全文获取类型
收费全文 | 2073篇 |
免费 | 115篇 |
国内免费 | 378篇 |
专业分类
化学 | 129篇 |
晶体学 | 2篇 |
力学 | 50篇 |
综合类 | 25篇 |
数学 | 2083篇 |
物理学 | 277篇 |
出版年
2024年 | 5篇 |
2023年 | 35篇 |
2022年 | 25篇 |
2021年 | 34篇 |
2020年 | 42篇 |
2019年 | 65篇 |
2018年 | 54篇 |
2017年 | 51篇 |
2016年 | 62篇 |
2015年 | 40篇 |
2014年 | 79篇 |
2013年 | 234篇 |
2012年 | 58篇 |
2011年 | 89篇 |
2010年 | 67篇 |
2009年 | 122篇 |
2008年 | 163篇 |
2007年 | 128篇 |
2006年 | 149篇 |
2005年 | 143篇 |
2004年 | 107篇 |
2003年 | 127篇 |
2002年 | 114篇 |
2001年 | 94篇 |
2000年 | 82篇 |
1999年 | 79篇 |
1998年 | 75篇 |
1997年 | 45篇 |
1996年 | 51篇 |
1995年 | 20篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1974年 | 3篇 |
排序方式: 共有2566条查询结果,搜索用时 15 毫秒
251.
A *-ring R is called a nil *-clean ring if every element of R is a sum of a projection and a nilpotent.Nil *-clean rings are the *-version of nil-clean rings introduced by Diesl.This paper is about the nil *-clean property of rings with emphasis on matrix rings.We show that a *-ring R is nil *-clean if and only if J(R) is nil and R/J(R) is nil*-clean.For a 2-primal *-ring R,with the induced involution given by (aij)* =(a*ij)T,the nil *-clean property of Mn(R) is completely reduced to that of Mn(Z2).Consequently,Mn(R) is not a nil *-clean ring for n =3,4,and M2(R) is a nil *-clean ring if and only if J(R) is nil,R/J(R) is a Boolean ring and a*-a ∈ J(R) for all a ∈ R. 相似文献
252.
Ryan J. Zerr 《Proceedings of the American Mathematical Society》2006,134(6):1849-1856
Character groups associated with certain dimension groups are considered. It is shown how these character groups can be used to construct an AF groupoid whose dimension group is isomorphic to the original dimension group.
253.
A classical theorem of Robbins states that the edges of a graph may be oriented, in such a way that an oriented path exists between any source and destination, if and only if the graph is both connected and two-connected (it cannot be disconnected by the removal of an edge). In this paper, an algebraic version of Robbins' result becomes a lemma on Hilbert bases for free abelian groups, which is then applied to generalize his theorem to higher dimensional complexes. An application to cycle bases for graphs is given, and various examples are presented. 相似文献
254.
Geng Zhibin 《大学数学》1998,(2)
本文研究了Banach空间的弱序列紧性.Banach空间X称为有(w)性质,如果X(X的共轭空间)的每个有界序列有弱收敛子列.我们证明了,如果Banach空间X有(w)性质,那么lp(X)(1≤p<+∞)与c0(X)也有(w)性质. 相似文献
255.
Radu Balan Peter G. Casazza Dan Edidin Gitta Kutyniok 《Proceedings of the American Mathematical Society》2007,135(4):1007-1015
In this paper we establish a surprising new identity for Parseval frames in a Hilbert space. Several variations of this result are given, including an extension to general frames. Finally, we discuss the derived results.
256.
Fabio Rapallo 《Annals of the Institute of Statistical Mathematics》2007,59(4):727-740
Toric models have been recently introduced in the analysis of statistical models for categorical data. The main improvement
with respect to classical log-linear models is shown to be a simple representation of structural zeros. In this paper we analyze
the geometry of toric models, showing that a toric model is the disjoint union of a number of log-linear models. Moreover,
we discuss the connections between the parametric and algebraic representations. The notion of Hilbert basis of a lattice
is proved to allow a special representation among all possible parametrizations. 相似文献
257.
Fernando Rodriguez-Villegas 《Proceedings of the American Mathematical Society》2002,130(8):2251-2254
We prove that certain naturally arising polynomials have all of their roots on a vertical line. 相似文献
258.
In this paper we study some properties of a totally *-paranormal operator (defined below) on Hilbert space. In particular,
we characterize a totally *-paranormal operator. Also we show that Weyl’s theorem and the spectral mapping theorem hold for
totally *-paranormal operators through the local spectral theory. Finally, we show that every totally *-paranormal operator
satisfies an analogue of the single valued extension property for W
2(D, H) and some of totally *-paranormal operators have scalar extensions. 相似文献
259.
260.
William J. Rolli 《Journal of Mathematical Analysis and Applications》2006,321(1):388-395
In this paper, we use the characterization of frames, introduced in [W. Rolli, A characterization of frames for finite dimensional Hilbert spaces, preprint], to construct frames for finite dimensional Hilbert spaces. Furthermore this approach allows for the construction of frames with prescribed properties. 相似文献