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   699篇
  免费   32篇
  国内免费   47篇
耳鼻咽喉   4篇
儿科学   24篇
妇产科学   38篇
基础医学   52篇
口腔科学   25篇
临床医学   85篇
内科学   126篇
皮肤病学   10篇
神经病学   35篇
特种医学   182篇
外科学   34篇
综合类   23篇
预防医学   68篇
眼科学   3篇
药学   53篇
中国医学   1篇
肿瘤学   15篇
  2023年   4篇
  2018年   10篇
  2017年   7篇
  2016年   6篇
  2015年   32篇
  2014年   34篇
  2013年   69篇
  2012年   21篇
  2011年   18篇
  2010年   19篇
  2009年   21篇
  2008年   15篇
  2007年   40篇
  2006年   13篇
  2005年   12篇
  2004年   15篇
  2003年   7篇
  2002年   12篇
  2001年   7篇
  2000年   16篇
  1999年   9篇
  1998年   20篇
  1997年   26篇
  1996年   15篇
  1995年   22篇
  1994年   17篇
  1993年   13篇
  1992年   14篇
  1991年   13篇
  1990年   15篇
  1989年   22篇
  1988年   23篇
  1987年   13篇
  1986年   11篇
  1985年   10篇
  1984年   10篇
  1983年   10篇
  1982年   10篇
  1981年   6篇
  1980年   8篇
  1979年   4篇
  1976年   10篇
  1971年   7篇
  1969年   3篇
  1968年   3篇
  1966年   4篇
  1949年   4篇
  1948年   3篇
  1947年   6篇
  1841年   7篇
排序方式: 共有778条查询结果,搜索用时 15 毫秒
1.
2.
3.
Changes in atrial adenosine triphosphate (ATP) and the presence of postoperative arrhythmias were studied in 14 patients during routine coronary artery bypass grafting to 1) attempt to evaluate atrial preservation, and 2) determine if a relationship exists between changes in ATP and the development of postoperative arrhythmias. Atrial biopsies were obtained at the time of cannulation (preischemic sample) and after the removal of the aortic crossclamp (postischemic sample). Methods of myocardial protection included systemic hypothermia (28 degrees C), periodic reinfusion of crystalloid cardioplegia into the aortic root and completed vein grafts, and iced slush in the pericardial well. Atrial temperature was monitored. Preischemic ATP was 0.412 +/- 0.32 mu mol/gm, and the postischemic value was 0.220 +/- 0.13 mu mol/gm (p less than .02). Atrial temperature routinely decreased to 13-18 degrees C after cardioplegic infusion but rose to 24 degrees C between infusions. There was no correlation between postoperative supraventricular arrhythmias (4 patients) and changes in ATP. In conclusion, routine coronary artery bypass grafting with standard methods of cardiac preservation does not appear to satisfactorily preserve atrial tissue. The clinical correlation and significance of this remains to be elucidated.  相似文献   
4.
5.
6.
7.
8.
9.
An RNA-binding motif (RBM) gene family has been identified on the human Y chromosome that maps to the same deletion interval as the 'azoospermia factor' (AZF). We have identified the homologous gene family (Rbm) on the mouse Y with a view to investigating the proposal that this gene family plays a role in spermatogenesis. At least 25 and probably >50 copies of Rbm are present on the mouse Y chromosome short arm located between Sry and the centromere. As in the human, a role in spermatogenesis is indicated by a germ cell-specific pattern of expression in the testis, but there are distinct differences in the pattern of expression between the two species. Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are female due to a position effect resulting in non-expression of Sry ; sex-reversing such mice with an Sry transgene produces males with a high incidence of abnormal sperm, making this the third deletion interval on the mouse Y that affects some aspect of spermatogenesis. Most of the copies of Rbm map to this deletion interval, and the Yd1males have markedly reduced Rbm expression, suggesting that RBM deficiency may be responsible for, or contribute to, the abnormal sperm development. In man, deletion of the functional copies of RBM is associated with meiotic arrest rather than sperm anomalies; however, the different effects of deletion are consistent with the differences in expression between the two species.   相似文献   
10.
A 9.7 kb segment encompassing exons 7-10 of the adrenoleukodystrophy (ALD) locus of the X chromosome has duplicated to specific locations near the pericentromeric regions of human chromosomes 2p11,10p11, 16p11 and 22q11. Comparative sequence analysis reveals 92-96% nucleotide identity, indicating that the autosomal ALD paralogs arose relatively recently during the course of higher primate evolution (5-10 million years ago). Analysis of sequences flanking the duplication region identifies the presence of an unusual GCTTTTTGC repeat which may be a sequence-specific integration site for the process of pericentromeric- directed transposition. The breakpoint sequence and phylogenetic analysis predict a two-step transposition model, in which a duplication from Xq28 to pericentromeric 2p11 occurred once, followed by a rapid distribution of a larger duplicon cassette among the pericentromeric regions. In addition to facilitating more effective mutation detection among ALD patients, these findings provide further insight into the molecular basis underlying a pericentromeric-directed mechanism for non- homologous interchromosomal exchange.   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