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   3001篇
  免费   80篇
  国内免费   22篇
化学   1926篇
晶体学   21篇
力学   59篇
数学   580篇
物理学   517篇
  2023年   15篇
  2022年   69篇
  2021年   72篇
  2020年   70篇
  2019年   81篇
  2018年   67篇
  2017年   58篇
  2016年   121篇
  2015年   107篇
  2014年   129篇
  2013年   224篇
  2012年   192篇
  2011年   204篇
  2010年   143篇
  2009年   147篇
  2008年   179篇
  2007年   172篇
  2006年   137篇
  2005年   115篇
  2004年   93篇
  2003年   70篇
  2002年   77篇
  2001年   31篇
  2000年   38篇
  1999年   27篇
  1998年   17篇
  1997年   21篇
  1996年   34篇
  1995年   26篇
  1994年   22篇
  1993年   18篇
  1992年   25篇
  1991年   12篇
  1990年   20篇
  1989年   12篇
  1988年   18篇
  1987年   12篇
  1986年   9篇
  1985年   14篇
  1984年   23篇
  1983年   14篇
  1982年   15篇
  1981年   12篇
  1980年   15篇
  1979年   10篇
  1978年   21篇
  1977年   20篇
  1976年   11篇
  1969年   6篇
  1968年   8篇
排序方式: 共有3103条查询结果,搜索用时 15 毫秒
981.
The notion of strongly n-convex functions with modulus c>0 is introduced and investigated. Relationships between such functions and n-convex functions in the sense of Popoviciu as well as generalized convex functions in the sense of Beckenbach are given. Characterizations by derivatives are presented. Some results on strongly Jensen n-convex functions are also given.  相似文献   
982.
We show how the Dixon?s system of first order equations of motion for the particle with inner dipole structure together with the side Mathisson constraint follows from rather general construction of the ‘Hamilton system’ developed by Weyssenhoff, Rund and Grässer to describe the phase space counterpart of the evolution under the ordinary Euler–Poisson differential equation of the parameter-invariant variational problem with second derivatives. One concrete expression of the ‘Hamilton function’ leads to the General Relativistic form of the fourth order equation of motion known to describe the quasi-classical ‘quiver’ particle in Special Relativity. The corresponding Lagrange function including velocity and acceleration coincides in the flat space of Special Relativity with the one considered by Bopp in an attempt to give an approximate variational formulation of the motion of self-radiating electron, when expressed in terms of geometric quantities.  相似文献   
983.
Titiš J  Boča R 《Inorganic chemistry》2011,50(22):11838-11845
The magnetostructural D correlation for hexacoordinated cobalt(II) complexes is outlined. The structural and magnetic properties of a series of mononuclear cobalt(II) complexes with the general formulas [Co(II)(L)(6)]X(2), [Co(II)(L)(2)X(2)], and [Co(II)(L)(2)(H(2)O)(2)(car)(2)] have been investigated where the coordination sphere is formed by nitrogen/oxygen-donor heterocycle (L), carboxylato (car), aqua, and chlorido ligands. The chromophores of these compounds involve {CoN(6)}, {CoO(6)}, {CoO(4)O'(2)}, {CoN(2)O(2)O'(2)}, and {CoN(2)O(2)Cl(2)}. All complexes were subjected to magnetochemical investigation down to 2 K (SQUID susceptibility and magnetization measurements). Most of the studied complexes show magnetic behavior typical for zero-field-splitting systems. The magnetism of the complex [Co(H(2)O)(6)](6-OHnic)(2) reflects the presence of the magnetic angular momentum in the ground-state crystal-field term. The obtained values of the magnetic anisotropy (D or δ) have been correlated with the structural distortion of the coordination polyhedron. This correlation can be understood with the help of crystal-field theory, where the magnetic anisotropy parameters are related to the splitting of the lowest crystal-field multiplets.  相似文献   
984.
The processes of coagulation and gelation of sols in zirconium oxychloride aqueous solutions and the properties of hydrated zirconium dioxide sols (pH, particles size, dynamic viscosity) depending on the aging conditions of partially neutralized zirconium oxychloride feedstock solution-zirconyl hydroxychloride used for the synthesis and molar ratio of initial reagents (Zr/NaOH, Zr/CH(3)COO(-)) were first studied in the paper. The concentration and temperature limits of hydrated zirconium dioxide sols stability were determined. The coagulation constant, gelation activation energy, and gelation thermal effect values were found.  相似文献   
985.
986.
987.
A new dicopper(I) complex is reported that can be incorporated into extended architectures through multitopic carboxylate linkers; reversible carboxylate templation under pH control led to the formation of [2+2] and [3+3] metallomacrocycles.  相似文献   
988.
989.
Mono‐, di‐ and trialkyl derivatives of 'sulfabenzamide' (N‐4‐aminophenylsulfonylbenzamide) have been prepared and their electron ionization (EI) mass spectra examined. It is found that the fragmentation of N‐alkylsulfabenzamides (alkyl = CH3 to n‐C5H11) proceeds via a very specific rearrangement process. The proposed mechanism involves an intermediate formation of distonic molecular ions, and the driving force for this process is the formation of stable N‐alkylphenylcyanide cations [R‐N+ ? CC6H5]. The findings are confirmed by exact mass measurements, tandem mass spectrometry (MS/MS) experiments and deuterium labeling. Published in 2011 by John Wiley & Sons, Ltd.  相似文献   
990.
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