全文获取类型
收费全文 | 561922篇 |
免费 | 3576篇 |
国内免费 | 1182篇 |
专业分类
化学 | 264927篇 |
晶体学 | 8227篇 |
力学 | 30665篇 |
综合类 | 5篇 |
数学 | 84377篇 |
物理学 | 178479篇 |
出版年
2020年 | 4724篇 |
2019年 | 5697篇 |
2018年 | 12817篇 |
2017年 | 13206篇 |
2016年 | 13223篇 |
2015年 | 6061篇 |
2014年 | 9948篇 |
2013年 | 21713篇 |
2012年 | 19368篇 |
2011年 | 27600篇 |
2010年 | 19416篇 |
2009年 | 19586篇 |
2008年 | 25178篇 |
2007年 | 27273篇 |
2006年 | 17113篇 |
2005年 | 18516篇 |
2004年 | 15891篇 |
2003年 | 15034篇 |
2002年 | 14058篇 |
2001年 | 13829篇 |
2000年 | 10943篇 |
1999年 | 8151篇 |
1998年 | 7330篇 |
1997年 | 7218篇 |
1996年 | 6752篇 |
1995年 | 6125篇 |
1994年 | 6061篇 |
1993年 | 6080篇 |
1992年 | 6362篇 |
1991年 | 6738篇 |
1990年 | 6582篇 |
1989年 | 6547篇 |
1988年 | 6376篇 |
1987年 | 6336篇 |
1986年 | 5927篇 |
1985年 | 7493篇 |
1984年 | 7860篇 |
1983年 | 6605篇 |
1982年 | 7110篇 |
1981年 | 6682篇 |
1980年 | 6364篇 |
1979年 | 6902篇 |
1978年 | 7189篇 |
1977年 | 7085篇 |
1976年 | 7417篇 |
1975年 | 6720篇 |
1974年 | 6740篇 |
1973年 | 7194篇 |
1972年 | 5284篇 |
1971年 | 4466篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
A classification has been obtained for spaces which admit complete sets of motion integrals of the (3.1)-type and are spatially homogeneous. The metrics and Killing vectors have been found in explicit form for all types of these spaces. A classification by Bianchi is given for the spaces obtained. 相似文献
952.
An electrostatic interaction between two separate, grounded, uncharged, perfectly conducting spheres of different radii in a uniform electrostatic field is investigated. It is shown that at a small center-to-center distance of the spheres, the force of the polarization interaction between the spheres depends appreciably more weakly on that distance in comparison to the force of the electrostatic interaction of two elementary dipoles as it should be in view of the interaction between two like polarization charges. 相似文献
953.
The Fokker–Planck-type kinetic equation is constructed with the help of the evolution equation for the transverse energy of channelized particles, which in its turn is derived beyond the framework of perturbation theory proceeding from the condition of nonconcervation of the adiabatic invariant. 相似文献
954.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
955.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
956.
R. Adhikari A. Sil A. Raychaudhuri 《The European Physical Journal C - Particles and Fields》2002,25(1):125-130
We present a solution of the solar neutrino deficit using three flavors of neutrinos and R-parity non-conserving supersymmetry. In this model, in vacuum, the is massless and unmixed, mass and mixing being restricted to the - sector only, which we choose in consistency with the requirements of the atmospheric neutrino anomaly. The flavor changing
and flavor diagonal neutral currents present in the model and the three-flavor picture together produce an energy dependent
resonance-induced - mixing in the sun. This mixing plays a key role in the new solution to the solar neutrino problem. The best fit to the solar
neutrino rates and spectrum (1258-day SK and 241-day SNO data) requires a mass square difference of eV2 in vacuum between the two lightest neutrinos. This solution cannot accommodate a significant day-night effect for solar neutrinos
nor CP violation in terrestrial neutrino experiments.
Received: 26 December 2001 / Revised version: 16 February 2002 / Published online: 26 July 2002 相似文献
957.
Atomic-force microscopy was used to study the surface topography of SiGe structures grown by epitaxial deposition of Ge on profiled Si(111) substrates under electromigration conditions. Systems of highly ordered germanium nanosized islands with dimensions of 10–20 nm and a density of 6×1010 cm?2 were obtained. It is shown that the geometrical parameters of self-organizing nanoislands can be controlled by a proper choice of the growth and postgrowth annealing conditions for these structures. 相似文献
958.
Eremenko L. T. Oreshko G. V. Nesterenko D. A. Lagodzinskaya G. V. Eremenko I. L. 《Russian Chemical Bulletin》2002,51(1):157-159
The reactions of ethylene glycol mononitrate and glycerol 1,3-dinitrate with methylphosphonic dichloride afforded new nitroxyalkyl methylphosphonates. 相似文献
959.
960.
The literature on the synthesis of N-substituted xanthines by cyclization, recyclization, and N-substitution is reviewed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 3–27, January, 1991. 相似文献