全文获取类型
收费全文 | 13390篇 |
免费 | 946篇 |
国内免费 | 1059篇 |
专业分类
化学 | 2258篇 |
晶体学 | 29篇 |
力学 | 851篇 |
综合类 | 215篇 |
数学 | 9816篇 |
物理学 | 2226篇 |
出版年
2024年 | 18篇 |
2023年 | 141篇 |
2022年 | 161篇 |
2021年 | 243篇 |
2020年 | 313篇 |
2019年 | 317篇 |
2018年 | 319篇 |
2017年 | 345篇 |
2016年 | 329篇 |
2015年 | 280篇 |
2014年 | 550篇 |
2013年 | 1000篇 |
2012年 | 542篇 |
2011年 | 708篇 |
2010年 | 556篇 |
2009年 | 825篇 |
2008年 | 828篇 |
2007年 | 849篇 |
2006年 | 778篇 |
2005年 | 648篇 |
2004年 | 587篇 |
2003年 | 637篇 |
2002年 | 549篇 |
2001年 | 483篇 |
2000年 | 411篇 |
1999年 | 415篇 |
1998年 | 405篇 |
1997年 | 329篇 |
1996年 | 239篇 |
1995年 | 190篇 |
1994年 | 167篇 |
1993年 | 145篇 |
1992年 | 122篇 |
1991年 | 103篇 |
1990年 | 74篇 |
1989年 | 84篇 |
1988年 | 70篇 |
1987年 | 54篇 |
1986年 | 49篇 |
1985年 | 70篇 |
1984年 | 78篇 |
1983年 | 47篇 |
1982年 | 67篇 |
1981年 | 45篇 |
1980年 | 53篇 |
1979年 | 58篇 |
1978年 | 31篇 |
1977年 | 28篇 |
1976年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 61 毫秒
101.
Marion SCHEEPERS 《数学学报(英文版)》2007,23(7):1153-1162
We show that a set of real numbers is a Sierpinski set if, and only if, it satisfies a selection property similar to the familiar Menger property. 相似文献
102.
Covering numbers of precompact symmetric convex subsets of Hilbert spaces are investigated. Lower bounds are derived for sets containing orthogonal subsets with norms of their elements converging to zero sufficiently slowly. When these sets are convex hulls of sets with power-type covering numbers, the bounds are tight. The arguments exploit properties of generalized Hadamard matrices. The results are illustrated by examples from machine learning, neurocomputing, and nonlinear approximation. 相似文献
103.
We construct a new family of cyclic difference sets with parameters ((3
d
– 1)/2, (3
d – 1 – 1)/2, (3
d – 2 – 1)/2) for each odd d. The difference sets are constructed with certain maps that form Jacobi sums. These new difference sets are similar to Maschietti's hyperoval difference sets, of the Segre type, in characteristic two. We conclude by calculating the 3-ranks of the new difference sets. 相似文献
104.
105.
Juan Nieto 《Journal of Mathematical Analysis and Applications》2004,291(2):716-726
In this paper we study the stability of the following nonlinear drift-diffusion system modeling large population dynamics ∂tρ+div(ρU−ε∇ρ)=0, divU=±ρ, with respect to the viscosity parameter ε. The sign in the second equation depends on the attractive or repulsive character of the field U. A proof of the compactness and convergence properties in the vanishing viscosity regime is given. The lack of compactness in the attractive case is caused by the blow-up of the solution which depends on the mass and on the space dimension. Our stability result is connected, depending of the character of the potentials, with models in semiconductor theory or in biological population. 相似文献
106.
We propose a new approach towards proving that the fixed point property for ordered sets is preserved by products. This approach uses a characterization of fixed points in products via isotone relations. First explorations of classes of isotone relations are presented. These first explorations give us hope that this approach could lead to advances on the Product Problem. 相似文献
107.
本文结合代数教学中的实际情况.针对代数教学过程中出现的问题。提出了在代数教学过程中改进教学方法的几条措施. 相似文献
108.
Inna Bumagina 《Geometriae Dedicata》2004,106(1):211-230
A group is said to be Hopfian if every surjective endomorphism of the group is injective. We show that finitely generated subgroups of torsion-free hyperbolic groups are Hopfian. Our proof generalizes a theorem of Sela (Topology
35 (2) 1999, 301–321). 相似文献
109.
Dmitry Dolgopyat 《Transactions of the American Mathematical Society》2004,356(4):1637-1689
We consider a large class of partially hyperbolic systems containing, among others, affine maps, frame flows on negatively curved manifolds, and mostly contracting diffeomorphisms. If the rate of mixing is sufficiently high, the system satisfies many classical limit theorems of probability theory.
110.
Employing positive-definiteness arguments we analyse Boson field states, which combine classical and quantum mechanical features (signal and noise), in a constructive manner. Mathematically, they constitute Bauer simplexes within the convex, weak-*-compact state space of the C*-Weyl algebra, defined by a presymplectic test function space (smooth one-Boson wave functions) and are affinely homeomorphic to a state space of a classical field. The regular elements are expressed in terms of weak distributions (probability premeasures) on the dual test function space. The Bauer simplex arising from the bare vacuum is shown to generalize the quantum optical photon field states with positive P-functions. 相似文献