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   585929篇
  免费   19817篇
  国内免费   1402篇
化学   330513篇
晶体学   7765篇
力学   28389篇
综合类   17篇
数学   72704篇
物理学   167760篇
  2023年   5199篇
  2021年   7633篇
  2020年   10163篇
  2019年   8565篇
  2018年   10818篇
  2017年   9239篇
  2016年   17206篇
  2015年   11804篇
  2014年   15557篇
  2013年   29028篇
  2012年   21927篇
  2011年   23397篇
  2010年   20088篇
  2009年   19820篇
  2008年   22177篇
  2007年   21785篇
  2006年   19236篇
  2005年   17215篇
  2004年   15959篇
  2003年   14371篇
  2002年   14208篇
  2001年   15051篇
  2000年   11672篇
  1999年   8958篇
  1998年   7762篇
  1997年   7680篇
  1996年   7220篇
  1995年   6606篇
  1994年   6567篇
  1993年   6458篇
  1992年   6689篇
  1991年   7132篇
  1990年   6774篇
  1989年   6697篇
  1988年   6592篇
  1987年   6380篇
  1986年   6074篇
  1985年   7671篇
  1984年   7995篇
  1983年   6747篇
  1982年   7069篇
  1981年   6591篇
  1980年   6319篇
  1979年   6817篇
  1978年   7054篇
  1977年   7051篇
  1976年   7059篇
  1975年   6828篇
  1974年   6687篇
  1973年   6804篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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   
992.
993.
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   
994.
995.
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   
996.
A method is proposed for determining the technological residual stresses in glass shells of revolution based on the solution of inverse problems of shell theory with proper stresses and the use of experimental data obtained by the photoelastic method. Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 35, 1992, pp. 100–105.  相似文献   
997.
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   
998.
An analytic solution of a class of boundary-value problems of mathematical physics describing the transport of a mixture in the atmosphere is considered. To solve these problems we apply the substitution method and the Fourier method. The solution of a boundary problem describing the process of contamination of the atmosphere by various substances is presented in the form of a series. The result obtained is useful for the solution of problems concerning the protection of the atmosphere.Translated fromVychislitel'naya i Prikladnaya Matematika, No. 69, pp. 87–90, 1989.  相似文献   
999.
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   
1000.
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