全文获取类型
收费全文 | 163篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
化学 | 18篇 |
力学 | 1篇 |
数学 | 35篇 |
物理学 | 117篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 20篇 |
2012年 | 6篇 |
2011年 | 18篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有171条查询结果,搜索用时 15 毫秒
1.
Electron diffraction and lattice dynamical calculations are used to investigate the unit cells, space group symmetries and inherent displacive flexibility of the room-temperature average structures of AlPO4-8, AlPO4-16 and AlPO4-tridymite. The zero-frequency rigid unit modes (RUMs) of the idealized high-symmetry polymorphs thereof are also investigated along with their relationship to the lower-temperature polymorphism of these zeotypic aluminophosphates. The clear presence of satellite reflections in addition to the Bragg reflections (G) of the underlying Cmc21 parent structure in the case of AlPO4-8 shows that the true unit cell of the room-temperature polymorph has a doubled c-axis due to a condensed RUM mode. Structured diffuse scattering is also observed which can be related to the thermal excitation of RUM modes. In the case of AlPO4-tridymite, a complex F1 triclinic polymorph is observed and related to soft RUM modes while, in the case of AlPO4-16, a soft q=0 RUM mode is shown to be responsible for an observed phase transition in the case of the all SiO2 analogue of AlPO4-16. A large number of additional zero-frequency RUM modes also exist in the case of AlPO4-16. 相似文献
2.
Let be the first return time to of sums of increments given by a functional of a stationary Markov chain. We determine the asymptotic behavior of the survival probability, for an explicit constant . Our analysis is based on a connection between the survival probability and the running maximum of the time-reversed process, and relies on a functional central limit theorem for Markov chains. As applications, we recover known clustering results for the 3-color cyclic cellular automaton and the Greenberg–Hastings model, and we prove a new clustering result for the 3-color firefly cellular automaton. 相似文献
3.
D. Vollhardt 《Annalen der Physik》2012,524(1):1-19
Electronic correlations strongly influence the properties of matter. For example, they can induce a discontinuous transition from conducting to insulating behavior. In this paper basic terms of the physics of correlated electrons are explained. In particular, I describe some of the steps that led to the formulation of a comprehensive, non‐perturbative many‐body approach to correlated quantum many‐body systems, the dynamical mean‐field theory (DMFT). The DMFT becomes exact in the limit of high lattice dimensions (d → ∞) and allows one to go beyond the investigation of simple correlation models and thereby better understand, and even predict, the properties of electronically correlated materials. 相似文献
4.
The deployment of Small Cells in fourth generation (4G) communication systems is aimed at providing significant capacity improvements and higher availabilities. However, the design of Small Cell systems in indoor environments is especially challenging due to high shadowing attenuation induced by clutter and human blockage. This paper studies node cooperation and multiple relaying and proposes novel analytical formulas for the outage probability of cooperative Small Cells suffering from shadowing. The channel fading gains are modeled as correlated lognormal random variables, in order to reflect the properties of indoor propagation environments. Various cooperative strategies are considered, taking into account the use of one or two relays and different receiver combining techniques. In addition, the relative performance of each cooperative configuration and the benefit of cooperation over non-cooperation are investigated. Finally, interesting and useful insights are produced regarding the impact of the correlated lognormal environment parameters on the configuration of cooperative Small Cells. 相似文献
5.
6.
Marta Sanz-Solé 《Journal of Functional Analysis》2008,255(1):255-281
We consider a stochastic wave equation in space dimension three driven by a noise white in time and with an absolutely continuous correlation measure given by the product of a smooth function and a Riesz kernel. Let pt,x(y) be the density of the law of the solution u(t,x) of such an equation at points (t,x)∈]0,T]×R3. We prove that the mapping (t,x)?pt,x(y) owns the same regularity as the sample paths of the process {u(t,x),(t,x)∈]0,T]×R3} established in [R.C. Dalang, M. Sanz-Solé, Hölder-Sobolev regularity of the solution to the stochastic wave equation in dimension three, Mem. Amer. Math. Soc., in press]. The proof relies on Malliavin calculus and more explicitly, the integration by parts formula of [S. Watanabe, Lectures on Stochastic Differential Equations and Malliavin Calculus, Tata Inst. Fund. Res./Springer-Verlag, Bombay, 1984] and estimates derived from it. 相似文献
7.
Peixia Gao Sabine Wittevrongel Joris Walraevens Herwig Bruneel 《Mathematical Methods of Operations Research》2008,67(2):269-284
In this paper, we study the behavior of a discrete-time multiserver buffer system with infinite buffer size. Packets arrive
at the system according to a two-state Markovian arrival process. The service times of the packets are assumed to be constant,
equal to multiple slots. The behavior of the system is analyzed by means of an analytical technique based on probability generating
functions (PGF’s). Explicit expressions are obtained for the PGF’s of the system contents and the packet delay. From these,
the mean values, the variances and the tail distributions of the system contents and the packet delay are calculated. Numerical
examples are given to show the influence of various model parameters on the system behavior. 相似文献
8.
David P. Kratz 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(6):1060-1080
Over the last quarter century, improvements in the determination of the spectroscopic characteristics of the infrared-active trace species have enhanced our ability to retrieve quantitative distributions of temperatures, clouds, and abundances for various trace species within the Earth's atmosphere. These improvements have also allowed for refinements in the estimates of climatic effects attributed to changes in the Earth's atmospheric composition. Modeling efforts, however, have frequently experienced significant delays in assimilating improved spectroscopic information. Such is the case for highly parameterized models, where considerable effort is typically required to incorporate any revisions. Thus, a line-by-line radiative transfer model has been used to investigate the magnitude of the effects resulting from modifications to the spectroscopic information. Calculations from this line-by-line model have demonstrated that recent modifications to the HITRAN (High Resolution Transmission) line parameters, the continuum formulation, and the CO2 line-mixing formulation can significantly affect the interpretation of the high spectral resolution radiance and brightness temperature retrievals. For certain moderate-resolution satellite remote sensing channels, modifications to these spectroscopic parameters and formulations have shown the capacity to induce changes in the calculated radiances equivalent to brightness temperature differences of 1-2 K. Model calculations have further shown that modifications of the spectroscopic characteristics tend to have a modest effect on the determination of spectrally integrated radiances, fluxes, and radiative forcing estimates, with the largest differences being of order 1 W m−2 for the total thermal infrared fluxes, and of order 2-3% of the calculated radiative forcing at the tropopause attributed to the combined doubling of CO2, N2O, and CH4. The results from this investigation are intended to function as a guide to differentiate between cases where older parameterizations provide acceptable results, within specified accuracy bounds, and cases where upgrades to the latest spectroscopic database are necessary. 相似文献
9.
10.
We developed a new radiation parameterization of hydrofluorocarbons (HFCs), using the correlated k-distribution method and the high-resolution transmission molecular absorption (HITRAN) 2004 database. We examined the instantaneous and stratospheric adjusted radiative efficiencies of HFCs for clear-sky and all-sky conditions. We also calculated the radiative forcing of HFCs from preindustrial times to the present and for future scenarios given by the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (SRES, in short). Global warming potential and global temperature potential were then examined and compared on the basis of the calculated radiative efficiencies. Finally, we discuss surface temperature changes due to various HFC emissions. 相似文献