全文获取类型
收费全文 | 419251篇 |
免费 | 2748篇 |
国内免费 | 1022篇 |
专业分类
化学 | 209479篇 |
晶体学 | 6349篇 |
力学 | 20039篇 |
综合类 | 9篇 |
数学 | 57607篇 |
物理学 | 129538篇 |
出版年
2021年 | 2599篇 |
2020年 | 2924篇 |
2019年 | 3295篇 |
2018年 | 11531篇 |
2017年 | 12172篇 |
2016年 | 9694篇 |
2015年 | 4345篇 |
2014年 | 5864篇 |
2013年 | 14507篇 |
2012年 | 14531篇 |
2011年 | 23725篇 |
2010年 | 15406篇 |
2009年 | 15428篇 |
2008年 | 21514篇 |
2007年 | 24499篇 |
2006年 | 12246篇 |
2005年 | 16386篇 |
2004年 | 12652篇 |
2003年 | 11941篇 |
2002年 | 9984篇 |
2001年 | 10719篇 |
2000年 | 8295篇 |
1999年 | 6135篇 |
1998年 | 4857篇 |
1997年 | 4932篇 |
1996年 | 4738篇 |
1995年 | 4064篇 |
1994年 | 4130篇 |
1993年 | 3951篇 |
1992年 | 4558篇 |
1991年 | 4669篇 |
1990年 | 4481篇 |
1989年 | 4381篇 |
1988年 | 4314篇 |
1987年 | 4324篇 |
1986年 | 4043篇 |
1985年 | 5171篇 |
1984年 | 5348篇 |
1983年 | 4287篇 |
1982年 | 4522篇 |
1981年 | 4258篇 |
1980年 | 4045篇 |
1979年 | 4513篇 |
1978年 | 4737篇 |
1977年 | 4604篇 |
1976年 | 4590篇 |
1975年 | 4320篇 |
1974年 | 4297篇 |
1973年 | 4469篇 |
1972年 | 2979篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Palle E. T. Jorgensen 《Mathematische Zeitschrift》1989,201(4):455-476
Work supported in part by the NSF 相似文献
62.
A firm's logistics cost, including shipping and inventory-carrying, is a substantial percentage of its sales. Nevertheless, typical inventory-control methods ignore or insufficiently represent the shipping cost. This paper describes a recursive algorithm that determines the reorder cycle-time that minimizes total logistics cost. It allows for a realistic accounting of shipping cost, which is modelled here as a function of shipping distance and weight. The algorithm uses a relaxation procedure to identify a suitable initial approximation to the optimal order cycle-time and then, through a series of recursive steps, moves to the optimal result. We demonstrate the algorithm with a single item, with a group of items that share a common order cycle, and with multi-items when item demands are random variables. Experience with this algorithm indicates that it converges to the optimal result in a very few steps. 相似文献
63.
José E. Valdés 《Operations Research Letters》2006,34(1):49-52
Components C1 and C2 form a series system. Suppose we can allocate the spare R1 in parallel with C1 and the spare R2 in parallel with C2, or otherwise, allocate R1 with C2 and R2 with C1. In this paper, we compare these two options using hazard rate ordering. 相似文献
64.
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
65.
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
66.
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
67.
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
68.
69.
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
70.
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