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   804809篇
  免费   94720篇
  国内免费   955篇
  2018年   7096篇
  2017年   6766篇
  2016年   9983篇
  2015年   14669篇
  2014年   16760篇
  2013年   23236篇
  2012年   27076篇
  2011年   27540篇
  2010年   18388篇
  2009年   16834篇
  2008年   24205篇
  2007年   25076篇
  2006年   23176篇
  2005年   22455篇
  2004年   22297篇
  2003年   20978篇
  2002年   20326篇
  2001年   34910篇
  2000年   35029篇
  1999年   28067篇
  1998年   10566篇
  1997年   10783篇
  1996年   10350篇
  1995年   9647篇
  1994年   9475篇
  1993年   9361篇
  1992年   23063篇
  1991年   22383篇
  1990年   22009篇
  1989年   21452篇
  1988年   19528篇
  1987年   18755篇
  1986年   17531篇
  1985年   17211篇
  1984年   14537篇
  1983年   12582篇
  1982年   9738篇
  1981年   8796篇
  1980年   8194篇
  1979年   13688篇
  1978年   10857篇
  1977年   9847篇
  1976年   9177篇
  1975年   10183篇
  1974年   11128篇
  1973年   10905篇
  1972年   9797篇
  1971年   9045篇
  1970年   7605篇
  1969年   7460篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
151.

Background  

Recent studies point to a great diversity of non-ribosomal peptide synthesis systems with major roles in amino acid and co-factor biosynthesis, secondary metabolism, and post-translational modifications of proteins by peptide tags. The least studied of these systems are those utilizing tRNAs or aminoacyl-tRNA synthetases (AAtRS) in non-ribosomal peptide ligation.  相似文献   
152.
STACE, C. A. & JARVIS, C. E., 1985. TypiHcation of Linnaean taxa of annual Poaceae: Poeae related to Vulpia and Desmazeria. The status and typification of 15 Linnaean species of annual grasses related to Vulpia and Desmazeria are discussed. Of these 15, eight are represented by holotypes or lectotypes in LINN, two by lectotypes in Herb. A. van Royen (L), and one by a neotype in LINN. One (Festuca marina) is based on a pre-Linnaean polynomial and is represented by a lectotype in Herb. Sloane (BM); one (Cynosurus durus) has no known type specimens and we have chosen a Barrelier (1714) illustration as lectotype; one (Nardus aristatus) is an illegitimate name change for Nardus incurvus Gouan, for which we have selected a Scheuchzer (1719) illustration as lectotype; and finally Festuca incrassala appeared on a cancelled page of Species Plantarum and has no nomenclatural standing.  相似文献   
153.
Antibodies to calcitonin, parathyroid hormone and cortisol are detected in acute stage of infection-caused bronchial asthma. The appearance of antibodies is paralleled by marked hypercalcaemia. The antibodies may bind excessive hormones in the blood, preventing further hormonal imbalance. Ten-day treatment with glucocorticoids decreased the amount of antibodies possibly due to normalization of hormonal secretion and restoration of their balance. As a result, calcium blood levels returned to normal.  相似文献   
154.
155.
156.
157.
158.
159.
160.
Chromatophores from Rhodopseudomonas capsulata cells grown semiaerobically in the dark oxidize NADH, succinate, and dichlorophenolindophenol. In the presence of N3? these activities are inhibited, but light induces oxidation of dichlorophenolindophenol with O2 as a terminal electron acceptor. Cyanide also inhibits electron transport but much higher concentrations are required to inhibit the photooxidation than the dark oxidation. The photooxidation was studied in a mutant strain of Rhodopseudomonas capsulata (YIV) which cannot grow anaerobically in the light, but similarly to the wild type, grows in the presence of oxygen. Chromatophores from YIV mutant catalyze photophosphorylation and dark oxidation activities with the same properties as those of the wild type. However, the rate of photooxidation in the mutant is only one-third that of the wild type. Based on the differential inhibitor sensitivity and on the mutation it is suggested that the photooxidase is different from the two respiratory oxidases and that this photooxidation activity might be essential for growth of the cells under anaerobic conditions in the light.  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