全文获取类型
收费全文 | 5156篇 |
免费 | 393篇 |
国内免费 | 354篇 |
专业分类
化学 | 950篇 |
晶体学 | 10篇 |
力学 | 556篇 |
综合类 | 47篇 |
数学 | 2818篇 |
物理学 | 1522篇 |
出版年
2024年 | 7篇 |
2023年 | 60篇 |
2022年 | 98篇 |
2021年 | 106篇 |
2020年 | 104篇 |
2019年 | 106篇 |
2018年 | 96篇 |
2017年 | 137篇 |
2016年 | 153篇 |
2015年 | 117篇 |
2014年 | 259篇 |
2013年 | 406篇 |
2012年 | 189篇 |
2011年 | 326篇 |
2010年 | 283篇 |
2009年 | 306篇 |
2008年 | 328篇 |
2007年 | 380篇 |
2006年 | 301篇 |
2005年 | 233篇 |
2004年 | 245篇 |
2003年 | 206篇 |
2002年 | 153篇 |
2001年 | 125篇 |
2000年 | 122篇 |
1999年 | 120篇 |
1998年 | 112篇 |
1997年 | 101篇 |
1996年 | 68篇 |
1995年 | 77篇 |
1994年 | 69篇 |
1993年 | 73篇 |
1992年 | 58篇 |
1991年 | 49篇 |
1990年 | 32篇 |
1989年 | 34篇 |
1988年 | 30篇 |
1987年 | 35篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1970年 | 5篇 |
排序方式: 共有5903条查询结果,搜索用时 15 毫秒
1.
2.
3.
基于时变Copula模型,获得预测方差,确定单个基金收益率序列的边缘分布.利用常见的静态Copula和时变Copula模型对基金收益率序列间两两相依关系进行建模并进行对比分析.应用研究表明,基于MCMC方法的时变Copula模型能更有效地度量基金收益率序列的风险. 相似文献
4.
Heinrich Saller 《International Journal of Theoretical Physics》2002,41(8):1491-1509
Unstable particles, together with their stable decay products, constitute probability collectives that are defined as Hilbert spaces with dimension higher than one, nondecomposable in a particle basis. Their structure is considered in the framework of Birkhoff-von Neumann's Hilbert subspace lattices. Bases with particle states are related to bases with a diagonal scalar product by a Hilbert-bein involving the characteristic decay parameters (in some analogy to the n-bein structures of metrical manifolds). Probability predictions as expectation values, involving unstable particles, have to take into account all members of the higher dimensional collective. For example, the unitarity structure of the S-matrix for an unstable particle collective can be established by a transformation with its Hilbert-bein. 相似文献
5.
根据Pegg-Barnett位相定义, 计算了一种新的奇偶非线性相干态的位相概率分布函数, 利用数值计算方法研究了它们的位相统计性质. 数值计算结果表明:新的奇偶非线性相干态的位相特性与通常奇偶相干态的位相特性截然不同. 相似文献
6.
带干扰的多险种风险模型 总被引:2,自引:0,他引:2
由于保险公司风险经营规模不断扩大,用单一险种的模型来描述风险过程存在局限性,本文讨论了带干扰多险种风险模型,应用鞅论方法,得出伦德伯格不等式和最终破产概率公式。 相似文献
7.
We propose a framework, based on classical mixture theory, to describe the isothermal flow of an incompressible fluid through a deformable inelastic porous solid. The modeling of the behavior of the inelastic solid takes into account changes in the elastic response due to evolution in the microstructure of the material. We apply the model to a compression layer problem. The mathematical problem generated by the model is a free boundary problem. 相似文献
8.
Shunlong Luo 《Foundations of Physics》2002,32(11):1757-1772
We formulate an elementary statistical game which captures the essence of some fundamental quantum experiments such as photon polarization and spin measurement. We explore and compare the significance of the principle of maximum Shannon entropy and the principle of minimum Fisher information in solving such a game. The solution based on the principle of minimum Fisher information coincides with the solution based on an invariance principle, and provides an informational explanation of Malus' law for photon polarization. There is no solution based on the principle of maximum Shannon entropy. The result demonstrates the merits of Fisher information, and the demerits of Shannon entropy, in treating some fundamental quantum problems. It also provides a quantitative example in support of a general philosophy: Nature intends to hide Fisher information, while obeying some simple rules. 相似文献
9.
Evolutionary algorithms are applied as problem-independent optimization algorithms. They are quite efficient in many situations. However, it is difficult to analyze even the behavior of simple variants of evolutionary algorithms like the (1+1) EA on rather simple functions. Nevertheless, only the analysis of the expected run time and the success probability within a given number of steps can guide the choice of the free parameters of the algorithms. Here static (1+1) EAs with a fixed mutation probability are compared with dynamic (1+1) EAs with a simple schedule for the variation of the mutation probability. The dynamic variant is first analyzed for functions typically chosen as example-functions for evolutionary algorithms. Afterwards, it is shown that it can be essential to choose the suitable variant of the (1+1) EA. More precisely, functions are presented where each static (1+1) EA has exponential expected run time while the dynamic variant has polynomial expected run time. For other functions it is shown that the dynamic (1+1) EA has exponential expected run time while a static (1+1) EA with a good choice of the mutation probability has polynomial run time with overwhelming probability. 相似文献
10.
The Boltzmann distribution used in the steady-state analysis of the simulated annealing algorithm gives rise to several scale invariant properties. Scale invariance is first presented in the context of parallel independent processors and then extended to an abstract form based on lumping states together to form new aggregate states. These lumped or aggregate states possess all of the mathematical characteristics, forms and relationships of states (solutions) in the original problem in both first and second moments. These scale invariance properties therefore permit new ways of relating objective function values, conditional expectation values, stationary probabilities, rates of change of stationary probabilities and conditional variances. Such properties therefore provide potential applications in analysis, statistical inference and optimization. Directions for future research that take advantage of scale invariance are also discussed. 相似文献