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   344388篇
  免费   1806篇
  国内免费   424篇
化学   160811篇
晶体学   5284篇
力学   19194篇
综合类   3篇
数学   47787篇
物理学   113539篇
  2021年   3472篇
  2020年   3788篇
  2019年   4621篇
  2018年   6811篇
  2017年   7027篇
  2016年   8837篇
  2015年   4062篇
  2014年   7662篇
  2013年   14069篇
  2012年   11759篇
  2011年   13629篇
  2010年   11306篇
  2009年   11480篇
  2008年   13110篇
  2007年   12808篇
  2006年   11599篇
  2005年   10004篇
  2004年   9632篇
  2003年   8984篇
  2002年   9204篇
  2001年   9037篇
  2000年   7070篇
  1999年   5295篇
  1998年   5013篇
  1997年   4797篇
  1996年   4309篇
  1995年   3824篇
  1994年   3881篇
  1993年   3885篇
  1992年   3950篇
  1991年   4394篇
  1990年   4312篇
  1989年   4354篇
  1988年   4059篇
  1987年   4072篇
  1986年   3803篇
  1985年   4435篇
  1984年   4751篇
  1983年   4051篇
  1982年   4273篇
  1981年   3902篇
  1980年   3628篇
  1979年   4128篇
  1978年   4316篇
  1977年   4501篇
  1976年   4469篇
  1975年   4211篇
  1974年   4076篇
  1973年   4238篇
  1972年   3546篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Journal of Nanoparticle Research - It was shown that the thermoelastic martensite transformation B2 ? B19 inside nanoparticles surrounded by amorphous matrix in Ni–Ti–Cu alloys as...  相似文献   
82.
The article develops the principles of optimal control theory for probability distributions on the configuration space of a controlled dynamical system. Necessary conditions of optimality are derived in the form of the Pontryagin principle for various classes of problems. Analytical representations in the space of distributions and observables are considered. Special modes are examined. The relationship between distribution control theory and nonlocal optimization problems is demonstrated.  相似文献   
83.
The nonprimary subgroups of the symmetric group S 9 are investigated. Embedding properties of these subgroups are listed in a table. Properties such as abnormality, pronormality, paranormality, weak normality, etc. were checked with the help of a computer. Algorithms and codes of the first author were used for this purpose. The research leans upon the technique of Burnside marks, as well as upon pertinent information on the table of marks of S 9 from the computer algebra package GAP. The subgroups were investigated up to conjugacy; the total number of conjugacy classes of nonprimary subgroups of S 9 is 432. Some subgroups were additionally checked by other programs based on the double coset method. Bibliography: 24 titles.  相似文献   
84.
The thermal expansion coefficients and the thermal conductivity of Bridgman-grown crystals of CuGa1−x InxTe2 solid solutions are investigated. It is found that the thermal expansion coefficient varies with x linearly, while the thermal conductivity is minimal when x=0.5. The Debye temperature and the rms dynamic atomic displacements are calculated from experimental data. It is shown that the Debye temperature decreases and the rms displacements in the crystal lattice sharply increase as the In content in the solid solutions grows.  相似文献   
85.
86.
87.
In the present paper, the notion of norm series with respect to the norm residue symbol is generalized to high-dimensional local fields. Necessary and sufficient conditions for the existence of norm series are obtained. Bibliography: 12 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 60–83.  相似文献   
88.
The results of optical study and quantum-chemical simulation of a conjugated organic system, 2-cyclooctylamino-5-nitropyridine (COANP)-fullerene, performed to determine its potential for application as a limiter of visible and near-IR laser radiation and as a material for diffraction elements in systems for reversible recording of optical information, are presented. Complexation between a COANP molecule and fullerene is considered as one of the main mechanisms responsible for the corresponding properties of this system. For the first time, nonlinear optical characteristics of COANP-C60 and COANP-C70 systems are comparatively studied and the intermolecular interaction between a COANP molecule and fullerene is analyzed on the quantum-chemical level.  相似文献   
89.
    
  相似文献   
90.
We investigate Banach spaces possessing (or not possessing) the approximation properties AP s, 0 < s ≤ 1, in connection with the following known question in the geometric theory of operators: under which conditions on Banach spaces X and Y and on positive numbers r and p does the p-nuclearity of the second adjoint of a continuous operator T from X to Y imply the p-nuclearity of T? Actually, we give necessary and sufficient conditions under which this question is answered affirmatively. In addition, the corresponding counterexamples are obtained in the maximally strong form. For instance, it is shown (and this statement is a significant strengthening of the previous results of that sort) that there exists a pair of separable Banach spaces Z and W such that the spaces Z ** and W have Schauder bases, while for every p, 1 ≤ p < 2, there is a non-p-nuclear operator from W to Z with a p-nuclear second adjoint. Earlier, in similar examples, the corresponding spaces did not possess even the Grothendieck approximation property. The technique developed in this paper does not allow us to treat the case p > 2. That case will be studied in a forthcoming paper of the author. Bibliography: 11 titles.  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