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   293863篇
  免费   34671篇
  国内免费   149篇
  2018年   2410篇
  2016年   3097篇
  2015年   4063篇
  2014年   4938篇
  2013年   6769篇
  2012年   7732篇
  2011年   7947篇
  2010年   5220篇
  2009年   5054篇
  2008年   7173篇
  2007年   7353篇
  2006年   7245篇
  2005年   6943篇
  2004年   6830篇
  2003年   6647篇
  2002年   6489篇
  2001年   17291篇
  2000年   17480篇
  1999年   13327篇
  1998年   3874篇
  1997年   4131篇
  1996年   3863篇
  1995年   3494篇
  1994年   3473篇
  1993年   3547篇
  1992年   10414篇
  1991年   10343篇
  1990年   9815篇
  1989年   9648篇
  1988年   9006篇
  1987年   8388篇
  1986年   7574篇
  1985年   7424篇
  1984年   5857篇
  1983年   5095篇
  1982年   3625篇
  1981年   3199篇
  1980年   3041篇
  1979年   5367篇
  1978年   4133篇
  1977年   3779篇
  1976年   3314篇
  1975年   3792篇
  1974年   3970篇
  1973年   3908篇
  1972年   3433篇
  1971年   3191篇
  1970年   2831篇
  1969年   2748篇
  1968年   2417篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
923.
924.
Intermittent illumination increased H2 and C2H4 yields per unit of light from growing cells and from nitrogren-starved cells by 1.7- and 1.35-fold, respectively, as compared with continuous illumination.  相似文献   
925.
In de-rooted seedlings of Amaranthus caudatus L., betacyanin synthesis induced by white light or cytokinin was inhibited by abscisic acid (ABA) or a mixture of gibberellins A4 and A7 (GA4/7). The GA4/7 and ABA effects were additive. Thus ABA inhibited the cytokinin action but had no effect on the gibberellin response.  相似文献   
926.
Since deaths of waterfowls have frequently been observed in Lake Kahoku near Kanazawa city, Japan, we attempted an ecological study on Clostridium botulinum type C in four other lakes as well as Lake Kahoku. One hundred and twenty-nine (56%) of 230 soil samples collected gave rise to lethal toxicity in mice with the characteristic “wasp-waist” symptom. All of the 51 samples arbitrarily selected were neutralized by C. botulinum type C antitoxic serum. A further seasonal study throughout the year at a given shore area of Lake Kahoku disclosed that nearly all samples gave rise to toxicity due to C. botulinum type C during the autumn season when the most waterfowls congregate. Toxigenic strains of C. botulinum type C were isolated together with nontoxigenic strains that were culturally and biochemically similar to the toxigenic strains. Both the toxigenic and nontoxigenic strains were equally agglutinable by an antiserum prepared against one of the nontoxigenic strains. Further extensive studies on the specificity of the agglutination method for identification were performed with 112 strains of 46 clostridial species. None of the strains used except some strains of C. novyi type A and a strain of C. botulinum type D was agglutinable. Based on the findings for cultural, biochemical, and agglutinable properties, the nontoxigenic strains were identified as C. botulinum type C. Also, C. novyi type A isolates showing colonies covered with a small pearly layer zone but surrounded by an aberrantly wide lecithinase zone are discussed.  相似文献   
927.
928.
929.
The proton magnetic resonance (PMR) spectra of thyroid cell membranes and their total lipid extracts, in the presence of 1-anilino-8-naphthalenesulfonate (ANS), have been studied. The addition of ANS causes a shifting of the head group PMR signal, a splitting of the signal into two components and an increase in total spectral intensity. The data suggest that ANS interacts with phospholipid in the membrane as it does in total lipid vesicles. Evidence is also presented for the removal of lipids from the membrane, by ANS, and the subsequent formation of micelles. The membrane results are compatred with our earlier work on the interaction of ANS with egg phosphatidycholine (P.C.) vesicles and the results are used in explaining the inhibition of iodide transport in isolated thyroid slices.  相似文献   
930.
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