全文获取类型
收费全文 | 685篇 |
免费 | 41篇 |
国内免费 | 58篇 |
专业分类
化学 | 29篇 |
晶体学 | 1篇 |
力学 | 25篇 |
综合类 | 18篇 |
数学 | 613篇 |
物理学 | 98篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 19篇 |
2017年 | 28篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 88篇 |
2012年 | 22篇 |
2011年 | 36篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 39篇 |
2007年 | 49篇 |
2006年 | 42篇 |
2005年 | 37篇 |
2004年 | 31篇 |
2003年 | 27篇 |
2002年 | 31篇 |
2001年 | 21篇 |
2000年 | 28篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 6篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有784条查询结果,搜索用时 31 毫秒
671.
In this paper we use the Euler-Seidel method for deriving new identities for hyperharmonic and r-Stirling numbers. The exponential generating function is determined for hyperharmonic numbers, which result is a generalization
of Gosper’s identity. A classification of second order recurrence sequences is also given with the help of this method.
相似文献
672.
The push-pull character of two series of donor-acceptor azines has been quantified by 13C, 15N chemical shift differences of the partial C(1)N(1) and N(2)C(2) double bonds in the central linking C(1)N(1)-N(2)C(2) unit and by the quotient of the occupations of the bonding π and anti-bonding π∗ orbitals of these bonds. Excellent correlation of the latter push-pull parameter with the corresponding bond lengths dCN strongly recommend both the occupation quotients π∗/π and the corresponding bond lengths as reasonable sensors for quantifying the push, pull character along the CN-NC linking unit, for the donor-acceptor quality of the two series of azines and for the molecular hyperpolarizability ß0 of these compounds. Within this context, reasonable conclusions concerning the interplay of steric hindrance in the chromophore, push-pull character and hyperpolarizability of the azines and their application as NLO materials will be drawn. 相似文献
673.
采用组合差商法对色散方程ut=auxxx(a为常数)的初边值问题,构造了两组互为对称带参数的三层显式差分格式.它们空间宽度为4,其局部截断误差为O(τ+h3),绝对稳定.而且计算时无方向性的约束,即不管a的符号如何,每一组格式均可以计算.最后给出了数值例子,数值结果表明了理论分析的正确性. 相似文献
674.
In this paper, we prove that the Toeplitz operator with finite Blaschke product symbol Sψ(z) on Nφ has at least m non-trivial minimal reducing subspaces, where m is the dimension of H^2(Гω)⊙φ(ω)H^2(Гω). Moreover, the restriction of Sψ(z) on any of these minimal reducing subspaces is unitary equivalent to the Bergman shift Mz. 相似文献
675.
676.
This study discusses generalized Rayleigh quotient and high efficiency finite element discretization schemes. Some results are as follows: 1) Rayleigh quotient accelerate technique is extended to nonselfadjoint problems. Generalized Rayleigh quotients of operator form and weak form are defined and the basic relationship between approximate eigenfunction and its generalized Rayleigh quotient is established. 2) New error estimates are obtained by replacing the ascent of exact eigenvalue with the ascent of fin... 相似文献
677.
678.
This article concerns a ring property called pseudo-reduced-over-center that is satisfied by free algebras over commutative reduced rings.The properties of radicals of pseudo-reduced-over-center rings are investigated,especially related to polynomial rings.It is proved that for pseudo-reduced-over-center rings of nonzero characteristic,the centers and the pseudo-reduced-over-center property are preserved through factor rings modulo nil ideals.For a locally finite ring R,it is proved that if R is pseudo-reduced-over-center,then R is commutative and R/J(R) is a commutative regular ring with J(R) nil,where J(R) is the Jacobson radical of R. 相似文献
679.
680.