3篇
  1971年   4篇
  1958年   6篇
  1954年   3篇
  1953年   1篇
  1951年   1篇
  1950年   1篇
  1949年   5篇
排序方式: 共有734条查询结果,搜索用时 62 毫秒
711.
This study assessed the knowledge and perception of human biological materials (HBM) and biorepositories among three study groups in South Korea. The relationship between the knowledge and the perception among different groups was also examined by using factor and regression analyses. In a self‐reporting survey of 440 respondents, the expert group was found more likely to be knowledgeable and positively perceived than the others. Four factors emerged: Sale and Consent, Flexible Use, Self‐Confidence, and Korean Bioethics and Biosafety Action restriction perception. The results indicate that those who are well aware of the existence of biobanks were more positively inclined to receive the Sale and Consent perception. As a result of the need for high quality HBMs and the use of appropriate sampling procedures for every aspect of the collection and use process, the biorepository community should pay attention to ethical, legal, and policy issues.  相似文献   
712.
The Diascia (Scrophulariaceae) window: an orientation cue for oil-collecting beeS. Flowers of Diascia section Racemosae are characterized by an unusual translucent 'window' at the base of the upper corolla lip which is bright yellow with maroon flecks and varies from a nearly flat to a deeply cone-shaped depression. The inner epidermal cells of the window are also variable in shape ranging from lenticular to long papillate. In contrast to the surrounding corolla which strongly reflects ultraviolet light, the window tissue is strongly ultraviolet absorptive due to the presence of ultraviolet absorbing flavonoids in the epidermal cellS. Observations in natural and experimental situations suggest that the window is used as an orientation cue by oil-collecting bees.  相似文献   
713.
714.
The Ca2+ sensor calmodulin (CaM) regulates numerous proteins involved in G protein-coupled receptor (GPCR) signaling. CaM binds directly to some GPCRs, including the dopamine D2 receptor. We confirmed that the third intracellular loop of the D2 receptor is a direct contact point for CaM binding using coimmunoprecipitation and a polyHis pull-down assay, and we determined that the D2-like receptor agonist 7-OH-DPAT increased the colocalization of the D2 receptor and endogenous CaM in both 293 cells and in primary neostriatal cultures. The N-terminal three or four residues of D2-IC3 were required for the binding of CaM; mutation of three of these residues in the full-length receptor (I210C/K211C/I212C) decreased the coprecipitation of the D2 receptor and CaM and also significantly decreased D2 receptor signaling, without altering the coupling of the receptor to G proteins. Taken together, these findings suggest that binding of CaM to the dopamine D2 receptor enhances D2 receptor signaling.  相似文献   
715.
716.
The Gelechioidea (>18 000 species), one of the largest superfamilies of Lepidoptera, are a major element of terrestrial ecosystems and include important pests and biological model species. Despite much recent progress, our understanding of the classification, phylogeny and evolution of Gelechioidea remains limited. Building on recent molecular studies of this superfamily and a recently revised family/subfamily classification, we provide an independent estimate of among‐family relationships, with little overlap in gene sample. We analysed up to five nuclear genes, totalling 6633 bp, for each of 77 gelechioids, plus up to 14 additional genes, for a total of 14 826 bp, in 45 of those taxa and all 19 outgroup taxa. Our maximum‐likelihood (ML) analyses, like those of previous authors, strongly support monophyly for most multiply‐sampled families and subfamilies, but very weakly support most relationships above the family level. Our tree looks superficially divergent from that of the most recent molecular study of gelechioids, but when the previous tree is re‐rooted to accord maximally with ours, the two phylogenies agree entirely on the deepest‐level divergences in Gelechioidea, and strongly though incompletely on among‐family relationships within the major groups. This concordance between independent studies is evidence that the groupings (or at least the unrooted branching order) are probably accurate, despite the low bootstrap values. After re‐rooting, both trees divide the families into three monophyletic groups: a ‘Gelechiid Assemblage,’ consisting of Gelechiidae and Cosmopterigidae; a ‘Scythridid Assemblage,’ consisting of Stathmopodidae, Scythrididae, Blastobasidae, Elachistidae, Momphidae, Coleophoridae and Batrachedridae; and a ‘Depressariid Assemblage,’ consisting of Autostichidae, Xyloryctidae, Lecithoceridae, Oecophoridae, Depressariidae and Lypusidae. Within the largest family, Gelechiidae, our results strongly support the pairing of Anomologinae with Gelechiinae, in accordance with a recent study of this family. Relationships among the other subfamilies, however, conflict moderately to strongly between studies, leaving the intrafamily phylogeny unsettled. Within the ‘Scythridid Assemblage,’ both trees support an ‘SSB clade’ consisting of Blastobasidae + (Scythrididae + Stathmopodidae), strongly resolved only in our results. Coleophoridae + Batrachedridae is supported, albeit weakly, in both trees, and only Momphidae differ in position between studies. Within the ‘Depressariid Assemblage,’ both trees support an ‘AXLO’ clade consisting of Autostichidae, Xyloryctidae, Lecithoceridae and Oecophoridae. The monophyly of this clade and relationships therein are supported weakly in previous results but strongly in ours. The recently re‐defined family Depressariidae is paraphyletic in our tree, but the evidence against depressariid monophyly is very weak. There is moderate support for a core group of Depressariidae consisting, among the seven subfamilies we sampled, of Depressariinae, Aeolanthinae and Hypertrophinae. We show that gelechioids have a higher total number and percentage of species that are saprophagous as larvae than any other apoditrysian superfamily, that saprophagy is concentrated primarily in the ‘AXLO clade,’ and that the ancestral gelechioid condition was probably feeding on live plants. Among the living‐plant feeders, concealed external feeding was probably the ancestral state. The multiple origins of internal feeding of various kinds, including leaf mining (otherwise almost unknown in Apoditrysia), are restricted mostly to the Scythridid and Gelechiid Assemblages. The traits that predispose or permit lineages to adopt these unusual life histories are worthy of study.  相似文献   
717.
718.
1. Aposematic coloration in prey promotes its survival by conspicuously advertising unpalatability to predators. Although classical examples of aposematic signals involve constant presentation of a signal at a distance, some animals suddenly display warning colours only when they are attacked. 2. Characteristics of body parts suddenly displayed, such as conspicuous coloration or eyespot pattern, may increase the survival of the prey by startling the predator, and/or by signalling unpalatability to the predators at the moment of attack. 3. The adaptive value of such colour patterns suddenly displayed by unpalatable prey has not been studied. We experimentally blackened the red patch in the conspicuous red–white–black hindwing pattern displayed by an unpalatable insect Lycorma delicatula White (Hemiptera: Fulgoridae) in response to predator's attack. 4. There was no evidence that the presence of the red patch increased prey survival over several weeks. We hypothesise that predators generalised from the red–white–black patches on the hindwings of unpalatable L. delicatula to any similar wing display as a signal of unpalatability. Because a higher proportion of males than females stay put at their resting sites, displaying their wings in response to repeated attacks by predators, wing damage was more frequent in males than in females. 5. To our knowledge, this is the first experimental test of an adaptive role of aposematic signals presented by unpalatable prey during sudden displays triggered by direct predatory attack.  相似文献   
719.
720.
A taxonomic study of Korean Myrmecopora Saulcy is presented. Myrmecopora (Lamproxenusa) rufescens (Sharp) previously reported by Ahn was an incorrect identification of M. (L.) reticulata Assing. Diagnoses, habitus photographs and line drawings of diagnostic characters are provided.  相似文献   
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