全文获取类型
收费全文 | 5484篇 |
免费 | 506篇 |
国内免费 | 476篇 |
专业分类
化学 | 2243篇 |
晶体学 | 28篇 |
力学 | 746篇 |
综合类 | 95篇 |
数学 | 1975篇 |
物理学 | 1379篇 |
出版年
2024年 | 4篇 |
2023年 | 36篇 |
2022年 | 82篇 |
2021年 | 117篇 |
2020年 | 128篇 |
2019年 | 118篇 |
2018年 | 119篇 |
2017年 | 158篇 |
2016年 | 186篇 |
2015年 | 111篇 |
2014年 | 225篇 |
2013年 | 351篇 |
2012年 | 302篇 |
2011年 | 275篇 |
2010年 | 293篇 |
2009年 | 299篇 |
2008年 | 292篇 |
2007年 | 373篇 |
2006年 | 340篇 |
2005年 | 319篇 |
2004年 | 254篇 |
2003年 | 268篇 |
2002年 | 203篇 |
2001年 | 175篇 |
2000年 | 173篇 |
1999年 | 168篇 |
1998年 | 135篇 |
1997年 | 120篇 |
1996年 | 104篇 |
1995年 | 67篇 |
1994年 | 108篇 |
1993年 | 80篇 |
1992年 | 75篇 |
1991年 | 45篇 |
1990年 | 43篇 |
1989年 | 34篇 |
1988年 | 30篇 |
1987年 | 36篇 |
1986年 | 36篇 |
1985年 | 35篇 |
1984年 | 31篇 |
1983年 | 10篇 |
1982年 | 28篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1969年 | 3篇 |
排序方式: 共有6466条查询结果,搜索用时 312 毫秒
1.
Claudius Gros 《Entropy (Basel, Switzerland)》2021,23(2)
Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed. 相似文献
2.
3.
Second-order random wave solutions for interfacial internal waves in N-layer density-stratified fluid
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper studies the random internal wave equations describing the density interface displacements and the velocity potentials of N-layer stratified fluid contained between two rigid walls at the top and bottom. The density interface displacements and the velocity potentials were solved to the second-order by an expansion approach used by Longuet-Higgins (1963) and Dean (1979) in the study of random surface waves and by Song (2004) in the study of second- order random wave solutions for internal waves in a two-layer fluid. The obtained results indicate that the first-order solutions are a linear superposition of many wave components with different amplitudes, wave numbers and frequencies, and that the amplitudes of first-order wave components with the same wave numbers and frequencies between the adjacent density interfaces are modulated by each other. They also show that the second-order solutions consist of two parts: the first one is the first-order solutions, and the second one is the solutions of the second-order asymptotic equations, which describe the second-order nonlinear modification and the second-order wave-wave interactions not only among the wave components on same density interfaces but also among the wave components between the adjacent density interfaces. Both the first-order and second-order solutions depend on the density and depth of each layer. It is also deduced that the results of the present work include those derived by Song (2004) for second-order random wave solutions for internal waves in a two-layer fluid as a particular case. 相似文献
4.
西部开发中能源配置模型的研究 总被引:3,自引:0,他引:3
开发西部丰富的能源资源,解决东部地区能源紧缺的矛盾,是东西部经济合作、优势互补、东西联动双赢战略研究的一项重要课题.在国家投资主体和市场经济条件下,以能源消费效益最大为目标,建立了基于边际效益均衡的能源空间配置优化模型;兼顾经济效益与环境效益的能源部门配置优化模型.结果显示,各地区、部门要获得更多的能源,就必须提高能源的使用效率,提高能源消费的边际效益,降低污染排放水平. 相似文献
5.
Dean A. Carlson 《Journal of Mathematical Analysis and Applications》2002,276(2):561-588
The method of equivalent variational methods, originally due to Carathéodory for free problems in the calculus of variations is extended to investigate feedback Nash equilibria for a class of n-person differential games. Both the finite-horizon and infinite-horizon cases are considered. Examples are given to illustrate the presented results. 相似文献
6.
7.
PANG Jin-qiao WU Ze-qing YAN Jun 《原子与分子物理学报》2006,23(Z1):37-40
The effects of highly doubly excited states on ionization balance are investigated. In the calculation, A Collisional-Radiative model in Detailed-Configuration-Accounting (DCA) is applied to population calculations for NLTE plasmas. Configuration-averaged rate coefficients that needed in the rate equations are obtained based on the first order perturbation theory. The Hatree-Fock-Slater self-consistent-field method is used to calculate the electron wave functions. The mean ionization stage of high-Z plasma Lu is presented. The comparison shows that the mean ionization stage increases more than 3 stages when doubly excited states 5l6l' and 5l5l' are not included in the population calculations. 相似文献
8.
Mathematical economics has a long history and covers many interdisciplinary areas between mathematics and economics. At its center lies the theory of market equilibrium. The purpose of this expository article is to introduce mathematicians to price decentralization in general equilibrium theory. In particular, it concentrates on the role of positivity in the theory of convex economic analysis and the role of normal cones in the theory of non-convex economies. 相似文献
9.
We study a model of a queueing system with two complementary products/services. In our model, there is one M/M/1 system and another facility that provides instantaneous service. The two services are complementary and the customer has no benefit from obtaining just one of them. We investigate the model under various price structures and ownership assumptions.AMS subject classification: 90B22, 91A10The authors are equal in their contribution to this paper. This paper is submitted by the first author to the Tokyo Institute of Technology as partial fulfillment of the requirements for the Ph.D. program in the Department of Value and Decision Sciences, and the order of names was chosen in compliance with program conditions. This research was supported by the Israel Science Foundation (grant No. 237/02). 相似文献
10.
An analytical solution of a linearized problem of the emission of periodic internal waves by part of a plane which oscillates with a small amplitude in an arbitrary direction in a viscous exponentially stratified fluid is constructed. Solutions of the dispersion equation are given for all positions of the emitting surface (arbitrary, vertical, horizontal, and critical when one of the beam propagation directions is collinear with the emitting surface). The possibility of transition to the case of a uniform fluid, which is important for applications, is analyzed. 相似文献