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   312654篇
  免费   3424篇
  国内免费   664篇
化学   168643篇
晶体学   4442篇
力学   13007篇
综合类   11篇
数学   37287篇
物理学   93352篇
  2020年   2723篇
  2019年   2822篇
  2018年   3761篇
  2017年   3724篇
  2016年   5792篇
  2015年   3779篇
  2014年   5498篇
  2013年   13336篇
  2012年   10196篇
  2011年   12403篇
  2010年   8505篇
  2009年   8056篇
  2008年   11630篇
  2007年   11702篇
  2006年   10890篇
  2005年   9819篇
  2004年   8846篇
  2003年   7972篇
  2002年   7803篇
  2001年   8081篇
  2000年   6356篇
  1999年   4914篇
  1998年   4320篇
  1997年   4262篇
  1996年   4164篇
  1995年   3819篇
  1994年   4020篇
  1993年   3796篇
  1992年   4168篇
  1991年   4044篇
  1990年   4000篇
  1989年   3788篇
  1988年   3895篇
  1987年   3797篇
  1986年   3582篇
  1985年   4854篇
  1984年   5073篇
  1983年   4271篇
  1982年   4451篇
  1981年   4366篇
  1980年   4309篇
  1979年   4246篇
  1978年   4598篇
  1977年   4485篇
  1976年   4547篇
  1975年   4188篇
  1974年   4187篇
  1973年   4354篇
  1972年   3012篇
  1971年   2531篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Some features of the kinetics of the hydrolysis of apple protopectin have been studied on the basis of an analysis of monosaccharide residues of the pectin substances and determinations of characteristic viscosity. It has been shown that the fine regulation of the physicochemical parameters of the hydrolysis of protopectin leads to the formation of pectin substances with different properties.  相似文献   
23.
24.
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   
25.
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   
26.
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   
27.
28.
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   
29.
The electrical conductivity of hydrosols of ultradispersed diamonds was studied. The electromembrane method for cleaning and concentrating of ultradispersed diamonds in hydrosols was considered. The influence exerted by the concentration of the dispersed phase on the electrical characteristics of the cleaning process was analyzed. A mathematical relation making it possible to evaluate the output characteristics of the process and to determine the geometrical characteristics of the apparatus was proposed.  相似文献   
30.
The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters.  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