全文获取类型
收费全文 | 1005篇 |
免费 | 56篇 |
专业分类
1061篇 |
出版年
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 26篇 |
2014年 | 34篇 |
2013年 | 40篇 |
2012年 | 65篇 |
2011年 | 74篇 |
2010年 | 47篇 |
2009年 | 39篇 |
2008年 | 49篇 |
2007年 | 46篇 |
2006年 | 46篇 |
2005年 | 48篇 |
2004年 | 45篇 |
2003年 | 40篇 |
2002年 | 39篇 |
2001年 | 21篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有1061条查询结果,搜索用时 9 毫秒
111.
Social,contextual, and individual factors affecting the occurrence and acoustic structure of drumming bouts in wild chimpanzees (Pan troglodytes) 下载免费PDF全文
Magdalena Babiszewska Anne Marijke Schel Claudia Wilke Katie E. Slocombe 《American journal of physical anthropology》2015,156(1):125-134
The production of structured and repetitive sounds by striking objects is a behavior found not only in humans, but also in a variety of animal species, including chimpanzees (Pan troglodytes). In this study we examined individual and social factors that may influence the frequency with which individuals engage in drumming behavior when producing long distance pant hoot vocalizations, and analyzed the temporal structure of those drumming bouts. Male chimpanzees from Budongo Forest, Uganda, drummed significantly more frequently during travel than feeding or resting and older individuals were significantly more likely to produce drumming bouts than younger ones. In contrast, we found no evidence that the presence of estrus females, high ranking males and preferred social partners in the caller's vicinty had an effect on the frequency with which an individual accompanied their pant hoot vocalization with drumming. Through acoustic analyses, we demonstrated that drumming sequences produced with pant hoots may have contained information on individual identity and that qualitatively, there was individual variation in the complexity of the temporal patterns produced. We conclude that drumming patterns may act as individually distinctive long‐distance signals that, together with pant hoot vocalizations, function to coordinate the movement and spacing of dispersed individuals within a community, rather than as signals to group members in the immediate audience. Am J Phys Anthropol 156:125–134, 2015 © 2014 Wiley Periodicals, Inc. 相似文献
112.
Habermann FA André S Kaltner H Kübler D Sinowatz F Gabius HJ 《Histochemistry and cell biology》2011,135(6):539-552
Gene divergence has given rise to the galectin family of mammalian lectins. Since selective binding to distinct β-galactosides
underlies the known bioactivities of galectins, they could find application in cyto- and histochemistry. The pertinent question
on the characteristics of their individual reactivity profiles therefore needs to be answered. Toward this end, comparative
studies of a panel of galectins in defined systems are required. We here characterise the staining profiles of seven human
lectins as well as five natural derivatives originating from proteolytic truncation and serine phosphorylation and one engineered
variant. As test system, bovine germinal vesicle oocytes with their glycoprotein envelope (zona pellucida), which presents
bi- to tetraantennary complex-type N-glycans with N-acetyllactosamine repeats and core fucosylation, were processed. Technically, confocal laser scanning microscopy was used,
first with plant lectins to map the sialylation status. Hereby, α2,3/6-sialylation was detected in the superficial filamentous
meshwork of the zona pellucida, while sialic acid-free glycan chains were found to characterise the main inner part of the
compact layer of the zona pellucida. Galectin staining was specific and non-uniform. Significant differences in reactivity
were detected for the superficial filamentous meshwork and the compact layer of the zona pellucida between galectins-1 to
-4 versus galectins-8 and -9. The typical staining profiles intimate a spatially organised display of N-glycans in the different layers of the zona pellucida, underscoring the potential of galectins as cyto- and histochemical
tools. Our results encourage further comparative analysis and research to trace the underlying structural and/or topological
properties. 相似文献
113.
Williams ME Wilke SA Daggett A Davis E Otto S Ravi D Ripley B Bushong EA Ellisman MH Klein G Ghosh A 《Neuron》2011,71(4):640-655
Our understanding of mechanisms that regulate the differentiation of specific classes of synapses is limited. Here, we investigate the formation of synapses between hippocampal dentate gyrus (DG) neurons and their target CA3 neurons and find that DG neurons preferentially form synapses with CA3 rather than DG or CA1 neurons in culture, suggesting that specific interactions between DG and CA3 neurons drive synapse formation. Cadherin-9 is expressed selectively in DG and CA3 neurons, and downregulation of cadherin-9 in CA3 neurons leads to a selective decrease in the number and size of DG synapses onto CA3 neurons. In addition, loss of cadherin-9 from DG or CA3 neurons in vivo leads to striking defects in the formation and differentiation of the DG-CA3 mossy fiber synapse. These observations indicate that cadherin-9 bidirectionally regulates DG-CA3 synapse development and highlight the critical role of differentially expressed molecular cues in establishing specific connections in the mammalian brain. 相似文献
114.
