全文获取类型
收费全文 | 5324篇 |
免费 | 395篇 |
国内免费 | 4篇 |
出版年
2023年 | 31篇 |
2022年 | 48篇 |
2021年 | 140篇 |
2020年 | 72篇 |
2019年 | 100篇 |
2018年 | 124篇 |
2017年 | 97篇 |
2016年 | 144篇 |
2015年 | 256篇 |
2014年 | 304篇 |
2013年 | 353篇 |
2012年 | 427篇 |
2011年 | 375篇 |
2010年 | 216篇 |
2009年 | 221篇 |
2008年 | 268篇 |
2007年 | 265篇 |
2006年 | 225篇 |
2005年 | 222篇 |
2004年 | 219篇 |
2003年 | 210篇 |
2002年 | 191篇 |
2001年 | 67篇 |
2000年 | 36篇 |
1999年 | 49篇 |
1998年 | 50篇 |
1997年 | 39篇 |
1996年 | 45篇 |
1995年 | 37篇 |
1994年 | 32篇 |
1993年 | 41篇 |
1992年 | 41篇 |
1991年 | 28篇 |
1990年 | 29篇 |
1989年 | 19篇 |
1988年 | 41篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 30篇 |
1983年 | 26篇 |
1982年 | 33篇 |
1981年 | 31篇 |
1980年 | 21篇 |
1978年 | 30篇 |
1977年 | 17篇 |
1976年 | 24篇 |
1975年 | 18篇 |
1974年 | 27篇 |
1973年 | 17篇 |
排序方式: 共有5723条查询结果,搜索用时 15 毫秒
941.
Felix Schaller Antonio M. Fernandes Christine Hodler Claudia Münch Juan J. Pasantes Wolfram Rietschel Werner Schempp 《PloS one》2010,5(9)
The male-specific regions of the Y chromosome (MSY) of the human and the chimpanzee (Pan troglodytes) are fully sequenced. The most striking difference is the dramatic rearrangement of large parts of their respective MSYs. These non-recombining regions include ampliconic gene families that are known to be important for male reproduction,and are consequently under significant selective pressure. However, whether the published Y-chromosomal pattern of ampliconic fertility genes is invariable within P. troglodytes is an open but fundamental question pertinent to discussions of the evolutionary fate of the Y chromosome in different primate mating systems. To solve this question we applied fluorescence in situ hybridisation (FISH) of testis-specific expressed ampliconic fertility genes to metaphase Y chromosomes of 17 chimpanzees derived from 11 wild-born males and 16 bonobos representing seven wild-born males. We show that of eleven P. troglodytes Y-chromosomal lines, ten Y-chromosomal variants were detected based on the number and arrangement of the ampliconic fertility genes DAZ (deleted in azoospermia) and CDY (chromodomain protein Y)—a so-far never-described variation of a species'' Y chromosome. In marked contrast, no variation was evident among seven Y-chromosomal lines of the bonobo, P. paniscus, the chimpanzee''s closest living relative. Although, loss of variation of the Y chromosome in the bonobo by a founder effect or genetic drift cannot be excluded, these contrasting patterns might be explained in the context of the species'' markedly different social and mating behaviour. In chimpanzees, multiple males copulate with a receptive female during a short period of visible anogenital swelling, and this may place significant selection on fertility genes. In bonobos, however, female mate choice may make sperm competition redundant (leading to monomorphism of fertility genes), since ovulation in this species is concealed by the prolonged anogenital swelling, and because female bonobos can occupy high-ranking positions in the group and are thus able to determine mate choice more freely. 相似文献
942.
943.
944.
Felix Rückert Gihan Dawelbait Christof Winter Arndt Hartmann Axel Denz Ole Ammerpohl Michael Schroeder Hans Konrad Schackert Bence Sipos Günter Kl?ppel Holger Kalthoff Hans-Detlev Saeger Christian Pilarsky Robert Grützmann 《PloS one》2010,5(8)
Background
Pancreatic ductal adenocarcinoma (PDAC) remains an important cause of cancer death. Changes in apoptosis signaling in pancreatic cancer result in chemotherapy resistance and aggressive growth and metastasizing. The aim of this study was to characterize the apoptosis pathway in pancreatic cancer computationally by evaluation of experimental data from high-throughput technologies and public data bases. Therefore, gene expression analysis of microdissected pancreatic tumor tissue was implemented in a model of the apoptosis pathway obtained by computational protein interaction prediction.Methodology/Principal Findings
Apoptosis pathway related genes were assembled from electronic databases. To assess expression of these genes we constructed a virtual subarray from a whole genome analysis from microdissected native tumor tissue. To obtain a model of the apoptosis pathway, interactions of members of the apoptosis pathway were analysed using public databases and computational prediction of protein interactions. Gene expression data were implemented in the apoptosis pathway model. 19 genes were found differentially expressed and 12 genes had an already known pathophysiological role in PDAC, such as Survivin/BIRC5, BNIP3 and TNF-R1. Furthermore we validated differential expression of IL1R2 and Livin/BIRC7 by RT-PCR and immunohistochemistry. Implementation of the gene expression data in the apoptosis pathway map suggested two higher level defects of the pathway at the level of cell death receptors and within the intrinsic signaling cascade consistent with references on apoptosis in PDAC. Protein interaction prediction further showed possible new interactions between the single pathway members, which demonstrate the complexity of the apoptosis pathway.Conclusions/Significance
Our data shows that by computational evaluation of public accessible data an acceptable virtual image of the apoptosis pathway might be given. By this approach we could identify two higher level defects of the apoptosis pathway in PDAC. We could further for the first time identify IL1R2 as possible candidate gene in PDAC. 相似文献945.
