全文获取类型
收费全文 | 202616篇 |
免费 | 1473篇 |
国内免费 | 425篇 |
专业分类
化学 | 104512篇 |
晶体学 | 3391篇 |
力学 | 10271篇 |
综合类 | 10篇 |
数学 | 21827篇 |
物理学 | 64503篇 |
出版年
2021年 | 1968篇 |
2020年 | 2008篇 |
2019年 | 2566篇 |
2018年 | 3656篇 |
2017年 | 3668篇 |
2016年 | 4806篇 |
2015年 | 2343篇 |
2014年 | 4295篇 |
2013年 | 8578篇 |
2012年 | 6829篇 |
2011年 | 8039篇 |
2010年 | 6454篇 |
2009年 | 6639篇 |
2008年 | 7629篇 |
2007年 | 7592篇 |
2006年 | 6690篇 |
2005年 | 5915篇 |
2004年 | 5636篇 |
2003年 | 5161篇 |
2002年 | 5152篇 |
2001年 | 5604篇 |
2000年 | 4135篇 |
1999年 | 3132篇 |
1998年 | 2699篇 |
1997年 | 2757篇 |
1996年 | 2540篇 |
1995年 | 2211篇 |
1994年 | 2326篇 |
1993年 | 2225篇 |
1992年 | 2522篇 |
1991年 | 2645篇 |
1990年 | 2552篇 |
1989年 | 2622篇 |
1988年 | 2531篇 |
1987年 | 2550篇 |
1986年 | 2411篇 |
1985年 | 3032篇 |
1984年 | 3101篇 |
1983年 | 2596篇 |
1982年 | 2562篇 |
1981年 | 2527篇 |
1980年 | 2335篇 |
1979年 | 2708篇 |
1978年 | 2671篇 |
1977年 | 2870篇 |
1976年 | 2872篇 |
1975年 | 2664篇 |
1974年 | 2602篇 |
1973年 | 2711篇 |
1972年 | 2085篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
751.
752.
T. M. Shneidman G. G. Adamian N. V. Antonenko S. P. Ivanova R. V. Jolos W. Scheid 《Physics of Atomic Nuclei》2003,66(2):206-217
Based on the dinuclear system concept, the role of bending vibrations in creation of the angular momentum of primary fission fragments is investigated. For 252Cf spontaneous fission, the angular momenta of the fragments are calculated as a function of the neutron multiplicity and compared with available experimental data. Different cluster compositions of the 252Cf fission modes at the scission point are considered. 相似文献
753.
P. M. Larionov A. N. Malov M. M. Mandrik N. A. Maslov A. M. Orishich 《Journal of Applied Spectroscopy》2003,70(1):38-42
We investigated the laser-induced fluorescence spectra (LIF) of porcine cardiac tissues with different degrees of viability. The data obtained are compared with the results of routine histological investigations and also with the experiments performed with the use of fluorescent probes. It has been found with a high degree of reliability that the loss of the viability of the myocardium tissue leads to the alteration of its LIF spectra. This can be used for low-invasive rapid control of transplant viability in the process of its preparation and during surgery. 相似文献
754.
Lasing and discharge in mixtures of SF6 with hydrogen and hydrocarbons are investigated. If the chemical reaction is initiated by a self-sustained discharge (a generator
with both an inductive and capacitive energy storage can be used), the maximum lasing efficiency is attained at high values
of the ratio E/p (where E is the electric field intensity and p is the pressure in the mixture) if shaped electrodes and preionization of the discharge gap are employed. For the first time,
the lasing efficiency obtained in a nonchain HF laser is as high as 10% of the energy deposit and 4.5% of the stored energy
for a specific radiation energy of ≈140 J/(l atm). At high efficiencies, the emission spectrum of the nonchain HF laser significantly
broadens and cascade lasing at P(3-2) → P(2-1) → P(1-0) vibrational transitions for several rotational lines is realized. 相似文献
755.
Baidyshev V. S. Udodov V. N. Popov A. A. Potekaev A. I. 《Russian Physics Journal》2003,46(12):1193-1198
The paper offers a method for calculating phase diagrams of polytype transformations in close-packed crystals based on the generalized axial Ising's model of finite dimensions at non-zero temperatures. Using the Metropolis algorithm, the behavior of systems with polytype transitions is studied under the conditions of changing external shear stress and temperature. The longest polytype period considered here is taken to be 30 close-packed planes. 相似文献
756.
Automotive disc brake squeal 总被引:3,自引:0,他引:3
Disc brake squeal remains an elusive problem in the automotive industry. Since the early 20th century, many investigators have examined the problem with experimental, analytical, and computational techniques, but there is as yet no method to completely suppress disc brake squeal. This paper provides a comprehensive review and bibliography of works on disc brake squeal. In an effort to make this review accessible to a large audience, background sections on vibrations, contact and disc brake systems are also included. 相似文献
757.
A solution to the problem of nonlinear surface vibration of a charged ideal liquid drop is found in a third-order approximation in initial multimode deformation of the equilibrium spherical shape by the method of many scales. It is shown that the spectrum of modes that are responsible for the shape of the drop at an arbitrary time instant depends considerably on the spectrum of modes governing the initial deformation of the drop. The latter spectrum also has an effect on nonlinear corrections to the vibration frequencies and, consequently, on a nonlinear correction to the critical Rayleigh parameter, which specifies the stability of the drop against self-charge. 相似文献
758.
Behavior of a poro-elastic material bonded onto a vibrating plate is investigated in the low-frequency range. From the analysis of dissipation mechanisms, a model accounting for damping added by the porous layer on the plate is derived. This analysis is based on a 3-D finite element formulation including poro-elastic elements based on Biot displacement theory. First, dissipated powers related to thermal, viscous and viscoelastic dissipation are explicited. Then a generic configuration (simply-supported aluminium plate with a bonded porous layer and mechanical excitation) is studied. Thermal dissipation is found negligible. Viscous dissipation can be optimized as a function of airflow resistivity. It can be the major phenomenon within soft materials, but for most foams viscoelastic dissipation is dominant. Consequently an equivalent plate model is proposed. It includes shear in the porous layer and only viscoelasticity of the skeleton. Excellent agreement is found with the full numerical model. 相似文献
759.
S. N. Molotkov 《Journal of Experimental and Theoretical Physics》2003,97(5):1053-1074
A principally new approach ensuring secure key distribution via an open quantum communication channel is proposed. In contrast to the existing schemes, in which the security is based upon special properties of nonorthogonal states in the Hilbert space, the security of the proposed scheme relies on a spacetime structure of states and on certain constraints imposed by special relativity. Using these factors, it is possible to provide for secure key transmission using practically arbitrary quantum states. 相似文献
760.
The problem of transition radiation generated by relativistic particles incident on atomic strings in a crystal at a small angle is considered. Conditions are obtained under which the problem of transition radiation reduces to that of radiation generated by a collision with a filament-like target. It is shown that the angular distribution of transition radiation is symmetric with respect to the atomic-string axis. 相似文献