全文获取类型
收费全文 | 392367篇 |
免费 | 4091篇 |
国内免费 | 1264篇 |
专业分类
化学 | 211929篇 |
晶体学 | 6332篇 |
力学 | 16717篇 |
综合类 | 9篇 |
数学 | 41503篇 |
物理学 | 121232篇 |
出版年
2020年 | 3105篇 |
2019年 | 3391篇 |
2018年 | 4145篇 |
2017年 | 3976篇 |
2016年 | 6367篇 |
2015年 | 4289篇 |
2014年 | 6454篇 |
2013年 | 17204篇 |
2012年 | 13200篇 |
2011年 | 16026篇 |
2010年 | 10809篇 |
2009年 | 10533篇 |
2008年 | 14398篇 |
2007年 | 14345篇 |
2006年 | 13767篇 |
2005年 | 12273篇 |
2004年 | 11327篇 |
2003年 | 10052篇 |
2002年 | 9772篇 |
2001年 | 11391篇 |
2000年 | 8869篇 |
1999年 | 6947篇 |
1998年 | 5469篇 |
1997年 | 5553篇 |
1996年 | 5344篇 |
1995年 | 4868篇 |
1994年 | 4660篇 |
1993年 | 4481篇 |
1992年 | 5180篇 |
1991年 | 5038篇 |
1990年 | 4935篇 |
1989年 | 4783篇 |
1988年 | 4745篇 |
1987年 | 4795篇 |
1986年 | 4397篇 |
1985年 | 5887篇 |
1984年 | 6076篇 |
1983年 | 5011篇 |
1982年 | 5339篇 |
1981年 | 5250篇 |
1980年 | 5049篇 |
1979年 | 5248篇 |
1978年 | 5558篇 |
1977年 | 5410篇 |
1976年 | 5393篇 |
1975年 | 5058篇 |
1974年 | 4965篇 |
1973年 | 5115篇 |
1972年 | 3374篇 |
1967年 | 3190篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
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
52.
Exact closed-form solutions are exhibited for the Hopf equation for stationary incompressible 3D Navier-Stokes flow, for the cases of homogeneous forced flow (including a solution with depleted nonlinearity) and inhomogeneous flow with arbitrary boundary conditions. This provides an exact method for computing two- and higher-point moments, given the mean flow. 相似文献
53.
I. L. Davies K. E. Markides M. L. Lee M. W. Raynor K. D. Bartle 《Journal of separation science》1989,12(4):193-207
Although coupled liquid chromatographygas chromatography (LC-GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC-GC applications have been published in the last two years (1987–88) alone. This review categorizes LC-GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled-column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on-line trace enrichment-GC) have also been included in this review. 相似文献
54.
55.
H. Mazaheri 《分析论及其应用》2006,22(2):141-145
The concepts of quasi-Chebyshev and weakly-Chebyshev and σ-Chebyshev were defined [3 - 7], andas a counterpart to best approximation in normed linear spaces, best coapprozimation was introduced by Franchetti and Furi^[1]. In this research, we shall define τ-Chebyshev subspaces and τ-cochebyshev subspaces of a Banach space, in which the property τ is compact or weakly-compact, respectively. A set of necessary and sufficient theorems under which a subspace is τ-Chebyshev is defined. 相似文献
56.
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
57.
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
58.
Johan Håstad 《Random Structures and Algorithms》2006,29(4):466-474
We show that the operations of permuting columns and rows separately and independently mix a square matrix in constant time. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2006 相似文献
59.
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
60.
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