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   1466884篇
  免费   25975篇
  国内免费   7883篇
化学   745791篇
晶体学   21124篇
力学   77681篇
综合类   115篇
数学   252062篇
物理学   403969篇
  2021年   13667篇
  2020年   16027篇
  2019年   16156篇
  2018年   17266篇
  2017年   15932篇
  2016年   30061篇
  2015年   21324篇
  2014年   30633篇
  2013年   74666篇
  2012年   44771篇
  2011年   47726篇
  2010年   41936篇
  2009年   43233篇
  2008年   45070篇
  2007年   42548篇
  2006年   42972篇
  2005年   38569篇
  2004年   37233篇
  2003年   33688篇
  2002年   33531篇
  2001年   33806篇
  2000年   28037篇
  1999年   24077篇
  1998年   21644篇
  1997年   21439篇
  1996年   21424篇
  1995年   19387篇
  1994年   18877篇
  1993年   18463篇
  1992年   19036篇
  1991年   19187篇
  1990年   18406篇
  1989年   18401篇
  1988年   18064篇
  1987年   17928篇
  1986年   16869篇
  1985年   23206篇
  1984年   24246篇
  1983年   20323篇
  1982年   21846篇
  1981年   21076篇
  1980年   20398篇
  1979年   20876篇
  1978年   21984篇
  1977年   21658篇
  1976年   21388篇
  1975年   20145篇
  1974年   19817篇
  1973年   20237篇
  1972年   14717篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Three types of transparency of a semiconductor superlattice, namely, self-induced, induced, and selective transparency, were studied. The conditions of their existence and the causes of their destruction were revealed. It was shown that the state of self-induced transparency, which is unstable in a harmonic field, can be stable in a biharmonic field.  相似文献   
994.
995.
For either of the two reflection spectra of cadmium difluoride that are known from experiments, a complete set of the fundamental optical functions is calculated in the energy range 4–45 eV with the Kramers-Kronig relationships. The basic features of the optical spectra are established, and a hypothesis for their origin is suggested based on the known theoretical results for the band structure.  相似文献   
996.
Technical Physics - Analytical models for the magnetization vector field B m in a uniaxial ferromagnetic film are studied. Some of them are found to closely approximate B m even if the quality...  相似文献   
997.
Magnetoplasma waves and inhomogeneous (complex) waves in an infinite semiconductor superlattice in a magnetic field are studied, and dispersion curves are obtained. It is shown analytically and numerically that, in periodic structures, among inhomogeneous waves, there are many complex waves for which the imaginary part of the wave vector is greater than the real part. The effect of dissipation in a medium on the dispersion curves of magnetoplasma waves is examined. The dependence of the minimum phase velocity on the collision frequency and the magnetic field strength is studied.  相似文献   
998.
An analytical expression for the concentration profile of a low-soluble diffusant in a sample is derived for a high-capacity diffusion source. The model is checked by determining the diffusion coefficient of yttrium in beryllium.  相似文献   
999.
The cross section of absorption of electromagnetic radiation by a fine spherical metal particle is calculated. The influence of the skin effect on the absorption cross-section is estimated for an arbitrary ratio between the free path and size of the particle. The results of this work are compared with those obtained earlier in the framework of classical electrodynamics. It is shown that taking into account the kinetic effects modifies essentially the known data for the skin effect in a spherical particle.  相似文献   
1000.
A theory of a planar disk-shaped RF plasma source under anomalous skin effect conditions is developed. In the absence of an external magnetic field, such conditions are satisfied for transverse electromagnetic waves with phase velocities below the electron thermal velocity, and, in the presence of this field, they are satisfied for electron cyclotron waves with frequencies corresponding to the resonant absorption line. For each of these cases, the RF field power deposited in a plasma with given parameters is determined and the equivalent plasma resistance is calculated.  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