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   15622篇
  免费   716篇
  国内免费   144篇
化学   10099篇
晶体学   61篇
力学   326篇
综合类   1篇
数学   2943篇
物理学   3052篇
  2023年   135篇
  2022年   119篇
  2021年   351篇
  2020年   425篇
  2019年   502篇
  2018年   386篇
  2017年   294篇
  2016年   599篇
  2015年   565篇
  2014年   553篇
  2013年   917篇
  2012年   1084篇
  2011年   1292篇
  2010年   686篇
  2009年   566篇
  2008年   920篇
  2007年   849篇
  2006年   847篇
  2005年   783篇
  2004年   613篇
  2003年   476篇
  2002年   452篇
  2001年   251篇
  2000年   184篇
  1999年   186篇
  1998年   166篇
  1997年   170篇
  1996年   177篇
  1995年   154篇
  1994年   120篇
  1993年   109篇
  1992年   82篇
  1991年   73篇
  1990年   67篇
  1989年   45篇
  1988年   62篇
  1987年   59篇
  1986年   60篇
  1985年   78篇
  1984年   64篇
  1983年   44篇
  1982年   70篇
  1981年   59篇
  1980年   47篇
  1979年   54篇
  1978年   58篇
  1977年   45篇
  1976年   53篇
  1975年   36篇
  1974年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This paper contains new representations of the 3D elasticity and thermoelasticity problems, expressed in terms of regular quaternion functions, which in 3D and 4D have properties analogous to those of complex analytical functions in 2D. The known and some new results, described in the paper, are used to formulate boundary 3D problems, related to the theory. The formulae obtained are very similar to those given by Muskhelishvili for 2D boundary problems. The obtained representations can be used for development of a 3D boundary element method in numerical analysis.  相似文献   
82.
It has been shown by the19F NMR method that the relative polarities of nitrogenelement bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and PPh3Au derivatives increase in the order N-H19F NMR. It has been found that these reactions occur by a bimolecular associative mechanism and that the N-H bond is substantially less reactive than the N-Hg and N-Au bonds, which have identical reactivities within the limits of sensitivity of the method used.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1574–1580, August, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 93-03-5528).  相似文献   
83.
The intensity of surface enhanced Raman scattering from benzoic acid derivatives on mildly roughened, thermally evaporated Ag films shows a remarkably strong dependence on metal grain size. Large grained (slowly deposited) films give a superior response, by up to a factor of 10, to small grained (quickly deposited) films, with films of intermediate grain size yielding intermediate results. The optical field amplification underlying the enhancement mechanism is due to the excitation of surface plasmon polaritons (SPPs). Since surface roughness characteristics, as determined by STM, remain relatively constant as a function of deposition rate, it is argued that the contrast in Raman scattering is due to differences in elastic grain boundary scattering of SPPs (leading to different degrees of internal SPP damping), rather than differences in the interaction of SPPs with surface inhomogeneities.  相似文献   
84.
The goal of this work is to describe the irreducible representations of the quantum Heisenberg algebra and the unitary irreducible representation of one of its real forms. The solution of this problem is obtained through the investigation of theleft spectrum of the quantum Heisenberg algebra using the result about spectra of generic algebras of skew differential operators (cf. [R]).  相似文献   
85.
Toric cubes     
A toric cube is a subset of the standard cube defined by binomial inequalities. These basic semialgebraic sets are precisely the images of standard cubes under monomial maps. We study toric cubes from the perspective of topological combinatorics. Explicit decompositions as CW-complexes are constructed. Their open cells are interiors of toric cubes and their boundaries are subcomplexes. The motivating example of a toric cube is the edge-product space in phylogenetics, and our work generalizes results known for that space.  相似文献   
86.
The problem of optimal prediction in the stochastic linear regression model with infinitely many parameters is considered. We suggest a prediction method that outperforms asymptotically the ordinary least squares predictor. Moreover, if the random errors are Gaussian, the method is asymptotically minimax over ellipsoids in ?2. The method is based on a regularized least squares estimator with weights of the Pinsker filter. We also consider the case of dynamic linear regression, which is important in the context of transfer function modeling.  相似文献   
87.
88.
89.
90.
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