首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   140292篇
  免费   23074篇
  国内免费   11052篇
  174418篇
  2024年   280篇
  2023年   1583篇
  2022年   3582篇
  2021年   6227篇
  2020年   5874篇
  2019年   8329篇
  2018年   8073篇
  2017年   7256篇
  2016年   8641篇
  2015年   10759篇
  2014年   11837篇
  2013年   12768篇
  2012年   12489篇
  2011年   11122篇
  2010年   8892篇
  2009年   7118篇
  2008年   6972篇
  2007年   5873篇
  2006年   5193篇
  2005年   4247篇
  2004年   3692篇
  2003年   3423篇
  2002年   2994篇
  2001年   2446篇
  2000年   2099篇
  1999年   1970篇
  1998年   1170篇
  1997年   1096篇
  1996年   1014篇
  1995年   890篇
  1994年   858篇
  1993年   652篇
  1992年   857篇
  1991年   659篇
  1990年   489篇
  1989年   467篇
  1988年   361篇
  1987年   354篇
  1986年   276篇
  1985年   291篇
  1984年   163篇
  1983年   169篇
  1982年   104篇
  1981年   86篇
  1980年   63篇
  1979年   77篇
  1977年   59篇
  1975年   56篇
  1974年   52篇
  1973年   56篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Several styryl-based compounds were evaluated for their capacity to act as inhibitors of the non-receptor tyrosine protein kinase p56lck. Our results demonstrate that alpha-cyanocinnamamide compounds can inhibit both the in vitro tyrosine autophosphorylation of p56lck as well as p56lck phosphorylation of exogenous substrates. Compound 67B-83-A was found to inhibit p56lck protein kinase activity with a calculated IC50 of 7 to 10 microM. This compound did not significantly inhibit the tyrosine protein kinase activity of the epidermal growth factor receptor and was found to be a less effective tyrosine protein kinase inhibitor for other members of the src family of protein kinases.  相似文献   
63.
64.
Sophora japonica is a medium-size deciduous tree belonging to Leguminosae family and famous for its high ecological, economic and medicinal value. Here, we reveal a draft genome of S. japonica, which was ∼511.49 Mb long (contig N50 size of 17.34 Mb) based on Illumina, Nanopore and Hi-C data. We reliably assembled 110 contigs into 14 chromosomes, representing 91.62% of the total genome, with an improved N50 size of 31.32 Mb based on Hi-C data. Further investigation identified 271.76 Mb (53.13%) of repetitive sequences and 31,000 protein-coding genes, of which 30,721 (99.1%) were functionally annotated. Phylogenetic analysis indicates that S. japonica separated from Arabidopsis thaliana and Glycine max ∼107.53 and 61.24 million years ago, respectively. We detected evidence of species-specific and common-legume whole-genome duplication events in S. japonica. We further found that multiple TF families (e.g. BBX and PAL) have expanded in S. japonica, which might have led to its enhanced tolerance to abiotic stress. In addition, S. japonica harbours more genes involved in the lignin and cellulose biosynthesis pathways than the other two species. Finally, population genomic analyses revealed no obvious differentiation among geographical groups and the effective population size continuously declined since 2 Ma. Our genomic data provide a powerful comparative framework to study the adaptation, evolution and active ingredients biosynthesis in S. japonica. More importantly, our high-quality S. japonica genome is important for elucidating the biosynthesis of its main bioactive components, and improving its production and/or processing.  相似文献   
65.
66.
67.
In enzyme engineering, the main targets for enhancing properties are enzyme activity, stereoselective specificity, stability, substrate range, and the development of unique functions. With the advent of genetic code extension technology, non-natural amino acids (nnAAs) are able to be incorporated into proteins in a site-specific or residue-specific manner, which breaks the limit of 20 natural amino acids for protein engineering. Benefitting from this approach, numerous enzymes have been engineered with nnAAs for improved properties or extended functionality. In the present review, we focus on applications and strategies for using nnAAs in enzyme engineering. Notably, approaches to computational modelling of enzymes with nnAAs are also addressed. Finally, we discuss the bottlenecks that currently need to be addressed in order to realise the broader prospects of this genetic code extension technique.  相似文献   
68.
69.
70.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号