全文获取类型
收费全文 | 296356篇 |
免费 | 3968篇 |
国内免费 | 1018篇 |
专业分类
化学 | 154755篇 |
晶体学 | 3888篇 |
力学 | 12425篇 |
综合类 | 19篇 |
数学 | 42744篇 |
物理学 | 87511篇 |
出版年
2021年 | 2645篇 |
2020年 | 2819篇 |
2019年 | 3050篇 |
2018年 | 5081篇 |
2017年 | 4956篇 |
2016年 | 6504篇 |
2015年 | 4691篇 |
2014年 | 6076篇 |
2013年 | 13731篇 |
2012年 | 14434篇 |
2011年 | 15373篇 |
2010年 | 10343篇 |
2009年 | 9628篇 |
2008年 | 12510篇 |
2007年 | 12612篇 |
2006年 | 11891篇 |
2005年 | 14366篇 |
2004年 | 12797篇 |
2003年 | 10126篇 |
2002年 | 8025篇 |
2001年 | 7777篇 |
2000年 | 6042篇 |
1999年 | 4655篇 |
1998年 | 3695篇 |
1997年 | 3646篇 |
1996年 | 3511篇 |
1995年 | 3091篇 |
1994年 | 2993篇 |
1993年 | 2860篇 |
1992年 | 3342篇 |
1991年 | 3226篇 |
1990年 | 3119篇 |
1989年 | 2869篇 |
1988年 | 2855篇 |
1987年 | 2830篇 |
1986年 | 2629篇 |
1985年 | 3486篇 |
1984年 | 3712篇 |
1983年 | 2956篇 |
1982年 | 3225篇 |
1981年 | 3190篇 |
1980年 | 3000篇 |
1979年 | 3085篇 |
1978年 | 3187篇 |
1977年 | 3099篇 |
1976年 | 3282篇 |
1975年 | 2986篇 |
1974年 | 2945篇 |
1973年 | 3078篇 |
1972年 | 1917篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
42.
T. Kumita Y. Kamiya M. Babzien I. Ben-Zvi K. Kusche I. V. Pavlishin I. V. Pogorelsky D. P. Siddons V. Yakimenko T. Hirose T. Omori J. Urakawa K. Yokoya D. Cline F. Zhou 《Laser Physics》2006,16(2):267-271
Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions. 相似文献
43.
An algorithm is proposed which allows one to construct higher symmetries of arbitrary order for some special classes of hyperbolic
systems possessing integrals. The Pohlmeyer-Lund-Regge system and the open two-dimensional Toda lattices are shown to belong
to the class of systems where our algorithm is applicable.
__________
Translated from Fundamental’naya i Prikladnaya Matematika (Fundamental and Applied Mathematics), Vol. 10, No. 1, Geometry
of Integrable Models, 2004. 相似文献
44.
General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
D.T. Son 《Annals of Physics》2006,321(1):197-224
We show that the Lagrangian for interacting nonrelativistic particles can be coupled to an external gauge field and metric tensor in a way that exhibits a nonrelativistic version of general coordinate invariance. We explore the consequences of this invariance on the example of the degenerate Fermi gas at infinite scattering length, where conformal invariance also plays an important role. We find the most general effective Lagrangian consistent with both general coordinate and conformal invariance to leading and next-to-leading orders in the momentum expansion. At the leading order the Lagrangian contains one phenomenological constant and reproduces the results of the Thomas-Fermi theory and superfluid hydrodynamics. At the next-to-leading order there are two additional constants. We express various physical quantities through these constants. 相似文献
45.
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
46.
47.
48.
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
49.
A. D. Smirnov 《Journal of Applied Spectroscopy》1991,54(1):33-38
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 1, pp. 46–50, January, 1991. 相似文献
50.
Michel Hébert 《Archive for Mathematical Logic》1991,31(2):133-143
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform. 相似文献