全文获取类型
收费全文 | 485787篇 |
免费 | 5653篇 |
国内免费 | 1642篇 |
专业分类
化学 | 264598篇 |
晶体学 | 7149篇 |
力学 | 20103篇 |
综合类 | 12篇 |
数学 | 57156篇 |
物理学 | 144064篇 |
出版年
2020年 | 3734篇 |
2019年 | 4008篇 |
2018年 | 4931篇 |
2017年 | 4755篇 |
2016年 | 7659篇 |
2015年 | 5243篇 |
2014年 | 7734篇 |
2013年 | 21666篇 |
2012年 | 16257篇 |
2011年 | 20035篇 |
2010年 | 13391篇 |
2009年 | 13248篇 |
2008年 | 18766篇 |
2007年 | 19070篇 |
2006年 | 18105篇 |
2005年 | 16414篇 |
2004年 | 14751篇 |
2003年 | 13265篇 |
2002年 | 13026篇 |
2001年 | 14391篇 |
2000年 | 11168篇 |
1999年 | 8687篇 |
1998年 | 7229篇 |
1997年 | 7106篇 |
1996年 | 6957篇 |
1995年 | 6166篇 |
1994年 | 5995篇 |
1993年 | 5839篇 |
1992年 | 6380篇 |
1991年 | 6336篇 |
1990年 | 6017篇 |
1989年 | 5784篇 |
1988年 | 6013篇 |
1987年 | 5706篇 |
1986年 | 5465篇 |
1985年 | 7622篇 |
1984年 | 7831篇 |
1983年 | 6380篇 |
1982年 | 6936篇 |
1981年 | 6882篇 |
1980年 | 6506篇 |
1979年 | 6773篇 |
1978年 | 6900篇 |
1977年 | 6875篇 |
1976年 | 6848篇 |
1975年 | 6590篇 |
1974年 | 6463篇 |
1973年 | 6746篇 |
1972年 | 4137篇 |
1971年 | 3333篇 |
排序方式: 共有10000条查询结果,搜索用时 945 毫秒
941.
Processing-induced residual strains in solid cylinders of Nickel 200 were investigated using phase shifting moiré interferometry. Two different experimental approaches were used to study the strains produced during Tungsten-inert gas spot welding. A comparison of results for a ‘hot/fast’ and a ‘cool/slow’ weld demonstrate the capabilities of the general approach. Both experimental methods revealed distinct differences in the residual displacement and strain fields between the two types of welds. 相似文献
942.
An investigation on nonconnectedness of numerical range for monic matrix polynomials L(λ) is undertaking here. The distribution of eigenvalues of L(λ) to the components of numerical range and some other algebraic properties are also presented. 相似文献
943.
944.
The number-phase uncertainty relations arerevisited in view of the recent discovery of a propercovariant phase observable. The high-amplitude limits ofthe coherent-state expectations of the moment operators of the phase observable are determined and thebehavior of the number-phase uncertainty product in thatlimit is investigated. 相似文献
945.
T. N. Mamedov V. N. Duginov A. V. Stoykov I. L. Chaplygin D. Herlach U. Zimmermann V. N. Gorelkin J. Major M. Schefzik 《JETP Letters》1998,68(1):64-70
The residual polarization of negative muons in crystal silicon samples with phosphorus (P: 1.6×1013 cm−3) and antimony (Sb: 2×1018 cm−3) impurities is investigated. The measurements are made in a 1000 G magnetic field oriented in a direction transverse to the
muon spin in the temperature range 4–300 K. The relaxation rate and shift of the precession frequency in the silicon sample
with the phosphorus impurity are measured more accurately than previously. It is found that in antimony-doped silicon the
acceptor center
μ
A1 at temperatures below 30 K can be in both ionized and neutral states. The experimental data are interpreted on the basis
of spin-lattice relaxation of the magnetic moment of an acceptor center, formation of acceptor-donor pairs, and recombination
of charge carriers at the acceptor. Preliminary measurements showed a nonzero residual polarization of negative muons in germanium.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 61–66 (10 July 1998) 相似文献
946.
The electronic spectrum of an icosahedral quasicrystal with a central-atom decoration of the Amman-Mackay network is investigated
in the tight-binding approximation. The quasicrystal is described as a structural limit of the optimal cubic approximants
with increasing period. The electronic spectra for the first four optimal cubic approximants do not contain the hierarchical
gap structure which is typical for the Cantor set of the spectrum of a one-dimensional quasicrystal. At the same time, as
the order of the approximant increases, the spectrum becomes singular throughout the entire energy scale.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 557–562 (25 April 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
947.
On the basis of exactly solvable stationary models for the Schrödinger equation, we develop a procedure for solving the nonstationary Schödinger equation in an explicit analytic form. We investigate the formation of the nonadiabatic geometric phase during cyclic evolution of a quantum system. 相似文献
948.
High resolution finite difference schemes for solving the nonlinear model Boltzmann equations are presented for the computations of rarefied gas flows. The discrete ordinate method is first applied to remove the velocity space dependency of the distribution function which renders the model Boltzmann equation in phase space to a set of hyperbolic conservation laws with source terms in physical space. Then a high order essentially nonoscillatory method due to Harten et al. (J. Comput. Phys. 71, 231, 1987) is adapted and extended to solve them. Explicit methods using operator splitting and implicit methods using the lower-upper factorization are described to treat multidimensional problems. The methods are tested for both steady and unsteady rarefied gas flows to illustrate its potential use. The computed results using model Boltzmann equations are found to compare well both with those using the direct simulation Monte Carlo results in the transitional regime flows and those with the continuum Navier-Stokes calculations in near continuum regime flows. 相似文献
949.
950.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献