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   326078篇
  免费   39352篇
  国内免费   21107篇
  386537篇
  2021年   3915篇
  2020年   3312篇
  2019年   3958篇
  2018年   3953篇
  2017年   3742篇
  2016年   4652篇
  2015年   6087篇
  2014年   7888篇
  2013年   9282篇
  2012年   11294篇
  2011年   11577篇
  2010年   8252篇
  2009年   8160篇
  2008年   10478篇
  2007年   10463篇
  2006年   10167篇
  2005年   9400篇
  2004年   8695篇
  2003年   8222篇
  2002年   7898篇
  2001年   18695篇
  2000年   18752篇
  1999年   14091篇
  1998年   4295篇
  1997年   4395篇
  1996年   4067篇
  1995年   3655篇
  1994年   3586篇
  1993年   3667篇
  1992年   10508篇
  1991年   10433篇
  1990年   9895篇
  1989年   9704篇
  1988年   9084篇
  1987年   8425篇
  1986年   7623篇
  1985年   7478篇
  1984年   5876篇
  1983年   5112篇
  1982年   3688篇
  1981年   3214篇
  1979年   5361篇
  1978年   4124篇
  1977年   3755篇
  1976年   3303篇
  1975年   3781篇
  1974年   3950篇
  1973年   3895篇
  1972年   3425篇
  1971年   3185篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
923.
924.
925.
926.
Energy calculations have been carried out on high-symmetry cuboctahedral Ni-Al nanoalloy clusters, of varying composition, with the interatomic interactions modelled by the Gupta many-body potential. Relaxations of cuboctahedral fragments cut from the bulk lattice of Ni3Al, with 13-561 atoms, were undertaken, as were relaxations of high symmetry clusters with 55 and 147 atoms. The lowest energy isomers were found to be dominated by three factors: the tendency toward mixing due to the favourable energy of mixing, ΔmixE; the size difference between nickel and aluminium; and the higher cohesive and surface energy of nickel compared to aluminium. The latter two factors favour Al-segregation to the surface. The most stable Ni:Al composition approaches 3:1 for larger clusters.  相似文献   
927.
928.
929.
The total population affected with non-Hodgkin's lymphoma and treated by means of radiotherapy or combined radio-chemotherapy between 1960 and 1985 at the Medical Academy Dresden was analysed as to prognosis. 247 patients were classified according to the previous German scheme, 79 were subdivided on the basis of the recommendations laid down in the Kiel classification. The remission rates and survival curves achieved will stand out the comparison with international literature (remission rates of the low malignancy group amounted to 85.3 p.c. and those of the high malignancy group to 80.0 p.c.; the 5-years survival rates of the low malignancy group amounted to 61.9 p.c. and those of the high malignancy group to 41.7 p.c.). The influence of histology, clinical stage and involvement of organs is discussed on the basis of our results and informations obtained in literature. Our analysis confirms the high importance which must be attached to a common radiologic-internal outpatient-department for co-ordinating the diagnostic and therapeutical programme.  相似文献   
930.
Antioxidant protein 2 (AOP2), a member of the newly defined family of thiol-specific antioxidant proteins, has been shown to remove H(2)O(2) and protect proteins and DNA from oxidative stress. Here we report that LEDGF is one of the regulatory factors for the AOP2 gene. We found that LEDGF bound to the heat shock element and to stress-related elements in the AOP2 promoter. It trans-activated expression of AOP2-CAT in COS-7 cells and lens epithelial cells overexpressing LEDGF. Mutations in the heat shock element and stress-related elements of the AOP2 promoter reduced LEDGF-dependent trans-activation. Lens epithelial cells showed a higher level of AOP2 mRNA in the presence of LEDGF. Cells overexpressing LEDGF exhibited a higher level of AOP2 protein, the level of which was directly related to the increase in cellular protection. Thus, LEDGF, by activating the AOP2 gene, protected and enhanced the survival of cells under oxidative stress.  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