全文获取类型
收费全文 | 2398篇 |
免费 | 172篇 |
国内免费 | 229篇 |
专业分类
化学 | 184篇 |
晶体学 | 1篇 |
力学 | 51篇 |
综合类 | 86篇 |
数学 | 2175篇 |
物理学 | 302篇 |
出版年
2024年 | 3篇 |
2023年 | 30篇 |
2022年 | 58篇 |
2021年 | 42篇 |
2020年 | 59篇 |
2019年 | 74篇 |
2018年 | 66篇 |
2017年 | 80篇 |
2016年 | 73篇 |
2015年 | 54篇 |
2014年 | 82篇 |
2013年 | 186篇 |
2012年 | 89篇 |
2011年 | 101篇 |
2010年 | 122篇 |
2009年 | 135篇 |
2008年 | 178篇 |
2007年 | 159篇 |
2006年 | 145篇 |
2005年 | 126篇 |
2004年 | 108篇 |
2003年 | 120篇 |
2002年 | 103篇 |
2001年 | 97篇 |
2000年 | 94篇 |
1999年 | 70篇 |
1998年 | 69篇 |
1997年 | 48篇 |
1996年 | 46篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2799条查询结果,搜索用时 15 毫秒
1.
2.
3.
A Necessary and Sufficient Condition for the Existence of a Heterochromatic Spanning Tree in a Graph
Kazuhiro Suzuki 《Graphs and Combinatorics》2006,22(2):261-269
We prove the following theorem. An edge-colored (not necessary to be proper) connected graph G of order n has a heterochromatic spanning tree if and only if for any r colors (1≤r≤n−2), the removal of all the edges colored with these r colors from G results in a graph having at most r+1 components, where a heterochromatic spanning tree is a spanning tree whose edges have distinct colors. 相似文献
4.
Given a tree
with leaf set X, there are certain ways of arranging the elements of X in a circular order so that
can be embedded in the plane and ‘preserve’ this ordering. We investigate some new combinatorial properties of these ‘circular orderings.’ We then use these properties to establish two results concerning dissimilarity maps on X that are induced by edge-weighted trees with leaf set X. 相似文献
5.
Michael T. Jury David W. Kribs 《Proceedings of the American Mathematical Society》2005,133(1):213-222
Given a row contraction of operators on a Hilbert space and a family of projections on the space that stabilizes the operators, we show there is a unique minimal joint dilation to a row contraction of partial isometries that satisfy natural relations. For a fixed row contraction the set of all dilations forms a partially ordered set with a largest and smallest element. A key technical device in our analysis is a connection with directed graphs. We use a Wold decomposition for partial isometries to describe the models for these dilations, and we discuss how the basic properties of a dilation depend on the row contraction.
6.
7.
Mrio J. Edmundo 《Mathematical Logic Quarterly》2005,51(6):639-641
We show that if G is a definably compact, definably connected definable group defined in an arbitrary o‐minimal structure, then G is divisible. Furthermore, if G is defined in an o‐minimal expansion of a field, k ∈ ? and pk : G → G is the definable map given by pk (x ) = xk for all x ∈ G , then we have |(pk )–1(x )| ≥ kr for all x ∈ G , where r > 0 is the maximal dimension of abelian definable subgroups of G . (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
9.
10.
Searching in trees 总被引:1,自引:0,他引:1
Frank Recker 《Discrete Applied Mathematics》2004,140(1-3):169-183
In (Discrete Math. 17 (1977)181) Rivest introduced the search complexity of binary trees and proved that among all binary trees with a fixed search complexity the smallest ones are the so-called Fibonacci trees. This result is extended for q-trees. The structure of the smallest q-trees is again Fibonacci-like but more complicated than in the binary case. In addition an upper bound for the asymptotic growth of these trees is given. 相似文献