全文获取类型
收费全文 | 651篇 |
免费 | 23篇 |
国内免费 | 10篇 |
专业分类
化学 | 2篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 561篇 |
物理学 | 115篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 41篇 |
2019年 | 41篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 17篇 |
2015年 | 28篇 |
2014年 | 48篇 |
2013年 | 101篇 |
2012年 | 26篇 |
2011年 | 31篇 |
2010年 | 19篇 |
2009年 | 32篇 |
2008年 | 31篇 |
2007年 | 38篇 |
2006年 | 27篇 |
2005年 | 18篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 8篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有684条查询结果,搜索用时 496 毫秒
31.
B. Podobnik D. F. Fu H. E. Stanley P. Ch. Ivanov 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):47-52
We develop a stochastic process with two coupled variables where
the absolute values of each variable exhibit long-range power-law
autocorrelations and are also long-range cross-correlated. We investigate how
the scaling exponents characterizing power-law autocorrelation and long-range
cross-correlation behavior in the absolute values of the generated variables
depend on the two parameters in our model. In particular, if the
autocorrelation is stronger, the cross-correlation is also stronger. We test
the utility of our approach by comparing the autocorrelation and
cross-correlation properties of the time series generated by our model with
data on daily returns over ten years for two major financial indices, the
Dow Jones and the S&P500, and on daily returns of two well-known
company stocks, IBM and Microsoft, over five years. 相似文献
32.
We prove the equivalence of the three different definitions of the viscosity solution for the integro-differential equation with the Lévy operator. The two of the definitions are known in the preceding works of the author and the others, and the last one is new. A construction of a sequence of the approximating test functions to the subsolution (or the supersolution) is indispensable for the proof, and it is done explicitly in the paper. 相似文献
33.
34.
J. Török S. Krishnamurthy J. Kertész S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):697-701
We introduce a model for the slow relaxation of an energy landscape caused by its local interaction with a random walker whose
motion is dictated by the landscape itself. By choosing relevant measures of time and potential this self-quenched dynamics can be mapped on to the “True” Self-Avoiding Walk model. This correspondence reveals that the average distance of
the walker at time t from its starting point is , where for one dimension and 1/2 for all higher dimensions. Furthermore, the evolution of the landscape is similar to that in growth
models with extremal dynamics.
Received 8 August 2000 相似文献
35.
Temporal scaling and infinite variance are two stylized features often seen together in times series of complex systems. We find that because of their infinite moments samples from fractional Lévy flights produce bi-linear scaling functions which may be incorrectly attributed as evidence of multifractality. We argue that it is unnecessary to consider truncated fractional Lévy flights which are inherently problematic. 相似文献
36.
Nicole Bäuerle Anja Blatter Alfred Müller 《Mathematical Methods of Operations Research》2008,67(1):161-186
In this paper we investigate dependence properties and comparison results for multidimensional Lévy processes. In particular
we address the questions, whether or not dependence properties and orderings of the copulas of the distributions of a Lévy
process can be characterized by corresponding properties of the Lévy copula, a concept which has been introduced recently
in Cont and Tankov (Financial modelling with jump processes. Chapman & Hall/CRC, Boca Raton, 2004) and Kallsen and Tankov
(J Multivariate Anal 97:1551–1572, 2006). It turns out that association, positive orthant dependence and positive supermodular dependence of Lévy processes can be characterized in terms of the Lévy measure as well as in terms of the Lévy copula. As
far as comparisons of Lévy processes are concerned we consider the supermodular and the concordance order and characterize
them by orders of the Lévy measures and by orders of the Lévy copulas, respectively. An example is given that the Lévy copula
does not determine dependence concepts like multivariate total positivity of order 2 or conditionally increasing in sequence. Besides these general results we specialize our findings for subfamilies of Lévy processes. The last section contains some
applications in finance and insurance like comparison statements for ruin times, ruin probabilities and option prices which
extends the current literature.
Anja Blatter was supported by the Deutsche Forschungsgemeinschaft (DFG). 相似文献
37.
Hsin-Hung Shih 《Journal of Functional Analysis》2008,255(3):657-680
By using a method of truncation, we derive the closed form of the Segal-Bargmann transform of Lévy white noise functionals associated with a Lévy process with the Lévy spectrum without the moment condition. Besides, a sufficient and necessary condition to the existence of Lévy stochastic integrals is obtained. 相似文献
38.
In this paper, we investigate the long-range dependence of fractional Lévy processes on Gel’fand triple and construct stochastic
integral with respect to fractional Lévy processes for a class of deterministic integrands.
相似文献
39.
Stochastic Configuration Network (SCN) has a powerful capability for regression and classification analysis. Traditionally, it is quite challenging to correctly determine an appropriate architecture for a neural network so that the trained model can achieve excellent performance for both learning and generalization. Compared with the known randomized learning algorithms for single hidden layer feed-forward neural networks, such as Randomized Radial Basis Function (RBF) Networks and Random Vector Functional-link (RVFL), the SCN randomly assigns the input weights and biases of the hidden nodes in a supervisory mechanism. Since the parameters in the hidden layers are randomly generated in uniform distribution, hypothetically, there is optimal randomness. Heavy-tailed distribution has shown optimal randomness in an unknown environment for finding some targets. Therefore, in this research, the authors used heavy-tailed distributions to randomly initialize weights and biases to see if the new SCN models can achieve better performance than the original SCN. Heavy-tailed distributions, such as Lévy distribution, Cauchy distribution, and Weibull distribution, have been used. Since some mixed distributions show heavy-tailed properties, the mixed Gaussian and Laplace distributions were also studied in this research work. Experimental results showed improved performance for SCN with heavy-tailed distributions. For the regression model, SCN-Lévy, SCN-Mixture, SCN-Cauchy, and SCN-Weibull used less hidden nodes to achieve similar performance with SCN. For the classification model, SCN-Mixture, SCN-Lévy, and SCN-Cauchy have higher test accuracy of 91.5%, 91.7% and 92.4%, respectively. Both are higher than the test accuracy of the original SCN. 相似文献
40.
Dynamics of a stochastic rumor propagation model incorporating media coverage and driven by Lévy noise 下载免费PDF全文
Liang-An Huo 《中国物理 B》2021,30(8):80201-080201
With the development of information technology, rumors propagate faster and more widely than in the past. In this paper, a stochastic rumor propagation model incorporating media coverage and driven by Lévy noise is proposed. The global positivity of the solution process is proved, and further the basic reproductive number R0 is obtained. When R0 < 1, the dynamical process of system with Lévy jump tends to the rumor-free equilibrium point of the deterministic system, and the rumor tends to extinction; when R0 > 1, the rumor will keep spreading and the system will oscillate randomly near the rumor equilibrium point of the deterministic system. The results show that the oscillation amplitude is related to the disturbance of the system. In addition, increasing media coverage can effectively reduce the final spread of rumors. Finally, the above results are verified by numerical simulation. 相似文献