全文获取类型
收费全文 | 19032篇 |
免费 | 607篇 |
国内免费 | 708篇 |
专业分类
化学 | 4073篇 |
晶体学 | 859篇 |
力学 | 448篇 |
综合类 | 69篇 |
数学 | 12372篇 |
物理学 | 2526篇 |
出版年
2023年 | 76篇 |
2022年 | 164篇 |
2021年 | 163篇 |
2020年 | 160篇 |
2019年 | 433篇 |
2018年 | 484篇 |
2017年 | 337篇 |
2016年 | 341篇 |
2015年 | 322篇 |
2014年 | 622篇 |
2013年 | 1033篇 |
2012年 | 615篇 |
2011年 | 1248篇 |
2010年 | 1299篇 |
2009年 | 1451篇 |
2008年 | 1435篇 |
2007年 | 1455篇 |
2006年 | 1168篇 |
2005年 | 913篇 |
2004年 | 846篇 |
2003年 | 660篇 |
2002年 | 565篇 |
2001年 | 418篇 |
2000年 | 371篇 |
1999年 | 359篇 |
1998年 | 320篇 |
1997年 | 284篇 |
1996年 | 367篇 |
1995年 | 326篇 |
1994年 | 317篇 |
1993年 | 294篇 |
1992年 | 229篇 |
1991年 | 131篇 |
1990年 | 119篇 |
1989年 | 121篇 |
1988年 | 81篇 |
1987年 | 88篇 |
1986年 | 97篇 |
1985年 | 131篇 |
1984年 | 81篇 |
1983年 | 54篇 |
1982年 | 76篇 |
1981年 | 63篇 |
1980年 | 41篇 |
1979年 | 24篇 |
1978年 | 37篇 |
1977年 | 45篇 |
1976年 | 36篇 |
1974年 | 17篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
21.
F. Balibrea 《Topology and its Applications》2006,153(12):2092-2095
Recently, Forti, Paganoni and Smítal constructed an example of a triangular map of the unite square, F(x,y)=(f(x),g(x,y)), possessing periodic orbits of all periods and such that no infinite ω-limit set of F contains a periodic point. In this note we show that the above quoted map F has a homoclinic orbit. As a consequence, we answer in the negative the problem presented by A.N. Sharkovsky in the eighties whether, for a triangular map of the square, existence of a homoclinic orbit implies the existence of an infinite ω-limit set containing a periodic point. It is well known that, for a continuous map of the interval, the answer is positive. 相似文献
22.
Kunyu Guo 《Journal of Functional Analysis》2004,213(2):380-411
This paper mainly concerns defect operators and defect functions of Hardy submodules, Bergman submodules over the unit ball, and Hardy submodules over the polydisk. The defect operator (function) carries key information about operator theory (function theory) and structure of analytic submodules. The problem when a submodule has finite defect is attacked for both Hardy submodules and Bergman submodules. Our interest will be in submodules generated by polynomials. The reason for choosing such submodules is to understand the interaction of operator theory, function theory and algebraic geometry. 相似文献
23.
We show that there are close relations between extremal problems in dual Brunn-Minkowski theory and isotropic-type properties for some Borel measures on the sphere. The methods we use allow us to obtain similar results in the context of Firey-Brunn-Minkowski theory. We also study reverse inequalities for dual mixed volumes which are related with classical positions, such as ?-position or isotropic position. 相似文献
24.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
25.
Andrei K. Lerner 《Archiv der Mathematik》2005,85(6):538-543
We show that the Hardy-Littlewood maximal operator and a class of Calderón-Zygmund singular integrals satisfy the strong type
modular inequality in variable Lp spaces if and only if the variable exponent p(x) ∼ const.
Received: 15 September 2004 相似文献
26.
Nonlocal vertex algebras generated by formal vertex operators 总被引:2,自引:0,他引:2
Haisheng Li 《Selecta Mathematica, New Series》2005,11(3-4):349-397
This is the first paper in a series to study vertex algebra-like objects arising from infinite-dimensional quantum groups
(quantum affine algebras and Yangians). In this paper we lay the foundations for this study. For any vector space W, we study what we call quasi compatible subsets of Hom (W,W((x))) and we prove that any maximal quasi compatible subspace has a natural nonlocal (namely noncommutative) vertex algebra
structure with W as a natural faithful quasi module in a certain sense, and that any quasi compatible subset generates a nonlocal vertex algebra
with W as a quasi module. In particular, taking W to be a highest weight module for a quantum affine algebra we obtain a nonlocal vertex algebra with W as a quasi module. We also formulate and study a notion of quantum vertex algebra and we give general constructions of nonlocal
vertex algebras, quantum vertex algebras and their modules. 相似文献
27.
28.
We investigate heteroclinic orbits between equilibria and rotating waves for scalar semilinear parabolic reaction-advection-diffusion equations with periodic boundary conditions. Using zero number properties of the solutions and the phase shift equivariance of the equation, we establish a necessary and sufficient condition for the existence of a heteroclinic connection between any pair of hyperbolic equilibria or rotating waves. 相似文献
29.
30.
Dmitri I. Panyushev 《Advances in Mathematics》2004,186(2):307-316
We study Abelian ideals of a Borel subalgebra consisting of long roots. It is shown that methods of Cellini and Papi can be extended to this situation. A uniform expression for the number of long Abelian ideals is given. We also show that there is a one-to-one correspondence between the long Abelian ideals and B-stable commutative subalgebras in the little adjoint representation of the Langlands dual Lie algebra. 相似文献