全文获取类型
收费全文 | 2418篇 |
免费 | 159篇 |
国内免费 | 74篇 |
专业分类
化学 | 76篇 |
晶体学 | 1篇 |
力学 | 4篇 |
综合类 | 29篇 |
数学 | 2436篇 |
物理学 | 105篇 |
出版年
2024年 | 12篇 |
2023年 | 46篇 |
2022年 | 70篇 |
2021年 | 45篇 |
2020年 | 98篇 |
2019年 | 92篇 |
2018年 | 86篇 |
2017年 | 83篇 |
2016年 | 57篇 |
2015年 | 47篇 |
2014年 | 80篇 |
2013年 | 207篇 |
2012年 | 68篇 |
2011年 | 125篇 |
2010年 | 127篇 |
2009年 | 231篇 |
2008年 | 185篇 |
2007年 | 138篇 |
2006年 | 145篇 |
2005年 | 86篇 |
2004年 | 84篇 |
2003年 | 82篇 |
2002年 | 69篇 |
2001年 | 57篇 |
2000年 | 56篇 |
1999年 | 51篇 |
1998年 | 44篇 |
1997年 | 37篇 |
1996年 | 22篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有2651条查询结果,搜索用时 15 毫秒
941.
942.
P.S. Ranjini 《Applied mathematics and computation》2011,218(3):699-702
The aim of this paper is to investigate the Zagreb indices of the line graphs of the tadpole graphs, wheel graphs and ladder graphs using the subdivision concepts. 相似文献
943.
In this paper, we study suborbital graphs for congruence subgroup Γ0(n) of the modular group Γ to have hyperbolic paths of minimal lengths. It turns out that these graphs give rise to a special continued fraction which is a special case of very famous fraction coming out from Pringsheim’s theorem. 相似文献
944.
Márcia R. Cerioli Fabiano de S. Oliveira Jayme L. Szwarcfiter 《Discrete Applied Mathematics》2011,159(7):532-543
Given an interval graph G, the interval count problem is that of computing the minimum number IC(G) of interval lengths needed to represent G. Although the problem of deciding whether IC(G)=1 is equivalent to that of recognizing unit-interval graphs, which is a well-known problem having several efficient recognition approaches, very little is known about deciding efficiently whether IC(G)=k for fixed k≥2. We provide efficient computations of the interval count of generalizations of threshold graphs. 相似文献
945.
A new coloring theorem of Kneser graphs 总被引:1,自引:0,他引:1
Peng-An Chen 《Journal of Combinatorial Theory, Series A》2011,118(3):1062-1071
In 1997, Johnson, Holroyd and Stahl conjectured that the circular chromatic number of the Kneser graphs KG(n,k) is equal to the chromatic number of these graphs. This was proved by Simonyi and Tardos (2006) [13] and independently by Meunier (2005) [10], if χ(KG(n,k)) is even. In this paper, we propose an alternative version of Kneser's coloring theorem to confirm the Johnson-Holroyd-Stahl conjecture. 相似文献
946.
Strongly perfect graphs have been studied by several authors (e.g. Berge and Duchet (1984) [1], Ravindra (1984) [12] and Wang (2006) [14]). In a series of two papers, the current paper being the first one, we investigate a fractional relaxation of strong perfection. Motivated by a wireless networking problem, we consider claw-free graphs that are fractionally strongly perfect in the complement. We obtain a forbidden induced subgraph characterization and display graph-theoretic properties of such graphs. It turns out that the forbidden induced subgraphs that characterize claw-free graphs that are fractionally strongly perfect in the complement are precisely the cycle of length 6, all cycles of length at least 8, four particular graphs, and a collection of graphs that are constructed by taking two graphs, each a copy of one of three particular graphs, and joining them in a certain way by a path of arbitrary length. Wang (2006) [14] gave a characterization of strongly perfect claw-free graphs. As a corollary of the results in this paper, we obtain a characterization of claw-free graphs whose complements are strongly perfect. 相似文献
947.
Trapezoid graphs are the intersection family of trapezoids where every trapezoid has a pair of opposite sides lying on two parallel lines. These graphs have received considerable attention and lie strictly between permutation graphs (where the trapezoids are lines) and cocomparability graphs (the complement has a transitive orientation). The operation of “vertex splitting”, introduced in (Cheah and Corneil, 1996) [3], first augments a given graph G and then transforms the augmented graph by replacing each of the original graph’s vertices by a pair of new vertices. This “splitted graph” is a permutation graph with special properties if and only if G is a trapezoid graph. Recently vertex splitting has been used to show that the recognition problems for both tolerance and bounded tolerance graphs is NP-complete (Mertzios et al., 2010) [11]. Unfortunately, the vertex splitting trapezoid graph recognition algorithm presented in (Cheah and Corneil, 1996) [3] is not correct. In this paper, we present a new way of augmenting the given graph and using vertex splitting such that the resulting algorithm is simpler and faster than the one reported in (Cheah and Corneil, 1996) [3]. 相似文献
948.
949.
950.
We consider the structure of Kr‐free graphs with large minimum degree, and show that such graphs with minimum degree δ>(2r ? 5)n/(2r ? 3) are homomorphic to the join Kr ? 3∨H, where H is a triangle‐free graph. In particular this allows us to generalize results from triangle‐free graphs and show that Kr‐free graphs with such a minimum degree have chromatic number at most r +1. We also consider the minimum‐degree thresholds for related properties. Copyright © 2010 John Wiley & Sons, Ltd. 66:319‐331, 2011 相似文献