全文获取类型
收费全文 | 2601篇 |
免费 | 503篇 |
国内免费 | 185篇 |
专业分类
化学 | 145篇 |
晶体学 | 3篇 |
力学 | 155篇 |
综合类 | 28篇 |
数学 | 2028篇 |
物理学 | 930篇 |
出版年
2024年 | 3篇 |
2023年 | 39篇 |
2022年 | 58篇 |
2021年 | 65篇 |
2020年 | 43篇 |
2019年 | 65篇 |
2018年 | 55篇 |
2017年 | 69篇 |
2016年 | 91篇 |
2015年 | 68篇 |
2014年 | 133篇 |
2013年 | 232篇 |
2012年 | 120篇 |
2011年 | 175篇 |
2010年 | 155篇 |
2009年 | 200篇 |
2008年 | 207篇 |
2007年 | 215篇 |
2006年 | 192篇 |
2005年 | 139篇 |
2004年 | 132篇 |
2003年 | 139篇 |
2002年 | 79篇 |
2001年 | 92篇 |
2000年 | 87篇 |
1999年 | 58篇 |
1998年 | 52篇 |
1997年 | 53篇 |
1996年 | 51篇 |
1995年 | 30篇 |
1994年 | 39篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有3289条查询结果,搜索用时 15 毫秒
991.
Strong optical feedback in a birefringent dual frequency He--Ne laser with a
high reflectivity feedback mirror has been investigated for the first time.
The output characteristics of two orthogonally polarized modes are
demonstrated in two different optical feedback cases: one is for both modes
being fed back and the other is for only one of the modes being fed back.
Strong mode competition can be observed between the two modes with strong
optical feedback. And when one mode's intensity is near its maximum, the
other mode is nearly extinguished. When both modes are fed back into the
laser cavity, the mode competition is stronger than when only one mode is
fed back. The difference in initial intensity between the two orthogonally
polarized modes plays an important role in the mode competition, which has
been experimentally and theoretically demonstrated. 相似文献
992.
This paper presents chaos synchronization between two different
four-dimensional (4D) hyperchaotic Chen systems by nonlinear feedback
control laws. A modified 4D hyperchaotic Chen system is obtained by
changing the nonlinear function of the 4D hyperchaotic Chen system,
furthermore, an electronic circuit to realize two different 4D
hyperchaotic Chen systems is designed. With nonlinear feedback
control method, chaos synchronization between two different 4D
hyperchaotic Chen systems is achieved. Based on the stability theory,
the functions of the nonlinear feedback control for synchronization
of two different 4D hyperchaotic Chen systems is derived, the range
of feedback gains is determined. Numerical simulations are shown to
verify the theoretical results. 相似文献
993.
Intensity modulation in single-mode microchip Nd:YAG lasers with asymmetric external cavity
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Intensity modulation induced by the asymmetric external cavity in
single-mode microchip Nd:YAG lasers is presented. Two kinds of experimental
results are discussed based on multiple feedback effects. In one case, the
intensity modulation curve is a normal sine wave, whose fringe frequency is
four times higher than that of a conventional optical feedback system,
caused by multiple feedback effects. In the other case, the intensity modulation
curve is the overlapping of the above quadruple-frequency signal and
conventional optical feedback signal, which is determined by the additional
phase difference induced by the asymmetric external cavity. The theoretical
analyses are in good agreement with the experimental results. The
quadruple-frequency modulation of the laser output intensity can greatly
increase the resolution of displacement measurement of an optical feedback
system. 相似文献
994.
Synchronization between two different chaotic systems with nonlinear feedback control 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper presents chaos synchronization between two different chaotic
systems by using a nonlinear controller, in which the nonlinear functions of
the system are used as a nonlinear feedback term. The feedback controller is
designed on the basis of stability theory, and the area of feedback gain is
determined. The artificial simulation results show that this control method
is commendably effective and feasible. 相似文献
995.
The variable cross feedback(VCF)method is proposed to control the nonlinear chaos system. The control principle is introduced,and the Peroxidase-Oxidase(PO)system is taken as a typical example to demonstrate the effectiveness of this method. The dynamical behaviors of the PO system controlled using the VCF method are given by computer numerical simulation. The results show that the return map of the system can be changed into the finite isolated points from the assemblage of discrete points having regular distribution and structure by appropriately 相似文献
996.
Control of chaos by a delayed continuous feedback is studied experimentally in a gas discharge plasma. The power spectrum, the maximum of Lyapunov exponents and the time series of the signals all indicate that the period-1 unstable periodic orbit is controlled successfully. The dependence of the control on the delay time and the feedback gain as well as the strength of white noise is also investigated in detail. The experimental results show that the scaling index of the control versus the strength of white noise is 1.995, which is very close to that obtained from the simple logistic map. 相似文献
997.
998.
A control method for congested traffic in the coupled map car-following model 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Based on the pioneer work of Konishi et al, a new control
method is presented to suppress the traffic congestion in the
coupled map (CM) car-following model under an open boundary.
A control signal concluding the velocity differences of the two
vehicles in front is put forward. The condition under which the
traffic jam can be contained is analyzed. The results are
compared with that presented by Konishi et al [Phys.
Rev. 1999 E 60 4000--4007]. The simulation results show that
the temporal behavior obtained by our method is better than that by
the Konishi's et al. method, although both the methods could
suppress the traffic jam. The simulation results are consistent
with the theoretical analysis. 相似文献
999.
In this article, we investigate cascading failures in
complex networks by introducing a feedback. To characterize the
effect of the feedback, we define a procedure that involves a
self-organization of trip distribution during the process of
cascading failures. For this purpose, user equilibrium with variable
demand is used as an alternative way to determine the traffic flow
pattern throughout the network. Under the attack, cost function
dynamics are introduced to discuss edge overload in complex networks,
where each edge is assigned a finite capacity (controlled by
parameter α). We find that scale-free networks without
considering the effect of the feedback are expected to be very
sensitive to α as compared with random networks, while this
situation is largely improved after introducing the feedback. 相似文献
1000.
In this paper, the output feedback control of uncertain chaotic systems is addressed via an adaptive robust fuzzy approach.
Fuzzy logic systems are employed to approximate uncertain nonlinear functions in the chaotic systems. Because only partial
information of the system’s states is needed to be known, an observer is given to estimate the unmeasured states. Compared
with the existing results in the observer design, the prior knowledge on dynamic uncertainties is relaxed and a class of more
general chaotic systems is considered as well as robustness to the approximation error is improved. It can be proven that
the closed-loop system is stable in the sense that all the variables are bounded. Simulation example for the unified chaotic
systems is given to verify the effectiveness of the proposed method.
This work was supported in part by the National Natural Science Foundation of China (60874056) and the Foundation of Educational
Department of Liaoning Province (2008312). 相似文献