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   84261篇
  免费   6069篇
  国内免费   3104篇
  2023年   1330篇
  2022年   1209篇
  2021年   2558篇
  2020年   2669篇
  2019年   3701篇
  2018年   3232篇
  2017年   2327篇
  2016年   2303篇
  2015年   2880篇
  2014年   5452篇
  2013年   6803篇
  2012年   4154篇
  2011年   5407篇
  2010年   4105篇
  2009年   4439篇
  2008年   4592篇
  2007年   4617篇
  2006年   4099篇
  2005年   3573篇
  2004年   3181篇
  2003年   2550篇
  2002年   2272篇
  2001年   1465篇
  2000年   1183篇
  1999年   1157篇
  1998年   1052篇
  1997年   829篇
  1996年   778篇
  1995年   820篇
  1994年   743篇
  1993年   591篇
  1992年   587篇
  1991年   510篇
  1990年   408篇
  1989年   360篇
  1988年   308篇
  1987年   280篇
  1986年   230篇
  1985年   456篇
  1984年   674篇
  1983年   491篇
  1982年   534篇
  1981年   427篇
  1980年   374篇
  1979年   325篇
  1978年   272篇
  1977年   252篇
  1976年   240篇
  1975年   192篇
  1974年   169篇
排序方式: 共有10000条查询结果,搜索用时 94 毫秒
101.
Alternative ORFs (AltORFs) are unannotated sequences in genome that encode novel peptides or proteins named alternative proteins (AltProts). Although ribosome profiling and bioinformatics predict a large number of AltProts, mass spectrometry as the only direct way of identification is hampered by the short lengths and relative low abundance of AltProts. There is an urgent need for improvement of mass spectrometry methodologies for AltProt identification. Here, we report an approach based on size-exclusion chromatography for simultaneous enrichment and fractionation of AltProts from complex proteome. This method greatly simplifies the variance of AltProts discovery by enriching small proteins smaller than 40 kDa. In a systematic comparison between 10 methods, the approach we reported enabled the discovery of more AltProts with overall higher intensities, with less cost of time and effort compared to other workflows. We applied this approach to identify 89 novel AltProts from mouse liver, 39 of which were differentially expressed between embryonic and adult mice. During embryonic development, the upregulated AltProts were mainly involved in biological pathways on RNA splicing and processing, whereas the AltProts involved in metabolisms were more active in adult livers. Our study not only provides an effective approach for identifying AltProts but also novel AltProts that are potentially important in developmental biology.  相似文献   
102.
Volatile chemicals in the environment provide ethologically important information to many animals. However, how animals learn to use this information is only beginning to be understood. This review highlights recent experimental advances elucidating olfactory learning in rodents, ranging from adaptations to the environment to task-dependent refinement and multisensory associations. The broad range of phenomena, mechanisms, and brain areas involved demonstrate the complex and multifaceted nature of olfactory learning.  相似文献   
103.
104.
《Molecular cell》2020,77(4):810-824.e8
  1. Download : Download high-res image (128KB)
  2. Download : Download full-size image
  相似文献   
105.
《Molecular cell》2020,77(6):1294-1306.e5
  1. Download : Download high-res image (114KB)
  2. Download : Download full-size image
  相似文献   
106.
The melanocyte-stimulating hormone receptor (MC1-R) is a central regulator of mammalian coat colour, encoded by the extension locus. In cattle, the dominant extension allele ED is associated with the production of black pigment in coloured areas. Genotyping of the MC1-R gene in a bull with mosaic expression of red vs. black pigment verified the existence of the ED allele, in spite of the fact that the majority of the animal is red coloured. No further mutations were found within the ED variant of the MC1-R gene, which was inherited from a completely red mother (genotype ED/e).  相似文献   
107.
The work of prominent Russian biologist Alexander Gavrilovich Gurwitsch (1874–1954) on the theory of organism development are reviewed. Alexander Gurwitsch introduced the concept of embryonic (morphogenetic, biological, and cellular) field and proposed several revisions of it from 1912 to 1944. Although neither of them can be considered as a final theory of development, his the persistent search for the invariant law that allows the shape (spatial structure) to be proposed for each next developmental stage from the previous shape is of imperishable methodological interest. Alexander Gurwitsch anticipated many ideas of the future theory of self-organization. His theoretical constructions are explicit and experiment-oriented but absolutely not esoteric. They represent a highly important and original contribution to theoretical biology and are an essential step to further development of the ontogenetic theory.  相似文献   
108.
109.
Due to the ubiquity of epoxy resin compounds and their potential role in increasing the risk for reproductive dysfunction and cancer, the need for an assessment of human exposure is urgent. Therefore, we developed a method for measuring bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) metabolites in human blood samples using high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–MS). Human blood samples were processed using enzymatic deconjugation of the glucuronides followed by a novel sample preparation procedure using a solid-phase-cartridge column. This selective analytical method permits rapid detection of the metabolites, free BPA and a hydrolysis product of BADGE (BADGE-4OH) with detection limits in the low nanogram per milliliter range (0.1 ng ml−1 of BPA and 0.5 ng ml−1 of BADGE-4OH). The sample extraction was achieved by Oasis HLB column on gradient elution. The recoveries of BPA and BADGE-4OH added to human plasma samples were above 70.0% with a standard deviation of less than 5.0%. This selective, sensitive and accurate method will assist in elucidating potential associations between human exposure to epoxy-based compounds and adverse health effects.  相似文献   
110.
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