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   72807篇
  免费   2478篇
  国内免费   270篇
化学   45316篇
晶体学   447篇
力学   1502篇
综合类   1篇
数学   12177篇
物理学   16112篇
  2022年   481篇
  2021年   700篇
  2020年   1053篇
  2019年   906篇
  2018年   839篇
  2017年   799篇
  2016年   1904篇
  2015年   1612篇
  2014年   1882篇
  2013年   3730篇
  2012年   3676篇
  2011年   4330篇
  2010年   2281篇
  2009年   1955篇
  2008年   4075篇
  2007年   3857篇
  2006年   3660篇
  2005年   3348篇
  2004年   2772篇
  2003年   2318篇
  2002年   2214篇
  2001年   1272篇
  2000年   1167篇
  1999年   889篇
  1998年   820篇
  1997年   851篇
  1996年   976篇
  1995年   795篇
  1994年   863篇
  1993年   917篇
  1992年   795篇
  1991年   646篇
  1990年   655篇
  1989年   539篇
  1988年   563篇
  1987年   577篇
  1986年   492篇
  1985年   855篇
  1984年   810篇
  1983年   721篇
  1982年   801篇
  1981年   744篇
  1980年   709篇
  1979年   633篇
  1978年   659篇
  1977年   626篇
  1976年   576篇
  1975年   541篇
  1974年   488篇
  1973年   464篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar...  相似文献   
32.
33.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution.  相似文献   
34.
35.
36.
37.
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De  相似文献   
38.
39.
ISO Guide 35 deals with RM stability issues and scrutinizes the evaluation of stability testing results under the assumption that either there is no trend at all (a rather rare situation), or any observed deterministic change is insignificant and thus can be neglected. However, market demands for reliable reference materials are obviously not limited to stable or at least seemingly stable materials. In many analytical applications, analytes and measurands under consideration are known, or at least suspected, to be unstable on time scales that may vary widely from measurand to measurand. The Federal Institute for Materials Research and Testing (BAM) has developed (and successfully uses) an integrated approach in its certification practice. The approach is based on an initial stability study and subsequent post-certification monitoring. Data evaluation is model-based and takes advantage of all information collected in the stability testing scheme(s). It thus allows one to deal with any kind of instability observed, to assess limiting time intervals at any stress condition in the range tested, to estimate a final expiry date for materials with detected instabilities or the maximum admissible re-testing interval for seemingly stable materials, and to assess maximum admissible stress loads during delivery of the material to the customer. The article describes (and exemplifies) typical study layout, the model selection, and the integrated data assessment.  相似文献   
40.
Abstract Under a suitable ellipticity condition, we show that classical SG-pseudodifferential operators of nonnegative order possess complex powers. We show that the powers are again classical and derive an explicit formula for all homogeneous components. Keywords: Complex power, Weighted symbols, Noncompact manifolds  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