全文获取类型
收费全文 | 1492篇 |
免费 | 60篇 |
国内免费 | 101篇 |
专业分类
化学 | 104篇 |
晶体学 | 1篇 |
力学 | 59篇 |
综合类 | 28篇 |
数学 | 1215篇 |
物理学 | 246篇 |
出版年
2023年 | 16篇 |
2022年 | 18篇 |
2021年 | 29篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 30篇 |
2017年 | 36篇 |
2016年 | 41篇 |
2015年 | 19篇 |
2014年 | 76篇 |
2013年 | 112篇 |
2012年 | 39篇 |
2011年 | 55篇 |
2010年 | 64篇 |
2009年 | 106篇 |
2008年 | 98篇 |
2007年 | 85篇 |
2006年 | 80篇 |
2005年 | 65篇 |
2004年 | 44篇 |
2003年 | 51篇 |
2002年 | 59篇 |
2001年 | 47篇 |
2000年 | 43篇 |
1999年 | 52篇 |
1998年 | 43篇 |
1997年 | 43篇 |
1996年 | 31篇 |
1995年 | 18篇 |
1994年 | 24篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有1653条查询结果,搜索用时 15 毫秒
51.
We study Markov jump decision processes with both continuously and instantaneouslyacting decisions and with deterministic drift between jumps. Such decision processes were recentlyintroduced and studied from discrete time approximations point of view by Van der Duyn Schouten.Weobtain necessary and sufficient optimality conditions for these decision processes in terms of equations and inequalities of quasi-variational type. By means of the latter we find simple necessaryand sufficient conditions for the existence of stationary optimal policies in such processes with finite state and action spaces, both in the discounted and average per unit time reward cases. 相似文献
52.
Carter T. Butts 《The Journal of mathematical sociology》2019,43(1):40-57
Exponential family random graph models (ERGMs) can be understood in terms of a set of structural biases that act on an underlying reference distribution. This distribution determines many aspects of the behavior and interpretation of the ERGM families incorporating it. One important innovation in this area has been the development of an ERGM reference model that produces realistic behavior when generalized to sparse networks of varying sizes. Here, we show that this model can be derived from a latent dynamic process in which tie formation takes place within small local settings between which individuals move. This derivation provides one possible micro-process interpretation of the sparse ERGM reference model and sheds light on the conditions under which constant mean degree scaling can emerge. 相似文献
53.
《Operations Research Letters》2019,47(4):257-263
We consider optimal intervention methods under budget constraints when financial systems face economic shocks. We propose two policies formulated by mixed-integer linear programs where regulators inject cash into institutions. One is to minimize systemic losses, and the other is to minimize the number of defaulting institutions. Using publicly available data on the Korean financial system, we construct its entire network and apply stress scenarios to the system to compare the performances of intervention strategies and derive insights on their workings. 相似文献
54.
Zvi Artstein 《Optimization》2019,68(1):81-98
ABSTRACTAn optimization problem of maximizing an integral of a function over a family of probability measures is considered. The problem is a generalization of a well-studied variational problem in mathematical economics, concerning optimal allocations. The specific generalization that we examine arises also in the limit of singularly perturbed optimal control problems. We examine the mathematical problem and allude to the singular perturbation motivation. 相似文献
55.
56.
57.
58.
Pierre Del Moral 《随机分析与应用》2018,36(3):413-442
In this article, we consider importance sampling (IS) and sequential Monte Carlo (SMC) methods in the context of one-dimensional random walks with absorbing barriers. In particular, we develop a very precise variance analysis for several IS and SMC procedures. We take advantage of some explicit spectral formulae available for these models to derive sharp and explicit estimates; this provides stability properties of the associated normalized Feynman–Kac semigroups. Our analysis allows one to compare the variance of SMC and IS techniques for these models. The work in this article is one of the few to consider an in-depth analysis of an SMC method for a particular model-type as well as variance comparison of SMC algorithms. 相似文献
59.
目的 探讨早期干预对极低出生体重早产儿智能发育的影响,为极低出生体重早产儿的早期干预提供依据。方法 239 例极低出生体重早产儿为早产随访组,采用鲍秀兰早期教育资料制定的干预计划,进行系统干预,并与326 例失访的早产儿童以及与随访组相似的326 例正常儿童进行对照分析。采用Gesell 儿童发育量表等标准化工具进行发育评估。结果 早产随访组Gesell 儿童发育量表5 项均分、总发育商(developmental quotient,DQ)总分与早产失访组相比差异均有统计学差异(均P<0.05)。结论 早期干预能显著促进极低出生体重早产儿的智能发育,提高患儿的生活质量。 相似文献
60.
Stability criteria in terms of two measures for functional differential equation with variable‐time impulses
下载免费PDF全文
![点击此处可从《Mathematical Methods in the Applied Sciences》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chao Liu Chuandong Li Tingwen Huang Hui Wang 《Mathematical Methods in the Applied Sciences》2015,38(14):2922-2936
This paper focuses on the stability in terms of two measures for functional differential equation with variable‐time impulses. Being different from most of existing literatures, the impulses of functional differential equation are assumed to be closely associated to the current state. We propose a new comparison principle for the considered systems and establish several stability criteria in terms of two measures. Also, the theoretical results are applied in a class of delayed neural network systems with variable‐tine impulses, and numerical simulations are introduced to illustrate the effectiveness of our results. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献