全文获取类型
收费全文 | 15972篇 |
免费 | 1756篇 |
国内免费 | 1125篇 |
专业分类
化学 | 2186篇 |
晶体学 | 27篇 |
力学 | 931篇 |
综合类 | 312篇 |
数学 | 8949篇 |
物理学 | 2939篇 |
无线电 | 3509篇 |
出版年
2024年 | 38篇 |
2023年 | 201篇 |
2022年 | 256篇 |
2021年 | 356篇 |
2020年 | 432篇 |
2019年 | 422篇 |
2018年 | 436篇 |
2017年 | 513篇 |
2016年 | 636篇 |
2015年 | 447篇 |
2014年 | 835篇 |
2013年 | 1339篇 |
2012年 | 804篇 |
2011年 | 980篇 |
2010年 | 881篇 |
2009年 | 966篇 |
2008年 | 1004篇 |
2007年 | 1056篇 |
2006年 | 913篇 |
2005年 | 822篇 |
2004年 | 700篇 |
2003年 | 674篇 |
2002年 | 637篇 |
2001年 | 507篇 |
2000年 | 474篇 |
1999年 | 409篇 |
1998年 | 341篇 |
1997年 | 277篇 |
1996年 | 254篇 |
1995年 | 221篇 |
1994年 | 164篇 |
1993年 | 141篇 |
1992年 | 117篇 |
1991年 | 103篇 |
1990年 | 67篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 31篇 |
1986年 | 48篇 |
1985年 | 46篇 |
1984年 | 34篇 |
1983年 | 23篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 87 毫秒
81.
标度系统一致性矩阵容量的计算方法 总被引:4,自引:0,他引:4
吕跃进 《数学的实践与认识》2003,33(9):102-107
本文研究正互反矩阵的变换性质 ,提出一种保持正互反矩阵一致性程度的等价分类 ,为计算各种标度系统下的一致矩阵容量提供了计算方法 相似文献
82.
Let Um be an m×m Haar unitary matrix and U[m,n] be its n×n truncation. In this paper the large deviation is proven for the empirical eigenvalue density of U[m,n] as m/n→λ and n→∞. The rate function and the limit distribution are given explicitly. U[m,n] is the random matrix model of quq, where u is a Haar unitary in a finite von Neumann algebra, q is a certain projection and they are free. The limit distribution coincides with the Brown measure of the operator quq. 相似文献
83.
§ 1 IntroductionLetRn×mdenotetherealn×mmatrixspace ,Rn×mr itssubsetwhoseelementshaverankr ,ORn×nthesetofalln×northogonalmatrices,SRn×n(SRn×n≥ ,SRn×n>)thesetofalln×nrealsymmetric (symmetricpositivesemidefinite ,positivedefinite)matrices.ThenotationA>0 (≥ 0 ,<0 ,≤ 0 )m… 相似文献
84.
In this paper, we study the linearization of the Cauchy problem and the mixed problem for the system of Grad--Hermite moments in nonequilibrium thermodynamics in the neighborhood of the equilibrium state. Stability conditions for solutions of the Cauchy problem are proved as a generalization of the classical Hermite--Biller theorem on stable polynomials. For the mixed problem, we prove an analog of the Vishik--Lyusternik theorem on small singular perturbations of general elliptic problems. The last observation allows us to introduce the Shapiro--Lopatinskii condition, which implies the well-posedness of the mixed problem. 相似文献
85.
This note investigates two long-standing conjectures on the Krull dimension of integer-valued polynomial rings and of polynomial rings in the context of (locally) essential domains.
86.
87.
Y. Brihaye S. Giller C. Gonera P. Kosinski P. Maslanka 《Czechoslovak Journal of Physics》2004,54(11):1185-1190
The dynamical systems of identical particles admitting quadratic integrals of motion are classified. The relevant integrals are explicitly constructed and their relation to separation of variables in Hamilton-Jacobi equation is clarified. 相似文献
88.
89.
In this paper we extend a result of Semrl stating that every 2-local automorphism of the full operator algebra on a separable infinite dimensional Hilbert space is an automorphism. In fact, besides separable Hilbert spaces, we obtain the same conclusion for the much larger class of Banach spaces with Schauder bases. The proof rests on an analogous statement concerning the 2-local automorphisms of matrix algebras for which we present a short proof. The need to get such a proof was formulated in Semrl's paper.
90.
The problem of generating a matrix A with specified eigen‐pair, where A is a symmetric and anti‐persymmetric matrix, is presented. An existence theorem is given and proved. A general expression of such a matrix is provided. We denote the set of such matrices by ??????En. The optimal approximation problem associated with ??????En is discussed, that is: to find the nearest matrix to a given matrix A* by A∈??????En. The existence and uniqueness of the optimal approximation problem is proved and the expression is provided for this nearest matrix. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献