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   913篇
  免费   109篇
  2022年   11篇
  2021年   17篇
  2020年   10篇
  2019年   15篇
  2018年   13篇
  2017年   13篇
  2016年   27篇
  2015年   46篇
  2014年   35篇
  2013年   49篇
  2012年   47篇
  2011年   45篇
  2010年   36篇
  2009年   23篇
  2008年   35篇
  2007年   25篇
  2006年   44篇
  2005年   34篇
  2004年   38篇
  2003年   30篇
  2002年   29篇
  2001年   15篇
  2000年   31篇
  1999年   15篇
  1998年   14篇
  1997年   9篇
  1996年   8篇
  1995年   7篇
  1994年   10篇
  1992年   18篇
  1991年   15篇
  1990年   10篇
  1989年   16篇
  1987年   14篇
  1986年   7篇
  1985年   14篇
  1984年   11篇
  1983年   8篇
  1982年   9篇
  1981年   10篇
  1980年   13篇
  1979年   11篇
  1978年   12篇
  1975年   8篇
  1974年   7篇
  1973年   9篇
  1971年   7篇
  1970年   12篇
  1969年   7篇
  1967年   6篇
排序方式: 共有1022条查询结果,搜索用时 15 毫秒
21.
The incidence of congenital heart disease is approximately 1 per cent of all live births. Approximately 60 per cent of patients who die of congenital heart disease do so at less than two years of age. Very few patients with such lesions live beyond 45 years at the very most. In about 70 per cent of patients who are born with cardiac anomalies, the lesions are either of kinds that are already being operated upon successfully or for which operations are now being attempted and often are helpful.  相似文献   
22.
A novel experimental method was developed which allows the determination of the threshold concentration of sucrose by use of a linear sucrose gradient in water. With this method a continuous tasting of the test-liquid is possible. A panel of 15 persons experienced in taste-testing was used. Three gradients of different steepness were applied: 0 to 1.5% (w/w) sucrose in 2 min (I), 3 min (II) and 4 min (III). The results of the new method were compared with those of the standard method (DIN). With gradients I and II we found values which were significantly higher than those of the standard method (I: 0.49% (w/w); II: 0.46% (w/w); DIN: 0.31% (w/w)), whereas with gradient III the same threshold value was found as with the DIN-Method (III: 0.32% (w/w)).  相似文献   
23.
24.
25.
26.
Using standard hybridoma technology and hierarchical screening, monoclonal antibodies (MAbs) were obtained with specific reactivity against two developmental stages of Globodera pallida. The procedure was based on enzyme-linked immunosorbent assay (ELISA) with homogenates prepared from second-stage juveniles, young adult females, and potato roots. Hybridomas were formed by fusing myelomas with splenocytes derived from mice immunized with either infective juveniles or females of G. pallida. About 600 hybridoma lines were screened from the fusion involving the mouse immunized with juveniles. Two MAbs (LJMAbl &2) were identified with high reactivity toward second-stage juveniles but no reactivity with either potato roots or females of G. pallida. A total of 630 cell lines was screened from the corresponding fusion involving the spleen of a mouse receiving immunogens from adult female nematodes. One MAb (LFMAbl) was obtained with the required specificity against only adult female G. pallida. This work extends the application of monoclonal antibodies in nematology from valuable probes for research and species identification to recognition of developmental stages. These specific MAbs have potential value in plant breeding programs for screening for resistant lines unable to support nematode development.  相似文献   
27.
28.
This article documents an unexpected regional difference in the shapes of later Acheulean hand-axes. Almost 1,200 handaxes from 17 sites located in Europe, East Africa, India, and the Near East were measured using a polar coordinate technique and compared using discriminant analysis and analysis of variance. One group of handaxes, those from Israel, clearly stood apart. The reasons for this distinction are unclear but may relate to raw material, time, or, perhaps, cultural tradition.  相似文献   
29.
30.
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