全文获取类型
收费全文 | 1644篇 |
免费 | 563篇 |
国内免费 | 99篇 |
专业分类
化学 | 154篇 |
晶体学 | 2篇 |
力学 | 265篇 |
综合类 | 16篇 |
数学 | 184篇 |
物理学 | 1685篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 29篇 |
2020年 | 33篇 |
2019年 | 28篇 |
2018年 | 37篇 |
2017年 | 58篇 |
2016年 | 73篇 |
2015年 | 74篇 |
2014年 | 111篇 |
2013年 | 139篇 |
2012年 | 115篇 |
2011年 | 126篇 |
2010年 | 128篇 |
2009年 | 132篇 |
2008年 | 157篇 |
2007年 | 143篇 |
2006年 | 114篇 |
2005年 | 113篇 |
2004年 | 72篇 |
2003年 | 97篇 |
2002年 | 91篇 |
2001年 | 61篇 |
2000年 | 51篇 |
1999年 | 40篇 |
1998年 | 33篇 |
1997年 | 26篇 |
1996年 | 31篇 |
1995年 | 27篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有2306条查询结果,搜索用时 15 毫秒
991.
Finite element analysis of the clamp band joint 总被引:1,自引:0,他引:1
In this paper, the clamp band joint commonly used to connect cylindrical shells with end flanges is modeled using the finite element analysis software ANSYS. The joint model is validated by a series of static experiments. Then the response of the joint components to the preload and the axial load is analyzed in detail, from which the axial load capability, the axial stiffness and the damping characteristics of the clamp band joint are discussed. Finally, parametric studies are carried out to investigate the effects of the preload, the wedge angle, the friction coefficient, and the number and size of the V-segment on the behavior of the clamp band joint. This paper presents the general mechanical behavior of the clamp band joint subjected to axial loads. 相似文献
992.
Tejal N. ShahP.N. Gajjar 《Physics letters. A》2012,376(4):438-441
Concept of exponential mass variation of oscillators along the chain length of N oscillators is proposed in the present Letter. The temperature profile and thermal conductivity of one-dimensional (1D) exponential mass graded harmonic and anharmonic lattices are studied on the basis of Fermi-Pasta-Ulam (FPU) β model. Present findings conclude that the exponential mass graded chain provide higher conductivity than that of linear mass graded chain. The exponential mass graded anharmonic chain generates the thermal rectification of 70-75% which is better than linear mass graded materials, so far. Thus instead of using linear mass graded material, the use of exponential mass graded material will be a better and genuine choice for controlling the heat flow at nano-scale. 相似文献
993.
We study theoretically the level shift of the Dirac oscillator perturbed by any sharply peaked potential approaching a surface delta potential. A Green function method is used to obtain closed expressions for all partial waves and parities. 相似文献
994.
Synchronized neuronal activity has been observed at all levels of human and any other nervous systems and was suggested as particularly relevant in information processing and coding. In the present paper we investigate the synchronization of bursting neuronal activity. Motivated by the fact that in neural systems the interplay between the network structure and the dynamics taking place on it is closely interrelated, we develop a spatial network representation of neural architecture in which we can tune the network organization between a scale-free network with dominating long-range connections and a homogeneous network with mostly adjacent neurons connected. Our results reveal that the most synchronized response is obtained for the intermediate regime where long- as well as short-range connections constitute the neural architecture. Moreover, the optimal response is additionally enhanced when the speed of signal propagation is optimized. 相似文献
995.
Taking a close look at the Infeld–Hull ladder operators for the Kratzer oscillator system, V(x) = [x2 + β(β ? 1)x?2]/2, we deduce and explicitly construct energy‐raising and ‐lowering operators for the generalized Morse potential system V(z) = (Ae?4αz ? Be?2αz)/2, through a canonical transformation that exists between the two systems. For the Morse potential system, we obtain a system of raising and lowering operators P±(n) (n = 0, 1, 2, 3, … , nmax) with the specific property that P±(n)Φn = c±(n)Φn±1, where Φn denotes the nth energy eigenfunction. While P?(0) annihilates the ground‐state Φ0, the operator P+(nmax), instead of annihilating the highest bound‐state Φ, actually knocks it out of the L2 space spanned by the discrete bound states and becomes inadmissible. Yet, raising and lowering operators ± with proper end‐of‐spectrum behavior (i.e., ?|0〉 = 0 and +|nmax〉 = 0) can be constructed in a straightforward way in the energy representation. We show that the operators +, ?, and 0 (where 0 ≡ (1/2)[ +, ?]) form a su(2) algebra only if we restrict them to the (N ? 1)‐dimensional subspace spanned by the lowest (N ? 1) basis vectors, but not in the full (N + 1)‐dimensional space spanned by the discrete bound states [N ≡ nmax ≡ integral part of (1/2)(B/(2α ) ? 1)]. Realization of this su(2) algebra in the position representation (when restricted to the (N ? 1)‐dimensional subspace) is also given. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
996.
A.L. Morales A.J. Nieto P. Pintado G. Herranz 《Journal of magnetism and magnetic materials》2010,322(21):3584-275
Measurements of the ΔE-effect and magnetomechanical damping are reported for crystalline pure nickel under several states of internal stresses. The different internal stresses are obtained by means of a wide variety of heat treatments and studied via microscopic examination and measurement. The influence of the heating temperature, the heating time and the cooling method on the magnetoelastic properties is studied. Our results make it possible to select the most suitable heat treatment for each application and to optimize the magnetoelastic response of nickel. Relative variations from 2% to 13% can be obtained in the ΔE-effect, whereas relative variations from 40.0% to 99.9% are possible in magnetomechanical damping, in terms of specific damping capacity. 相似文献
997.
Jian-Li Hou 《Physics letters. A》2010,374(7):929-932
The synchronization process of coupled phase oscillators is further investigated in this Letter. Coupled with a new adaptive scheme, the network can be stable in a middle state which oscillates between the synchronization state and the asynchronous state, namely there exists a third steady state. We call this novel phenomenon ‘order-oscillation’. Related results and detailed analysis are given at last. 相似文献
998.
In the bi-dimensional parameter space of an impact-pair system, shrimp-shaped periodic windows are embedded in chaotic regions. We show that a weak periodic forcing generates new periodic windows near the unperturbed one with its shape and periodicity. Thus, the new periodic windows are parameter range extensions for which the controlled periodic oscillations substitute the chaotic oscillations. We identify periodic and chaotic attractors by their largest Lyapunov exponents. 相似文献
999.
在球坐标系中研究了一类具有运动边界与含时频率的环状非球谐振子模型势的Schrdinger方程.应用坐标变换将运动边界转化为固定边界,从而获得了系统的精确波函数.研究表明,系统的角向波函数是一个推广的缔合勒让德多项式,径向波函数可以表示为贝赛耳函数.最后我们简单讨论了指数运动边界和指数含时频率这一特殊情况. 相似文献
1000.
运用跃变旋转矢量法,即通过旋转矢量的起点、长度和相位的变化规律对受到空气弱阻尼作用和滑动摩擦力作用的弹簧振子的振动进行了研究.讨论了在滑动摩擦力作用下空气阻尼为临界阻尼和欠阻尼情况下的弹簧振子的运动,根据阻尼和初值情况得出不同的振动曲线.并对弹簧振子4种相图和相图旋转矢量进行了比较. 相似文献