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   38103篇
  免费   3348篇
  国内免费   4251篇
  45702篇
  2024年   116篇
  2023年   469篇
  2022年   1091篇
  2021年   1704篇
  2020年   1329篇
  2019年   1593篇
  2018年   1446篇
  2017年   1158篇
  2016年   1475篇
  2015年   2290篇
  2014年   2776篇
  2013年   2986篇
  2012年   3592篇
  2011年   3260篇
  2010年   2085篇
  2009年   1856篇
  2008年   2412篇
  2007年   1975篇
  2006年   1858篇
  2005年   1580篇
  2004年   1524篇
  2003年   1336篇
  2002年   1215篇
  2001年   670篇
  2000年   555篇
  1999年   473篇
  1998年   393篇
  1997年   272篇
  1996年   231篇
  1995年   253篇
  1994年   196篇
  1993年   168篇
  1992年   186篇
  1991年   144篇
  1990年   115篇
  1989年   143篇
  1988年   102篇
  1987年   84篇
  1986年   82篇
  1985年   75篇
  1984年   70篇
  1983年   52篇
  1982年   53篇
  1981年   30篇
  1980年   18篇
  1979年   30篇
  1978年   25篇
  1977年   25篇
  1975年   18篇
  1971年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
G Khoury  P Gruss  R Dhar  C J Lai 《Cell》1979,18(1):85-92
  相似文献   
32.
A double-stranded ribonucleic acid (dsRNA) was isolated from coremial extracts of wild type P. claviforme, by methylated-albumin kieselguhr chromatography. Differential centrifugations of the coremial extracts from WT and Sh mutant strains yielded two classes of virus-like particles (VLP), of dimensions 25-30 nm, and 50-70 nm. The possible ecological significance of fungal viruses is discussed.  相似文献   
33.
Aging is a major risk factor for many diseases,especially in highly prevalent cardiopulmonary comorbidities and infectious diseases including Coronavirus Diseas...  相似文献   
34.
Mitogenomes have been widely used for phylogenetic reconstruction of various Dipteran groups, but specifically for chironomid, they have not been carried out to resolve the relationships. Diamesinae (Diptera: Chironomidae) are important bioindicators for freshwater ecosystem monitoring, but its evolutionary history remains uncertain for lack of information. Here, coupled with one previously published and 30 new mitogenomes of Diamesinae, we carried out comparative mitogenomic analysis and phylogenetic analysis. Mitogenomes of Diamesinae were conserved in structure, and all genes arranged in the same order as the ancestral insect mitogenome. All protein‐coding genes in Diamesinae were under stronger purifying selection than those of other nonbiting midge species, which may exhibit signs of adaptation to life at cold living conditions. Phylogenetic analyses strongly supported the monophyly of Diamesinae, with Boreheptagyiini deeply nested within Diamesini. In addition, phylogenetic relationship of selected six genera was resolved, except Sympotthastia remained unstable. Our study revealed that the mitogenomes of Diamesinae are highly conserved, and they are practically useful for phylogenetic inference.  相似文献   
35.
36.
37.
38.
The DNA methyltransferases (DNMTs) were found in mammals to maintain DNA methylation. Among them, DNMT1 was the first identified, and it is an attractive target for tumour chemotherapy. DC_05 and DC_517 have been reported in our previous work, which is non-nucleoside DNMT1 inhibitor with low micromolar IC50 values and significant selectivity towards other S-adenosyl-L-methionine (SAM)-dependent protein methyltransferases. In this study, through a process of similarity-based analog searching, a series of DNMT1 inhibitors were designed, synthesized, and evaluated as anticancer agents. SAR studies were conducted based on enzymatic assays. And most of the compounds showed strong inhibitory activity on human DNMT1, especially WK-23 displayed a good inhibitory effect on human DNMT1 with an IC50 value of 5.0 µM. Importantly, the pharmacokinetic (PK) profile of WK-23 was obtained with quite satisfying oral bioavailability and elimination half-life. Taken together, WK-23 is worth developing as DNMT1-selective therapy for the treatment of malignant tumour.  相似文献   
39.
40.
Microtubules (MTs) are cytoskeletal fibers that undergo dynamic instability (DI), a remarkable process involving phases of growth and shortening separated by stochastic transitions called catastrophe and rescue. Dissecting DI mechanism(s) requires first characterizing and quantifying these dynamics, a subjective process that often ignores complexity in MT behavior. We present a Statistical Tool for Automated Dynamic Instability Analysis (STADIA) that identifies and quantifies not only growth and shortening, but also a category of intermediate behaviors that we term “stutters.” During stutters, the rate of MT length change tends to be smaller in magnitude than during typical growth or shortening phases. Quantifying stutters and other behaviors with STADIA demonstrates that stutters precede most catastrophes in our in vitro experiments and dimer-scale MT simulations, suggesting that stutters are mechanistically involved in catastrophes. Related to this idea, we show that the anticatastrophe factor CLASP2γ works by promoting the return of stuttering MTs to growth. STADIA enables more comprehensive and data-driven analysis of MT dynamics compared with previous methods. The treatment of stutters as distinct and quantifiable DI behaviors provides new opportunities for analyzing mechanisms of MT dynamics and their regulation by binding proteins.  相似文献   
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