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   805523篇
  免费   94796篇
  国内免费   955篇
  2018年   7098篇
  2017年   6776篇
  2016年   10004篇
  2015年   14682篇
  2014年   16778篇
  2013年   23272篇
  2012年   27109篇
  2011年   27570篇
  2010年   18404篇
  2009年   16867篇
  2008年   24251篇
  2007年   25109篇
  2006年   23222篇
  2005年   22482篇
  2004年   22325篇
  2003年   21015篇
  2002年   20368篇
  2001年   34938篇
  2000年   35046篇
  1999年   28075篇
  1998年   10575篇
  1997年   10784篇
  1996年   10350篇
  1995年   9647篇
  1994年   9477篇
  1993年   9365篇
  1992年   23079篇
  1991年   22396篇
  1990年   22026篇
  1989年   21463篇
  1988年   19541篇
  1987年   18762篇
  1986年   17538篇
  1985年   17216篇
  1984年   14540篇
  1983年   12599篇
  1982年   9741篇
  1981年   8802篇
  1980年   8209篇
  1979年   13690篇
  1978年   10859篇
  1977年   9846篇
  1976年   9186篇
  1975年   10190篇
  1974年   11125篇
  1973年   10906篇
  1972年   9799篇
  1971年   9051篇
  1970年   7608篇
  1969年   7463篇
排序方式: 共有10000条查询结果,搜索用时 15 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