全文获取类型
收费全文 | 21339篇 |
免费 | 504篇 |
国内免费 | 464篇 |
专业分类
化学 | 4099篇 |
晶体学 | 941篇 |
力学 | 396篇 |
综合类 | 47篇 |
数学 | 13028篇 |
物理学 | 3796篇 |
出版年
2023年 | 62篇 |
2022年 | 195篇 |
2021年 | 159篇 |
2020年 | 167篇 |
2019年 | 424篇 |
2018年 | 458篇 |
2017年 | 310篇 |
2016年 | 359篇 |
2015年 | 347篇 |
2014年 | 642篇 |
2013年 | 1392篇 |
2012年 | 562篇 |
2011年 | 1669篇 |
2010年 | 1450篇 |
2009年 | 1366篇 |
2008年 | 1467篇 |
2007年 | 1435篇 |
2006年 | 1090篇 |
2005年 | 939篇 |
2004年 | 843篇 |
2003年 | 650篇 |
2002年 | 661篇 |
2001年 | 465篇 |
2000年 | 443篇 |
1999年 | 417篇 |
1998年 | 420篇 |
1997年 | 317篇 |
1996年 | 356篇 |
1995年 | 356篇 |
1994年 | 341篇 |
1993年 | 255篇 |
1992年 | 255篇 |
1991年 | 177篇 |
1990年 | 183篇 |
1989年 | 173篇 |
1988年 | 115篇 |
1987年 | 129篇 |
1986年 | 92篇 |
1985年 | 162篇 |
1984年 | 115篇 |
1983年 | 73篇 |
1982年 | 93篇 |
1981年 | 123篇 |
1980年 | 107篇 |
1979年 | 64篇 |
1978年 | 110篇 |
1977年 | 93篇 |
1976年 | 95篇 |
1975年 | 39篇 |
1974年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Common fixed-point results are established for a new class of noncommuting selfmaps. We apply them to obtain several invariant approximation results which unify, extend, and complement well-known results. 相似文献
102.
Nicola Fusco Michele Gori Francesco Maggi 《NoDEA : Nonlinear Differential Equations and Applications》2006,13(4):425-433
An approximation theorem for families of weakly coercive convex functions by means of countably many smooth families of convex
functions is proved. As a consequence, the classical “three-fold” lower semicontinuity theorem for integral functionals of
the Calculus of Variations by James Serrin is unified in one single statement. 相似文献
103.
Our object of study is the asymptotic behavior of the sequence of polynomials orthogonal with respect to the discrete Sobolev
inner product <formula> \langle f, g \rangle = ∈t_{E} f(ξ) \overline{g(ξ)} ρ(ξ) |d ξ|+ f(Z) A g(Z)^H, </formula> where E is a rectifiable Jordan curve or arc in the complex plane
f(Z) = (f(z_1), \ldots, f^{(l_1)}(z_1) , \ldots , f(z_m) , \ldots ,f^{(l_m)}(z_m)),
A is an M \times M Hermitian matrix, M l
1
+ ⋅s + l
m
+ m , |d ξ| denotes the arc length measure, ρ is a nonnegative function on E , and z
i
∈Ω,
i=1,2,\ldots,m , where Ω is the exterior region to E .
July 23, 1999. Dates revised: September 11, 2000 and February 16, 2001. Date accepted: February 26, 2001. 相似文献
104.
105.
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
106.
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
107.
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
108.
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
109.
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
110.
《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