全文获取类型
收费全文 | 803篇 |
免费 | 18篇 |
国内免费 | 54篇 |
专业分类
化学 | 15篇 |
力学 | 5篇 |
综合类 | 1篇 |
数学 | 775篇 |
物理学 | 79篇 |
出版年
2023年 | 12篇 |
2022年 | 18篇 |
2021年 | 23篇 |
2020年 | 21篇 |
2019年 | 23篇 |
2018年 | 17篇 |
2017年 | 19篇 |
2016年 | 10篇 |
2015年 | 18篇 |
2014年 | 37篇 |
2013年 | 131篇 |
2012年 | 24篇 |
2011年 | 52篇 |
2010年 | 49篇 |
2009年 | 56篇 |
2008年 | 57篇 |
2007年 | 51篇 |
2006年 | 41篇 |
2005年 | 17篇 |
2004年 | 25篇 |
2003年 | 29篇 |
2002年 | 15篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 18篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有875条查询结果,搜索用时 156 毫秒
71.
关于丢番图方程(ax~m±1)/(ax±1)=y~n与(ax~m±1)/(ax±1)=y~n+1 总被引:10,自引:0,他引:10
罗家贵 《数学年刊A辑(中文版)》2004,(6)
本文证明了方程(1.4)没有x是一个n次完全幂的整数解(a,x,y,m,n),从而推广了乐茂华的结论:方程(1.1)没有x是一个n次完全幂的整数解(x,y,m,n),并有条件的得到了方程(1.5)的全部解. 相似文献
72.
N. Mazars 《商业与工业应用随机模型》1989,5(3):203-231
Binary coherent system theory has played an important part in reliability. Its extension to (‘degradable’ or ‘multistate’ or) multinary systems has recently been considered in various papers, through various definitions. This paper studies the most general model for multinary systems, proposes a unified viewpoint on multinary coherent systems and gives unified arguments to apply and to investigate further the binary and multinary cases. In a more detailed way, the ‘helpful bridge’ lately proposed by Block and Savits1 between the binary and multinary cases is completed and multinary systems then can be studied in terms of monotone binary coherent systems, introduced in a companion paper.2 Through various results, multinary systems are examined in terms of structure functions and of life functions; fundamental relations for their analysis are obtained with their set characterizations; the main axis that can be retained among the numerous types of coherence is emphasized, in a unified way, through relevance; reliability models are examined through performance processes, life lengths and performance functions; and Birnbaum's factors of importance are thoroughly extended to the multinary case. Fundamental results proposed in previous studies are thus completed with a shorter unified approach. 相似文献
73.
Generic initial ideals of Artinian ideals having Lefschetz properties or the strong Stanley property
For a standard Artinian k-algebra A=R/I, we give equivalent conditions for A to have the weak (or strong) Lefschetz property or the strong Stanley property in terms of the minimal system of generators of gin(I). Using the equivalent condition for the weak Lefschetz property, we show that some graded Betti numbers of gin(I) are determined just by the Hilbert function of I if A has the weak Lefschetz property. Furthermore, for the case that A is a standard Artinian k-algebra of codimension 3, we show that every graded Betti number of gin(I) is determined by the graded Betti numbers of I if A has the weak Lefschetz property. And if A has the strong Lefschetz (respectively Stanley) property, then we show that the minimal system of generators of gin(I) is determined by the graded Betti numbers (respectively by the Hilbert function) of I. 相似文献
74.
In this paper we give a unified framework for the construction of complex valued harmonic morphisms from the real, complex and quaternionic Grassmannians and their non-compact duals. This gives a positive answer to the corresponding open existence problem in the real and quaternionic cases.
Mathematics Subject Classifications (2000): 58E20, 53C43, 53C12The author is a member of EDGE, Research Training Network HPRN-CT-2000-00101 相似文献
75.
S. Giotopoulos 《Journal of Mathematical Analysis and Applications》2002,270(1):129-142
This paper provides an abstract characterization of quasitriangular algebras of operators on a separable Hilbert space. The main tool used is the (purely algebraic) concept of a single element. An element s of an algebra A is called single element of A if whenever asb=0 for some a, b in A, at least one of as,sb is zero. A part of this work is of independent interest and this is an attempt to determine an involution in a Banach algebra. 相似文献
76.
MINIMAL SURFACES IN 3—DIMENSIONAL SOLVABLE LIE GROUPS 总被引:1,自引:0,他引:1
J. INOGUCHI 《数学年刊B辑(英文版)》2003,24(1):73-84
The author studies minimal surfaces in 3-dimensional solvable Lie groups with left invariant Riemannian metrics. A Weierstraβ type integral representation formula for minimal surfaces is obtained. 相似文献
77.
J.C. Califano A. Uribe J.L. Chang C.L. Becker J.J. Napier V. Kishore D. Zhou G. Love K. Gernhardt J.C. Tolle 《Tetrahedron》2005,61(37):8821-8829
Oligomers of arginine, such as octa-d-arginine amide, are excellent transporters for active drugs through cell membranes and tissue. The synthesis of octa-d-arginine amide, as the nonahydrochloride salt, was approached via a solution phase synthetic route involving the preparation of an octa-d-ornithine intermediate, which was then converted into the desired octa-d-arginine compound through a guanidinylation step. The multi-step synthesis was carried out at pilot scale, resulting in the preparation of 700 g of the target molecule. No chromatographic purification was needed at any step of the process. 相似文献
78.
Portfolio optimization under D.C. transaction costs and minimal transaction unit constraints 总被引:1,自引:0,他引:1
This paper addresses itself to a portfolio optimization problem under nonconvex transaction costs and minimal transaction unit constraints. Associated with portfolio construction is a fee for purchasing assets. Unit transaction fee is larger when the amount of transaction is smaller. Hence the transaction cost is usually a concave function up to certain point. When the amount of transaction increases, the unit price of assets increases due to illiquidity/market impact effects. Hence the transaction cost becomes convex beyond certain bound. Therefore, the net expected return becomes a general d.c. function (difference of two convex functions). We will propose a branch-and-bound algorithm for the resulting d.c. maximization problem subject to a constraint on the level of risk measured in terms of the absolute deviation of the rate of return of a portfolio. Also, we will show that the minimal transaction unit constraints can be incorporated without excessively increasing the amount of computation. 相似文献
79.
A graph is singular of nullity η if zero is an eigenvalue of its adjacency matrix with multiplicity η. If η(G)=1, then the core of G is the subgraph induced by the vertices associated with the non-zero entries of the zero-eigenvector. A connected subgraph of G with the least number of vertices and edges, that has nullity one and the same core as G, is called a minimal configuration. A subdivision of a graph G is obtained by inserting a vertex on every edge of G. We review various properties of minimal configurations. In particular, we show that a minimal configuration is a tree if and only if it is a subdivision of some other tree. 相似文献
80.
四元数矩阵理论中的几个概念间的关系 总被引:17,自引:0,他引:17
本文指出并改正文[1]中的错误,给出弱特征多项式[2]与重特征多项式[3]间的显式关系,同时也给出行列式[2]与重行列式[4]间的显式关系,最后讨论了左特征值、右特征值、特征值和特征根之间的关系及最小多项式与弱特征多项式根之间的关系. 相似文献