全文获取类型
收费全文 | 6560篇 |
免费 | 553篇 |
国内免费 | 416篇 |
专业分类
化学 | 308篇 |
晶体学 | 4篇 |
力学 | 189篇 |
综合类 | 168篇 |
数学 | 6401篇 |
物理学 | 459篇 |
出版年
2024年 | 16篇 |
2023年 | 108篇 |
2022年 | 168篇 |
2021年 | 171篇 |
2020年 | 236篇 |
2019年 | 255篇 |
2018年 | 242篇 |
2017年 | 255篇 |
2016年 | 188篇 |
2015年 | 117篇 |
2014年 | 262篇 |
2013年 | 537篇 |
2012年 | 268篇 |
2011年 | 373篇 |
2010年 | 381篇 |
2009年 | 538篇 |
2008年 | 467篇 |
2007年 | 363篇 |
2006年 | 405篇 |
2005年 | 288篇 |
2004年 | 249篇 |
2003年 | 229篇 |
2002年 | 211篇 |
2001年 | 194篇 |
2000年 | 171篇 |
1999年 | 160篇 |
1998年 | 140篇 |
1997年 | 99篇 |
1996年 | 66篇 |
1995年 | 71篇 |
1994年 | 55篇 |
1993年 | 41篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有7529条查询结果,搜索用时 343 毫秒
41.
In this note we show how 1-factors in the middle two layers of the discrete cube can be used to construct 2-factors in the
Odd graph (the Kneser graph of (k − 1)-sets from a (2k − 1)-set). In particular, we use the lexical matchings of Kierstead and Trotter, and the modular matchings of Duffus, Kierstead
and Snevily, to give explicit constructions of two different 2-factorisations of the Odd graph.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
42.
Yao Ping HOU 《数学学报(英文版)》2005,21(4):955-960
A signed graph is a graph with a sign attached to each edge. This paper extends some fundamental concepts of the Laplacian matrices from graphs to signed graphs. In particular, the relationships between the least Laplacian eigenvalue and the unbalancedness of a signed graph are investigated. 相似文献
43.
本文得到了广义区间空间中几个参数型非空交定理,并用此结果证明了一些新型极大极小定理,截口定理,重合定理,以及变分不等式解的存在性定理。本文中的结果包含(1,3,5-12,14-16)中相应结果。 相似文献
44.
Yoshikazu Takada 《Annals of the Institute of Statistical Mathematics》1998,50(2):325-335
This paper gives a condition which implies the nonexistence of parametric statistical procedures with bounded risk or error performance characteristics. Many examples for which such a condition is satisfied are considered. 相似文献
45.
For given a graph H, a graphic sequence π = (d
1, d
2,..., d
n) is said to be potentially H-graphic if there is a realization of π containing H as a subgraph. In this paper, we characterize the potentially (K
5 − e)-positive graphic sequences and give two simple necessary and sufficient conditions for a positive graphic sequence π to
be potentially K
5-graphic, where K
r is a complete graph on r vertices and K
r-e is a graph obtained from K
r by deleting one edge. Moreover, we also give a simple necessary and sufficient condition for a positive graphic sequence
π to be potentially K
6-graphic.
Project supported by National Natural Science Foundation of China (No. 10401010). 相似文献
46.
In a graph, a cluster is a set of vertices, and two clusters are said to be non-intersecting if they are disjoint or one of them is contained in the other. A clustered graph C consists of a graph G and a set of non-intersecting clusters. In this paper, we assume that C has a compound planar drawing and each cluster induces a biconnected subgraph. Then we show that such a clustered graph admits a drawing in the plane such that (i) edges are drawn as straight-line segments with no edge crossing and (ii) the boundary of the biconnected subgraph induced by each cluster is a convex polygon. 相似文献
47.
属性区间识别理论模型研究及其应用 总被引:15,自引:3,他引:12
根据程乾生教授创立的属性识别理论模型[1] ,提出了属性测度区间的概念 ,建立了属性区间识别理论模型 ,并在自然科学学术期刊质量评价中进行了应用 . 相似文献
48.
Dirichlet boundary value problems for perturbed second-order differential equations on a half line are investigated in this paper. The methods mainly depend on the calculus of variations to the classical functionals. Sufficient conditions are obtained for the existence of the solutions. 相似文献
49.
We prove that, for any given vertex ν* in a series-parallel graph G, its edge set can be partitioned into κ = min{κ′(G) + 1, δ(G)} subsets such that each subset covers all the vertices of G possibly except for ν*, where δ(G) is the minimum degree of G and κ′(G) is the edge-connectivity of G. In addition, we show that the results in this paper are best possible and a polynomial time algorithm can be obtained for
actually finding such a partition by our proof. 相似文献
50.
Xuechao Li 《Graphs and Combinatorics》2006,22(4):503-513
In this paper, we give new lower bounds for the size of Δ-critical graphs with Δ=8,9 which improve the partial results of
Luo [6] and Y. Zhao [12]. 相似文献