全文获取类型
收费全文 | 62077篇 |
免费 | 5292篇 |
国内免费 | 3910篇 |
专业分类
化学 | 5292篇 |
晶体学 | 103篇 |
力学 | 4985篇 |
综合类 | 501篇 |
数学 | 11046篇 |
物理学 | 12283篇 |
综合类 | 37069篇 |
出版年
2024年 | 250篇 |
2023年 | 714篇 |
2022年 | 1327篇 |
2021年 | 1433篇 |
2020年 | 1556篇 |
2019年 | 1339篇 |
2018年 | 1336篇 |
2017年 | 1759篇 |
2016年 | 1972篇 |
2015年 | 1974篇 |
2014年 | 3136篇 |
2013年 | 3578篇 |
2012年 | 3634篇 |
2011年 | 3970篇 |
2010年 | 3138篇 |
2009年 | 3688篇 |
2008年 | 3370篇 |
2007年 | 4162篇 |
2006年 | 3641篇 |
2005年 | 3284篇 |
2004年 | 2939篇 |
2003年 | 2570篇 |
2002年 | 2321篇 |
2001年 | 1869篇 |
2000年 | 1752篇 |
1999年 | 1541篇 |
1998年 | 1260篇 |
1997年 | 1118篇 |
1996年 | 953篇 |
1995年 | 839篇 |
1994年 | 769篇 |
1993年 | 664篇 |
1992年 | 588篇 |
1991年 | 509篇 |
1990年 | 479篇 |
1989年 | 336篇 |
1988年 | 319篇 |
1987年 | 254篇 |
1986年 | 174篇 |
1985年 | 151篇 |
1984年 | 139篇 |
1983年 | 74篇 |
1982年 | 101篇 |
1981年 | 64篇 |
1980年 | 32篇 |
1979年 | 41篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1976年 | 15篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
We give an account of the appearance and first developments of the statistical model of atoms proposed by Thomas and Fermi, focusing on the main results achieved by Fermi and his group in Rome. Particular attention is addressed to the unknown contribution to this subject by Majorana, anticipating some important results reached later by leading physicists. 相似文献
103.
Marco Pretti 《Journal of statistical physics》2003,111(3-4):993-1015
In this article we deal with the variational approach to cactus trees (Husimi trees) and the more common recursive approach, that are in principle equivalent for finite systems. We discuss in detail the conditions under which the two methods are equivalent also in the analysis of infinite (self-similar) cactus trees, usually investigated to the purpose of approximating ordinary lattice systems. Such issue is hardly ever considered in the literature. We show (on significant test models) that the phase diagram and the thermodynamic quantities computed by the variational method, when they deviates from the exact bulk properties of the cactus system, generally provide a better approximation to the behavior of a corresponding ordinary system. Generalizing a property proved by Kikuchi, we also show that the numerical algorithm usually employed to perform the free energy minimization in the variational approach is always convergent. 相似文献
104.
Let Um be an m×m Haar unitary matrix and U[m,n] be its n×n truncation. In this paper the large deviation is proven for the empirical eigenvalue density of U[m,n] as m/n→λ and n→∞. The rate function and the limit distribution are given explicitly. U[m,n] is the random matrix model of quq, where u is a Haar unitary in a finite von Neumann algebra, q is a certain projection and they are free. The limit distribution coincides with the Brown measure of the operator quq. 相似文献
105.
Numerical schemes for systems with multiple spatio-temporal scales are investigated. The multiscale schemes use asymptotic results for this type of systems which guarantee the existence of an effective dynamics for some suitably defined modes varying slowly on the largest scales. The multiscale schemes are analyzed in general, then illustrated on a specific example of a moderately large deterministic system displaying chaotic behavior due to Lorenz. Issues like consistency, accuracy, and efficiency are discussed in detail. The role of possible hidden slow variables as well as additional effects arising on the diffusive time-scale are also investigated. As a byproduct we obtain a rather complete characterization of the effective dynamics in Lorenz model. 相似文献
106.
A. M. Povolotsky V. B. Priezzhev Chin-Kun Hu 《Journal of statistical physics》2003,111(5-6):1149-1182
An asymmetric stochastic process describing the avalanche dynamics on a ring is proposed. A general kinetic equation which incorporates the exclusion and avalanche processes is considered. The Bethe ansatz method is used to calculate the generating function for the total distance covered by all particles. It gives the average velocity of particles which exhibits a phase transition from an intermittent to continuous flow. We calculated also higher cumulants and the large deviation function for the particle flow. The latter has the universal form obtained earlier for the asymmetric exclusion process and conjectured to be common for all models of the Kardar–Parisi–Zhang universality class. 相似文献
107.
Nonlinear susceptibility of a quantum dot (QD) embedded in a two-sided cavity, is studied theoretically from a weak-coupling to a strong-coupling regime. In the relevance of a quantum logic gate, the corresponding nonlinear phase shifts (Kerr effect) are estimated for coherent wavepackets including one photon on average. In the weak-coupling regime, the phase shift enhances strongly as a function of a coupling constant between the cavity photon and QD, and eventually saturates in the strong-coupling regime. We also show transmission spectra to evaluate the efficiency of the phase shift. Although the efficiency decreases monotonically in the weak-coupling regime, it rises in the strong-coupling regime. 相似文献
108.
109.
南淝河水质S-P模型参数K1、K2的估值 总被引:3,自引:2,他引:1
对南淝河河流水质S-P模型中碳化BOD衰减系数K1和大气复氧系数K2分段进行了估值.根据实验测定数据,用最小二乘法、图解法和两点法等3种方法对K1进行了估值,应用公式估算法对K2进行了估值,并对估值的结果与南淝河的有机污染状况进行了对比和分析,从而为模型提供准确的参数值,也为南淝河的水污染控制和水质规划提供有益的借鉴. 相似文献
110.
介绍了研究传输控制协议 (TCP)拥塞控制问题的各种分析模型 ,指出了研究TCP拥塞控制的主要目标 .对当前国内外的研究动态给予了讨论 ,并对当前现有模型根据其流量范围和使用的分析工具进行了分类概括 .最后概要地阐述了在端到端和在网络中进行拥塞控制的相互关系 相似文献