全文获取类型
收费全文 | 5333篇 |
免费 | 411篇 |
国内免费 | 4篇 |
出版年
2023年 | 26篇 |
2022年 | 64篇 |
2021年 | 141篇 |
2020年 | 81篇 |
2019年 | 91篇 |
2018年 | 160篇 |
2017年 | 123篇 |
2016年 | 173篇 |
2015年 | 264篇 |
2014年 | 290篇 |
2013年 | 350篇 |
2012年 | 453篇 |
2011年 | 464篇 |
2010年 | 251篇 |
2009年 | 237篇 |
2008年 | 315篇 |
2007年 | 335篇 |
2006年 | 314篇 |
2005年 | 253篇 |
2004年 | 219篇 |
2003年 | 231篇 |
2002年 | 201篇 |
2001年 | 36篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 33篇 |
1997年 | 30篇 |
1996年 | 23篇 |
1995年 | 26篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1974年 | 13篇 |
1969年 | 10篇 |
1965年 | 10篇 |
1960年 | 10篇 |
排序方式: 共有5748条查询结果,搜索用时 272 毫秒
81.
Bharat Joshi Michele Bastiani Scott S. Strugnell Cecile Boscher Robert G. Parton Ivan R. Nabi 《The Journal of cell biology》2013,200(5):681-692
Maintenance of epithelial cell adhesion is crucial for epidermal morphogenesis and homeostasis and relies predominantly on the interaction of keratins with desmosomes. Although the importance of desmosomes to epidermal coherence and keratin organization is well established, the significance of keratins in desmosome organization has not been fully resolved. Here, we report that keratinocytes lacking all keratins show elevated, PKC-α–mediated desmoplakin phosphorylation and subsequent destabilization of desmosomes. We find that PKC-α activity is regulated by Rack1–keratin interaction. Without keratins, desmosomes assemble but are endocytosed at accelerated rates, rendering epithelial sheets highly susceptible to mechanical stress. Re-expression of the keratin pair K5/14, inhibition of PKC-α activity, or blocking of endocytosis reconstituted both desmosome localization at the plasma membrane and epithelial adhesion. Our findings identify a hitherto unknown mechanism by which keratins control intercellular adhesion, with potential implications for tumor invasion and keratinopathies, settings in which diminished cell adhesion facilitates tissue fragility and neoplastic growth. 相似文献
82.
Joshua B. Slee Ivan S. Alferiev Robert J. Levy Stanley J. Stachelek 《Journal of visualized experiments : JoVE》2014,(90)
The foreign body reaction occurs when a synthetic surface is introduced to the body. It is characterized by adsorption of blood proteins and the subsequent attachment and activation of platelets, monocyte/macrophage adhesion, and inflammatory cell signaling events, leading to post-procedural complications. The Chandler Loop Apparatus is an experimental system that allows researchers to study the molecular and cellular interactions that occur when large volumes of blood are perfused over polymeric conduits. To that end, this apparatus has been used as an ex vivo model allowing the assessment of the anti-inflammatory properties of various polymer surface modifications. Our laboratory has shown that blood conduits, covalently modified via photoactivation chemistry with recombinant CD47, can confer biocompatibility to polymeric surfaces. Appending CD47 to polymeric surfaces could be an effective means to promote the efficacy of polymeric blood conduits. Herein is the methodology detailing the photoactivation chemistry used to append recombinant CD47 to clinically relevant polymeric blood conduits and the use of the Chandler Loop as an ex vivo experimental model to examine blood interactions with the CD47 modified and control conduits. 相似文献
83.
84.
85.
86.
87.
88.
