全文获取类型
收费全文 | 1335篇 |
免费 | 90篇 |
国内免费 | 44篇 |
专业分类
化学 | 190篇 |
晶体学 | 2篇 |
力学 | 177篇 |
综合类 | 26篇 |
数学 | 411篇 |
物理学 | 663篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 40篇 |
2021年 | 17篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 34篇 |
2017年 | 28篇 |
2016年 | 38篇 |
2015年 | 41篇 |
2014年 | 73篇 |
2013年 | 80篇 |
2012年 | 70篇 |
2011年 | 77篇 |
2010年 | 83篇 |
2009年 | 67篇 |
2008年 | 98篇 |
2007年 | 100篇 |
2006年 | 49篇 |
2005年 | 43篇 |
2004年 | 46篇 |
2003年 | 41篇 |
2002年 | 44篇 |
2001年 | 31篇 |
2000年 | 44篇 |
1999年 | 36篇 |
1998年 | 28篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 13篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有1469条查询结果,搜索用时 15 毫秒
81.
E. Skladnik-Sadowska J. Baranowski M. Milanese R. Moroso J. Pouzo M. Sadowski J. Zebrowski 《Radiation measurements》2001,34(1-6):315-318
The paper reports the application of Solid-State Nuclear Track Detectors to study the pulsed plasma-ion streams emitted from plasma-focus (PF) type discharges, which were performed within a low-energy PACO device constructed at Instituto de Fisica Arroyo Seco. The PACO device was operated under static initial gas conditions or with dynamic gas puffing. Studies of the structure of the fast deuteron beams were carried out within an energy range from 80 keV to about 2 MeV. Studies of ion energy and an ion angular distribution were also performed. The measurements showed that the fast deuterons are emitted in many “narrow” micro-beams, as in other larger PF devices. The anisotropy of the deuteron angular distribution was explained by the stochastic character of the formation of local ion sources within the PF discharge column. 相似文献
82.
All-optical microwave filters are important parts of fiber-optic microwave/millimeter wave processing systems. In this paper, two novel passive tunable all-optical microwave filters based on fiber loop and chirped fiber Bragg gratings (CFBGs) are demonstrated, where the frequency response of the both filters can be continuously tuned by adjusting the wavelength of the input light. The required free spectral range (FSR) of the filters can be obtained by carefully controlling the length of fiber loop and the positions of the CFBGs in the fiber loop. Experimental results prove the feasibility of the proposed filtering structures. 相似文献
83.
Based on the idea of unknown input observers (UIOs), this Letter considers the problem of chaos secure communication within the master-slave configuration. The unknown constant disturbance of parameters in chaotic systems and the unknown input in chaotic signals can be regarded as messages to be recovered in the slave end. If certain conditions are satisfied, we can recover all the unknown messages by designing the UIO based slave. Theoretical analysis and simulation results fully verify the effectiveness of the proposed scheme. 相似文献
84.
L. V. Perova 《Computational Mathematics and Mathematical Physics》2008,48(6):1001-1023
Propagation of small perturbations in a two-layer inviscid stratified fluid is studied. It is assumed that the higher density fluid occupies the lower unbounded half-space, while the lower density fluid occupies the upper unbounded half-space. The source of the excitation is a plane wave traveling along the interface of the fluids. An explicit analytical solution to the problem is constructed, and its existence and uniqueness are proved. The long-time wave pattern developing in the fluids is analyzed. 相似文献
85.
Degenerate cascade fluorescence: Optical spectral-line narrowing via a single microwave cavity
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)
《中国物理 B》2021,30(6):64211-064211
For a three-level atom, two nondegenerate(even microwave and optical) electric dipole transitions are usually allowed; for either of these, the fluorescence spectra are well-described in terms of spontaneous transitions from a triplet of dressed sublevels to an adjacent lower-lying triplet. When the three dressed sublevels are equally spaced from each other, a remarkable feature known as degenerate cascade fluorescence takes place, which displays a five-peaked structure. We show that a single cavity can make all the spectral lines extremely narrow, whether they arise from cavity-coupled or cavity-free transitions. This effect is based on intrinsic cascade lasing feedback and makes it possible to use a single microwave cavity(even a bad cavity) to narrow the spectral lines in the optical frequency regime. 相似文献
86.
