全文获取类型
收费全文 | 6887篇 |
免费 | 122篇 |
国内免费 | 111篇 |
专业分类
化学 | 413篇 |
晶体学 | 1篇 |
力学 | 246篇 |
综合类 | 30篇 |
数学 | 5459篇 |
物理学 | 971篇 |
出版年
2024年 | 8篇 |
2023年 | 45篇 |
2022年 | 65篇 |
2021年 | 66篇 |
2020年 | 165篇 |
2019年 | 144篇 |
2018年 | 114篇 |
2017年 | 109篇 |
2016年 | 120篇 |
2015年 | 139篇 |
2014年 | 327篇 |
2013年 | 776篇 |
2012年 | 344篇 |
2011年 | 443篇 |
2010年 | 364篇 |
2009年 | 485篇 |
2008年 | 441篇 |
2007年 | 469篇 |
2006年 | 330篇 |
2005年 | 184篇 |
2004年 | 180篇 |
2003年 | 146篇 |
2002年 | 153篇 |
2001年 | 170篇 |
2000年 | 143篇 |
1999年 | 115篇 |
1998年 | 120篇 |
1997年 | 105篇 |
1996年 | 108篇 |
1995年 | 91篇 |
1994年 | 49篇 |
1993年 | 53篇 |
1992年 | 35篇 |
1991年 | 30篇 |
1990年 | 61篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 57篇 |
1984年 | 59篇 |
1983年 | 25篇 |
1982年 | 51篇 |
1981年 | 47篇 |
1980年 | 35篇 |
1979年 | 25篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 3篇 |
排序方式: 共有7120条查询结果,搜索用时 227 毫秒
71.
A simple method for diagnosis of railway wheel defects using fuzzy-logic is proposed. The method is based on vibration measurements at different train speeds on healthy wheels and wheels with defects known a priori. The measured vibrations are statistically analyzed and confidence intervals for healthy and defective wheels depending on train speed and frequency of analysis are established. To facilitate the implementation of the method a fuzzy-logic is adopted. The fuzzy-logic model stores the obtained experience in a database and performs the decision making on damage extent and consequently the need of preventive maintenance. In view of the obtained results, the advantages and the limitations of the proposed approach as well as suggestions for further improvements are presented and discussed. 相似文献
72.
This paper is concerned with processes which are max-plus counterparts of
Markov diffusion processes governed by Ito sense stochastic differential
equations. Concepts of max-plus martingale and max-plus stochastic differential
equation are introduced. The max-plus counterparts of backward and forward
PDEs for Markov diffusions turn out to be first-order PDEs of
Hamilton–Jacobi–Bellman type. Max-plus additive integrals and a max-plus
additive dynamic programming principle are considered. This leads to
variational inequalities of Hamilton–Jacobi–Bellman type. 相似文献
73.
给出模糊半群上的模糊同余的概念,并进一步研究它的一些基本代数性质。同时研究带有模糊半群上的模糊同余扩张性质(FCEPF)的半群类,得到一个半群有模糊半群上的模糊同余扩张性质、有模糊同余扩张性质(FCEP)、有同余扩张性质(CEP)三个条件是等价的。 相似文献
74.
近些年来,许多处理近似问题的方法陆续被提出,其中利用Rough集理论计算两个集合的并和交的Rough隶属函数方法是被用较多的一种方法,但毕竟该方法精度较差。为此,介绍了一种精度较高的计算两个集合的并和交的Rough隶属函数方法,它克服了前者利用Rough集理论计算Rough隶属函数的复杂性,而迎来了简单和高精度的特点。 相似文献
75.
El Kebir Boukas Peng Shi Sing Kiong Nguang 《Journal of Mathematical Analysis and Applications》2003,282(1):241-255
This paper studies the problem of stochastic stability and disturbance attenuation for a class of linear continuous-time uncertain systems with Markovian jumping parameters. The uncertainties are assumed to be nonlinear and state, control and external disturbance dependent. A sufficient condition is provided to solve the above problem. An H∞ controller is designed such that the resulting closed-loop system is stochastically stable and has a disturbance attenuation γ for all admissible uncertainties. It is shown that the control law is in terms of the solutions of a set of coupled Riccati inequalities. A numerical example is included to demonstrate the potential of the proposed technique. 相似文献
76.
The purpose of this paper is to present general approaches for bounding some multi-stage stochastic programs from above. The results are based on restricting the solution set, such that the remaining multi-stage stochastic program is easy to solve. An example where the methods can be applied is presented.Supported in part by NATO Collaborative Research Grant No. 0785/87. 相似文献
77.
Rüdiger Schultz Leen Stougie Maarten H. van der Vlerk 《Mathematical Programming》1998,83(1-3):229-252
In this paper we present a framework for solving stochastic programs with complete integer recourse and discretely distributed right-hand side vector, using Gröbner basis methods from computational algebra to solve the numerous second-stage integer programs. Using structural properties of the expected integer recourse function, we prove that under mild conditions an optimal solution is contained in a finite set. Furthermore, we present a basic scheme to enumerate this set and suggest improvements to reduce the number of function evaluations needed. 相似文献
78.
A class of long-range predictive adaptive fuzzy relational controllers is presented. The plant behavior is described over an extended time horizon by a fuzzy relational model which is identified based on input-output closed-loop observations of the plant variables. In this class of adaptive controllers the control law attempts to minimize a quadratic cost over an extended control horizon. When used with linear models, this approach has revealed a significant potential for overcoming the limitations of one-step ahead schemes, such as the stabilization of non-minimum phase plants. Here, a uniform framework is adopted for implementing both the fuzzy model and the fuzzy controller, namely distributed fuzzy relational structures gaining from their massive parallel processing features and from the learning capabilities typical of the connectivist approaches. Issues such as maintenance during the adaptation process of the meaning of linguistic terms used at both fuzzy systems interfaces are addressed, namely by introducing a new design methodology for on-line fuzzy systems interface adaptation. The examples presented reinforce the claim of the usefulness of this new approach. 相似文献
79.
The solvability of a class of forward-backward stochastic differential equations (SDEs for short) over an arbitrarily prescribed time duration is studied. The authors design a stochastic relaxed control problem, with both drift and difftusion all being controlled, so that the solvability problem is converted to a problem of finding the nodal set of the viscosity solution to a certain Hamilton-Jacobi-Bellman equation. This method overcomes the fatal difficulty encountered in the traditional contraction mapping approach to the existence theorem of such SDEs. 相似文献
80.
Mark C. Veraar 《Proceedings of the American Mathematical Society》2007,135(5):1477-1486
In this paper we prove the equivalence of decoupling inequalities for stochastic integrals and one-sided randomized versions of the UMD property of a Banach space as introduced by Garling.