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   1410625篇
  免费   25962篇
  国内免费   7877篇
化学   707636篇
晶体学   20954篇
力学   76487篇
综合类   114篇
数学   249727篇
物理学   389546篇
  2021年   13645篇
  2020年   16048篇
  2019年   16226篇
  2018年   16023篇
  2017年   14671篇
  2016年   29557篇
  2015年   21328篇
  2014年   30699篇
  2013年   74768篇
  2012年   41958篇
  2011年   42307篇
  2010年   40306篇
  2009年   42124篇
  2008年   40746篇
  2007年   37407篇
  2006年   39549篇
  2005年   34399篇
  2004年   33980篇
  2003年   31254篇
  2002年   31540篇
  2001年   29909篇
  2000年   25697篇
  1999年   23041篇
  1998年   21329篇
  1997年   21217篇
  1996年   21319篇
  1995年   19312篇
  1994年   18802篇
  1993年   18327篇
  1992年   18356篇
  1991年   18624篇
  1990年   17791篇
  1989年   17868篇
  1988年   17480篇
  1987年   17398篇
  1986年   16294篇
  1985年   22745篇
  1984年   23980篇
  1983年   20162篇
  1982年   21784篇
  1981年   20995篇
  1980年   20332篇
  1979年   20558篇
  1978年   21831篇
  1977年   21424篇
  1976年   21132篇
  1975年   19830篇
  1974年   19482篇
  1973年   19949篇
  1972年   14426篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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   
994.
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   
995.
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   
996.
997.
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   
998.
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   
999.
1000.
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   
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