全文获取类型
收费全文 | 5295篇 |
免费 | 1309篇 |
国内免费 | 511篇 |
专业分类
化学 | 154篇 |
晶体学 | 8篇 |
力学 | 813篇 |
综合类 | 252篇 |
数学 | 4102篇 |
物理学 | 1786篇 |
出版年
2024年 | 39篇 |
2023年 | 127篇 |
2022年 | 155篇 |
2021年 | 173篇 |
2020年 | 111篇 |
2019年 | 147篇 |
2018年 | 100篇 |
2017年 | 152篇 |
2016年 | 144篇 |
2015年 | 219篇 |
2014年 | 374篇 |
2013年 | 289篇 |
2012年 | 328篇 |
2011年 | 389篇 |
2010年 | 376篇 |
2009年 | 405篇 |
2008年 | 358篇 |
2007年 | 341篇 |
2006年 | 333篇 |
2005年 | 303篇 |
2004年 | 333篇 |
2003年 | 270篇 |
2002年 | 177篇 |
2001年 | 177篇 |
2000年 | 159篇 |
1999年 | 146篇 |
1998年 | 142篇 |
1997年 | 170篇 |
1996年 | 123篇 |
1995年 | 126篇 |
1994年 | 96篇 |
1993年 | 76篇 |
1992年 | 70篇 |
1991年 | 63篇 |
1990年 | 61篇 |
1989年 | 44篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1959年 | 1篇 |
排序方式: 共有7115条查询结果,搜索用时 718 毫秒
941.
942.
LI Dong-Xi XU Wei WANG Liang XU Yong 《理论物理通讯》2008,50(8):396-402
The phenomenon of stochastic resonance of a bistable system subjected to linear time-delayed feedback loops driven by multiplieative Gaussian coloured noise and additive Gaussian white noise is investigated. Firstly, the analytic expression of the quasi-steady distribution function Ps (x, t) is derived by applying the unified coloured noise approximation and the Novikov Theorem; Secondly, the expression of the signal-to-noise ratio (SNR) is obtained in the adiabatic limit to quantify the stochastic resonance. Finally, tile effects of the linear coefficient a, the nonlinear coefficient b, the linear time-delayed feedback coefficient c and the delay time r on Ps(x,t) and SNR^± are discussed. It is found that the effects of the linear coefficient and the nonlinear coefficient, the positive linear time-delayed feedback coefficient and the negative linear time-delayed feedback coefficient, the positive delayed time and the negative delayed time on Ps(x,t) and SNR^± are different, respectively. This discussion would be helpful to the study of the system reliability and controlling stochastic resonance. 相似文献
943.
LI Jing-Hui 《理论物理通讯》2008,50(11):1159-1164
In this paper, an electric system with two dichotomous resistors is investigated. It is shown that this system can display two stochastic resonances, which are the amplitude of the periodic response as the functions of the two dichotomous resistors strengthes respectively. In the limits of Gaussian white noise and shot white noise (i.e., the two noises are both Gaussian white noise or shot white noise) no phenomena of resonance appear. By further study, we find that when the system is with three or more multiplicative telegraphic noises, there are three or more stochastic resonances. 相似文献
944.
ZHANG Ji-Qian CHEN Han-Shuang WANG Mao-Sheng 《理论物理通讯》2008,50(10):903-906
We consider the dynamics of locally coupled calcium oscillation systems, each cell is subjected to extracellular contaminated signal, which contains common sub-threshold signal and independent Gaussian noise. It is found that intermediate noise can enhance synchronized oscillations of calcium ions, where the frequency of noise-induced oscillations is matched with the one of sub-threshold external signal. We show that synchronization is enhanced as a result of the entrainment of external signal. Furthermore, the effect of coupling strength is considered. We find above-mentioned phenomenon exists only when coupling strength is very small. Our findings may exhibit that noise can enhance the detection of feeble external signal through the mechanism of synchronization of intercellular calcium ions. 相似文献
945.
Entanglement in One-Dimensional Random XY Spin Chain with Dzyaloshinskii--Moriya Interaction 下载免费PDF全文
The impurities of exchange couplings, external magnetic fields and Dzyaloshinskii-Moriya (DM) interaction considered as Gaussian distribution, and the entanglement in one-dimensional random XY spin systems is investigated by the method of solving the different spin-spin correlation functions and the average magnetization per spin. The entanglement dynamics at central locations of ferromagnetic and antiferromagnetic chains have been studied by varying the three impurities and the strength of DM interaction. (i) For the ferromagnetic spin chain, the weak DM interaction can improve the amount of entanglement to a large value, and the impurities have the opposite effect on the entanglement below and above critical DM interaction. (ii) For the antiferromagnetic spin chain, DM interaction can enhance the entanglement to a steady value. Our results imply that DM interaction strength, the impurity and exchange couplings (or magnetic field) play competing roles in enhancing quantum entanglement. 相似文献
946.
We investigate the effects of intrinsic noise on Turing pattern formation near the onset of bifurcation from the homogeneous state to Turing pattern in the reaction-diffusion Brusselator. By performing stochastic simulations of the master equation and using Gillespie's algorithm, we check the spatiotemporal behaviour influenced by internal noises. We demonstrate that the patterns of occurrence frequency for the reaction and diffusion pro- cesses are also spatially ordered and temporally stable. Turing patterns are found to be robust against intrinsic fluctuations. Sfochastic simulations also reveal that under the influence of intrinsic noises, the onset of Turing instability is advanced in comparison to that predicted deterministically. 相似文献
947.
We consider the fluctuation of mesoscopic RLC circuit at finite temperature since a resistance always produces Joule heat when the circuit is working. By virtue of the thermo field dynamics and the coherent thermo state representation we show that the quantum mechanical zero-point fluctuations of both charge and current increase with the rising temperature and the resistance value. 相似文献
948.
949.
利用随机光滑动力系统的Chebyshev正交多项式逼近方法,研究了双边约束条件下随机van der Pol系统的分岔现象.数值研究表明,双边约束随机van der Pol系统中不仅存在着丰富的倍周期分岔现象,还存在非光滑系统中所特有的擦边分岔.着重研究了随机非光滑系统中的擦边分岔,分析了随机因素对非光滑动力系统中擦边分岔的影响.研究表明,Chebyshev多项式逼近也是研究随机非光滑系统动力学行为的一种有效方法.
关键词:
非光滑动力系统
随机 van der Pol系统
擦边分岔
双边约束 相似文献
950.
研究了一类非零键渗透率满足均匀分布的随机多孔介质逾渗模型-数值计算了该模型系统渗透率在临界点处的标度指数-结果表明该指数并不能看作是普适常数,而与均匀分布的参数有关-这意味着即使非零键渗透率值的概率密度函数满足负一阶矩存在条件,系统渗透率在逾渗临界点处的标度指数仍然依赖于分布函数的具体参数,并不是常数-这一数值结果与Sahimi对此问题的结论不同-
关键词:
逾渗
随机多孔介质
标度指数
渗透率 相似文献