An overview of spectroscopic diagnostics techniques for low temperature plasmas is presented with an emphasis to electron number density — Ne measurement. Stark broadening of non-hydrogenic atom and positive ion spectral lines is given. The attention is drawn to experimental techniques used for line intensity and line profile measurement. Self-absorption test, importance of Abel inversion, deconvolution of experimental line profiles and measurement of line asymmetry are treated in some detail in order to improve Ne measurements. Finally the sources of theoretical and experimental Stark broadening data are reviewed and some details discussed. 相似文献
87.
Zhengjun Liu Lie XuChuang Lin Jingmin DaiShutian Liu 《Optics and Lasers in Engineering》2011,49(4):542-546
An image encryption is discussed based on the random phase encoding method in gyrator domains. An iterative structure of image encryption is designed for introducing more random phases to encrypt image. These random phase functions are generated by a two-dimensional chaotic mapping with the help of computer. The random phases are utilized for increasing the security of this encryption algorithm. In the chaotic mapping relation, the initial value and expression can serve as the key of algorithm. The mapping relation is considered secretly for storage and transmission in practical application in comparison to traditional algorithms. The angle parameter of gyrator transform is an additional key. Some numerical simulations have been given to validate the performance of the encryption scheme. 相似文献
88.
We consider a quadratic Liénard equation with an unbounded homoclinic loop, which is a solution tending in forward and backward time to a non-hyperbolic equilibrium point located at infinity. Under small time-periodic perturbation, this equilibrium becomes a normally hyperbolic line of singularities at infinity. We show that the perturbed system may present homoclinic bifurcations, leading to the existence of transverse intersections between the stable and unstable manifolds of such a normally hyperbolic line of singularities. The global study concerning the infinity is performed using the Poincaré compactification in polar coordinates, from which we obtain a system defined on a set equivalent to a solid torus in R3, whose boundary plays the role of the infinity. The transversality of the manifolds is proved using the Melnikov method and implies, via the Birkhoff-Smale Theorem, a complex dynamical behaviour of the perturbed system solutions in the finite part of the phase space. Numerical simulations are performed in order to illustrate this behaviour, which could be called “the chaos arising from infinity”, since it depends on the global structure of the Liénard equation, including the points at infinity. Although applied to a particular case, the analysis presented provides a geometrical approach to study periodic perturbations of homoclinic (or heteroclinic) loops to infinity of any planar polynomial vector field. 相似文献
89.
V. PyragasK. Pyragas 《Physics letters. A》2011,375(44):3866-3871
We propose a simple adaptive delayed feedback control algorithm for stabilization of unstable periodic orbits with unknown periods. The state dependent time delay is varied continuously towards the period of controlled orbit according to a gradient-descent method realized through three simple ordinary differential equations. We demonstrate the efficiency of the algorithm with the Rössler and Mackey-Glass chaotic systems. The stability of the controlled orbits is proven by computation of the Lyapunov exponents of linearized equations. 相似文献
90.
Alexander E. HramovAlexey A. Koronovskii Maria K. KurovskayaOlga I. Moskalenko 《Physics letters. A》2011,375(15):1646-1652
In this Letter we compare the characteristics of two types of the intermittent behavior (type-I intermittency in the presence of noise and eyelet intermittency taking place in the vicinity of the chaotic phase synchronization boundary) supposed hitherto to be different phenomena. We show that these effects are the same type of dynamics observed under different conditions. The correctness of our conclusion is confirmed by the consideration of different sample systems, such as quadratic map, Van der Pol oscillator and Rössler system. Consideration of the problem concerning the upper boundary of the intermittent behavior also confirms the validity of the statement on the equivalence of type-I intermittency in the presence of noise and eyelet intermittency observed in the onset of phase synchronization. 相似文献