全文获取类型
收费全文 | 9152篇 |
免费 | 1011篇 |
国内免费 | 535篇 |
专业分类
化学 | 392篇 |
晶体学 | 3篇 |
力学 | 967篇 |
综合类 | 166篇 |
数学 | 7211篇 |
物理学 | 1959篇 |
出版年
2024年 | 9篇 |
2023年 | 114篇 |
2022年 | 115篇 |
2021年 | 181篇 |
2020年 | 237篇 |
2019年 | 202篇 |
2018年 | 227篇 |
2017年 | 327篇 |
2016年 | 360篇 |
2015年 | 250篇 |
2014年 | 442篇 |
2013年 | 676篇 |
2012年 | 495篇 |
2011年 | 463篇 |
2010年 | 404篇 |
2009年 | 486篇 |
2008年 | 542篇 |
2007年 | 537篇 |
2006年 | 529篇 |
2005年 | 470篇 |
2004年 | 373篇 |
2003年 | 393篇 |
2002年 | 363篇 |
2001年 | 351篇 |
2000年 | 309篇 |
1999年 | 278篇 |
1998年 | 227篇 |
1997年 | 193篇 |
1996年 | 165篇 |
1995年 | 165篇 |
1994年 | 82篇 |
1993年 | 68篇 |
1992年 | 73篇 |
1991年 | 67篇 |
1990年 | 53篇 |
1989年 | 34篇 |
1988年 | 48篇 |
1987年 | 47篇 |
1986年 | 36篇 |
1985年 | 47篇 |
1984年 | 41篇 |
1983年 | 21篇 |
1982年 | 35篇 |
1981年 | 15篇 |
1980年 | 38篇 |
1979年 | 31篇 |
1978年 | 13篇 |
1977年 | 22篇 |
1976年 | 20篇 |
1975年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This paper derives the optimal trajectories in a general fluid network with server control. The stationary optimal policy in the complete state space is constructed. The optimal policy is constant on polyhedral convex cones. An algorithm is derived that computes these cones and the optimal policy. Generalized Klimov indices are introduced, they are used for characterizing myopic and time-uniformly optimal policies.Received: November 2004 / Revised: February 2005The research of this author has been supported by the project ‘‘Stochastic Networks’’ of the Netherlands Organisation for Scientific Research NWO. 相似文献
32.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
33.
Oracle inequality is a relatively new statistical tool for the analysis of nonparametric adaptive estimates. Oracle is a good pseudo-estimate that is based on both data and an underlying estimated curve. An oracle inequality shows how well an adaptive estimator mimics the oracle for a particular underlying curve. The most advanced oracle inequalities have been recently obtained by Cavalier and Tsybakov (2001) for Stein type blockwise estimates used in filtering a signal from a stationary white Gaussian process. The authors also conjecture that a similar result can be obtained for Efromovich–Pinsker (EP) type blockwise estimators where their approach, based on Stein's formula for risk calculation, does not work. This article proves the conjecture and extends it upon more general models which include not stationary and dependent processes. Other possible extensions, a discussion of practical implications and a numerical study are also presented. 相似文献
34.
Most of the methods used in the ARCH literature for selecting the appropriate model are based on evaluating the ability of the models to describe the data. An alternative model selection approach is examined based on the evaluation of the predictability of the models in terms of standardized prediction errors. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
35.
36.
Clemens Heuberger 《Periodica Mathematica Hungarica》2004,49(2):65-89
We study digit expansions with arbitrary integer digits in base q (q integer) and the Fibonacci base such that the sum of the absolute values of the digits is minimal. For the Fibonacci case, we describe a unique minimal expansion and give a greedy algorithm to compute it. Additionally, transducers to calculate minimal expansions from other expansions are given. For the case of even integer bases q, similar results are given which complement those given in [6]. 相似文献
37.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls. 相似文献
38.
We present a new approach to the a posteriori error analysis of stable Galerkin approximations of reaction–convection–diffusion problems. It relies upon a non-standard variational formulation of the exact problem, based on the anisotropic wavelet decomposition of the equation residual into convection-dominated scales and diffusion-dominated scales. The associated norm, which is stronger than the standard energy norm, provides a robust (i.e., uniform in the convection limit) control over the streamline derivative of the solution. We propose an upper estimator and a lower estimator of the error, in this norm, between the exact solution and any finite dimensional approximation of it. We investigate the behaviour of such estimators, both theoretically and through numerical experiments. As an output of our analysis, we find that the lower estimator is quantitatively accurate and robust. 相似文献
39.
40.
Takayuki Abe 《Mathematical Methods in the Applied Sciences》2004,27(9):1007-1048
This paper is concerned with the standard Lp estimate of solutions to the resolvent problem for the Stokes operator on an infinite layer with ‘Neumann–Dirichlet‐type’ boundary condition. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献