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   7327篇
  免费   697篇
  国内免费   448篇
  2023年   235篇
  2022年   249篇
  2021年   427篇
  2020年   383篇
  2019年   380篇
  2018年   337篇
  2017年   275篇
  2016年   278篇
  2015年   342篇
  2014年   459篇
  2013年   499篇
  2012年   351篇
  2011年   346篇
  2010年   308篇
  2009年   353篇
  2008年   335篇
  2007年   339篇
  2006年   321篇
  2005年   263篇
  2004年   211篇
  2003年   184篇
  2002年   159篇
  2001年   121篇
  2000年   101篇
  1999年   86篇
  1998年   65篇
  1997年   87篇
  1996年   85篇
  1995年   73篇
  1994年   66篇
  1993年   59篇
  1992年   54篇
  1991年   58篇
  1990年   55篇
  1989年   48篇
  1988年   38篇
  1987年   27篇
  1986年   19篇
  1985年   45篇
  1984年   37篇
  1983年   29篇
  1982年   45篇
  1981年   40篇
  1979年   34篇
  1978年   22篇
  1977年   17篇
  1976年   22篇
  1975年   24篇
  1974年   17篇
  1973年   23篇
排序方式: 共有8472条查询结果,搜索用时 609 毫秒
1.
《Cell reports》2020,30(1):112-123.e4
  1. Download : Download high-res image (131KB)
  2. Download : Download full-size image
  相似文献   
2.
W D Davies  J Pittard  B E Davidson 《Gene》1985,33(3):323-331
Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background.  相似文献   
3.
Two new species of Haptoglossa , one zoosporic, H. northumbrica , and one aplanosporic, H. polymorphs, , were isolated from samples of manure and horse dung in north-east England. The zoosporic H. northumbrica is morphologically similar to H. dickii but differs in having slightly smaller infection gun cells with a unique internal arrangement of cones in the apical missile chamber. The thallus of the aplanosporic H. polymorpha is similar to H. heteromorpha but produces three different types of aplanospore. The smaller cysts either develop into broad, arcuate gun cells or form curved adhesive cells that have a rounded base. These curved adhesive cells have very different internal ultrastructural organization. The large cysts develop into infection cells that are morphologically similar to the curved adhesive cells, but their internal structure has not yet been observed.  相似文献   
4.
《Cell reports》2020,30(6):1690-1701.e4
  1. Download : Download high-res image (107KB)
  2. Download : Download full-size image
  相似文献   
5.
6.
Candida auris is an emerging species responsible for life-threatening infections. Its ability to be resistant to most systemic antifungal classes and its capacity to persist in a hospital environment have led to health concerns. Currently, data about environmental reservoirs are limited but remain essential in control of C. auris spread. The aim of our study was to explore the interactions between C. auris and two free-living amoeba (FLA) species, Vermamoeba vermiformis and Acanthamoeba castellanii, potentially found in the same water environment. Candida auris was incubated with FLA trophozoites or their culture supernatants. The number of FLA and yeasts was determined at different times and transmission electron microscopy (TEM) was performed. Supernatants of FLAs promoted yeast survival and proliferation. Internalization of viable C. auris within both FLA species was also evidenced by TEM. A water environmental reservoir of C. auris can therefore be considered through FLAs and contamination of the hospital water networks would consequently be possible.  相似文献   
7.
8.
《Cell reports》2020,30(1):61-68.e4
  1. Download : Download high-res image (250KB)
  2. Download : Download full-size image
  相似文献   
9.
Summary In comparison to cassava grown in monoculture the root infection of cassava with vesicular-arbuscular mycorrhiza was increased by crop rotation with grain legumes in the field. This was also found when cassava was intercropped with legumes and fertilized. A possible specificity of mycorrhizal fungi to increase the yield of one species more than the other when grown in association, is discussed.  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