全文获取类型
收费全文 | 5703篇 |
免费 | 414篇 |
国内免费 | 4篇 |
出版年
2023年 | 26篇 |
2022年 | 66篇 |
2021年 | 142篇 |
2020年 | 86篇 |
2019年 | 92篇 |
2018年 | 171篇 |
2017年 | 136篇 |
2016年 | 182篇 |
2015年 | 265篇 |
2014年 | 301篇 |
2013年 | 362篇 |
2012年 | 475篇 |
2011年 | 480篇 |
2010年 | 256篇 |
2009年 | 246篇 |
2008年 | 336篇 |
2007年 | 353篇 |
2006年 | 331篇 |
2005年 | 265篇 |
2004年 | 228篇 |
2003年 | 243篇 |
2002年 | 207篇 |
2001年 | 44篇 |
2000年 | 39篇 |
1999年 | 36篇 |
1998年 | 34篇 |
1997年 | 31篇 |
1996年 | 25篇 |
1995年 | 25篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 37篇 |
1991年 | 31篇 |
1990年 | 26篇 |
1989年 | 34篇 |
1988年 | 19篇 |
1986年 | 18篇 |
1985年 | 28篇 |
1984年 | 31篇 |
1983年 | 25篇 |
1982年 | 22篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1974年 | 20篇 |
1973年 | 13篇 |
1969年 | 13篇 |
排序方式: 共有6121条查询结果,搜索用时 472 毫秒
91.
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
92.
93.
N. T. Moldogazieva K. V. Shaitan K. B. Tereshkina Yu. M. Antonov A. A. Terentiev 《Biophysics》2007,52(4):365-374
A comparative study of the conformation dynamics of the human alpha-fetoprotein fragment LDSYQCT and heptapeptides derived from it by point substitutions has revealed a significant influence of electrostatic interactions on the set of preferred conformations and dynamics of amino acid residues when the peptides with blocked termini are examined at ? = 1. Peptide flexibility rises when the termini are left free (charged). At ? = 10 or 80, the set of probable conformations for all residues expands to much the same extent, i.e., at higher permittivity of the medium the dynamic effects of amino acid changes are leveled off. 相似文献
94.
95.
E A Arsen'eva T I Vorotyntseva S L Aleksandrov M Khapava V K Antonov 《Biokhimii?a (Moscow, Russia)》1978,43(1):17-22
A radioimmunochemical method of determination of leucine-binding protein and a method, based on the selective absorption of the protein and its complex with leucine on DEAE-cellulose, has been developed. The protein content in the E. coli cells at different stage of growth has been determined by the radioimmunochemical and equilibrium dialysis methods. It was shown that the protein content in the cells is practically independent of the growth-phase. 相似文献
96.
97.
98.
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
99.
Study of the Ion Composition of the Diffuse Vacuum Arc on a Hot Cathode by the Time-of-Flight Method
Melnikov A. D. Usmanov R. A. Amirov R. Kh. Antonov N. N. Gavrikov A. V. Liziakin G. D. Polistchook V. P. Smirnov V. P. 《Plasma Physics Reports》2020,46(6):611-616
Plasma Physics Reports - The study of a diffuse vacuum arc (DVA) is of interest in connection with the developing methods of plasma processing of the spent nuclear fuel (SNF). This type of... 相似文献
100.
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