全文获取类型
收费全文 | 257618篇 |
免费 | 2745篇 |
国内免费 | 901篇 |
专业分类
化学 | 122154篇 |
晶体学 | 3279篇 |
力学 | 13543篇 |
综合类 | 8篇 |
数学 | 50784篇 |
物理学 | 71496篇 |
出版年
2021年 | 1337篇 |
2020年 | 1641篇 |
2019年 | 1600篇 |
2018年 | 12220篇 |
2017年 | 12105篇 |
2016年 | 9382篇 |
2015年 | 3119篇 |
2014年 | 3487篇 |
2013年 | 8064篇 |
2012年 | 10023篇 |
2011年 | 17670篇 |
2010年 | 10723篇 |
2009年 | 10932篇 |
2008年 | 13590篇 |
2007年 | 15380篇 |
2006年 | 7039篇 |
2005年 | 7445篇 |
2004年 | 7018篇 |
2003年 | 6900篇 |
2002年 | 5757篇 |
2001年 | 6484篇 |
2000年 | 4814篇 |
1999年 | 3615篇 |
1998年 | 2658篇 |
1997年 | 2706篇 |
1996年 | 2715篇 |
1995年 | 2449篇 |
1994年 | 2440篇 |
1993年 | 2295篇 |
1992年 | 2762篇 |
1991年 | 2696篇 |
1990年 | 2544篇 |
1989年 | 2481篇 |
1988年 | 2426篇 |
1987年 | 2458篇 |
1986年 | 2254篇 |
1985年 | 2880篇 |
1984年 | 2869篇 |
1983年 | 2312篇 |
1982年 | 2341篇 |
1981年 | 2187篇 |
1980年 | 2183篇 |
1979年 | 2455篇 |
1978年 | 2506篇 |
1977年 | 2437篇 |
1976年 | 2333篇 |
1975年 | 2206篇 |
1974年 | 2188篇 |
1973年 | 2180篇 |
1972年 | 1405篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Palle E. T. Jorgensen 《Mathematische Zeitschrift》1989,201(4):455-476
Work supported in part by the NSF 相似文献
32.
33.
Graham Smith 《The Journal of the Operational Research Society》1989,40(9):761-770
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
34.
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
35.
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
36.
T. Senthil 《Annals of Physics》2006,321(7):1669-1681
Heavy electron metals on the verge of a quantum phase transition to magnetism show a number of unusual non-Fermi liquid properties which are poorly understood. This article discusses in a general way various theoretical aspects of this phase transition with an eye toward understanding the non-Fermi liquid phenomena. We suggest that the non-Fermi liquid quantum critical state may have a sharp Fermi surface with power law quasiparticles but with a volume not set by the usual Luttinger rule. We also discuss the possibility that the electronic structure change associated with the possible Fermi surface reconstruction may diverge at a different time/length scale from that associated with magnetic phenomena. 相似文献
37.
We consider the problem of maximizing a linear fractional function on the Pareto efficient frontier of two other linear fractional functions. We present a finite pivoting-type algorithm that solves the maximization problem while computing simultaneously the efficient frontier. Application to multistage efficiency analysis is discussed. An example demonstrating the computational procedure is included. 相似文献
38.
de Souza P. A. Garg V. K. Klingelhöfer G. Gellert R. Gütlich P. 《Hyperfine Interactions》2002,139(1-4):705-714
A portable Mössbauer spectrometer, developed for extraterrestrial applications, opens up new industrial applications of MBS. But for industrial applications, an available tool for fast data analysis is also required, and it should be easy to handle. The analysis of Mössbauer spectra and their parameters is a barrier for the popularity of this wide-applicable spectroscopic technique in industry. Based on experience, the analysis of a Mössbauer spectrum is time-consuming and requires the dedication of a specialist. However, the analysis of Mössbauer spectra, from the fitting to the identification of the sample phases, can be faster using by genetic algorithms, fuzzy logic and artificial neural networks. Industrial applications are very specific ones and the data analysis can be performed using these algorithms. In combination with an automatic analysis, the Mössbauer spectrometer can be used as a probe instrument which covers the main industrial needs for an on-line monitoring of its products, processes and case studies. Some of these real industrial applications will be discussed. 相似文献
39.
Franz H. Asthalter T. Dommach M. Ehnes A. Messel K. Sergueev I. 《Hyperfine Interactions》2002,141(1-4):131-134
The present status of the new nuclear resonance beamline PETRA 1 at HASYLAB, DESY, Hamburg is described. Besides an overview
of the experimental setup some examples of recent experiments are given. Those cover the main applications, i.e., inelastic
scattering from iron alloys and quasielastic scattering from glass-forming liquids.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
40.
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