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   21675篇
  免费   2092篇
  国内免费   11篇
  23778篇
  2022年   148篇
  2021年   234篇
  2020年   167篇
  2019年   219篇
  2018年   264篇
  2017年   252篇
  2016年   381篇
  2015年   765篇
  2014年   829篇
  2013年   1060篇
  2012年   1283篇
  2011年   1345篇
  2010年   868篇
  2009年   833篇
  2008年   1132篇
  2007年   1218篇
  2006年   1144篇
  2005年   1164篇
  2004年   1148篇
  2003年   954篇
  2002年   963篇
  2001年   368篇
  2000年   316篇
  1999年   346篇
  1998年   319篇
  1997年   222篇
  1996年   188篇
  1995年   179篇
  1994年   177篇
  1993年   178篇
  1992年   246篇
  1991年   231篇
  1990年   199篇
  1989年   237篇
  1988年   201篇
  1987年   195篇
  1986年   170篇
  1985年   204篇
  1984年   192篇
  1983年   168篇
  1982年   171篇
  1981年   158篇
  1980年   120篇
  1979年   137篇
  1978年   130篇
  1977年   137篇
  1976年   119篇
  1974年   125篇
  1973年   123篇
  1972年   114篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
241.
242.
243.
Although Montreal is in an endemic area, significant clinical histoplasmosis with systemic manifestations has been, until recently, infrequently diagnosed. However, since the autumn of 1963, 31 cases of clinically significant histoplasmosis have been seen by the authors. These were divided into two groups: (1) patients in whom the diagnosis was established on the basis of histological and/or cultural demonstration of the fungus; (2) patients in whom the diagnosis was based on a positive histoplasmin skin test, a complement fixation antibody titre of 1:32 or greater and compatible clinical and radiological findings. An additional group of 11 patients who presented with erythema multiforme was investigated and a heretofore unrecognized relationship between histoplasmosis and erythema multiforme was established.  相似文献   
244.
245.
246.
A versatile and simple continuous-culture apparatus is described. With this apparatus, independent control of limiting growth factors and other nutrilites is possible and the conditions of each experiment are reproducible. In view of the synchronized speed of the feeder syringes, flow variation troubles are not encountered. The device allows the performance of growth experiments at different dilution rates simultaneously in a single run which makes the comparison of the results more reliable. The operation of the device has been tested successfully with a study of adenine deaminase induction in yeast.  相似文献   
247.
Three single-strain cultures, Streptococcus lactis C2, S. cremoris R1, and S. diacetilactis DRC2, were frozen and stored in skim milk, in skim milk containing apple juice, and in skim milk containing one of the following additives: glycerol (10%, v/v), dimethyl sulfoxide (10%, v/v), l-malic acid (0.5 and 2.0%, w/v), acetamide (0.5 and 2.0%, w/v), or succinimide (0.5 and 2.0%, w/v). Cultures were frozen and stored at -23.3 C, frozen and stored at -196 C in liquid nitrogen, or frozen at -196 C and stored at -23.3 C. Cultures frozen and stored at -196 C in liquid nitrogen gave the greatest recovery of viable cells. The number of cells surviving after storage at -23.3 C was greater when the cells had been frozen in liquid N2 than when they had been frozen at -23.3 C. All strains stored at -23.3 C showed a decrease in numbers of surviving cells; additives, particularly l-malic acid and apple juice, were advantageous in preserving the viability of the S. lactis C2 and S. cremoris R1 strains, but had little or no effect on the survival of S. diacetilactis DRC2. l-Malic acid and apple juice stimulated acid production for all cultures in activity tests following incubation after thawing, whereas glycerol and dimethyl sulfoxide retarded its development.  相似文献   
248.
249.
250.
Mapping of Temperature-Sensitive Mutants in Bacteriophage T5   总被引:9,自引:1,他引:8       下载免费PDF全文
  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