Lihua Zhang Fenghui Yuan Junhong Bai Hongtao Duan Xueying Gu Longyu Hou Yao Huang Mingan Yang Jin‐Sheng He Zhenhua Zhang Lijun Yu Changchun Song David A. Lipson Donatella Zona Walter Oechel Ivan A. Janssens Xiaofeng Xu 《Ecology letters》2020,23(5):821-830
Grassland ecosystems account for more than 10% of the global CH4 sink in soils. A 4‐year field experiment found that addition of P alone did not affect CH4 uptake and experimental addition of N alone significantly suppressed CH4 uptake, whereas concurrent N and P additions suppressed CH4 uptake to a lesser degree. A meta‐analysis including 382 data points in global grasslands corroborated these findings. Global extrapolation with an empirical modelling approach estimated that contemporary N addition suppresses CH4 sink in global grassland by 11.4% and concurrent N and P deposition alleviates this suppression to 5.8%. The P alleviation of N‐suppressed CH4 sink is primarily attributed to substrate competition, defined as the competition between ammonium and CH4 for the methane mono‐oxygenase enzyme. The N and P impacts on CH4 uptake indicate that projected increases in N and P depositions might substantially affect CH4 uptake and alter the global CH4 cycle. 相似文献
89.
Microbial carbon limitation: The need for integrating microorganisms into our understanding of ecosystem carbon cycling 总被引:2,自引:0,他引:2
Jennifer L. Soong Lucia Fuchslueger Sara Maraon‐Jimenez Margaret S. Torn Ivan A. Janssens Josep Penuelas Andreas Richter 《Global Change Biology》2020,26(4):1953-1961
Numerous studies have demonstrated that fertilization with nutrients such as nitrogen, phosphorus, and potassium increases plant productivity in both natural and managed ecosystems, demonstrating that primary productivity is nutrient limited in most terrestrial ecosystems. In contrast, it has been demonstrated that heterotrophic microbial communities in soil are primarily limited by organic carbon or energy. While this concept of contrasting limitations, that is, microbial carbon and plant nutrient limitation, is based on strong evidence that we review in this paper, it is often ignored in discussions of ecosystem response to global environment changes. The plant‐centric perspective has equated plant nutrient limitations with those of whole ecosystems, thereby ignoring the important role of the heterotrophs responsible for soil decomposition in driving ecosystem carbon storage. To truly integrate carbon and nutrient cycles in ecosystem science, we must account for the fact that while plant productivity may be nutrient limited, the secondary productivity by heterotrophic communities is inherently carbon limited. Ecosystem carbon cycling integrates the independent physiological responses of its individual components, as well as tightly coupled exchanges between autotrophs and heterotrophs. To the extent that the interacting autotrophic and heterotrophic processes are controlled by organisms that are limited by nutrient versus carbon accessibility, respectively, we propose that ecosystems by definition cannot be ‘limited’ by nutrients or carbon alone. Here, we outline how models aimed at predicting non‐steady state ecosystem responses over time can benefit from dissecting ecosystems into the organismal components and their inherent limitations to better represent plant–microbe interactions in coupled carbon and nutrient models. 相似文献
90.
Cristin J. Monaco Corey J. A. Bradshaw David J. Booth Bronwyn M. Gillanders David S. Schoeman Ivan Nagelkerken 《Global Change Biology》2020,26(10):5564-5573
Climate change is redistributing marine and terrestrial species globally. Life‐history traits mediate the ability of species to cope with novel environmental conditions, and can be used to gauge the potential redistribution of taxa facing the challenges of a changing climate. However, it is unclear whether the same traits are important across different stages of range shifts (arrival, population increase, persistence). To test which life‐history traits most mediate the process of range extension, we used a 16‐year dataset of 35 range‐extending coral‐reef fish species and quantified the importance of various traits on the arrival time (earliness) and degree of persistence (prevalence and patchiness) at higher latitudes. We show that traits predisposing species to shift their range more rapidly (large body size, broad latitudinal range, long dispersal duration) did not drive the early stages of redistribution. Instead, we found that as diet breadth increased, the initial arrival and establishment (prevalence and patchiness) of climate migrant species in temperate locations occurred earlier. While the initial incursion of range‐shifting species depends on traits associated with dispersal potential, subsequent establishment hinges more on a species’ ability to exploit novel food resources locally. These results highlight that generalist species that can best adapt to novel food sources might be most successful in a future ocean. 相似文献