全文获取类型
收费全文 | 33881篇 |
免费 | 1280篇 |
国内免费 | 1198篇 |
专业分类
化学 | 9003篇 |
晶体学 | 1055篇 |
力学 | 600篇 |
综合类 | 159篇 |
数学 | 16930篇 |
物理学 | 5476篇 |
无线电 | 3136篇 |
出版年
2023年 | 138篇 |
2022年 | 294篇 |
2021年 | 341篇 |
2020年 | 416篇 |
2019年 | 661篇 |
2018年 | 688篇 |
2017年 | 588篇 |
2016年 | 678篇 |
2015年 | 609篇 |
2014年 | 1130篇 |
2013年 | 2109篇 |
2012年 | 1034篇 |
2011年 | 2348篇 |
2010年 | 2008篇 |
2009年 | 2157篇 |
2008年 | 2157篇 |
2007年 | 2199篇 |
2006年 | 1815篇 |
2005年 | 1624篇 |
2004年 | 1607篇 |
2003年 | 1361篇 |
2002年 | 1230篇 |
2001年 | 873篇 |
2000年 | 826篇 |
1999年 | 714篇 |
1998年 | 662篇 |
1997年 | 545篇 |
1996年 | 622篇 |
1995年 | 553篇 |
1994年 | 560篇 |
1993年 | 428篇 |
1992年 | 408篇 |
1991年 | 267篇 |
1990年 | 253篇 |
1989年 | 251篇 |
1988年 | 170篇 |
1987年 | 205篇 |
1986年 | 150篇 |
1985年 | 225篇 |
1984年 | 165篇 |
1983年 | 83篇 |
1982年 | 132篇 |
1981年 | 166篇 |
1980年 | 159篇 |
1979年 | 130篇 |
1978年 | 161篇 |
1977年 | 144篇 |
1976年 | 128篇 |
1974年 | 57篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
281.
Claire Cates Haulk John Drew Charles R. Johnson J. Hunter Tart 《Linear and Multilinear Algebra》1997,43(1):35-51
For a given n-by-n matrix A, we consider the set of matrices which commute with A and all of whose principal submatrices commute with the corresponding principal submatrices of A. The properties of this set are examined, with particular attention to its dimension. 相似文献
282.
Zbigniew Lonc 《Order》1994,11(2):149-158
We show that in an ordered setP of width 3 there always exists a fibre (i.e., a subset intersecting each maximal nontrivial antichain) of size at most 11/18|P|. This improves previously known results.Research supported by Polish KBN Grant 2 2037 92 03. 相似文献
283.
Scott McCullough 《Integral Equations and Operator Theory》1992,15(1):43-71
Kernels over the unit disk for which a version of Carathéodory interpolation is true are characterized in a simple computationally verifiable manner. 相似文献
284.
We show that it is a NP-complete problem to decide whether a finite poset arises as the (Birkhoff) dual of the Frattini sublattice of some finite distributive lattice.This work was supported in part by Swiss NSF grant 20-32644.91. 相似文献
285.
Erik Woldt 《Journal of Physics and Chemistry of Solids》2002,63(4):699-704
The paper investigates whether a change from a homogeneous to an inhomogeneous dislocation distribution, assumed to be caused by a slight additional deformation, can lead to an increase of the recrystallization temperature of a deformed metal. In this case, the higher temperature would indicate a more stable deformation structure despite the increase of stored energy. The recrystallization temperature is related to the growth rate. Hence, the steady state velocity of a recrystallization front moving either parallel or vertically to the stripes of a simplified two-dimensional heterogeneous dislocation distribution of parallel sections of higher and lower dislocation densities is calculated. The results show that if a front growths through the high and low density sections in series an overall slower rate despite higher mean dislocation density is, indeed, possible. However, growing in the parallel arrangement always leads to a higher growth rate compared with the homogeneous case of slightly less stored energy. Since in a real structure the faster growth is likely to succeed, the recrystallization temperature observed will be lowered with additional deformation in accordance with experimental experience. 相似文献
286.
Motivated by the work of Crapo and Rota [6] on the lifting of a projective complex, we introduce a class of invariant operations associated to integral-weighted graphs, which we call graphical operations. Such operations generalize the sixth harmonic of a quadranguler set on a projective line. We determine the expansion of the graphical operations in terms of multi-linear bracket polynomials in a Grassmann-Cayley algebra. Reducibility and compositions of such invariant operations are also investigated with a number of examples.Supported by Courant Instructorship, New York University. 相似文献
287.
Given an integer n ≥ 2, let λ(n) := (log n)/(log γ(n)), where γ(n) = Π
p|n p, stand for the index of composition of n, with λ(1) = 1. We study the distribution function of (λ(n) – 1) log n as n runs through particular sets of integers, such as the shifted primes, the values of a given irreducible cubic polynomial
and the shifted powerful numbers.
Research supported in part by a grant from NSERC.
Research supported by the Applied Number Theory Research Group of the Hungarian Academy of Science and by a grant from OTKA.
Professor M.V. Subbarao passed away on February 15, 2006.
Received: 3 March 2006 Revised: 28 October 2006 相似文献
288.
《Linear and Multilinear Algebra》2007,55(6):521-533
For each k≥ 0, those nonsingular matrices that transform the set of totally nonzero vectors with k sign variations into (respectively, onto) itself are studied. Necessary and sufficient conditions are provided. The cases k=0,1,2,n-3,n-2,n-1 are completely characterized. 相似文献
289.
Piotr W. Nowak 《Journal of Functional Analysis》2007,243(1):323-344
We introduce a quasi-isometry invariant related to Property A and explore its connections to various other invariants of finitely generated groups. This allows to establish a direct relation between asymptotic dimension on one hand and isoperimetry and random walks on the other. We apply these results to reprove sharp estimates on isoperimetric profiles of some groups and to answer some questions in dimension theory. 相似文献
290.
R.J. Gardner 《Advances in Mathematics》2007,216(1):358-386
This paper develops a significant extension of E. Lutwak's dual Brunn-Minkowski theory, originally applicable only to star-shaped sets, to the class of bounded Borel sets. The focus is on expressions and inequalities involving chord-power integrals, random simplex integrals, and dual affine quermassintegrals. New inequalities obtained include those of isoperimetric and Brunn-Minkowski type. A new generalization of the well-known Busemann intersection inequality is also proved. Particular attention is given to precise equality conditions, which require results stating that a bounded Borel set, almost all of whose sections of a fixed dimension are essentially convex, is itself essentially convex. 相似文献