全文获取类型
收费全文 | 4372篇 |
免费 | 427篇 |
国内免费 | 2篇 |
出版年
2023年 | 20篇 |
2022年 | 50篇 |
2021年 | 81篇 |
2020年 | 43篇 |
2019年 | 43篇 |
2018年 | 67篇 |
2017年 | 73篇 |
2016年 | 127篇 |
2015年 | 204篇 |
2014年 | 219篇 |
2013年 | 260篇 |
2012年 | 337篇 |
2011年 | 280篇 |
2010年 | 211篇 |
2009年 | 181篇 |
2008年 | 255篇 |
2007年 | 230篇 |
2006年 | 228篇 |
2005年 | 238篇 |
2004年 | 234篇 |
2003年 | 204篇 |
2002年 | 177篇 |
2001年 | 73篇 |
2000年 | 64篇 |
1999年 | 55篇 |
1998年 | 44篇 |
1997年 | 31篇 |
1996年 | 29篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 31篇 |
1992年 | 33篇 |
1991年 | 37篇 |
1990年 | 27篇 |
1989年 | 36篇 |
1988年 | 45篇 |
1987年 | 26篇 |
1986年 | 32篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1982年 | 22篇 |
1981年 | 15篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1974年 | 14篇 |
1973年 | 15篇 |
1970年 | 19篇 |
1969年 | 15篇 |
排序方式: 共有4801条查询结果,搜索用时 31 毫秒
951.
952.
953.
954.
Campylobacter jejuni outer membrane vesicle‐associated proteolytic activity promotes bacterial invasion by mediating cleavage of intestinal epithelial cell E‐cadherin and occludin 下载免费PDF全文
Abdi Elmi Fauzy Nasher Heena Jagatia Ozan Gundogdu Mona Bajaj‐Elliott Brendan Wren Nick Dorrell 《Cellular microbiology》2016,18(4):561-572
Outer membrane vesicles (OMVs) play an important role in the pathogenicity of Gram‐negative bacteria. Campylobacter jejuni produces OMVs that trigger IL‐8, IL‐6, hBD‐3 and TNF‐α responses from T84 intestinal epithelial cells and are cytotoxic to Caco‐2 IECs and Galleria mellonella larvae. Proteomic analysis of 11168H OMVs identified the presence of three proteases, HtrA, Cj0511 and Cj1365c. In this study, 11168H OMVs were shown to possess proteolytic activity that was reduced by pretreatment with specific serine protease inhibitors. OMVs isolated from 11168H htrA, Cj0511 or Cj1365c mutants possess significantly reduced proteolytic activity. 11168H OMVs are able to cleave both E‐cadherin and occludin, but this cleavage is reduced with OMVs pretreated with serine protease inhibitors and also with OMVs isolated from htrA or Cj1365c mutants. Co‐incubation of T84 monolayers with 11168H OMVs results in a visible reduction in both E‐cadherin and occludin. The addition of 11168H OMVs to the co‐culture of live 11168H bacteria with T84 cells results in enhanced levels of bacterial adhesion and invasion in a time‐dependent and dose‐dependent manner. Further investigation of the cleavage of host cell structural proteins by C. jejuni OMVs should enhance our understanding of the interactions of this important pathogen with intestinal epithelial cells. 相似文献
955.
