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   202449篇
  免费   1960篇
  国内免费   502篇
化学   110690篇
晶体学   3650篇
力学   7997篇
综合类   11篇
数学   19196篇
物理学   63367篇
  2020年   1726篇
  2019年   1922篇
  2018年   2236篇
  2017年   2355篇
  2016年   3517篇
  2015年   2194篇
  2014年   3549篇
  2013年   9089篇
  2012年   6510篇
  2011年   8021篇
  2010年   5701篇
  2009年   5657篇
  2008年   7164篇
  2007年   7077篇
  2006年   6707篇
  2005年   6057篇
  2004年   5530篇
  2003年   5108篇
  2002年   4874篇
  2001年   6144篇
  2000年   4626篇
  1999年   3523篇
  1998年   2748篇
  1997年   2707篇
  1996年   2595篇
  1995年   2444篇
  1994年   2331篇
  1993年   2172篇
  1992年   2829篇
  1991年   2732篇
  1990年   2675篇
  1989年   2691篇
  1988年   2714篇
  1987年   2721篇
  1986年   2593篇
  1985年   3309篇
  1984年   3314篇
  1983年   2601篇
  1982年   2710篇
  1981年   2765篇
  1980年   2536篇
  1979年   2880篇
  1978年   2865篇
  1977年   2981篇
  1976年   2818篇
  1975年   2553篇
  1974年   2512篇
  1973年   2466篇
  1972年   1703篇
  1968年   1703篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
The problems of choosing the optimal mathematical model for a prescribed range of parameters of a pulsed action are discussed. A preliminary analysis performed by similarity and dimensional-analysis methods using interpolation equations of state of the matter shows that the complete system of equations of gasdynamics can be simplified by dropping individual terms which are not important in a given parameter range. The results of an analysis are presented in the form of nomograms, which also make it possible to identify the class of fast and energy-intensive gasdynamic processes more accurately than at an intuitive level. Zh. Tekh. Fiz. 68, 44–47 (May 1998)  相似文献   
182.
    
The solvent extraction of cobalt(II), nickel(II) and copper(II) using 2,4-pent-dione (Hacac) and 4-phenyl-2, 4-but-dione (Hbzac) is carried out by varying the reagent concentration and pH of the aqueous phase. Each of these metals is quantitatively separated (≈ 98%) from their binary mixtures with monovalent (Ag), divalent (Mn, Zn, Cd, Hg, Mg, Sn, Pb) and trivalent (Cr, Fe) metals. The extraction constants are calculated from the metal distribution data using linear regression analysis. The extracted species is MA2 in each case. A most significant result is separation of copper(II) from iron(III) which otherwise interferes when extracted from the acidic medium.  相似文献   
183.
The structure of the lattice of processes of a finite digraph with entries is investigated. Necessary and sufficient conditions for the isomorphism of a given lattice to the lattice of processes of a certain digraph are obtained. Bibliography: 5 titles. Translated by K. V. Shakhbazyan. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 202, 1992, pp. 135–153.  相似文献   
184.
185.
A method and computer program were developed for calculating the temperature of any part of a graphite furnace tube at any instant of time after onset of the heating cycle. Results for tubes of the Massman design show large differences in spatial temperature distributions during and at the end of the heating cycle when equilibrium is reached. When constant current is applied to contoured tubes, greater heating rates at the tube centres are obtained than with standard tubes.  相似文献   
186.
The ideas developed by Gell-Mann and Okubo in studying violation of unitary symmetry are used to describe violation of isototic invariance in strong interactions. The present consideration is performed for the example of the mass spectrum of the octet formed by baryons of spin-parity 1/2+: only for this family are the widths of its particles much less than the scale of the effects being investigated, their masses being known from experiments to a fairly high precision. The Gell-Mann-Okubo formula is generalized in such a way that relations both for the splitting between the isomultiplets of the octet and for the mass splitting within these isomultiplets follow from the new formula. Moreover, a relation between masses that describes their electromagnetic splitting and which coincides in form with the Coleman-Glashow relation also follows from this formula. The relations obtained for the masses of the baryons belonging to the octet in question are satisfied to a precision not poorer than 3%.  相似文献   
187.
We explore the phase diagram of the five-dimensional anisotropic Abelian Higgs model by Monte Carlo simulations. In particular, we study the transition between the confining phase and the four-dimensional layered Higgs phase. We find that, in a certain region of the lattice parameter space, this transition can be first order, and that each layer moves into the Higgs phase independently of the others (decoupling of layers). As the Higgs couplings vary, we find, using mean field techniques, that this transition may probably become second order. Received: 21 December 2001 / Published online: 12 April 2002  相似文献   
188.
A cooperative defect-deformation (DD) mechanism is developed for the nucleation of the quasi-monodisperse ensemble of nanoparticles in the low-temperature deposition of Ga atoms in the presence of laser radiation. A comparison with experiment is carried out, and a good agreement between the theoretical and experimental results has been obtained. In particular, in accordance with the DD model, it has been found that the arrangement of nanoparticles is characterized by a latent hexagonal order, and their shape is quasi-hexagonal. It has been shown that the characteristics of the deposited ensemble of nanoparticles can be controlled with the use of an anisotropic deformation.  相似文献   
189.
190.
Translated from Programmnoe Oborudovanie i Voprosy Prinyatiya Reshenii, pp. 152–184, 1989.  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