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   490892篇
  免费   59532篇
  国内免费   314篇
  550738篇
  2018年   4405篇
  2017年   4052篇
  2016年   6314篇
  2015年   9575篇
  2014年   10719篇
  2013年   14983篇
  2012年   17445篇
  2011年   17548篇
  2010年   11602篇
  2009年   10687篇
  2008年   15280篇
  2007年   15879篇
  2006年   14523篇
  2005年   14217篇
  2004年   13915篇
  2003年   13238篇
  2002年   12652篇
  2001年   22085篇
  2000年   22159篇
  1999年   17906篇
  1998年   6846篇
  1997年   6931篇
  1996年   6700篇
  1995年   6072篇
  1994年   6104篇
  1993年   5939篇
  1992年   14072篇
  1991年   13339篇
  1990年   13005篇
  1989年   12838篇
  1988年   11493篇
  1987年   11072篇
  1986年   10190篇
  1985年   9976篇
  1984年   8581篇
  1983年   7396篇
  1982年   5942篇
  1981年   5448篇
  1980年   4987篇
  1979年   7984篇
  1978年   6225篇
  1977年   5684篇
  1976年   5359篇
  1975年   5561篇
  1974年   6051篇
  1973年   5892篇
  1972年   5266篇
  1971年   4867篇
  1970年   4050篇
  1969年   3979篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
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   
73.
74.
75.
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   
76.
77.
An apparatus for polyacrylamide slab gel electrophoresis is decribed which combines all parts into one integral unit. It eliminates several steps in the process of sealing, pouring, and setting the gels. Construction is easy with modest workshop facilities and the design easily adapted to suit most requirements. The apparatus provides a high degree of versatility and is suitable for use with many slab gel electrophoretic techniques.  相似文献   
78.
79.
Conditions for breaking various medically important yeasts using glass beads, 30 ml Corex centrifuge tubes, and a Vortex mixer were determined. From 75–95% ofCandida hyphal cells and all species of yeasts exceptSporothrix schenckii were broken when 10 g of 0.45–0.50 mm glass beads, 50–300 mg of wet cells in 5 ml of buffer, and 90 s of vortexing were employed. Yeasts ofSporothrix schenckii broke more efficiently when 0.25–0.30 mm beads were used.  相似文献   
80.
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