全文获取类型
收费全文 | 4001篇 |
免费 | 288篇 |
国内免费 | 1篇 |
出版年
2023年 | 20篇 |
2022年 | 47篇 |
2021年 | 110篇 |
2020年 | 61篇 |
2019年 | 60篇 |
2018年 | 91篇 |
2017年 | 69篇 |
2016年 | 122篇 |
2015年 | 195篇 |
2014年 | 187篇 |
2013年 | 273篇 |
2012年 | 316篇 |
2011年 | 350篇 |
2010年 | 198篇 |
2009年 | 175篇 |
2008年 | 223篇 |
2007年 | 271篇 |
2006年 | 263篇 |
2005年 | 218篇 |
2004年 | 244篇 |
2003年 | 209篇 |
2002年 | 204篇 |
2001年 | 30篇 |
2000年 | 18篇 |
1999年 | 28篇 |
1998年 | 42篇 |
1997年 | 25篇 |
1996年 | 27篇 |
1995年 | 25篇 |
1994年 | 13篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1968年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有4290条查询结果,搜索用时 281 毫秒
111.
112.
Yakovlev Igor A. Carneros Elena Lee YeonKyeong Olsen Jorunn E. Fossdal Carl Gunnar 《Planta》2016,243(5):1237-1249
Planta - A significant number of epigenetic regulators were differentially expressed during embryogenesis at different epitype-inducing conditions. Our results support that methylation of DNA and... 相似文献
113.
114.
115.
Salinity tolerance is related to cyanide‐resistant alternative respiration in Medicago truncatula under sudden severe stress 下载免费PDF全文
Néstor Fernández Del‐Saz Igor Florez‐Sarasa María José Clemente‐Moreno Haytem Mhadhbi Jaume Flexas Alisdair R. Fernie Miquel Ribas‐Carbó 《Plant, cell & environment》2016,39(11):2361-2369
Salt respiration is defined as the increase of respiration under early salt stress. However, the response of respiration varies depending on the degree of salt tolerance and salt stress. It has been hypothesized that the activity of the alternative pathway may increase preventing over‐reduction of the ubiquinone pool in response to salinity, which in turn can increase respiration. Three genotypes of Medicago truncatula are reputed as differently responsive to salinity: TN1.11, A17 and TN6.18. We used the oxygen‐isotope fractionation technique to study the in vivo respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) in leaves and roots of these genotypes treated with severe salt stress (300 mM) during 1 and 3 days. In parallel, AOX capacity, gas exchange measurements, relative water content and metabolomics were determined in control and treated plants. Our study shows for first time that salt respiration is induced by the triggered AOP in response to salinity. Moreover, this phenomenon coincides with increased levels of metabolites such as amino and organic acids, and is shown to be related with higher photosynthetic rate and water content in TN6.18. 相似文献
116.
Pedro H. Prete Igor Cizauskas Antonio D. Brescovit 《Studies on Neotropical Fauna and Environment》2016,51(2):97-103
A new species of the spider genus Baalzebub Coddington from Brazil, B. acutum sp. nov., is described and illustrated based on 95 specimens collected from caves around the Iron Quadrangle in the state of Minas Gerais. This species is recognized by male palpal bulb with strong and large conductor covering almost entire embolus, and epigyne of females with long and tapered scape, which extends towards the spinners. Baalzebub acutum sp. nov. is the second species recorded from Brazil, the first for Brazilian caves, bringing the total number of species in the genus to seven in the world. 相似文献
117.
118.
Maria Paola Giovannoni Igor A. Schepetkin Letizia Crocetti Giovanna Ciciani Agostino Cilibrizzi Gabriella Guerrini 《Journal of enzyme inhibition and medicinal chemistry》2016,31(4):628-639
Compounds that can effectively inhibit the proteolytic activity of human neutrophil elastase (HNE) represent promising therapeutics for treatment of inflammatory diseases. We present here the synthesis, structure–activity relationship analysis, and biological evaluation of a new series of HNE inhibitors with a cinnoline scaffold. These compounds exhibited HNE inhibitory activity but had lower potency compared to N-benzoylindazoles previously reported by us. On the other hand, they exhibited increased stability in aqueous solution. The most potent compound, 18a, had a good balance between HNE inhibitory activity (IC50 value?=?56?nM) and chemical stability (t1/2?=?114?min). Analysis of reaction kinetics revealed that these cinnoline derivatives were reversible competitive inhibitors of HNE. Furthermore, molecular docking studies of the active products into the HNE binding site revealed two types of HNE inhibitors: molecules with cinnolin-4(1H)-one scaffold, which were attacked by the HNE Ser195 hydroxyl group at the amido moiety, and cinnoline derivatives containing an ester function at C-4, which is the point of attack of Ser195. 相似文献
119.
Jasminka Boskovic Elisabeth Bragado-Nilsson Bhargrav Saligram Prabhakar Igor Yefimenko Jaime Martínez-Gago Sergio Muñoz 《Cell cycle (Georgetown, Tex.)》2016,15(18):2431-2440
DNA replication is a key biological process that involves different protein complexes whose assembly is rigorously regulated in a successive order. One of these complexes is a replicative hexameric helicase, the MCM complex, which is essential for the initiation and elongation phases of replication. After the assembly of a double heterohexameric MCM2-7 complex at replication origins in G1, the 2 heterohexamers separate from each other and associate with Cdc45 and GINS proteins in a CMG complex that is capable of unwinding dsDNA during S phase. Here, we have reconstituted and characterized the purified human MCM2-7 (hMCM2-7) hexameric complex by co-expression of its 6 different subunits in insect cells. The conformational variability of the complex has been analyzed by single particle electron microscopy in the presence of different nucleotide analogs and DNA. The interaction with nucleotide stabilizes the complex while DNA introduces conformational changes in the hexamer inducing a cylindrical shape. Our studies suggest that the assembly of GINS and Cdc45 to the hMCM2-7 hexamer would favor conformational changes on the hexamer bound to ssDNA shifting the cylindrical shape of the complex into a right-handed spiral conformation as observed in the CMG complex bound to DNA. 相似文献
120.
Amit A. Upadhyay Aaron D. Fleetwood Ogun Adebali Robert D. Finn Igor B. Zhulin 《PLoS computational biology》2016,12(4)
Cellular receptors usually contain a designated sensory domain that recognizes the signal. Per/Arnt/Sim (PAS) domains are ubiquitous sensors in thousands of species ranging from bacteria to humans. Although PAS domains were described as intracellular sensors, recent structural studies revealed PAS-like domains in extracytoplasmic regions in several transmembrane receptors. However, these structurally defined extracellular PAS-like domains do not match sequence-derived PAS domain models, and thus their distribution across the genomic landscape remains largely unknown. Here we show that structurally defined extracellular PAS-like domains belong to the Cache superfamily, which is homologous to, but distinct from the PAS superfamily. Our newly built computational models enabled identification of Cache domains in tens of thousands of signal transduction proteins including those from important pathogens and model organisms. Furthermore, we show that Cache domains comprise the dominant mode of extracellular sensing in prokaryotes. 相似文献