Sumit Handa Blair G. Paul Jeffery F. Miller David L. Valentine Partho Ghosh 《BMC structural biology》2016,16(1):13
Background
Diversity-generating retroelements (DGRs) provide organisms with a unique means for adaptation to a dynamic environment through massive protein sequence variation. The potential scope of this variation exceeds that of the vertebrate adaptive immune system. DGRs were known to exist only in viruses and bacteria until their recent discovery in archaea belonging to the ‘microbial dark matter’, specifically in organisms closely related to Nanoarchaeota. However, Nanoarchaeota DGR variable proteins were unassignable to known protein folds and apparently unrelated to characterized DGR variable proteins.Results
To address the issue of how Nanoarchaeota DGR variable proteins accommodate massive sequence variation, we determined the 2.52 Å resolution limit crystal structure of one such protein, AvpA, which revealed a C-type lectin (CLec)-fold that organizes a putative ligand-binding site that is capable of accommodating 1013 sequences. This fold is surprisingly reminiscent of the CLec-folds of viral and bacterial DGR variable protein, but differs sufficiently to define a new CLec-fold subclass, which is consistent with early divergence between bacterial and archaeal DGRs. The structure also enabled identification of a group of AvpA-like proteins in multiple putative DGRs from uncultivated archaea. These variable proteins may aid Nanoarchaeota and these uncultivated archaea in symbiotic relationships.Conclusions
Our results have uncovered the widespread conservation of the CLec-fold in viruses, bacteria, and archaea for accommodating massive sequence variation. In addition, to our knowledge, this is the first report of an archaeal CLec-fold protein.956.
Eddy covariance captures four‐phase crassulacean acid metabolism (CAM) gas exchange signature in Agave 下载免费PDF全文
Nick A. Owen Órlaith Ní Choncubhair Jamie Males José Ignacio del Real Laborde Ramón Rubio‐Cortés Howard Griffiths Gary Lanigan 《Plant, cell & environment》2016,39(2):295-309
Mass and energy fluxes were measured over a field of Agave tequilana in Mexico using eddy covariance (EC) methodology. Data were gathered over 252 d, including the transition from wet to dry periods. Net ecosystem exchanges (FN,EC) displayed a crassulacean acid metabolism (CAM) rhythm that alternated from CO2 sink at night to CO2 source during the day, and partitioned canopy fluxes (FA,EC) showed a characteristic four‐phase CO2 exchange pattern. Results were cross‐validated against diel changes in titratable acidity, leaf‐unfurling rates, energy exchange fluxes and reported biomass yields. Projected carbon balance (g C m?2 year?1, mean ± 95% confidence interval) indicated the site was a net sink of ?333 ± 24, of which contributions from soil respiration were +692 ± 7, and FA,EC was ?1025 ± 25. EC estimated biomass yield was 20.1 Mg (dry) ha?1 year?1. Average integrated daily FA,EC was ?234 ± 5 mmol CO2 m?2 d?1 and persisted almost unchanged after 70 d of drought conditions. Regression analyses were performed on the EC data to identify the best environmental predictors of FA. Results suggest that the carbon acquisition strategy of Agave offers productivity and drought resilience advantages over conventional semi‐arid C3 and C4 bioenergy candidates. 相似文献
957.
958.
Felipe C. Wouters Blair Blanchette Jonathan Gershenzon Daniel G. Vassão 《Phytochemistry Reviews》2016,15(6):1127-1151
Benzoxazinoids are a class of indole-derived plant chemical defenses comprising compounds with a 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one skeleton and their derivatives. These phytochemicals are widespread in grasses, including important cereal crops such as maize, wheat and rye, as well as a few dicot species, and display a wide range of antifeedant, insecticidal, antimicrobial, and allelopathic activities. Although their overall effects against insect herbivores are frequently reported, much less is known about how their modes of action specifically influence insect physiology. The present review summarizes the biological activities of benzoxazinoids on chewing, piercing-sucking, and root insect herbivores. We show how within-plant distribution modulates the exposure of different herbivore feeding guilds to these defenses, and how benzoxazinoids may act as toxins, feeding deterrents and digestibility-reducing compounds under different conditions. In addition, recent results on the metabolism of benzoxazinoids by insects and their consequences for plant-herbivore interactions are addressed, as well as directions for future research. 相似文献
959.
960.
Anupama Reddy Joseph D. Growney Nick S. Wilson Caroline M. Emery Jennifer A. Johnson Rebecca Ward Kelli A. Monaco Joshua Korn John E. Monahan Mark D. Stump Felipa A. Mapa Christopher J. Wilson Janine Steiger Jebediah Ledell Richard J. Rickles Vic E. Myer Seth A. Ettenberg Robert Schlegel William R. Sellers Heather A. Huet Joseph Lehár 《PloS one》2016,11(1)