全文获取类型
收费全文 | 183篇 |
免费 | 14篇 |
国内免费 | 17篇 |
专业分类
化学 | 1篇 |
晶体学 | 1篇 |
力学 | 18篇 |
综合类 | 3篇 |
数学 | 166篇 |
物理学 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 27篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 24篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有214条查询结果,搜索用时 0 毫秒
81.
左半正规纯正半群是幂等元集形成左半正规带的纯正半群.本文讨论了具有逆断面的左半正规纯正半群上的一些性质;给出该类半群的一个构造定理。 相似文献
82.
Let K, L ⊂ ℝn be two convex bodies with non–empty interiors and with boundaries ∂K, ∂L, and let χ denote the Euler characteristic as defined in singular homology theory. We prove two translative integral formulas involving boundaries of convex bodies. It is shown that the integrals of the functions t ↦ χ(∂K ∩ (∂L + t)) and t ↦ χ(∂K ∩ (L + t)), t ∈ ℝn, with respect to an n–dimensional Haar measure of ℝn can be expressed in terms of certain mixed volumes of K and L. In the particular case where K and L are outer parallel bodies of convex bodies at distance r > 0, the result will be deduced from a recent (local) translative integral formula for sets with positive reach. The general case follows from this and from the following (global) topological result. Let Kr, Lr denote the outer parallel bodies of K, L at distance r ≥ 0. Establishing a conjecture of Firey (1978), we show that the homotopy type of ∂Kr ∩ ∂Lr and ∂Kr ∩ Lr, respectively, is independent of r ≥ 0 if K° ∩ L° ≠ ∅︁ and if ∂K and ∂L intersect almost transversally.As an immediate consequence of our translative integral formulas, we obtain a proof for two kinematic formulas which have also been conjectured by Firey . 相似文献
83.
S. R. Fenley 《Commentarii Mathematici Helvetici》1998,73(2):259-297
In this article we study the topology of Anosov flows in 3-manifolds. Specifically we consider the lifts to the universal
cover of the stable and unstable foliations and analyze the leaf spaces of these foliations. We completely determine the structure
of the non Hausdorff points in these leaf spaces. There are many consequences: (1) when the leaf spaces are non Hausdorff,
there are closed orbits in the manifold which are freely homotopic, (2) suspension Anosov flows are, up to topological conjugacy,
the only Anosov flows without free homotopies between closed orbits, (3) when there are infinitely many stable leaves (in
the universal cover) which are non separated from each other, then we produce a torus in the manifold which is transverse
to the Anosov flow and therefore is incompressible, (4) we produce non Hausdorff examples in hyperbolic manifolds and derive
important properties of the limit sets of the stable/unstable leaves in the universal cover.
Received: March 13, 1997 相似文献
84.
85.
Jørgen Bang‐Jensen Matthias Kriesell Alessandro Maddaloni Sven Simonsen 《Journal of Graph Theory》2016,83(4):406-420
The dicycle transversal number of a digraph D is the minimum size of a dicycle transversal of D, that is a set of vertices of D, whose removal from D makes it acyclic. An arc a of a digraph D with at least one cycle is a transversal arc if a is in every directed cycle of D (making acyclic). In [3] and [4], we completely characterized the complexity of following problem: Given a digraph D, decide if there is a dicycle B in D and a cycle C in its underlying undirected graph such that . It turns out that the problem is polynomially solvable for digraphs with a constantly bounded number of transversal vertices (including cases where ). In the remaining case (allowing arbitrarily many transversal vertices) the problem is NP‐complete. In this article, we classify the complexity of the arc‐analog of this problem, where we ask for a dicycle B and a cycle C that are arc‐disjoint, but not necessarily vertex‐disjoint. We prove that the problem is polynomially solvable for strong digraphs and for digraphs with a constantly bounded number of transversal arcs (but possibly an unbounded number of transversal vertices). In the remaining case (allowing arbitrarily many transversal arcs) the problem is NP‐complete. 相似文献
86.
87.
In this paper, we study the differentiable structure of the ω-subset of Sp(2n), which is formed by all matrices in Sp(2n) possessing ω as an eigenvalue, for ω on the unit circle in the complex plane. Based on this result the ω -index theory parametrized
by all ω on the unit circle for arbitrary symplectic paths is defined. 相似文献
88.
Limin Wang 《Southeast Asian Bulletin of Mathematics》2001,25(2):335-344
We characterize E-solid semigroups with inverse transversals and some special such semigroups in terms of congruences. Some properties of inverse congruences over completely simple semigroups are obtained.1991 MR Subject Classification: 20M10This work was supported by the Natural Science Foundation of Guangdong, China. 相似文献
89.
如果2个n阶不完全拉丁方重叠后正好产生r个不同的有序对,则称它们是,r-正交的,记作r—IMOLS(n,u),其中u为缺少的子拉丁方的阶数.进一步,如果第2个拉丁方是第1个拉丁方的转置,则称它们是,r-自正交的,记作r—ISOLS(n,u).本文给出当u∈{1,2,3,4}时,r—ISOLS(4m+u,u)的存在性. 相似文献
90.
利用格林*-关系刻画R和L并给出与它们相关的一些性质.利用R和L,得到恰当断面是拟理想的几个等价条件.最后,用两个结构构件R和L给出具有拟理想恰当断面的富足半群的一个结构定理.它比陈建飞在2000年给出的要简单. 相似文献