全文获取类型
收费全文 | 2048篇 |
免费 | 166篇 |
国内免费 | 155篇 |
专业分类
化学 | 72篇 |
力学 | 28篇 |
综合类 | 29篇 |
数学 | 2014篇 |
物理学 | 226篇 |
出版年
2023年 | 27篇 |
2022年 | 53篇 |
2021年 | 39篇 |
2020年 | 52篇 |
2019年 | 62篇 |
2018年 | 61篇 |
2017年 | 75篇 |
2016年 | 72篇 |
2015年 | 57篇 |
2014年 | 122篇 |
2013年 | 191篇 |
2012年 | 98篇 |
2011年 | 86篇 |
2010年 | 86篇 |
2009年 | 125篇 |
2008年 | 124篇 |
2007年 | 134篇 |
2006年 | 112篇 |
2005年 | 97篇 |
2004年 | 86篇 |
2003年 | 89篇 |
2002年 | 86篇 |
2001年 | 83篇 |
2000年 | 68篇 |
1999年 | 48篇 |
1998年 | 44篇 |
1997年 | 39篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2369条查询结果,搜索用时 15 毫秒
141.
142.
We establish an approximation criterion for essential self-adjointness of Dirichlet operators with nonconstant diffusion part on certain Banach spaces. 相似文献
143.
We continue our study on arithmetical Fourier series by considering two Fourier series which are related to Diophantine analysis. The first one was studied by Hardy and Littlewood in connection with the classification of numbers and the second one was studied by Hartman and Wintner by Lebesgue integration theory. 相似文献
144.
In the literature, decision models and techniques for supplier selection do not often consider inventory management of the items being purchased as part of the analysis. In this article, two mixed integer nonlinear programming models are proposed to select the best set of suppliers and determine the proper allocation of order quantities while minimizing the annual ordering, inventory holding, and purchasing costs under suppliers’ capacity and quality constraints. The first model allows independent order quantities for each supplier while the second model restricts all order quantities to be of equal size, as it would be required in a multi-stage (supply chain) inventory model. Illustrative examples are used to highlight the advantages of the proposed models over a previous model introduced in the literature. 相似文献
145.
Can a Brownian motion penetrate the two-dimensional Sierpinski gasket? This question was studied in [8], and an affirmative answer was given. In this paper, the problem is studied with a different approach, using Dirichlet forms and function space theory. The results obtained are somewhat different from, and from certain aspects more general than, the results in [8].
相似文献146.
Defenders concerned about protecting multiple targets can either protect them individually (through target hardening), or collectively (through overarching protections such as border security, public health, emergency response, or intelligence). Decision makers may find it relatively straightforward to choose which targets to harden, but are likely to find it more difficult to compare seemingly incommensurate forms of protection - e.g., target hardening, versus a reduction in the likelihood of weapons being smuggled across the border. Unfortunately, little previous research has addressed this question, and fundamental research is needed to provide guidance and practical solution approaches. In this paper, we first develop a model to optimally allocate resources between target hardening and overarching protection, then investigate the factors affecting the relative desirability of target hardening versus overarching protection, and finally apply our model to a case study involving critical assets in Wisconsin. The case study demonstrates the value of our method by showing that the optimal solution obtained using our model is in some cases substantially better than the historical budget allocation. 相似文献
147.
Damien Lamberton 《随机分析与应用》2013,31(3):603-623
Abstract In this article we investigate the rate of convergence of the so-called two-armed bandit algorithm. The behavior of the algorithm turns out to be highly non standard: no central limit theorem, possible occurrence of two different rates of convergence with positive probability. 相似文献
148.
Characteristic formulations for boundary conditions have demonstrated their effectiveness to handle inlets and outlets, especially to avoid acoustic wave reflections. At walls, however, most authors use simple Dirichlet or Neumann boundary conditions, where the normal velocity (or pressure gradient) is set to zero. This paper demonstrates that there are significant differences between characteristic and Dirichlet methods at a wall and that simulations are more stable when using walls modelled with a characteristic wave decomposition. The derivation of characteristic methods yields an additional boundary term in the continuity equation, which explains their increased stability. This term also allows to handle the two acoustic waves going towards and away from the wall in a consistent manner. Those observations are confirmed by stability matrix analysis and one‐ and two‐dimensional simulations of acoustic modes in cavities. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
149.
该文主要证明了在Dirichlet空间上由复合算子{C\-φ:φ∈Aut(D)}生成的代数为循环算子代数;同时对任意的解析映射φ:D→D,C\-φ都不可能为超循环算子给出了证明. 相似文献
150.
M. van den Berg 《Journal of Functional Analysis》2003,198(1):28-42
We obtain a formula for the asymptotic behaviour of the Dirichlet heat kernel for large time in terms of the survival probability of a Brownian motion, under the assumption that the latter decays subexponentially for large time. We also obtain a lower bound for the Dirichlet heat kernel for arbitrary open and connected sets in Euclidean space. 相似文献