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   179788篇
  免费   776篇
  国内免费   262篇
化学   89718篇
晶体学   2635篇
力学   9379篇
综合类   7篇
数学   20958篇
物理学   58129篇
  2020年   1849篇
  2019年   2288篇
  2018年   3396篇
  2017年   3523篇
  2016年   4158篇
  2015年   1852篇
  2014年   3588篇
  2013年   7053篇
  2012年   5536篇
  2011年   6592篇
  2010年   5514篇
  2009年   5635篇
  2008年   6364篇
  2007年   6328篇
  2006年   5620篇
  2005年   4986篇
  2004年   4822篇
  2003年   4369篇
  2002年   4524篇
  2001年   4999篇
  2000年   3691篇
  1999年   2831篇
  1998年   2608篇
  1997年   2457篇
  1996年   2255篇
  1995年   2048篇
  1994年   2008篇
  1993年   2041篇
  1992年   2074篇
  1991年   2382篇
  1990年   2314篇
  1989年   2385篇
  1988年   2265篇
  1987年   2294篇
  1986年   2127篇
  1985年   2657篇
  1984年   2671篇
  1983年   2317篇
  1982年   2372篇
  1981年   2275篇
  1980年   2078篇
  1979年   2395篇
  1978年   2548篇
  1977年   2639篇
  1976年   2732篇
  1975年   2539篇
  1974年   2471篇
  1973年   2635篇
  1972年   2154篇
  1971年   1975篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Polymer films with a dispersed liquid crystal were prepared by photopolymerization of (meth)acrylic monomers. The electrooptical properties of these films were studied. The influence exerted by the composition of the monomer mixture, cross-linking agents, and chain-transfer agent on the liquid crystal drop size and on the transmission of the polymer-liquid crystal films was examined.  相似文献   
94.
The luminescence characteristics of hydrated Ln3+ ions and their complexes with some acidic ligands have been investigated. The possibility of determining the stability of the complexes of lanthanides in solutions from the intensity of luminescence bands is shown. The influence of the characteristic features of the f-electron shell of Ln3+ on the formation of the spectrochemical series is discussed.  相似文献   
95.
The aim of this work is to study the dynamic formation and dissociation of trions and excitons in double barrier resonant tunneling diodes. We propose a system of rate equations that takes into account the formation, dissociation and annihilation of these complexes inside the quantum well. From the solutions of the coupled equations, we are able to study the modulation of excitons and trions formation in the device as a function of the applied bias. The results of our model agree qualitatively with the experiments showing the viability of these rate equations system to study the dynamics of complex systems.  相似文献   
96.
97.
The rotational spectra of 34SO2F2 and S18O16OF2 have been measured in their ground vibrational state between 9 and 110 GHz. Accurate rotational constants have been derived. Various experimental structures including the average structure have been determined. The ab initio structure has been calculated at the CCSD(T) level of theory. The different structures are compared and the best equilibrium structure is the ab initio structure: re(SO)=1.401 (3) Å, re(SF)=1.532 (3) Å, ∠e(OSO)=124.91(20)°, ∠e(FSF)=95.53 (20)°.  相似文献   
98.
The method of nonlinear moments, when used to solve the Boltzmann equation, necessitates the calculation of collision integral matrix elements. The matrix elements are hard to calculate numerically, especially at large indices. The asymptotics of the matrix elements are constructed. In terms of the model of pseudopower particle interaction, a formula free of summation is derived. This makes it possible to find the asymptotic behavior of linear and nonlinear elements when two indices are large. For an arbitrary interaction cross section, asymptotic expansions of linear and nonlinear matrix elements in one index are obtained. For Maxwellian molecules, asymptotic formulas are derived for three large indices.  相似文献   
99.
The fine-structure parameters of a series of configurations of the first ion of indium and the gyromagnetic ratios in intermediate coupling are calculated by a semiempirical method in the single-configuration approximation.  相似文献   
100.
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