全文获取类型
收费全文 | 351253篇 |
免费 | 2351篇 |
国内免费 | 1098篇 |
专业分类
化学 | 172693篇 |
晶体学 | 4896篇 |
力学 | 17835篇 |
综合类 | 7篇 |
数学 | 61436篇 |
物理学 | 97835篇 |
出版年
2021年 | 2399篇 |
2020年 | 2666篇 |
2019年 | 3070篇 |
2018年 | 14433篇 |
2017年 | 14267篇 |
2016年 | 11696篇 |
2015年 | 3947篇 |
2014年 | 5412篇 |
2013年 | 12118篇 |
2012年 | 12727篇 |
2011年 | 20981篇 |
2010年 | 13498篇 |
2009年 | 13720篇 |
2008年 | 16759篇 |
2007年 | 18785篇 |
2006年 | 9919篇 |
2005年 | 9979篇 |
2004年 | 9358篇 |
2003年 | 9137篇 |
2002年 | 8133篇 |
2001年 | 7942篇 |
2000年 | 6248篇 |
1999年 | 4619篇 |
1998年 | 4099篇 |
1997年 | 4000篇 |
1996年 | 3730篇 |
1995年 | 3135篇 |
1994年 | 3177篇 |
1993年 | 3225篇 |
1992年 | 3376篇 |
1991年 | 3486篇 |
1990年 | 3306篇 |
1989年 | 3332篇 |
1988年 | 3191篇 |
1987年 | 3115篇 |
1986年 | 2990篇 |
1985年 | 3816篇 |
1984年 | 4034篇 |
1983年 | 3274篇 |
1982年 | 3581篇 |
1981年 | 3357篇 |
1980年 | 3131篇 |
1979年 | 3390篇 |
1978年 | 3620篇 |
1977年 | 3638篇 |
1976年 | 3530篇 |
1975年 | 3364篇 |
1974年 | 3346篇 |
1973年 | 3469篇 |
1972年 | 2373篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
We study oscillation in a gyrotron with allowance for reflections from an output horn. Regions with different system behaviors,
such as stationary oscillation, self-modulation, and complex-dynamics regimes are found in the parameter plane. The scenarios
of appearance of chaotic oscillations are considered. It is shown that they can emerge via either a sequence of period-doubling
bifurcations or destruction of quasiperiodic motion. For chaotic attractors, Lyapunov exponents are calculated and their dimensions
are estimated on the basis of the Kaplan-Yorke formula. The dimension values turn out to be anomalously large, which is stipulated
by the presence of a large number of high-Q eigenmodes in the gyrotron cavity due to operation near the cutoff frequency of
an electrodynamic system.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 887–899, October 2006. 相似文献
22.
Let ir(G) and γ(G) be the irredundance number and the domination number of a graph G, respectively. A graph G is called irredundance perfect if ir(H)=γ(H), for every induced subgraph H of G. In this article we present a result which immediately implies three known conjectures on irredundance perfect graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 41: 292–306, 2002 相似文献
23.
24.
E. P. Gordov 《Russian Physics Journal》1981,24(11):1039-1041
An evolution operatior is described, which acts on the operators of a problem to take it into the solutions of the corresponding problem of semiclassical electrodynamics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 66–69, November, 1981. 相似文献
25.
26.
We establish soliton-like asymptotics for finite energy solutions to the Schrödinger equation coupled to a nonrelativistic classical particle. Any solution with initial state close to the solitary manifold converges to a sum of a travelling wave and an outgoing free wave. The convergence holds in global energy norm. The proof uses spectral theory and the symplectic projection onto the solitary manifold in the Hilbert phase space. 相似文献
27.
Jun-tao Chang Joerg Evers Marian O. Scully M. Suhail Zubairy 《量子光学学报》2006,12(B08):77-77
We propose a scheme to obtain the distance of two identical atoms placed inside the standing wave field by monitoring the collective resonance fluorescence spectrum emitted by the two particles. We find three different parameter ranges, depending on the distance of the atoms as compared to the transition wavelength. For large interparticle distances, dipole-dipole coupling is negligible, and the main system evolution arises from the interaction with the standing wave field. In the small-distance limit, the dynamics is dominated by the dipole-dipole interaction. Finally, in the intermediate region, a rich interplay of the various couplings arises, which however is lifted for strong driving laser fields. The present measurement procedure allows us to distinguish the three cases. In each of the cases, we show how to determine the distance of the two particles and their respective positions relative to the nodes of the standing wave field with fractional-wavelength precision. 相似文献
28.
The spatial structure of Bragg angles and the transfer functions of an acousto-optic cell are calculated for the cases of isotropic and anisotropic light diffraction in a uniaxial crystal. Their change with ultrasound frequency is traced. The possibility of image processing by acousto-optic filtration of the spatial spectrum of an image is considered. The results of experimental visualization of the transfer functions of a calcium molybdate crystal cell are presented. 相似文献
29.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems. 相似文献
30.
A. I. Magunov A. Ya. Faenov I. Yu. Skobelev T. A. Pikuz E. Biémont P. Quinet F. Blasco C. Bonte F. Dorchies T. Caillaud F. Salin C. Stenz 《Journal of Experimental and Theoretical Physics》2002,95(6):998-1005
The satellite structure of 1s2p 1,3 P 1-1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. 相似文献