全文获取类型
收费全文 | 192825篇 |
免费 | 39521篇 |
国内免费 | 27048篇 |
专业分类
化学 | 127410篇 |
晶体学 | 2274篇 |
力学 | 12937篇 |
综合类 | 645篇 |
数学 | 23586篇 |
物理学 | 92542篇 |
出版年
2024年 | 760篇 |
2023年 | 3007篇 |
2022年 | 4756篇 |
2021年 | 4908篇 |
2020年 | 5567篇 |
2019年 | 5897篇 |
2018年 | 5253篇 |
2017年 | 5428篇 |
2016年 | 7825篇 |
2015年 | 7776篇 |
2014年 | 8839篇 |
2013年 | 12589篇 |
2012年 | 14595篇 |
2011年 | 16359篇 |
2010年 | 15954篇 |
2009年 | 15794篇 |
2008年 | 10392篇 |
2007年 | 9417篇 |
2006年 | 8553篇 |
2005年 | 7893篇 |
2004年 | 7239篇 |
2003年 | 5798篇 |
2002年 | 5311篇 |
2001年 | 5198篇 |
2000年 | 4191篇 |
1999年 | 4803篇 |
1998年 | 4101篇 |
1997年 | 3823篇 |
1996年 | 4286篇 |
1995年 | 4281篇 |
1994年 | 4251篇 |
1993年 | 3969篇 |
1992年 | 3508篇 |
1991年 | 3075篇 |
1990年 | 2567篇 |
1989年 | 2444篇 |
1988年 | 2296篇 |
1987年 | 1552篇 |
1986年 | 1592篇 |
1985年 | 1211篇 |
1984年 | 1244篇 |
1983年 | 532篇 |
1982年 | 1039篇 |
1981年 | 848篇 |
1980年 | 851篇 |
1979年 | 579篇 |
1978年 | 570篇 |
1977年 | 663篇 |
1976年 | 1086篇 |
1972年 | 553篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Abstract
In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is
fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining
part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under
the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global
attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence
of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the
non-autonomous case by the limiting global attractor.
* Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”. 相似文献
192.
193.
Jian Shen Huizhong Zeng Zhihong Wang Shengbo Lu Huidong Huang Jingsong Liu 《Applied Surface Science》2006,252(22):8018-8021
Polycrystalline Pb(Zr0.55Ti0.45)O3 thin film was deposited on Pt/Ti/SiO2/Si(1 0 0) by radio-frequency-magnetron sputtering method, and the writing of charge bits on the surface of PZT thin film was studied by Kelvin probe force microscopy. It is found that the surface potential of the negative charge bits are higher than those of the corresponding positive ones. When ferroelectric polarization switching occurs, the potential difference becomes even more remarkable. A qualitative model was proposed to explain the origin of the asymmetric charge writing. It is demonstrated that the internal field in the interface layer, which is near the ferroelectric/electrode interface in ferroelectric film, is likely to be the cause for the occurrence of this phenomenon. 相似文献
194.
M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
195.
196.
197.
Zhong-Qing Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):374-403
An orthogonal system of rational functions is discussed. Some inverse inequalities, imbedding inequalities and approximation results are obtained. Two model problems are considered. The stabilities and convergences of proposed rational spectral schemes and rational pseudospectral schemes are proved. The techniques used in this paper are also applicable to other problems on the whole line. Numerical results show the efficiency of this approach. 相似文献
198.
Let R be a discrete nonsingular equivalence relation on a standard probability space , and let V be an ergodic strongly asymptotically central automorphism of R. We prove that every V-invariant cocycle with values in a Polish group G takes values in an abelian subgroup of G.
The hypotheses of this result are satisfied, for example, if A is a finite set, a closed, shift-invariant subset, V is the shift, μ a shift-invariant and ergodic probability measure on X, the two-sided tail-equivalence relation on X, a shift-invariant subrelation which is μ-nonsingular, and a shift-invariant cocycle. 相似文献
199.
This paper presents an instance of using FD-TD method to analyze the aperture field of circular groove guide horn antenna. This process is one part of a hybrid method to solve the radiation field of aperture antenna. To verify the calculated aperture field the radiation pattern is computed from it and compared with the measured one. Good agreement is reached. 相似文献
200.
A new method for controlling the quantum coherence of atom laser by applying input light with strong strength is presented
within the framework of quantum dynamical theory. Unlike the case of rotating wave approximation(RWA), we show that the non-classical
properties, such as sub-Poisson distribution and quadrature squeezed effect, can appear in the output atom laser beam with
time. By choosing suitable initial RF phase, a steady and brighter output of squeezed coherent atom laser is also available. 相似文献