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   1427552篇
  免费   25949篇
  国内免费   7813篇
化学   717683篇
晶体学   21058篇
力学   77241篇
综合类   107篇
数学   250052篇
物理学   395173篇
  2021年   13610篇
  2020年   16006篇
  2019年   16133篇
  2018年   16720篇
  2017年   15365篇
  2016年   29783篇
  2015年   21320篇
  2014年   30661篇
  2013年   74729篇
  2012年   42448篇
  2011年   43984篇
  2010年   41013篇
  2009年   42788篇
  2008年   41958篇
  2007年   38982篇
  2006年   39889篇
  2005年   35415篇
  2004年   34585篇
  2003年   31662篇
  2002年   31720篇
  2001年   31550篇
  2000年   26644篇
  1999年   23411篇
  1998年   21385篇
  1997年   21251篇
  1996年   21291篇
  1995年   19304篇
  1994年   18791篇
  1993年   18372篇
  1992年   18672篇
  1991年   18892篇
  1990年   18098篇
  1989年   18140篇
  1988年   17734篇
  1987年   17667篇
  1986年   16582篇
  1985年   22963篇
  1984年   24043篇
  1983年   20151篇
  1982年   21770篇
  1981年   21008篇
  1980年   20322篇
  1979年   20671篇
  1978年   21870篇
  1977年   21487篇
  1976年   21195篇
  1975年   19902篇
  1974年   19561篇
  1973年   19979篇
  1972年   14471篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
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   
992.
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   
993.
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   
994.
The mass spectrum of a coupled state is analytically determined. The mechanism of production of a constituent mass of particles forming a coupled state is explained. The change of the coupled state and constituent particle component masses attendant to changes of the coupling constant is analyzed. The mass spectrum of a two-gluon glueball is determined with allowance for spin-orbital and spin-spin interactions.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 33–41, December, 2004.  相似文献   
995.
996.
A semiempirical model is proposed for the calculation of electrical, magnetic and thermal parameters of the plasma of a high-frequency induction discharge. The model is based on solving a system of two-dimensional Maxwell equations written for a cylindrical coordinate system.  相似文献   
997.
A method of teaching of one of the divisions of electrodynamics devoted to relativity theory is suggested. The presentation is based on the four-dimensional formalism, which allows a number of fundamental physical phenomena to be considered from a unified position. The content is in full conformity with the approved standard programs for students and postgraduates of radio physical and radio technical specialities of universities. The methods can be useful to the teachers, scientific workers, and engineers concerned with other directions and specialities.  相似文献   
998.
999.
A possibility of application of semiconductor lasers of the visible range as exciting sources for Raman spectroscopy is studied. An experimental set-up for measuring Raman spectra of polycrystalline dielectrics and broad-gap semiconductors excited by a semiconductor laser with a wavelength of 640 nm was created. The conditions under which the spectral width of the lasing line of a semiconductor laser was within 10-3 cm-1 in the continuous mode with a power of 10 mW are realized. The characteristics of various types of exciting sources used in Raman spectroscopy are compared. The results of studies of the characteristic Raman spectra excited with a semiconductor laser in polycrystalline sulfur are presented.  相似文献   
1000.
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