全文获取类型
收费全文 | 2708篇 |
免费 | 226篇 |
国内免费 | 208篇 |
专业分类
化学 | 249篇 |
晶体学 | 2篇 |
力学 | 75篇 |
综合类 | 48篇 |
数学 | 2143篇 |
物理学 | 625篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 55篇 |
2021年 | 81篇 |
2020年 | 61篇 |
2019年 | 54篇 |
2018年 | 57篇 |
2017年 | 76篇 |
2016年 | 86篇 |
2015年 | 48篇 |
2014年 | 112篇 |
2013年 | 174篇 |
2012年 | 129篇 |
2011年 | 146篇 |
2010年 | 119篇 |
2009年 | 188篇 |
2008年 | 191篇 |
2007年 | 166篇 |
2006年 | 185篇 |
2005年 | 153篇 |
2004年 | 120篇 |
2003年 | 104篇 |
2002年 | 104篇 |
2001年 | 76篇 |
2000年 | 83篇 |
1999年 | 85篇 |
1998年 | 58篇 |
1997年 | 60篇 |
1996年 | 52篇 |
1995年 | 47篇 |
1994年 | 35篇 |
1993年 | 18篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有3142条查询结果,搜索用时 15 毫秒
1.
2.
相对论性无自旋粒子在Hartmann势场中运动的精确解 总被引:1,自引:1,他引:0
在标量势等于矢量势的条件下,本文获得了具有Hartmann型势的Klein-Gordon方程的精确解.给出了束缚态的精确的能谱方程和归一化的径向波函数,对于散射态,获得了按“k/2π标度”归一化的径向波函数和相移的解析计算公式.讨论了散射振幅的解析性质和波函数、能谱方程以及相移的非相对论近似. 相似文献
3.
The Boltzmann distribution used in the steady-state analysis of the simulated annealing algorithm gives rise to several scale invariant properties. Scale invariance is first presented in the context of parallel independent processors and then extended to an abstract form based on lumping states together to form new aggregate states. These lumped or aggregate states possess all of the mathematical characteristics, forms and relationships of states (solutions) in the original problem in both first and second moments. These scale invariance properties therefore permit new ways of relating objective function values, conditional expectation values, stationary probabilities, rates of change of stationary probabilities and conditional variances. Such properties therefore provide potential applications in analysis, statistical inference and optimization. Directions for future research that take advantage of scale invariance are also discussed. 相似文献
4.
Dominique Fourdrinier William E. Strawderman 《Annals of the Institute of Statistical Mathematics》2003,55(4):803-816
We consider estimation of loss for generalized Bayes or pseudo-Bayes estimators of a multivariate normal mean vector, θ. In
3 and higher dimensions, the MLEX is UMVUE and minimax but is inadmissible. It is dominated by the James-Stein estimator and by many others. Johnstone (1988,
On inadmissibility of some unbiased estimates of loss,Statistical Decision Theory and Related Topics, IV (eds. S. S. Gupta and J. O. Berger), Vol. 1, 361–379, Springer, New York) considered the estimation of loss for the usual
estimatorX and the James-Stein estimator. He found improvements over the Stein unbiased estimator of risk. In this paper, for a generalized
Bayes point estimator of θ, we compare generalized Bayes estimators to unbiased estimators of loss. We find, somewhat surprisingly,
that the unbiased estimator often dominates the corresponding generalized Bayes estimator of loss for priors which give minimax
estimators in the original point estimation problem. In particular, we give a class of priors for which the generalized Bayes
estimator of θ is admissible and minimax but for which the unbiased estimator of loss dominates the generalized Bayes estimator
of loss. We also give a general inadmissibility result for a generalized Bayes estimator of loss.
Research supported by NSF Grant DMS-97-04524. 相似文献
5.
Many real problems can be modelled as robust shortest path problems on interval digraphs, where intervals represent uncertainty about real costs and a robust path is not too far from the shortest path for each possible configuration of the arc costs.A branch and bound algorithm for this problem is presented. 相似文献
6.
Yoshikazu Takada 《Annals of the Institute of Statistical Mathematics》1998,50(2):325-335
This paper gives a condition which implies the nonexistence of parametric statistical procedures with bounded risk or error performance characteristics. Many examples for which such a condition is satisfied are considered. 相似文献
7.
Marianna Pensky 《Annals of the Institute of Statistical Mathematics》2002,54(1):83-99
The traditional empirical Bayes (EB) model is considered with the parameter being a location parameter, in the situation when the Bayes estimator has a finite degree of smoothness and, possibly, jump discontinuities at several points. A nonlinear wavelet EB estimator based on wavelets with bounded supports is constructed, and it is shown that a finite number of jump discontinuities in the Bayes estimator do not affect the rate of convergence of the prior risk of the EB estimator to zero. It is also demonstrated that the estimator adjusts to the degree of smoothness of the Bayes estimator, locally, so that outside the neighborhoods of the points of discontinuities, the posterior risk has a high rate of convergence to zero. Hence, the technique suggested in the paper provides estimators which are significantly superior in several respects to those constructed earlier. 相似文献
8.
Xiangtong Qi 《Discrete Applied Mathematics》2007,155(3):416-422
We study a machine scheduling model in which job scheduling and machine maintenance activities have to be considered simultaneously. We develop the worst-case bounds for some heuristic algorithms, including a sharper worst-case bound of the SPT schedule than the results in the literature, and another bound of the EDD schedule. 相似文献
9.
A. A. Maleev 《Computational Mathematics and Mathematical Physics》2006,46(12):2031-2039
Stationary and nonstationary Jacobi-like iterative processes for solving systems of linear algebraic equations are examined. For a system whose coefficient matrix A is an H-matrix, it is shown that the convergence rate of any Jacobi-like process is at least as high as that of the point Jacobi method as applied to a system with 〈A〉 as the coefficient matrix, where 〈A〉 is a comparison matrix of A. 相似文献
10.
In this paper, we introduce a new concept of semi-preemptive scheduling and we show how it can be used to derive a maximum-flow-based lower bound for the P|rj|Lmax which dominates the well-known preemptive lower bound. We show that, in some cases, the proposed bound strictly dominates the preemptive one while having the same complexity. 相似文献