全文获取类型
收费全文 | 533296篇 |
免费 | 4782篇 |
国内免费 | 1497篇 |
专业分类
化学 | 273799篇 |
晶体学 | 8382篇 |
力学 | 25276篇 |
综合类 | 16篇 |
数学 | 64633篇 |
物理学 | 167469篇 |
出版年
2021年 | 4285篇 |
2020年 | 4728篇 |
2019年 | 5314篇 |
2018年 | 7271篇 |
2017年 | 7405篇 |
2016年 | 10463篇 |
2015年 | 6067篇 |
2014年 | 10014篇 |
2013年 | 23863篇 |
2012年 | 18183篇 |
2011年 | 22007篇 |
2010年 | 16031篇 |
2009年 | 15881篇 |
2008年 | 20062篇 |
2007年 | 20086篇 |
2006年 | 18619篇 |
2005年 | 16430篇 |
2004年 | 15198篇 |
2003年 | 13616篇 |
2002年 | 13546篇 |
2001年 | 15499篇 |
2000年 | 11771篇 |
1999年 | 9180篇 |
1998年 | 7832篇 |
1997年 | 7729篇 |
1996年 | 7233篇 |
1995年 | 6486篇 |
1994年 | 6571篇 |
1993年 | 6220篇 |
1992年 | 6938篇 |
1991年 | 7110篇 |
1990年 | 6880篇 |
1989年 | 6670篇 |
1988年 | 6543篇 |
1987年 | 6615篇 |
1986年 | 6276篇 |
1985年 | 8081篇 |
1984年 | 8372篇 |
1983年 | 6992篇 |
1982年 | 7161篇 |
1981年 | 6850篇 |
1980年 | 6800篇 |
1979年 | 7021篇 |
1978年 | 7356篇 |
1977年 | 7233篇 |
1976年 | 7267篇 |
1975年 | 6725篇 |
1974年 | 6790篇 |
1973年 | 6987篇 |
1972年 | 4957篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
A. E. Angervaks S. A. Dimakov S. I. Kliment’ev A. I. Ryskin A. S. Shcheulin 《Optics and Spectroscopy》2002,93(2):307-314
The diffraction efficiency and the recording and relaxation times of dynamic reflection holograms, recorded in CdF2 crystals with bistable centers are studied experimentally in the temperature range 20–100°C. In the model experiments which measured the quality of the wave reflected from the hologram, the dynamic wavefront distortions are demonstrated to be efficiently compensated using a holographic corrector based on these crystals. CdF2 crystals with bistable centers are likely to be useful in solving problems of correction of laser light wavefront and image correction in observation telescopes with nonideal primary mirrors. 相似文献
102.
F. Iachello S. Oss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):307-314
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years.
We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century.
Received 21 November 2001 相似文献
103.
C. J. S. Clarke 《Israel Journal of Mathematics》1983,45(1):9-16
It is shown that any finite dimensionalC 0 manifold (connected and Hausdorff but otherwise unrestricted) has an atlas of cardinality not greater than that of the continuum; while if it has a Hölder continuous pseudo-Riemannian metric then there is a countable atlas. 相似文献
104.
A fast-frequency modulated (FM) diode laser has been optically narrowed using the technique of resonant optical feedback, to provide linewidths in each FM mode of ≈ 200 kHz peak-to-peak. With a drive frequency of 50 MHz and modulation index of 0.2, the FM laser has been used for the first time to obtain Doppler-free FM spectra of the Rb D1 line at 795 nm. The potential use of this system for laser frequency stabilisation is discussed. 相似文献
105.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
106.
107.
108.
109.
A. A. Abramov S. V. Kurochkin 《Computational Mathematics and Mathematical Physics》2006,46(6):949-954
A new method for calculating the radial spheroidal functions of the first kind is proposed for the arguments that are greater than unity in modulus. A well-known representation of these functions is refined and used for this purpose. The constructs and the software implementation proposed in the paper provide an efficient tool for the calculation of the functions with a desired accuracy in a wide range of parameters. 相似文献
110.
This paper examines the non-linear dynamic behaviour of a flexible shaft. The shaft is mounted on two journal bearings and the axial load is supported by a defective hydrodynamic thrust bearing at one end. The defect is a levelness defect of the rotor. The thrust bearing behaviour must be considered to be non-linear because of the effects of the defect. The shaft is modelled with typical beam finite elements including effects such as the gyroscopic effects. A modal technique is used to reduce the number of degrees of freedom. Results show that the thrust bearing defects introduce supplementary critical speeds. The linear approach is unable to show the supplementary critical speeds which are obtained only by using non-linear analysis. 相似文献