全文获取类型
收费全文 | 2343篇 |
免费 | 89篇 |
国内免费 | 214篇 |
专业分类
化学 | 123篇 |
晶体学 | 3篇 |
力学 | 143篇 |
综合类 | 42篇 |
数学 | 2194篇 |
物理学 | 141篇 |
出版年
2024年 | 1篇 |
2023年 | 24篇 |
2022年 | 26篇 |
2021年 | 41篇 |
2020年 | 53篇 |
2019年 | 74篇 |
2018年 | 94篇 |
2017年 | 95篇 |
2016年 | 83篇 |
2015年 | 42篇 |
2014年 | 94篇 |
2013年 | 351篇 |
2012年 | 87篇 |
2011年 | 96篇 |
2010年 | 85篇 |
2009年 | 115篇 |
2008年 | 150篇 |
2007年 | 138篇 |
2006年 | 116篇 |
2005年 | 117篇 |
2004年 | 111篇 |
2003年 | 112篇 |
2002年 | 102篇 |
2001年 | 72篇 |
2000年 | 56篇 |
1999年 | 49篇 |
1998年 | 59篇 |
1997年 | 42篇 |
1996年 | 23篇 |
1995年 | 24篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 5篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2646条查询结果,搜索用时 20 毫秒
101.
Extensions of crossed modules in Lie algebras with abelian kernel are studied, particularly backward and forward induced extensions and related properties. The set Opext((U, Q, ), (R, K, )) of congruence classes of extensions of (R, K, ) by (U, Q, ) is endowed with a K-vector space structure. This K-vector space appears in a five-term natural and exact sequence associated with an extension of crossed modules.2000 Mathematics Subject Classification: 17B56, 17B99, 18G99 相似文献
102.
We propose a new general definition of Volterra operators. Several types of evolutionary operators, including Volterra ones in the sense of A.N. Tikhonov, satisfy this definition. For equations with generalized Volterra operators we introduce the notions of local, global, and maximally extended solutions. For solutions to nonlinear equations we formulate the existence, uniqueness, and extendability conditions. The theorems proved in this paper imply both known and new results on the solvability of concrete equations. We adduce an example of the application of obtained results to the study of the Cauchy problem for functional differential equations. 相似文献
103.
We introduce the notion of n-fold track extensions of a category C by a natural system D and prove that such extensions represent classes in the cohomology of C with coefficients in D introduced by Baues–Wirsching. This generalizes a result of Huebschmann on the cohomology of groups. 相似文献
104.
Gert de Cooman Matthias C.M. Troffaes Enrique Miranda 《Journal of Mathematical Analysis and Applications》2008,340(2):982-999
This paper deals with n-monotone functionals, which constitute a generalisation of n-monotone set functions. Using the notion of exactness of a functional, we introduce a new notion of lower and upper integral which subsumes as particular cases most of the approaches to integration in the literature. As a consequence, we can characterise which types of integrals can be used to calculate the natural extension (the lower envelope of all linear extensions) of a positive bounded charge. 相似文献
105.
本文研究了群分次环的有限正规分次扩张问题.利用经典环论方法,得到一个群分次环与其有限正规分次扩张环之间关于分次Jacobson根和分次素根的关系,同时,给出了分次情形的Cutting down定理和Lying over定理. 相似文献
106.
Ample fields play an important role in possibility theory. These fields of subsets of a universe, which are additionally closed under arbitrary unions, act as the natural domains for possibility measures. A set provided with an ample field is then called an ample space. In this paper we generalise Wang's notions of product ample field and product ample space. We make a topological study of ample spaces and their products, and introduce ample subspaces, extensions and one-point extensions of ample spaces. In this way, a first step towards a mathematical theory of possibilistic processes is made. 相似文献
107.
108.
Gary F. Birkenmeier 《代数通讯》2013,41(12):5134-5151
In this paper the idea of an intrinsic extension of a ring, first proposed by Faith and Utumi, is generalized and studied in its own right. For these types of ring extensions, it is shown that, with relatively mild conditions on the base ring, R, a complete set of primitive idempotents (a complete set of left triangulating idempotents, a complete set of centrally primitive idempotents) can be constructed for an intrinsic extension, T, from a corresponding set in the base ring R. Examples and applications are given for rings that occur in functional analysis and group ring theory. 相似文献
109.
We study systematically the natural generalization of Schreier’s extension theory to obtain proper loops and show that this construction gives a rich family of examples of loops in all traditional common, important loop classes. 相似文献
110.
Marcin Peczarski 《Order》2008,25(2):91-103
We consider the Gold Partition Conjecture (GPC) that implies the 1/3–2/3 Conjecture. We prove the GPC in the case where every
element of the poset is incomparable with at most six others. The proof involves the extensive use of computers.
This paper contains results obtained using computer resources of the Interdisciplinary Centre for Mathematical and Computational
Modelling (ICM), University of Warsaw. 相似文献