全文获取类型
收费全文 | 428170篇 |
免费 | 4749篇 |
国内免费 | 1430篇 |
专业分类
化学 | 234891篇 |
晶体学 | 6250篇 |
力学 | 17841篇 |
综合类 | 10篇 |
数学 | 48236篇 |
物理学 | 127121篇 |
出版年
2020年 | 2992篇 |
2019年 | 3038篇 |
2018年 | 3429篇 |
2017年 | 3373篇 |
2016年 | 5998篇 |
2015年 | 4513篇 |
2014年 | 6353篇 |
2013年 | 18785篇 |
2012年 | 14409篇 |
2011年 | 17712篇 |
2010年 | 11506篇 |
2009年 | 11555篇 |
2008年 | 16578篇 |
2007年 | 16627篇 |
2006年 | 16131篇 |
2005年 | 14746篇 |
2004年 | 13276篇 |
2003年 | 11915篇 |
2002年 | 11696篇 |
2001年 | 13986篇 |
2000年 | 10588篇 |
1999年 | 8361篇 |
1998年 | 6424篇 |
1997年 | 6369篇 |
1996年 | 6332篇 |
1995年 | 5796篇 |
1994年 | 5540篇 |
1993年 | 5280篇 |
1992年 | 6141篇 |
1991年 | 6081篇 |
1990年 | 5732篇 |
1989年 | 5511篇 |
1988年 | 5734篇 |
1987年 | 5455篇 |
1986年 | 5165篇 |
1985年 | 7179篇 |
1984年 | 7278篇 |
1983年 | 5927篇 |
1982年 | 6259篇 |
1981年 | 6151篇 |
1980年 | 5902篇 |
1979年 | 6291篇 |
1978年 | 6368篇 |
1977年 | 6319篇 |
1976年 | 6210篇 |
1975年 | 6010篇 |
1974年 | 5855篇 |
1973年 | 6034篇 |
1972年 | 3644篇 |
1971年 | 2736篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A method using third order moments for estimating the regression coefficients as well as the latent state scores of the reduced-rank regression model when the latent variable(s) are non-normally distributed is presented in this paper. It is shown that the factor analysis type indeterminacy of the regression coefficient matrices is eliminated. A real life example of the proposed method is presented. Differences of this solution with the reduced-rank regression eigen solution are discussed. 相似文献
42.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 212–217, August, 1989. 相似文献
43.
Palle E. T. Jorgensen 《Mathematische Zeitschrift》1989,201(4):455-476
Work supported in part by the NSF 相似文献
44.
45.
J. P. Levine 《Inventiones Mathematicae》1989,96(3):571-592
46.
J. H. Eberly 《Laser Physics》2006,16(6):921-926
We examine the application of Schmidt mode analysis to pure-state entanglement. Several examples permitting exact analytic calculation of Schmidt eigenvalues and eigenfunctions are included, as well as evaluation of the associated degree of entanglement. 相似文献
47.
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
48.
The tape stripping technique is an experimental method frequently used for reconstruction of the in-depth distribution of various topically administered substances within the horny layer of human skin, e.g., compounds contained in sunscreens. Titanium dioxide (TiO2) nanoparticles (25–200 nm in diameter) are one such compound. Optical techniques which apply blue light are found to be suitable for reconstruction. However, the presence of particles affects the light propagation within the skin and therefore causes incorrect determination of strip thickness, leading to an improper reconstructed distribution of nanoparticle concentration revealed from the experimental data. This study evaluates the errors emerging from the use of blue (400 nm) and NIR (800 nm) radiation and finds the use of longer wavelength light more advantageous. Particles of different diameters are considered, and it is revealed that the application of small particles (25–60 nm) results in the lowest rate of error. 相似文献
49.
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
50.
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