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   924149篇
  免费   98633篇
  国内免费   630篇
  2018年   9206篇
  2017年   8731篇
  2016年   12182篇
  2015年   16279篇
  2014年   18858篇
  2013年   26874篇
  2012年   29987篇
  2011年   29984篇
  2010年   20178篇
  2009年   18399篇
  2008年   26119篇
  2007年   26792篇
  2006年   25398篇
  2005年   24027篇
  2004年   23844篇
  2003年   22656篇
  2002年   22032篇
  2001年   41717篇
  2000年   41954篇
  1999年   33177篇
  1998年   11258篇
  1997年   11688篇
  1996年   10888篇
  1995年   10298篇
  1994年   9939篇
  1993年   9940篇
  1992年   26615篇
  1991年   25625篇
  1990年   24857篇
  1989年   24200篇
  1988年   22391篇
  1987年   21227篇
  1986年   19928篇
  1985年   19828篇
  1984年   16444篇
  1983年   14062篇
  1982年   10886篇
  1981年   9882篇
  1980年   9293篇
  1979年   15818篇
  1978年   12324篇
  1977年   11444篇
  1976年   10523篇
  1975年   11830篇
  1974年   12985篇
  1973年   12745篇
  1972年   11719篇
  1971年   10586篇
  1970年   9264篇
  1969年   9027篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
We have identified mouse and human FKBP60, a new member of the FKBP gene family. FKBP60 shares strongest homology with FKBP65 and SMAP. FKBP60 contains a hydrophobic signal peptide at the N-terminus, 4 peptidyl-prolyl cis/trans isomerase (PPIase) domains and an endoplasmic reticulum retention motif (HDEL) at the C-terminus. Immunodetection of HA-tagged FKBP60 in NIH-3T3 cells suggests that FKBP60 is segregated to the endoplasmic reticulum. Northern blot analysis shows that FKBP60 is predominantly expressed in heart, skeletal muscle, lung, liver and kidney. With N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide as a substrate, recombinant GST-FKBP60 is shown to accelerate effectively the isomerization of the peptidyl-prolyl bond. This isomerization activity is inhibited by FK506. mFKBP60 binds Ca2+ in vitro, presumably by its C-terminal EF-hand Ca2+ binding motif, and is phosphorylated in vivo. hFKBP60 has been mapped to 7p12 and/or 7p14 by fluorescence in situ hybridization (FISH).  相似文献   
2.
3.
4.
A patient with chronic anemia is presented who radiologically showed prominent rugae of the stomach. Angiography demonstrated an arteriovenous malformation with a large feeding artery and prominent draining veins.  相似文献   
5.
6.
7.
8.
9.
Aim The Chilean endemic Dioscorea biloba (Dioscoreaceae) is a dioecious geophyte that shows a remarkable 600 km north–south disjunction in the peripheral arid area of the Atacama Desert. Its restricted present‐day distribution and probable Neogene origin indicate that its populations have a history linked to that of the Atacama Desert, making this an ideal model species with which to investigate the biogeography of the region. Location Chile, Atacama Desert and peripheral arid area. Methods Two hundred and seventy‐five individuals from nine populations were genotyped for seven nuclear microsatellite loci, and plastid trnL–F and trnT–L sequences were obtained for a representative subset of these. Analyses included the estimation of genetic diversity and population structure through clustering, Bayesian and analysis of molecular variance analyses, and statistical parsimony networks of chloroplast haplotypes. Isolation by distance was tested against alternative dispersal hypotheses. Results Microsatellite markers revealed moderate to high levels of genetic diversity within populations, with those from the southern Limarí Valley showing the highest values and northern populations showing less exclusive alleles. Bayesian analysis of microsatellite data identified three genetic groups that corresponded to geographical ranges. Chloroplast phylogeography revealed no haplotypes shared between northern and southern ranges, and little haplotype sharing between the two neighbouring southern valleys. Dispersal models suggested the presence of extinct hypothetical populations between the southern and northern ranges. Main conclusions Our results are consistent with prolonged isolation of the northern and southern groups, mediated by the life‐history traits of the species. Significant isolation was revealed at both large and moderate distances as gene flow was not evident even between neighbouring valleys. Bayesian analyses of microsatellite and chloroplast haplotype diversity identified the southern area of Limarí as the probable area of origin of the species. Our data do not support recent dispersal of D. biloba from the southern range into Antofagasta, but indicate the fragmentation of an earlier wider range, concomitant with the Pliocene–Pleistocene climatic oscillations, with subsequent extinctions of the Atacama Desert populations and the divergence of the peripheral ones as a consequence of genetic drift.  相似文献   
10.
Comparison of bone marrow extracellular matrices.   总被引:1,自引:0,他引:1  
We have compared the structure and composition of adult and fetal bovine bone marrow extracellular matrices. In contrast to fetal bone marrow, adult bone marrow has more oval fenestration and accumulation of adipocytes as well as lower protein content. These differences could be due to remodeling of bone marrow tissue as it develops. Zymogram analysis of matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) activities showed that fetal, but not adult bone marrow extract contained a 96-kDa MMP and TIMP-1 and -2. These activities may contribute to the structural differences between adult and fetal bone marrow tissues.  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