全文获取类型
收费全文 | 1277篇 |
免费 | 35篇 |
国内免费 | 87篇 |
专业分类
化学 | 5篇 |
晶体学 | 1篇 |
力学 | 20篇 |
综合类 | 16篇 |
数学 | 1152篇 |
物理学 | 205篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 9篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 25篇 |
2017年 | 27篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 27篇 |
2013年 | 101篇 |
2012年 | 66篇 |
2011年 | 53篇 |
2010年 | 37篇 |
2009年 | 70篇 |
2008年 | 81篇 |
2007年 | 78篇 |
2006年 | 72篇 |
2005年 | 55篇 |
2004年 | 52篇 |
2003年 | 43篇 |
2002年 | 50篇 |
2001年 | 48篇 |
2000年 | 50篇 |
1999年 | 43篇 |
1998年 | 33篇 |
1997年 | 30篇 |
1996年 | 26篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1978年 | 12篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1974年 | 3篇 |
排序方式: 共有1399条查询结果,搜索用时 15 毫秒
31.
Jean-Pierre Gabardo 《Journal of Functional Analysis》2009,256(3):635-672
We give a characterization for the weighted irregular Gabor tight frames or dual systems in L2(Rn) in terms of the distributional symplectic Fourier transform of a positive Borel measure on R2n naturally associated with the system and the short-time Fourier transform of the windows in the case where the window (or at least one of the windows in the case of dual systems) belongs to S(Rn). This result implies that, for certain classes of windows such as generalized Gaussians or “extreme-value” windows, the only weighted irregular Gabor tight frames (or even dual systems with both windows in the same class) that can be constructed with these windows are the trivial ones, corresponding to the measure μ=1 on R2n. Furthermore, we show that, if a such Gabor system admits a dual which is of Gabor type, then the Beurling density of the associated measure exists and is equal to one. 相似文献
32.
A unified higher-order dual for a nondifferentiable minimax programming problem is formulated. Weak, strong and strict converse
duality theorems are discussed involving generalized higher-order (F,α,ρ,d)-Type I functions.
The research of second author was supported by the Department of Atomic Energy, Government of India, under the NBHM Post Doctoral
Fellowship Program 40/9/2005-R&D II/2398. 相似文献
33.
James Allen Fill 《Journal of Theoretical Probability》2009,22(3):587-600
An (upward) skip-free Markov chain with the set of nonnegative integers as state space is a chain for which upward jumps may
be only of unit size; there is no restriction on downward jumps. In a 1987 paper, Brown and Shao determined, for an irreducible
continuous-time skip-free chain and any d, the passage time distribution from state 0 to state d. When the nonzero eigenvalues ν
j
of the generator on {0,…,d}, with d made absorbing, are all real, their result states that the passage time is distributed as the sum of d independent exponential random variables with rates ν
j
. We give another proof of their theorem. In the case of birth-and-death chains, our proof leads to an explicit representation
of the passage time as a sum of independent exponential random variables. Diaconis and Miclo recently obtained the first such
representation, but our construction is much simpler.
We obtain similar (and new) results for a fastest strong stationary time T of an ergodic continuous-time skip-free chain with stochastically monotone time-reversal started in state 0, and we also
obtain discrete-time analogs of all our results.
In the paper’s final section we present extensions of our results to more general chains.
Research supported by NSF grant DMS–0406104, and by The Johns Hopkins University’s Acheson J. Duncan Fund for the Advancement
of Research in Statistics. 相似文献
34.
Paola Ravelojaona 《European Journal of Operational Research》2019,272(2):780-791
This paper aims to present non-linear CES (Constant Elasticity of Substitution)–CET (Constant Elasticity of Transformation) Directional Distance Functions. These measures inherit the structure of the standard Directional Distance Functions and that of the CES–CET technology. These functions allow non-parametric estimation of efficiency scores through linear programming method. Besides, the CES –CET technology gives the opportunity to explore α-returns to scale assumption for the new distance functions. The duality theory is investigated through pseudo profit, cost and revenue functions. The dual standpoint provides non-linear adjusted prices that can occur into non-linear pricing practices. An application is proposed to give an illustrative example of the primal CES–CET Directional Distance Functions. 相似文献
35.
多复变中正规权Zygmund空间上的几个性质 总被引:1,自引:0,他引:1
本文讨论了多复变中单位球上正规权Zygmund空间Z_μ(B)的一些性质.首先给出了Z_μ(B)函数的一种积分表示,接着证明了Z_μ(B)是正规权Bergman空间A_v~1(B)的对偶空间,其对偶对按如下形式给出:■,其中v(p)=(1-ρ~2)~(β+1)μ~(-1)(ρ)(0≤ρ<1)并且β>max{0,b-1}.最后作为积分表示和对偶的一个应用,作者给出了Z_μ(B)中每个函数的一个原子分解. 相似文献
36.
本文讨论了二阶凸和二阶凹条件下的二阶对称对偶问题,并利用有效性和真有效性概念证明了弱对偶、强对偶、逆对偶及自对偶定理。 相似文献
37.
讨论自反Banach空间中的原——对偶锥线性优化问题的目标函数水平集的几何性质.在自反Banach空间中,证明了原目标函数水平集的最大模与对偶目标函数水平集的最大内切球半径几乎是成反比例的. 相似文献
38.
39.
Let L be an elliptic operator, we give arguments about the duality estimate between Morrey spaces and its pre-dual spaces characterized by the heat kernel associated to L that is given in [6],[8]. 相似文献
40.
L.Venkateswara Reddy R.N. Mukherjee 《Journal of Mathematical Analysis and Applications》1999,240(2):37
In this paper, a generalized ratio invexity concept has been applied for single objective fractional programming problems. A concept which has been invoked seems to be more general than the one used earlier by Khan and Hanson in such contexts. Further, duality results for fractional programs have also been obtained. 相似文献