全文获取类型
收费全文 | 736530篇 |
免费 | 6567篇 |
国内免费 | 1771篇 |
专业分类
化学 | 366518篇 |
晶体学 | 10666篇 |
力学 | 38196篇 |
综合类 | 26篇 |
数学 | 105676篇 |
物理学 | 223786篇 |
出版年
2021年 | 5824篇 |
2020年 | 6518篇 |
2019年 | 7316篇 |
2018年 | 13760篇 |
2017年 | 14098篇 |
2016年 | 15893篇 |
2015年 | 8070篇 |
2014年 | 12815篇 |
2013年 | 30236篇 |
2012年 | 25298篇 |
2011年 | 33751篇 |
2010年 | 23871篇 |
2009年 | 23716篇 |
2008年 | 31075篇 |
2007年 | 32970篇 |
2006年 | 24000篇 |
2005年 | 24075篇 |
2004年 | 21147篇 |
2003年 | 19619篇 |
2002年 | 18525篇 |
2001年 | 18886篇 |
2000年 | 14888篇 |
1999年 | 11443篇 |
1998年 | 9909篇 |
1997年 | 9844篇 |
1996年 | 9350篇 |
1995年 | 8419篇 |
1994年 | 8540篇 |
1993年 | 8099篇 |
1992年 | 8688篇 |
1991年 | 9117篇 |
1990年 | 8775篇 |
1989年 | 8540篇 |
1988年 | 8474篇 |
1987年 | 8316篇 |
1986年 | 7914篇 |
1985年 | 10245篇 |
1984年 | 10797篇 |
1983年 | 9095篇 |
1982年 | 9445篇 |
1981年 | 8974篇 |
1980年 | 8662篇 |
1979年 | 9069篇 |
1978年 | 9548篇 |
1977年 | 9356篇 |
1976年 | 9377篇 |
1975年 | 8873篇 |
1974年 | 8767篇 |
1973年 | 9107篇 |
1972年 | 6591篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
961.
Polarization-independent modulation of light in gyrotropic cubic crystals is investigated in the Bragg and intermediate diffraction regimes. It is found that, for crystals with considerable specific rotation, the photoelastic anisotropy is suppressed by the circular anisotropy and the observed diffraction efficiency depends weakly on the polarization azimuth of the incident light. Good agreement is obtained between modulation parameters calculated theoretically on the basis of the coupled wave theory and experimental results for a bismuth silicate crystal in the intermediate diffraction regime. 相似文献
962.
Photorefractive scattering occurs in rhodium-doped lithium niobate crystals irradiated by coherent light. The photorefractive scattering has both wide-angle and selective components. The results of experimental investigation of selective photorefractive scattering in LiNbO3:Rh crystals and calculation of the spatial structure of scattering are reported. The selective scattering is regarded as a kind of a frequency-degenerate fourwave vector interaction. 相似文献
963.
The spectral properties of multilayer interference systems formed by multiple replication of the symmetric ternary period ABCBA are investigated. The problem of synthesis of structures with suppression of adjacent bands of high reflection of the fourth, fifth, and sixth orders among their spectral characteristics is solved. It is shown that there are only six variants of selection of the optical thicknesses of layers in a period. When the high reflection bands of the fourth, fifth, and sixth orders are suppressed, the high reflection band of the first order remains in only four cases. The values of refractive indices of layers for which the problem hasa solution are found. The refractive indices of layers in all six cases are described by different relations determining the dependence of the refractive index of one of the components on arbitrarily selected refractive indices of the other two components. 相似文献
964.
In order to study the influence of seeded impurities on ITER like reactor operation the COREDIV code has been extended to include the transport of several sputtered and/or injected impurities. In the COREDIV code the core plasma is treated in the frame of 1D radial transport model whereas in the edge the 2D multifluid code EPIT is used. The EPIT code solves in the slab geometry the MHD equations for densities and velocities for all ions species as well as for electron and ion temperatures. The iteration scheme in the code leads to steady state solution of coupled core and SOL system. The numerical results for Carbon and Nickel plate and seeded impurities Silicon and Neon are presented. 相似文献
965.
Porous road surfaces offer an effective means of reducing the generation and propagation of noise from road traffic. However, the porosity of these surfaces can deteriorate over time, leading to a reduction in their noise reducing properties. Efficient methods are therefore required for monitoring this performance. Existing techniques for performing in-situ measurements of acoustic absorption are unsuitable for use within the traffic stream. Static measurements using time domain Maximum Length Sequence (MLS) based techniques have been demonstrated to offer advantages over traditional techniques, presenting the opportunity for measurements under dynamic conditions. This paper describes the design of a system for carrying out dynamic MLS-based measurements. Results are presented which demonstrate that stable dynamic measurements can be carried out at speeds of up to 30 km/h. 相似文献
966.
It was shown that nonionic surfactants (NS) can be determined by potentiometry using liquid NS-selective electrodes. The effect of medium acidity and foreign substances on the operation of liquid NS-selective electrodes was studied. Some properties of NS-selective electrodes were determined. 相似文献
967.
Summary In [6], we introduced and investigated the notions of strong β-I-open sets and strong β-I-continuous functions in ideal topological spaces. In this paper, we investigate further their important properties. 相似文献
968.
This paper deals with a singular perturbation of the stationary Stokes and Navier-Stokes systems. The term ε2Δp is added to the continuity equation, where ε is a small parameter. For a domain with cylindrical outlets to infinity and exponentially decaying data, existence and uniqueness of solutions under flux conditions at infinity are established for the linear problem and also for the nonlinear problem in the case of small data. Asymptotically exact estimates are proved for ε tending to zero. For sufficiently regular data, these estimates imply the convergence in H
loc
5/2−δ
for the velocity parts and in H
loc
3/2−δ
for the pressure parts, respectively. Bibliography: 17 titles.Dedicated to V. A. Solonnikov on the occasion of his 70th birthday__________Published in Zapiski Nauchnykh Seminarov POMI, Vol. 306, 2003, pp. 107–133. 相似文献
969.
970.