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   842篇
  免费   71篇
  2021年   16篇
  2020年   19篇
  2019年   18篇
  2018年   24篇
  2017年   8篇
  2016年   27篇
  2015年   46篇
  2014年   31篇
  2013年   55篇
  2012年   59篇
  2011年   49篇
  2010年   28篇
  2009年   32篇
  2008年   32篇
  2007年   30篇
  2006年   37篇
  2005年   36篇
  2004年   25篇
  2003年   35篇
  2002年   31篇
  2001年   11篇
  2000年   23篇
  1999年   11篇
  1998年   5篇
  1994年   4篇
  1992年   7篇
  1991年   7篇
  1990年   13篇
  1989年   8篇
  1988年   4篇
  1987年   7篇
  1986年   11篇
  1985年   8篇
  1984年   10篇
  1983年   17篇
  1980年   10篇
  1979年   12篇
  1978年   7篇
  1977年   8篇
  1976年   5篇
  1975年   8篇
  1974年   7篇
  1973年   7篇
  1972年   5篇
  1971年   9篇
  1970年   7篇
  1969年   4篇
  1968年   7篇
  1967年   4篇
  1966年   4篇
排序方式: 共有913条查询结果,搜索用时 93 毫秒
1.
2.
Purification and properties of the components from tropinin   总被引:16,自引:0,他引:16  
  相似文献   
3.
4.
Children free from infectious disease have been examined by indirect immunofluorescence for the presence of antibodies to the intracellular capsid antigen of Epstein-Barr virus (EBV). In the first year of life 46%, between 2 and 6 years of age 66%, and between 7 and 14 years 91%, of the children proved positive. The corresponding percentages for the presence of antibodies to cytomegalovirus (CMV) and herpes simplex virus were about 50%, irrespective of the children's age. Serum samples from 69 patients suffering from infectious mononucleosis (IM) were tested for anti-EBV antibodies. Of the 29 Paul-Bunnell-positive patients 22 had antibodies, 11 of them in high titres (greater than 1 : 80). Of the 40 Paul-Bunnell-negative cases only 21 had antibodies, 8 in high titres. Of the Paul-Bunnell-negative cases, 73% were found to have anti-CMV antibodies, 32% in high titre. The respective percentages for the Paul-Bunnell-positive cases were 42% and 10%.  相似文献   
5.
6.
7.
8.
9.
A study of 353 museum specimens of the Echis coloratus complex from its entire range of distribution revealed an undescribed species in the United Arab Emirates and northern Oman. The results of UPGMA clustering and principal coordinate analysis of 138 male and 142 female specimens yielded for both sexes two major clusters, one with specimens from the UAE and northern Oman and one from southern and western Arabia, the Levant and Egypt. The new species has a longer tail with higher subcaudal counts; the lower prenasal scale is often missing and the upper prenasal is frequently fused with the nasal; the subnasal is often missing or fused with the nasal. The gular scales between the chin‐shield and the preventrals are round or only slightly elongate, not elongate as in Echis coloratus, and their number is higher. Other differences in characters of the gular area indicate a different scale structure of the ventral surface of the head. The new species is allopatric or parapatric with E. coloratus, but sympatric with Echis carinatus sochureki.  相似文献   
10.
Infants'' sensitivity to ostensive signals, such as direct eye contact and infant-directed speech, is well documented in the literature. We investigated how infants interpret such signals by assessing common processing mechanisms devoted to them and by measuring neural responses to their compounds. In Experiment 1, we found that ostensive signals from different modalities display overlapping electrophysiological activity in 5-month-old infants, suggesting that these signals share neural processing mechanisms independently of their modality. In Experiment 2, we found that the activation to ostensive signals from different modalities is not additive to each other, but rather reflects the presence of ostension in either stimulus stream. These data support the thesis that ostensive signals obligatorily indicate to young infants that communication is directed to them.  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