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   493篇
  免费   4篇
化学   409篇
晶体学   5篇
力学   7篇
数学   8篇
物理学   68篇
  2021年   2篇
  2018年   2篇
  2016年   4篇
  2015年   8篇
  2014年   13篇
  2013年   30篇
  2012年   21篇
  2011年   30篇
  2010年   22篇
  2009年   14篇
  2008年   24篇
  2007年   24篇
  2006年   29篇
  2005年   24篇
  2004年   27篇
  2003年   15篇
  2002年   22篇
  2001年   4篇
  2000年   7篇
  1999年   6篇
  1998年   4篇
  1997年   7篇
  1995年   3篇
  1994年   2篇
  1993年   5篇
  1992年   6篇
  1991年   10篇
  1990年   5篇
  1989年   4篇
  1988年   8篇
  1987年   8篇
  1986年   6篇
  1985年   12篇
  1984年   10篇
  1983年   2篇
  1982年   10篇
  1981年   12篇
  1980年   10篇
  1979年   7篇
  1978年   5篇
  1977年   6篇
  1976年   3篇
  1975年   7篇
  1974年   5篇
  1973年   2篇
  1972年   2篇
  1967年   1篇
  1966年   1篇
  1963年   1篇
  1942年   1篇
排序方式: 共有497条查询结果,搜索用时 15 毫秒
71.
The dielectric-field correction on i.r. band shape in the liquid has been studied by using the Lorentz internal field. The deformation of the band shape is inappreciable for a weak absorption band that becomes measurable only at a sample thickness larger than 10μ. The shapes of the strong singlet and doublet bands of hexafluorobenzene at 1530 cm?1 and near 1000 cm?1, respectively, and also of the doublet band of carbon tetrachloride near 790 cm?1 have been measured in dilute solutions and compared with those for the pure liquid.  相似文献   
72.
The moment analyses were performed on the far-infrared absorption bands of CH3CN, CHCl3, CH2Cl2, and their deuterated compounds dissolved in nonpolar solvents. The values of torque acting on the solute molecules were estimated from the fourth moments. The band profiles were simulated by means of the continued-fraction representation of the time correlation function by Mori, using the moment values obtained. The third order long-time approximation of the correlation function yields essentially good simulations. The effective rotation angles of molecules between collisions were estimated from the first positive-to-negative turning points of the memory functions. The solvent effects on the torque and the rotation angle were consistent with each other.  相似文献   
73.
Structural elucidation including the absolute configuration was carried out on the trihydroxy C18 -fatty acids isolated from rice plant, Sasanishiki suffered from rice blast disease.  相似文献   
74.
75.
76.
77.
Phenol derivatives, which are one of the most important classes of aromatic compounds in organic chemistry, were synthesized by ruthenium-catalyzed ring-closing olefin metathesis (RCM) of 1,4,7-trien-3-ones with versatile substitution patterns. The RCM reaction for producing phenol derivatives was also successful with 1,5,7-trien-3-one as another precursor. Most of the phenols prepared here could not be obtained easily by conventional methods.  相似文献   
78.
We investigate a possible dynamical mechanism for spontaneous supersymmetrybreaking in N = 1 supergravity theories in 1 + 1 space-time dimensions. It will be shown that supersymmetry is never broken at the tree level, but it can be broken for a certain class of models by quantum effects due to trace anomalies of the energy-momentum tensor and the supercurrent.  相似文献   
79.
We consider the explicit connection between linear representations of supersymmetry and the non-linear realizations associated with the generic effective lagrangians of the Volkov-Akulov type. We specify and illustrate a systematic approach for deriving the appropriate phenomenological lagrangian by transforming a pedagogical linear model, in which supersymmetry is broken at the tree level, into its corresponding non-linear lagrangian, in close analogy to the linear σ model of pion dynamics. We discuss the significance and some properties of such phenomenological lagrangians.  相似文献   
80.
Trans-tetrahydrofuran-3-carbaldehydes are prepared by ruthenium-catalyzed isomerization of 4,7-dihydro-1,3-dioxepines and subsequent Lewis acid-catalyzed 1,3-alkyl migration.  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