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   494686篇
  免费   5003篇
  国内免费   1446篇
化学   260116篇
晶体学   7563篇
力学   21773篇
综合类   12篇
数学   61459篇
物理学   150212篇
  2020年   4209篇
  2019年   4636篇
  2018年   6473篇
  2017年   6180篇
  2016年   9192篇
  2015年   5870篇
  2014年   8761篇
  2013年   21760篇
  2012年   16724篇
  2011年   19955篇
  2010年   14095篇
  2009年   13735篇
  2008年   18487篇
  2007年   18401篇
  2006年   17263篇
  2005年   15763篇
  2004年   14401篇
  2003年   12833篇
  2002年   12555篇
  2001年   13489篇
  2000年   10625篇
  1999年   8218篇
  1998年   7144篇
  1997年   6931篇
  1996年   6762篇
  1995年   6092篇
  1994年   6256篇
  1993年   6038篇
  1992年   6529篇
  1991年   6612篇
  1990年   6371篇
  1989年   6118篇
  1988年   6227篇
  1987年   5970篇
  1986年   5669篇
  1985年   7717篇
  1984年   8013篇
  1983年   6656篇
  1982年   6925篇
  1981年   6806篇
  1980年   6667篇
  1979年   6725篇
  1978年   7114篇
  1977年   6911篇
  1976年   7075篇
  1975年   6527篇
  1974年   6548篇
  1973年   6737篇
  1972年   4708篇
  1971年   3946篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993.  相似文献   
43.
Addition of functionalized zinc-copper reagents to the title complexes proceeds in a highly diastereoselective fashion to afford dienol complexes. The relative configurations of adducts 3d were determined by single X-ray diffraction analysis.  相似文献   
44.
Skarping  G.  Dalene  M.  Brunmark  P. 《Chromatographia》1994,39(9-10):619-623
Chromatographia - An LC-MS method is described for the determination of 4,4′-MDA (4,4′-methylene dianiline) in hydrolysed urine as a biomarker for exposure to 4,4′-MDI...  相似文献   
45.
Alumaa  P.  Pentšuk  J. 《Chromatographia》1994,38(9-10):566-570
Chromatographia - A theoretical model is used to predict retention times of divalent metal cations in single-column ion chromatography using one or more ligands in the eluent. Stability constants...  相似文献   
46.
Twelve series of linear oligomers of four different degrees of polymerization (xn = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH2OH functionality. The glass transition temperature Tg of all the series was measured and thus examined as a function of xn. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any xn by different positive or negative Tg deviations from the common asymptotic Tg value. The results are also discussed in terms of copolymer end effect and of relation between Tg and end copolymeric composition.  相似文献   
47.
Publication list     
The helium atom in its ground state, subject to strong magnetic fields, is treated using a variational method. Trial functions consisting of Gaussians with nonlinear parameters variationally optimized are used. The form of these functions is a generalized s-symmetry-state properly modified to admit spatial deformation along the direction on which the magnetic field is applied. © 1994 John Wiley & Sons, Inc.  相似文献   
48.
A set of exact conditions is compiled for the purpose of developing and testing approximations for the exchange-correlation energy as a functional of the electron density. Special emphasis is placed upon recently developed density-scaling relationships. Commonly used generalized gradient approximations are compared against several of these conditions. A direct tabular comparison of these functionals (not of calculated properties) with one another is also made. © 1994 John Wiley & Sons, Inc.  相似文献   
49.
50.
We present the results of an experimental investigation of a RF splitting of57Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field.  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