全文获取类型
收费全文 | 499篇 |
免费 | 287篇 |
国内免费 | 209篇 |
专业分类
化学 | 278篇 |
晶体学 | 21篇 |
力学 | 95篇 |
综合类 | 6篇 |
数学 | 37篇 |
物理学 | 558篇 |
出版年
2024年 | 8篇 |
2023年 | 23篇 |
2022年 | 19篇 |
2021年 | 29篇 |
2020年 | 15篇 |
2019年 | 30篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 36篇 |
2015年 | 24篇 |
2014年 | 59篇 |
2013年 | 51篇 |
2012年 | 58篇 |
2011年 | 56篇 |
2010年 | 44篇 |
2009年 | 38篇 |
2008年 | 51篇 |
2007年 | 57篇 |
2006年 | 44篇 |
2005年 | 58篇 |
2004年 | 41篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 22篇 |
2000年 | 23篇 |
1999年 | 22篇 |
1998年 | 15篇 |
1997年 | 18篇 |
1996年 | 10篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有995条查询结果,搜索用时 15 毫秒
91.
The steady axis-symmetrical atmosphere dynamical equations are used for describing spiral structure of tropical cyclones under four-force (pressure gradient force, Coriolis force, centrifugal force, and friction force) balance, and the dynamical systems of three-dimensional (3D) velocity field are introduced. The qualitative analysis of the dynamical system shows that there are down 3D spiral structures in eye of tropical cyclone and tropical cyclone is 3D counterclockwise up spiral structure. These results are consistent with the observed tropical cyclone on the weather map. 相似文献
92.
We study the motion of a spiral wave controlled by a local periodic forcing imposed on a region around the spiral tip in an excitable medium. Three types of trajectories of spiral tip are observed: the epicycloid-like meandering, the resonant drift, and the hypocycloid-like meandering. The frequency of the spiral is sensitive to the local periodic forcing. The dependency of spiral frequency on the amplitude and size of local periodic forcing are presented. In addition, we show how the drift speed and direction are adjusted by the amplitude and phase of local periodic forcing, which is consistent with a theoretical analysis based on the weak deformation approximation. 相似文献
93.
Myosin V and myosin VI are two classes of two-headed molecular motors of the myosin superfamily that move processively along helical actin filaments in opposite directions. Here we present a hand-over-hand model for their processive movements. In the model, the moving direction of a dimeric molecular motor is automatically determined by the relative orientation between its two heads at free state and its head‘s binding orientation on track filament.This determines that myosin V moves toward the barbed end and myosin VI moves toward the pointed end of actin.During the moving period in one step, one head remains bound to actin for myosin V whereas two heads are detached for myosin VI: the moving manner is determined by the length of neck domain. This naturally explains the similar dynamic behaviours but opposite moving directions of myosin VI and mutant myosin V (the neck of which is truncated to only one-sixth of the native length). Because of different moving manners, myosin VI and mutant myosin V exhibit significantly broader step-size distribution than native myosin V. However, all the three motors give the same mean step size of -36nm (the pseudo-repeat of actin helix). All these theoretical results are in agreement with previous experimental ones. 相似文献
94.
ZDRAVKOVICS SATARICM.V 《中国物理快报》2005,22(4):850-852
We compare optical and acoustical frequencies in the Peyrard-Bishop-Dauxois model, i.e. an extended Peyrard-Bishop model, of DNA molecules. We discuss how ratio of those frequencies depends on a value of the harmonic constant of the helicoidal spring K. Also, we suggest that the most favourable mode could be a resonance mode. 相似文献
95.
Spirals generated from the excitable media within the Barkley model is investigated under the gradient electric fields by a numerical simulation. The spiral drift and spiral break up are observed when the amplitude of the electric fields is modulated by a constant signal or a chaotic signal. It is also verified that, even in the presence of the white noise, the whole system can reach homogeneous states after the spiral breakup, by using an adaptive strategy. 相似文献
96.
The dynamic behaviour of spiral tip in the light-sensitive Belousov-Zhabotinsky reaction under the influence of an externally applied light gradient was experimentally studied. The gradient causes different drifts for different spiral patterns. The centre of the spiral wave moved toward the region of lower light intensity. The direction of an additional perpendicular drift depended on the chirality of the spiral wave. The dependences of the drifting angle and the drifting velocity on light gradient have been measured. 相似文献
97.
Elimination of Spiral Waves and Competition between Travelling Wave Impulses and Spiral Waves 下载免费PDF全文
The interaction between travelling wave impulses and spiral waves is studied and the results of their competition are related to the exciting period. From the results, it is known that the formation and development of spiral waves in cardiac tissue depend on the period by which the travelling wave impulses are excited. A method is proposed to eliminate spiral waves, which is easily operated. 相似文献
98.
A theoretical scheme is derived to achieve the numerical simulation of helical flux compression generator (HFCG) design, by which not only any physical approximation is not made, but also numerical simulation can be fast obtained. In particular, an analytic formula to calculate the inductance is deduced, which is extremely close to the experimental results. The physical process of relevant interesting physical quantity, such as inductance, enlarging current, and magnetic flux density, can be calculated to compare with the experimentally quantitative results. 相似文献
99.
Spiral patterns are obtained in a dielectric barrier discharge system with water electrodes. The dynamics of spiral formation and transition is investigated. Wavelength characteristic of spiral patterns is also studied. Correlation measurements indicate that the wavelength of spiral pattern increases with the increasing gas gap width and oscillates with the increasing drive frequency. 相似文献
100.