Sun L Louie MC Vannella KM Wilke CA LeVine AM Moore BB Shanley TP 《American journal of physiology. Lung cellular and molecular physiology》2011,300(3):L341-L353
IL-10 is most commonly recognized as an anti-inflammatory cytokine possessing immunosuppressive effects necessary for regulated resolution of proinflammation. However, its role in the development of fibrosis during inflammatory resolution has not been clear. Few prior studies have linked IL-10 with the inhibition of fibrosis principally on the basis of regulating inflammation thought to be driving fibroproliferation. In contrast, in a model of long-term overexpression of IL-10, we observed marked induction of lung fibrosis in mice. The total cell number retrieved by bronchoalveolar lavage (BAL) increased 10-fold in the IL-10 overexpression (IL-10 OE) mice, with significant infiltration of T and B lymphocytes and collagen-producing cells. The presence of increased fibrocytes, isolated from collagenase-digested lungs, was identified by flow cytometry using dual staining of CD45 and collagen 1. Quantitative PCR analysis on an array of chemokine/chemokine receptor genes showed that receptor CCR2 and its ligand, CCL2, were highly upregulated in IL-10 OE mice, suggesting that IL-10-induced fibrocyte recruitment was CCL2/CCR2 specific. Given the prior association of alternatively activated (M(2)) macrophages with development of fibrosis in other disease states, we also examined the effect of IL-10 OE on the M(2) macrophage axis. We observed significantly increased numbers of M(2) macrophages in both BAL and whole lung tissue from the IL-10 OE mice. Administration of rabbit anti-CCL2 antiserum to IL-10 OE mice for three consecutive weeks significantly decreased fibrosis as evidenced by lung hydroxyproline content, compared with mice that received preimmune rabbit serum. These results indicate that overexpression of IL-10 induces fibrosis, in part, by fibrocyte recruitment and M(2) macrophage activation, and likely in a CCL2/CCR2 axis. 相似文献
115.
116.
Inoshima I Inoshima N Wilke GA Powers ME Frank KM Wang Y Bubeck Wardenburg J 《Nature medicine》2011,17(10):1310-1314
Staphylococcus aureus is a major cause of human disease, responsible for half a million infections and approximately 20,000 deaths per year in the United States alone. This pathogen secretes α-hemolysin, a pore-forming cytotoxin that contributes to the pathogenesis of pneumonia. α-hemolysin injures epithelial cells in vitro by interacting with its receptor, the zinc-dependent metalloprotease ADAM10 (ref. 6). We show here that mice harboring a conditional disruption of the Adam10 gene in lung epithelium are resistant to lethal pneumonia. Investigation of the molecular mechanism of toxin-receptor function revealed that α-hemolysin upregulates ADAM10 metalloprotease activity in alveolar epithelial cells, resulting in cleavage of the adherens junction protein E-cadherin. Cleavage is associated with disruption of epithelial barrier function, contributing to the pathogenesis of lethal acute lung injury. A metalloprotease inhibitor of ADAM10 prevents E-cadherin cleavage in response to Hla; similarly, toxin-dependent E-cadherin proteolysis and barrier disruption is attenuated in ADAM10-knockout mice. Together, these data attest to the function of ADAM10 as the cellular receptor for α-hemolysin. The observation that α-hemolysin can usurp the metalloprotease activity of its receptor reveals a previously unknown mechanism of pore-forming cytotoxin action in which pathologic insults are not solely the result of irreversible membrane injury and defines ADAM10 inhibition as a strategy to attenuate α-hemolysin-induced disease. 相似文献
117.
von Oheimb PV Albrecht C Riedel F Du L Yang J Aldridge DC Bössneck U Zhang H Wilke T 《PloS one》2011,6(10):e26307
Background
The Tibetan Plateau is not only the highest and largest plateau on earth; it is also home to numerous freshwater lakes potentially harbouring endemic faunal elements. As it remains largely unknown whether these lakes have continuously existed during the Last Glacial Maximum (LGM), questions arise as to whether taxa have been able to exist on the plateau since before the latest Pleistocene, from where and how often the plateau was colonized, and by which mechanisms organisms conquered remote high altitude lentic freshwater systems. In this study, species of the plateau-wide distributed freshwater gastropod genus Radix are used to answer these biogeographical questions.Methodology/Principal Findings
Based on a broad spatial sampling of Radix spp. on the Tibetan Plateau, and phylogenetic analyses of mtDNA sequence data, three probably endemic and one widespread major Radix clade could be identified on the plateau. Two of the endemic clades show a remarkably high genetic diversity, indicating a relatively great phylogenetic age. Phylogeographical analyses of individuals belonging to the most widely distributed clade indicate that intra-plateau distribution cannot be explained by drainage-related dispersal alone.Conclusions/Significance
Our study reveals that Radix spp. persisted throughout the LGM on the Tibetan Plateau. Therefore, we assume the continuous existence of suitable water bodies during that time. The extant Radix diversity on the plateau might have been caused by multiple colonization events combined with a relatively long intra-plateau evolution. At least one colonization event has a Palaearctic origin. In contrast to freshwater fishes, passive dispersal, probably by water birds, might be an important mechanism for conquering remote areas on the plateau. Patterns found in Radix spp. are shared with some terrestrial plateau taxa, indicating that Radix may be a suitable model taxon for inferring general patterns of biotic origin, dispersal and survival on the Tibetan Plateau. 相似文献118.
119.
Background
Male killing endosymbionts manipulate their arthropod host reproduction by only allowing female embryos to develop into infected females and killing all male offspring. Because the resulting change in sex ratio is expected to affect the evolution of sex-specific dispersal, we investigated under which environmental conditions strong sex-biased dispersal would emerge, and how this would affect host and endosymbiont metapopulation persistence. 相似文献120.
Mohamed Abd El Rahman Denise Haase Axel Rentzsch Julia Olchvary Hans-Joachim Sch?fers Wolfram Henn Stefan Wagenpfeil Hashim Abdul-Khaliq 《PloS one》2015,10(4)