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   18188篇
  免费   2732篇
  国内免费   2776篇
  2024年   115篇
  2023年   578篇
  2022年   605篇
  2021年   863篇
  2020年   899篇
  2019年   936篇
  2018年   761篇
  2017年   852篇
  2016年   803篇
  2015年   739篇
  2014年   914篇
  2013年   1260篇
  2012年   838篇
  2011年   834篇
  2010年   652篇
  2009年   870篇
  2008年   875篇
  2007年   949篇
  2006年   846篇
  2005年   781篇
  2004年   653篇
  2003年   675篇
  2002年   590篇
  2001年   479篇
  2000年   434篇
  1999年   430篇
  1998年   345篇
  1997年   291篇
  1996年   351篇
  1995年   309篇
  1994年   291篇
  1993年   266篇
  1992年   215篇
  1991年   242篇
  1990年   178篇
  1989年   180篇
  1988年   153篇
  1987年   167篇
  1986年   150篇
  1985年   175篇
  1984年   183篇
  1983年   112篇
  1982年   162篇
  1981年   102篇
  1980年   118篇
  1979年   95篇
  1978年   80篇
  1977年   76篇
  1976年   59篇
  1974年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Cell reports》2020,30(4):1152-1163.e4
  1. Download : Download high-res image (170KB)
  2. Download : Download full-size image
  相似文献   
2.
The literature relating to chemical, biochemical and biological aspects of the steroidal glycoalkaloid, α-tomatine, is reviewed. The alkaloid, which can be used as a starting compound for the synthesis of steroidal hormones, is toxic to a wide range of living organisms. The significance of tomatine to plants which elaborate it is discussed and some possible uses of the compound are mentioned.  相似文献   
3.
Samples of marine pleuston were collected from the sea-surface along considerable sections of the track of Eye of the Wind during its 2-year circumnavigational expedition 'Operation Drake' from November 1978 to October 1980. One hundred and eleven of the tow samples contained insects of the genus Halobates . They were assigned to four oceanic species: H. micans, H. sericeus, H. germanus and H. splendens; two coastal species: H. maculatus, H. princeps, and one undescribed species. Various development stages of the oceanic species were found. The locations, time of collection and surface temperatures where sea-skaters were collected are tabulated. Distributional boundaries and population densities of the oceanic species collected are discussed.  相似文献   
4.
In this paper very simple nonparametric classification rule for mixtures of discrete and continuous random variables is described. It is based on the method of nearest neighbor proposed by Cover and Hart (1967). The bounds on the limit of the nearest neighbor rule risks are given. Both lower and upper bound depend on the Bayes risk and the loss function. Finally the method is compared with other existing methods on some practical data set.  相似文献   
5.
Glucoamylase is a starch-hydrolyzing enzyme with a glycoprotein structure, used industrially for the conversion of starch to glucose, citric acid, corn syrups, and high-fructose sweeteners. This enzyme possesses an unusual type of structure in which many carbohydrate side chains are linked O-glycosidically to serine and threonine residues of the polypeptide chain. The carbohydrate side chains may be single monosaccharide residues or oligosaccharides of mannose, glucose, galactose, and in some cases N-acetylglucosamine. New data from experiments on the CNBr fragmentation of glucoamylase followed by chemical and immunological characterization of the fragments show that the carbohydrate side chains are distributed randomly along the polypeptide chain. Such a structure is appropriately termed a random model reprensentation for the glucoamylase molecule.  相似文献   
6.
  1. Download : Download high-res image (250KB)
  2. Download : Download full-size image
Highlights
  • •XL-MS reveals new PPIs in yeast mitochondria under glycerol and glucose condition.
  • •Significant but limited results from quantitative XL-MS experiments.
  • •Ndi1 participates in a CIII2CIV2 respiratory supercomplex.
  • •Min8 promotes assembly of Cox12 into an intermediate complex IV.
  相似文献   
7.
Three species of blackflies were found in emergence-trap samples taken overa period of 8 months from a second-order, forested, cold-stenothermal stream in southern Ontario. The emergence phenologies of the two common species, Prosimulium mixtum and Stegopterna mutata, are described and compared with their phenologies in other streams in North America. Hypotheses are presented for the poor faunal diversity and prolonged emergence of the two species in the stream studied. Emergence data are used to describe the pupal distribution in the stream.Wing-length measurements showed a distinct dimorphism in P. mixtum: females were larger than males. Adult size (except of P. mixtum females) varied among sampling sites in the stream and, in the case of S. mutata, this variation was time dependent.  相似文献   
8.
9.
  1. Download : Download high-res image (133KB)
  2. Download : Download full-size image
Highlights
  • •Flow cytometry analysis is used to isolate ASC speck(+) NPC cells.
  • •Proteome analysis of ASC speck(+) NPC cells reveals enriched mitochondrial OxPhos proteins.
  • •OxPhos proteins mediate NLRP3 inflammasome activation through mtROS.
  • •OxPhos proteins, NDUFB8 and ATP5B are correlated with NPC local recurrence.
  相似文献   
10.
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