全文获取类型
收费全文 | 2321篇 |
免费 | 223篇 |
国内免费 | 264篇 |
学科分类
数理化 | 2808篇 |
出版年
2023年 | 28篇 |
2022年 | 32篇 |
2021年 | 38篇 |
2020年 | 52篇 |
2019年 | 63篇 |
2018年 | 53篇 |
2017年 | 62篇 |
2016年 | 70篇 |
2015年 | 56篇 |
2014年 | 61篇 |
2013年 | 158篇 |
2012年 | 84篇 |
2011年 | 94篇 |
2010年 | 61篇 |
2009年 | 137篇 |
2008年 | 159篇 |
2007年 | 138篇 |
2006年 | 104篇 |
2005年 | 143篇 |
2004年 | 135篇 |
2003年 | 142篇 |
2002年 | 121篇 |
2001年 | 109篇 |
2000年 | 99篇 |
1999年 | 77篇 |
1998年 | 73篇 |
1997年 | 45篇 |
1996年 | 51篇 |
1995年 | 29篇 |
1994年 | 42篇 |
1993年 | 39篇 |
1992年 | 37篇 |
1991年 | 40篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 6篇 |
1972年 | 4篇 |
排序方式: 共有2808条查询结果,搜索用时 31 毫秒
1.
2.
3.
We consider the question whether, given a countable family of lattices in a locally compact abelian group G, there exist functions such that the resulting generalized shift-invariant system is a tight frame of . This paper develops a new approach to the study of generalized shift-invariant system via almost periodic functions, based on a novel unconditional convergence property. From this theory, we derive characterizing relations for tight and dual frame generators, we introduce the system bandwidth as a measure of the total bandwidth a generalized shift-invariant system can carry, and we show that the so-called Calderón sum is uniformly bounded from below for generalized shift-invariant frames. Without the unconditional convergence property, we show, counter intuitively, that even orthonormal bases can have arbitrary small system bandwidth. Our results show that the question of existence of frame generators for a general lattice system is rather subtle and depends on analytical and algebraic properties of the lattice system. 相似文献
4.
5.
Characterizations of ( m,n )-Jordan Derivations and ( m,n )-Jordan Derivable Mappings on Some Algebras 下载免费PDF全文
Let R be a ring, M be a R-bimodule and m, n be two fixed nonnegative integers with m + n = 0. An additive mapping δ from R into M is called an(m, n)-Jordan derivation if(m +n)δ(A~2) = 2 mAδ(A) + 2nδ(A)A for every A in R. In this paper, we prove that every(m, n)-Jordan derivation with m = n from a C*-algebra into its Banach bimodule is zero. An additive mappingδ from R into M is called a(m, n)-Jordan derivable mapping at W in R if(m + n)δ(AB + BA) =2mδ(A)B + 2 mδ(B)A + 2 nAδ(B) + 2 nBδ(A) for each A and B in R with AB = BA = W. We prove that if M is a unital A-bimodule with a left(right) separating set generated algebraically by all idempotents in A, then every(m, n)-Jordan derivable mapping at zero from A into M is identical with zero. We also show that if A and B are two unital algebras, M is a faithful unital(A, B)-bimodule and U = [A M N B] is a generalized matrix algebra, then every(m, n)-Jordan derivable mapping at zero from U into itself is equal to zero. 相似文献
6.
In this paper, we consider the equations of stationary motion of electrorheological fluids in any dimension . We show that the first gradient of local solutions to the system has optimal -regularity with some with respect to the one of the external force. This is achieved by comparison principle and a good -estimate. 相似文献
7.
张四保 《数学的实践与认识》2020,(7):273-276
设S(n)是Smarandache函数,其中n是一正整数.讨论Smarandache函数S(n)在数列F((2k),1)=F(n,1)=n2n+1(n=2k)与数列G(2n,1)=(2n)2n+1上的下界估计.基于初等方法证明了:当偶数n≥6时,有S(F((2k),1))=S(F(n,1))≥6×2n+1;当n≥4时,有S(G(2n,1))≥6×2n+1. 相似文献
8.
In this paper we study a double phase problem with an irregular obstacle. The energy functional under consideration is characterized by the fact that both ellipticity and growth switch between a type of polynomial and a type of logarithm, which can be regarded as a borderline case of the double phase functional with -growth. We obtain an optimal global Calderón–Zygmund type estimate for the obstacle problem with double phase in the borderline case. 相似文献
9.
10.
《Discrete Mathematics》2022,345(10):112996
In this paper, we determine the maximum size of digraphs on n vertices which avoid two distinct walks of length 3 with the same initial vertex and the same terminal vertex. The digraphs attaining this maximum size are also characterized. Combining this with previous results, we obtain a full solution to a problem proposed by X. Zhan in 2007. 相似文献