Jrg Schweiggert Gregor Habeck Sandra Hess Felix Mikus Roman Beloshistov Klaus Meese Shoji Hata KlausPeter Knobeloch Frauke Melchior 《The EMBO journal》2021,40(18)
Microtubule depolymerases of the kinesin‐13 family play important roles in various cellular processes and are frequently overexpressed in different cancer types. Despite the importance of their correct abundance, remarkably little is known about how their levels are regulated in cells. Using comprehensive screening on protein microarrays, we identified 161 candidate substrates of the multi‐subunit ubiquitin E3 ligase SCFFbxw5, including the kinesin‐13 member Kif2c/MCAK. In vitro reconstitution assays demonstrate that MCAK and its closely related orthologs Kif2a and Kif2b become efficiently polyubiquitylated by neddylated SCFFbxw5 and Cdc34, without requiring preceding modifications. In cells, SCFFbxw5 targets MCAK for proteasomal degradation predominantly during G2. While this seems largely dispensable for mitotic progression, loss of Fbxw5 leads to increased MCAK levels at basal bodies and impairs ciliogenesis in the following G1/G0, which can be rescued by concomitant knockdown of MCAK, Kif2a or Kif2b. We thus propose a novel regulatory event of ciliogenesis that begins already within the G2 phase of the preceding cell cycle. 相似文献
946.
Plants,microorganisms, and soil temperatures contribute to a decrease in methane fluxes on a drained Arctic floodplain
下载免费PDF全文
![点击此处可从《Global Change Biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Min Jung Kwon Felix Beulig Iulia Ilie Marcus Wildner Kirsten Küsel Lutz Merbold Miguel D. Mahecha Nikita Zimov Sergey A. Zimov Martin Heimann Edward A. G. Schuur Joel E. Kostka Olaf Kolle Ines Hilke Mathias Göckede 《Global Change Biology》2017,23(6):2396-2412
As surface temperatures are expected to rise in the future, ice‐rich permafrost may thaw, altering soil topography and hydrology and creating a mosaic of wet and dry soil surfaces in the Arctic. Arctic wetlands are large sources of CH4, and investigating effects of soil hydrology on CH4 fluxes is of great importance for predicting ecosystem feedback in response to climate change. In this study, we investigate how a decade‐long drying manipulation on an Arctic floodplain influences CH4‐associated microorganisms, soil thermal regimes, and plant communities. Moreover, we examine how these drainage‐induced changes may then modify CH4 fluxes in the growing and nongrowing seasons. This study shows that drainage substantially lowered the abundance of methanogens along with methanotrophic bacteria, which may have reduced CH4 cycling. Soil temperatures of the drained areas were lower in deep, anoxic soil layers (below 30 cm), but higher in oxic topsoil layers (0–15 cm) compared to the control wet areas. This pattern of soil temperatures may have reduced the rates of methanogenesis while elevating those of CH4 oxidation, thereby decreasing net CH4 fluxes. The abundance of Eriophorum angustifolium, an aerenchymatous plant species, diminished significantly in the drained areas. Due to this decrease, a higher fraction of CH4 was alternatively emitted to the atmosphere by diffusion, possibly increasing the potential for CH4 oxidation and leading to a decrease in net CH4 fluxes compared to a control site. Drainage lowered CH4 fluxes by a factor of 20 during the growing season, with postdrainage changes in microbial communities, soil temperatures, and plant communities also contributing to this reduction. In contrast, we observed CH4 emissions increased by 10% in the drained areas during the nongrowing season, although this difference was insignificant given the small magnitudes of fluxes. This study showed that long‐term drainage considerably reduced CH4 fluxes through modified ecosystem properties. 相似文献
947.
948.
The latitudinal diversity gradient in New World swallowtail butterflies is caused by contrasting patterns of out‐of‐ and into‐the‐tropics dispersal
下载免费PDF全文
![点击此处可从《Global Ecology and Biogeography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
949.
950.
Surface-attached microbial communities constitute a vast amount of life on our planet. They contribute to all major biogeochemical cycles, provide essential services to our society and environment, and have important effects on human health and disease. They typically consist of different interacting genotypes that arrange themselves non-randomly across space (referred to hereafter as spatial self-organization). While spatial self-organization is important for the functioning, ecology, and evolution of these communities, the underlying determinants of spatial self-organization remain unclear. Here, we performed a combination of experiments, statistical modeling, and mathematical simulations with a synthetic cross-feeding microbial community consisting of two isogenic strains. We found that two different patterns of spatial self-organization emerged at the same length and time scales, thus demonstrating pattern diversification. This pattern diversification was not caused by initial environmental heterogeneity or by genetic heterogeneity within populations. Instead, it was caused by nongenetic heterogeneity within populations, and we provide evidence that the source of this nongenetic heterogeneity is local differences in the initial spatial positionings of individuals. We further demonstrate that the different patterns exhibit different community-level properties; namely, they have different expansion speeds. Together, our results demonstrate that pattern diversification can emerge in the absence of initial environmental heterogeneity or genetic heterogeneity within populations and can affect community-level properties, thus providing novel insights into the causes and consequences of microbial spatial self-organization.Subject terms: Microbial ecology, Microbial ecology, Biofilms 相似文献