全文获取类型
收费全文 | 371023篇 |
免费 | 3200篇 |
国内免费 | 1223篇 |
专业分类
化学 | 184622篇 |
晶体学 | 5091篇 |
力学 | 19101篇 |
综合类 | 9篇 |
数学 | 65151篇 |
物理学 | 101472篇 |
出版年
2020年 | 2532篇 |
2019年 | 2728篇 |
2018年 | 13469篇 |
2017年 | 13317篇 |
2016年 | 11018篇 |
2015年 | 4127篇 |
2014年 | 5290篇 |
2013年 | 12543篇 |
2012年 | 13263篇 |
2011年 | 21838篇 |
2010年 | 13457篇 |
2009年 | 13526篇 |
2008年 | 17335篇 |
2007年 | 19502篇 |
2006年 | 10837篇 |
2005年 | 10922篇 |
2004年 | 10273篇 |
2003年 | 9827篇 |
2002年 | 8736篇 |
2001年 | 7902篇 |
2000年 | 6287篇 |
1999年 | 4818篇 |
1998年 | 4342篇 |
1997年 | 4292篇 |
1996年 | 4201篇 |
1995年 | 3745篇 |
1994年 | 3833篇 |
1993年 | 3526篇 |
1992年 | 3952篇 |
1991年 | 3947篇 |
1990年 | 3830篇 |
1989年 | 3705篇 |
1988年 | 3827篇 |
1987年 | 3695篇 |
1986年 | 3502篇 |
1985年 | 4735篇 |
1984年 | 4986篇 |
1983年 | 4131篇 |
1982年 | 4326篇 |
1981年 | 4257篇 |
1980年 | 4221篇 |
1979年 | 4177篇 |
1978年 | 4446篇 |
1977年 | 4328篇 |
1976年 | 4367篇 |
1975年 | 4055篇 |
1974年 | 4087篇 |
1973年 | 4258篇 |
1972年 | 2940篇 |
1971年 | 2449篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
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
12.
13.
E. G. Tarakanova 《Journal of Applied Spectroscopy》1991,54(4):357-362
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 4, pp. 581–587, April, 1991. 相似文献
14.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
G. E. Volovik 《JETP Letters》2002,76(5):240-244
An analogue of a black hole can be realized in the low-temperature laboratory. The horizon can be constructed for “relativistic” ripplons (surface waves) living on the brane. The brane is represented by the interface between two superfluid liquids, 3He-A and 3He-B, sliding along each other without friction. A similar experimental arrangement was recently used for the observation and investigation of the Kelvin-Helmholtz type of instability in superfluids [1]. The shear-flow instability in superfluids is characterized by two critical velocities. The lowest threshold measured in recent experiments [1] corresponds to the appearance of the ergoregion for ripplons. In the modified geometry, this will give rise to the black-hole event horizon in the effective metric experienced by ripplons. In the region behind the horizon, the brane vacuum is unstable due to interaction with the higher-dimensional world of bulk superfluids. The time of the development of instability can be made very long at low temperature. This will allow us to reach and investigate the second critical velocity—the proper Kelvin-Helmholtz instability threshold. The latter corresponds to the singularity inside the black hole, where the determinant of the effective metric becomes infinite. 相似文献
16.
17.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
18.
19.
H E Cline W E Lorensen R J Herfkens G A Johnson G H Glover 《Magnetic resonance imaging》1989,7(1):45-54
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting. 相似文献
20.
We describe in detail fundamental properties of continuity modules of various orders in the spaces L
p of functions defined on a finite segment. We establish some general estimates of seminorms in terms of continuity modules with the best known constants. An example of application of these results to the best approximations is considered. Bibliography: 32 titles. 相似文献