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   572946篇
  免费   4793篇
  国内免费   1519篇
化学   290140篇
晶体学   8393篇
力学   28688篇
综合类   24篇
数学   71805篇
物理学   180208篇
  2021年   5360篇
  2020年   5784篇
  2019年   6515篇
  2018年   8809篇
  2017年   8914篇
  2016年   12258篇
  2015年   6652篇
  2014年   11175篇
  2013年   25335篇
  2012年   20073篇
  2011年   24044篇
  2010年   18032篇
  2009年   17971篇
  2008年   22636篇
  2007年   22356篇
  2006年   20383篇
  2005年   18180篇
  2004年   16872篇
  2003年   15236篇
  2002年   15031篇
  2001年   16940篇
  2000年   12998篇
  1999年   9955篇
  1998年   8417篇
  1997年   8299篇
  1996年   7597篇
  1995年   6879篇
  1994年   6791篇
  1993年   6515篇
  1992年   7139篇
  1991年   7604篇
  1990年   7243篇
  1989年   7065篇
  1988年   6896篇
  1987年   6762篇
  1986年   6391篇
  1985年   8117篇
  1984年   8413篇
  1983年   6992篇
  1982年   7247篇
  1981年   6744篇
  1980年   6407篇
  1979年   7001篇
  1978年   7259篇
  1977年   7169篇
  1976年   7040篇
  1975年   6699篇
  1974年   6548篇
  1973年   6794篇
  1972年   4906篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
861.
862.
Institute of Bioorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 6, pp. 157–183, November–December, 1992.  相似文献   
863.
Y. Lansac  F. Fried  P. Maï  ssa 《Liquid crystals》1995,18(6):829-837
We describe the dynamics of phase separation and transition processes, in binary mesomorphic mixtures with the help of a system of two coupled partial derivative equations. We emphasize, both analytically and numerically, that, depending on the regions of the phase diagram, the dynamical behaviour may result either from a two step process (first the phase transition, then the phase separation) or from a process showing salient features of the Cahn-Hilliard spinodal decomposition (bicontinuous periodic networks in the transient stages). The dynamics of evolution of the domain patterns are illustrated with the help of numerical simulations in which homeotropic and planar anchorages are visualized.  相似文献   
864.
865.
We survey results concerning the representations of lattices as lattices of congruences and as lattices of equational theories. Recent results and open problems will be mentioned.To László Fuchs on the occasion of his 70th birthday  相似文献   
866.
867.
Light transmission of nematic liquid crystals dispersed in a polymeric matrix is investigated. The paper gives a theoretical analysis of light transmission by the liquid crystal-polymer and liquid crystaldye-polymer systems based on determination of the total cross section of extinction. The mathematical model is considered in the anomalous diffraction approximation. The theoretical calculations are in good agreement with experimental data obtained for films based on cyanodiphenyl dispersed into a polyvinyl acetate matrix.Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 118–122, November–December, 1993.Translated by L. Chernomorskaya  相似文献   
868.
A gas-discharge gold-vapor laser on self-terminating transitions with operating wavelength λ=312.2 nm has been used to develop a highly efficient system for image transfer. An optical scheme and all its parameters have been chosen optimal for image quality. It has been found both theoretically and experimentally that the best results on micron-structure image transfer are obtained with 2–5-times image reduction. Various types of masks have been used. A 1-µm structure has been resolved due to the choice of optimal exposure time of 10 ms under a period of pulse repetition (0.6 – 0.8) ms; in this case, the minimal fringe dimension was ≈2 µm with an image dimension of 2 mm for a laser tube 1.8 cm in diameter.  相似文献   
869.
A procedure for calculating the efficiency at which electrons are captured into axial channeling with a realistic axis potential is discussed. That region in the space of the electron's total transverse energy E and angular momentum L (integrals of motion) which corresponds to stable bound states of the electron with an atomic row is found. The temperature dependence of the capture coefficient is analyzed. As the crystal temperature is increased, the capture coefficient decreases, to a particularly noticeable extent for beams making a small angle with the crystallographic axis and for crystals having a high atomic number z.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 69–74, May, 1988.  相似文献   
870.
On the basis of numerical calculations and experimental studies we analyze the possibilities of measuring the electrophysical parameters of indium phosphide by means of infrared reflection spectra at wavelengths ranging from 5 to 200 m. We demonstrate that contactless nondestructive measurements of the electron density in the range 1016–1020 cm–3 can be made with a relative error not exceeding 15%, and of mobility with a relative error not exceeding 25%. A nomogram method is presented for rapid conversion of data from infrared reflection spectra into the parameters being measured.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 22–27, January, 1988.  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