全文获取类型
收费全文 | 19592篇 |
免费 | 818篇 |
国内免费 | 970篇 |
专业分类
化学 | 5704篇 |
晶体学 | 871篇 |
力学 | 720篇 |
综合类 | 83篇 |
数学 | 10418篇 |
物理学 | 3584篇 |
出版年
2024年 | 11篇 |
2023年 | 102篇 |
2022年 | 213篇 |
2021年 | 217篇 |
2020年 | 213篇 |
2019年 | 465篇 |
2018年 | 479篇 |
2017年 | 392篇 |
2016年 | 419篇 |
2015年 | 378篇 |
2014年 | 684篇 |
2013年 | 1120篇 |
2012年 | 632篇 |
2011年 | 1286篇 |
2010年 | 1304篇 |
2009年 | 1457篇 |
2008年 | 1461篇 |
2007年 | 1445篇 |
2006年 | 1203篇 |
2005年 | 968篇 |
2004年 | 896篇 |
2003年 | 709篇 |
2002年 | 616篇 |
2001年 | 454篇 |
2000年 | 401篇 |
1999年 | 386篇 |
1998年 | 329篇 |
1997年 | 319篇 |
1996年 | 382篇 |
1995年 | 322篇 |
1994年 | 327篇 |
1993年 | 286篇 |
1992年 | 215篇 |
1991年 | 147篇 |
1990年 | 121篇 |
1989年 | 120篇 |
1988年 | 83篇 |
1987年 | 97篇 |
1986年 | 102篇 |
1985年 | 129篇 |
1984年 | 77篇 |
1983年 | 57篇 |
1982年 | 79篇 |
1981年 | 70篇 |
1980年 | 38篇 |
1979年 | 24篇 |
1978年 | 33篇 |
1977年 | 44篇 |
1976年 | 32篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 656 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.
23.
24.
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
25.
A sample of 1233 events is used to study the general characteristics of {}^{16}O-Em interactions at 4.5 A GeV/c. Multiplicity and angular distributions of slow particles and correlations among them are discussed. The present data are compared with the corresponding results from the interactions of other projectiles at the same energy and also the same projectile at different energies. The results indicate that black particle production is independent of the energy and mass of the projectile, but for grey particles it is dependent on the mass of projectile. 相似文献
26.
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
27.
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
28.
29.
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
30.