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   1381342篇
  免费   25867篇
  国内免费   7756篇
化学   685156篇
晶体学   20976篇
力学   76194篇
综合类   108篇
数学   247717篇
物理学   384814篇
  2021年   13540篇
  2020年   15983篇
  2019年   16088篇
  2018年   15722篇
  2017年   14414篇
  2016年   29273篇
  2015年   21259篇
  2014年   30617篇
  2013年   74776篇
  2012年   39856篇
  2011年   39374篇
  2010年   39781篇
  2009年   41940篇
  2008年   38108篇
  2007年   34772篇
  2006年   36803篇
  2005年   32153篇
  2004年   31813篇
  2003年   29602篇
  2002年   29940篇
  2001年   28264篇
  2000年   24772篇
  1999年   22474篇
  1998年   21069篇
  1997年   21095篇
  1996年   21180篇
  1995年   19211篇
  1994年   18696篇
  1993年   18254篇
  1992年   18099篇
  1991年   18446篇
  1990年   17561篇
  1989年   17659篇
  1988年   17207篇
  1987年   17222篇
  1986年   16066篇
  1985年   22546篇
  1984年   23827篇
  1983年   19991篇
  1982年   21701篇
  1981年   20946篇
  1980年   20295篇
  1979年   20441篇
  1978年   21779篇
  1977年   21348篇
  1976年   21072篇
  1975年   19748篇
  1974年   19406篇
  1973年   19860篇
  1972年   14339篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
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   
992.
The motion of the front of crystallization and the growth of a film at the surface of a plate are analyzed in the case of a laminar and in the case of a turbulent flow mode. Conditions are determined under which there occurs a transition from a matt inhomogeneous structure to a transparent homogeneous structure of ice. It is shown that, for a film to be steadily preserved at the plate surface, the film thickness must be larger than a critical equilibrium-thickness value h b.c, in which case a transparent homogeneous structure of ice is formed. Otherwise, the film at the plate surface is unstable and disappears in the course of time. The icing of aircrafts is the most important application of the results obtained in this study.  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