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   5450篇
  免费   942篇
  国内免费   896篇
  2024年   22篇
  2023年   314篇
  2022年   375篇
  2021年   578篇
  2020年   528篇
  2019年   604篇
  2018年   462篇
  2017年   399篇
  2016年   387篇
  2015年   453篇
  2014年   567篇
  2013年   417篇
  2012年   276篇
  2011年   233篇
  2010年   126篇
  2009年   132篇
  2008年   108篇
  2007年   100篇
  2006年   112篇
  2005年   118篇
  2004年   88篇
  2003年   99篇
  2002年   80篇
  2001年   75篇
  2000年   74篇
  1999年   60篇
  1998年   43篇
  1997年   50篇
  1996年   45篇
  1995年   48篇
  1994年   46篇
  1993年   22篇
  1992年   42篇
  1991年   25篇
  1990年   18篇
  1989年   21篇
  1988年   18篇
  1987年   15篇
  1986年   9篇
  1985年   19篇
  1984年   26篇
  1983年   16篇
  1982年   20篇
  1981年   6篇
  1980年   4篇
  1979年   2篇
  1978年   3篇
  1977年   1篇
  1950年   2篇
排序方式: 共有7288条查询结果,搜索用时 15 毫秒
101.
Human housekeeping genes,revisited   总被引:1,自引:0,他引:1  
  相似文献   
102.
Methanobacterium sp. Mb1, a hydrogenotrophic methanogenic Archaeon, was isolated from a rural biogas plant producing methane-rich biogas from maize silage and cattle manure in Germany. Here we report the complete genome sequence of the novel methanogenic isolate Methanobacterium sp. Mb1 harboring a 2,029,766 bp circular chromosome featuring a GC content of 39.74%. The genome encodes two rRNA operons, 41 tRNA genes and 2021 coding sequences and represents the smallest genome currently known within the genus Methanobacterium.  相似文献   
103.
Abstract

A number of viruses are known to infect chrysanthemum plants, however in the present study a previously unknown potyvirus was detected using techniques such as ELISA, RT-PCR and hybridization. The ELISA-positive samples were amplified using a potyvirus group-specific primer which gave an amplification of ~850 bp. The amplified product was cloned and sequenced, and shows 72 – 73% homology with known potyviruses that infect chrysanthemums such as Potato virus Y potyvirus, Soyabean mosaic virus and Turnip mosaic potyvirus when compared to the sequence available in the database. However, present potyvirus isolates show 93% homology with Chilli veinal mottle virus and Pepper vein banding virus. The results were further confirmed by Northern hybridization. This is the first report of a potyvirus similar to Chilli veinal mottle virus, and Pepper vein banding virus infecting chrysanthemums.  相似文献   
104.
105.
106.
107.
108.
Campylobacter remains one of the most common bacterial causes of gastroenteritis worldwide. Tracking sources of this organism is challenging due to the large numbers of human cases, and the prevalence of this organism throughout the environment due to growth in a wide range of animal species. Many molecular subtyping methods have been developed to characterize Campylobacter species, but only a few are commonly used in molecular epidemiology studies. This review examines the applicability of these methods, as well as the role that emerging whole genome sequencing technologies will play in tracking sources of Campylobacter spp. infection.  相似文献   
109.
An NAD linked formate dehydrogenating enzyme which catalyzed the last step of methanol oxidation system was extracted from the methanol-grown Kloeckera sp. No. 2201. The specific activity of the enzyme in the extract of methanol-grown cells was found to be considerably higher than that of the glucose-grown cells. The enzyme was purified about 35-fold from the extract of methanol-grown cells by heat treatment, column chromatographies on DEAE-cellulose and on hydroxylapatite, and Sephadex G-200 gel filtration. The purified enzyme was shown to be homogeneous by analyses with electrophoresis and ultracentrifuga-tion. The purified enzyme was a kind of NAD: formate oxidoreductase (EC, 1.2.1.2) which catalyzed specifically the oxidation of formate to carbon dioxide. The Km values were 22 mm for formate and 0.1 mm for NAD. The enzyme was inactivated by potassium cyanide, sodium azide, and p-chloromercuribenzoate but not by any metal-chelating reagents tested. Other general properties of the enzyme were also investigated.  相似文献   
110.
Theaflavins, the oxidized products formed from tea leaf catechins during black tea fermentation, showed an antiviral activity on TMV. From the survey of the interactions of theaflavins with RNA and its related substances, it was presumed that theaflavins disturbed the replication cycle of TMV through binding to TMV-RNA.  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