全文获取类型
收费全文 | 2069篇 |
免费 | 163篇 |
国内免费 | 335篇 |
专业分类
化学 | 80篇 |
晶体学 | 1篇 |
力学 | 56篇 |
综合类 | 72篇 |
数学 | 2106篇 |
物理学 | 252篇 |
出版年
2024年 | 2篇 |
2023年 | 29篇 |
2022年 | 30篇 |
2021年 | 40篇 |
2020年 | 42篇 |
2019年 | 49篇 |
2018年 | 74篇 |
2017年 | 83篇 |
2016年 | 50篇 |
2015年 | 45篇 |
2014年 | 64篇 |
2013年 | 372篇 |
2012年 | 71篇 |
2011年 | 83篇 |
2010年 | 72篇 |
2009年 | 94篇 |
2008年 | 136篇 |
2007年 | 114篇 |
2006年 | 116篇 |
2005年 | 124篇 |
2004年 | 95篇 |
2003年 | 108篇 |
2002年 | 121篇 |
2001年 | 72篇 |
2000年 | 89篇 |
1999年 | 77篇 |
1998年 | 66篇 |
1997年 | 77篇 |
1996年 | 43篇 |
1995年 | 27篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2567条查询结果,搜索用时 265 毫秒
101.
ZhongKuiLIU JavedAHSAN 《数学学报(英文版)》2004,20(1):105-114
Let U be a flat right R-module and N an infinite cardinal number.A left R-module M is said to be (N,U)-coherent if every finitely generated submodule of every finitely generated M-projective module in σ[M] is (N,U)-finitely presented in σ[M].It is proved under some additional conditions that a left R-module M is (N,U)-coherent if and only if Л^Ni∈I U is M-flat as a right R-module if and only if the (N,U)-coherent dimension of M is equal to zero.We also give some characterizations of left (N,U)-coherent dimension of rings and show that the left N-coherent dimension of a ring R is the supremum of (N,U)-coherent dimensions of R for all flat right R-modules U. 相似文献
102.
David Masson 《Designs, Codes and Cryptography》2003,28(3):283-302
We study (generalized) designs supported by words of given composition. We characterize them in terms of orthogonality relations with Specht modules; we define some zonal functions for the symmetric group and we give a closed formula for them, indexed on ordered pair of semi-standard generalized tableaux: Hahn polynomials are a particular case. We derive an algorithm to test if a set is a design. We use it to search designs in some ternary self-dual codes. 相似文献
103.
104.
David Eisenbud Craig Huneke Bernd Ulrich 《Proceedings of the American Mathematical Society》2003,131(3):701-708
In this paper we show that the Rees algebra can be made into a functor on modules over a ring in a way that extends its classical definition for ideals. The Rees algebra of a module may be computed in terms of a ``maximal' map from to a free module as the image of the map induced by on symmetric algebras. We show that the analytic spread and reductions of can be determined from any embedding of into a free module, and in characteristic 0--but not in positive characteristic!--the Rees algebra itself can be computed from any such embedding.
105.
It is well-known that every quasi-p-injective module has C2-condition. In this note, it is shown that for a quasi-p-injective module M which is a self-generator, if M is projective, duo and semiperfect, then M is continuous. As a special case we re-obtain a result of Puninski-Wisbauer-Yousif saying that, a semiperfect ring R is right continuous if it is right duo, right p-injective.AMS Subject Classifications (1991): 16D50, 16D70, 16D80Supported by The Royal Golden Jubilee Project 相似文献
106.
Using multiplication algebras we introduce actor crossed modules of commutative algebras and use it to generalise some aspects from commutative algebras to crossed modules of commutative algebras. This is applied to the Peiffer pairings in the Moore complex of a simplicial commutative algebra. 相似文献
107.
L''. Holá 《Set-Valued Analysis》2003,11(2):133-151
Our paper studies the topology of uniform convergence on compact sets on the space of densely continuous forms (introduced by Hammer and McCoy (1997)), usco and minimal usco maps. We generalize and complete results from Hammer and McCoy (1997) concerning the space D(X,Y) of densely continuous forms from X to Y. Let X be a Hausdorff topological space, (Y,d) be a metric space and D
k
(X,Y) the topology of uniform convergence on compact sets on D(X,Y). We prove the following main results: D
k
(X,Y) is metrizable iff D
k
(X,Y) is first countable iff X is hemicompact. This result gives also a positive answer to question 4.1 of McCoy (1998). If moreover X is a locally compact hemicompact space and (Y,d) is a locally compact complete metric space, then D
k
(X,Y) is completely metrizable, thus improving a result from McCoy (1998). We study also the question, suggested by Hammer and McCoy (1998), when two compatible metrics on Y generate the same topologies of uniform convergence on compact sets on D(X,Y). The completeness of the topology of uniform convergence on compact sets on the space of set-valued maps with closed graphs, usco and minimal usco maps is also discussed. 相似文献
108.
Simion Breaz 《Czechoslovak Mathematical Journal》2003,53(2):479-489
We present general properties for almost-flat modules and we prove that a self-small right module is almost flat as a left module over its endomorphism ring if and only if the class of g-static modules is closed under the kernels. 相似文献
109.
Let be an Artin algebra, let mod be the category of finitely generated -modules, and let Amod be a contravariantly finite and extension closed subcategory. For an indecomposable and not Ext-projective module CA, we compute the almost split sequence 0ABC0 in A from the almost split sequence 0DTrCEC0 in mod. Since the computation is particularly simple if the minimal right A-approximation of DTrC is indecomposable for all indecomposable and not Ext-projective CA, we manufacture subcategories A with the desired property using orthogonal subcategories. The method of orthogonal subcategories is applied to compute almost split sequences for relatively projective and prinjective modules. 相似文献
110.
We investigate the minimal number of generators and the depth of divisorial ideals over normal semigroup rings. Such ideals are defined by the inhomogeneous systems of linear inequalities associated with the support hyperplanes of the semigroup. The main result is that for every bound C there exist, up to isomorphism, only finitely many divisorial ideals I such that (I)C. It follows that there exist only finitely many Cohen–Macaulay divisor classes. Moreover, we determine the minimal depth of all divisorial ideals and the behaviour of and depth in arithmetic progressions in the divisor class group.The results are generalized to more general systems of linear inequalities whose homogeneous versions define the semigroup in a not necessarily irredundant way. The ideals arising this way can also be considered as defined by the nonnegative solutions of an inhomogeneous system of linear diophantine equations.We also give a more ring-theoretic approach to the theorem on minimal number of generators of divisorial ideals: it turns out to be a special instance of a theorem on the growth of multigraded Hilbert functions. 相似文献