全文获取类型
收费全文 | 278642篇 |
免费 | 2489篇 |
国内免费 | 735篇 |
专业分类
化学 | 130816篇 |
晶体学 | 4015篇 |
力学 | 14729篇 |
综合类 | 7篇 |
数学 | 42955篇 |
物理学 | 89344篇 |
出版年
2021年 | 1032篇 |
2020年 | 1183篇 |
2019年 | 1200篇 |
2018年 | 10519篇 |
2017年 | 11458篇 |
2016年 | 6657篇 |
2015年 | 3009篇 |
2014年 | 2754篇 |
2013年 | 8143篇 |
2012年 | 11105篇 |
2011年 | 21183篇 |
2010年 | 12678篇 |
2009年 | 12741篇 |
2008年 | 18599篇 |
2007年 | 22192篇 |
2006年 | 7515篇 |
2005年 | 14156篇 |
2004年 | 9821篇 |
2003年 | 8804篇 |
2002年 | 6578篇 |
2001年 | 6288篇 |
2000年 | 4976篇 |
1999年 | 3571篇 |
1998年 | 2753篇 |
1997年 | 2691篇 |
1996年 | 2831篇 |
1995年 | 2414篇 |
1994年 | 2300篇 |
1993年 | 2155篇 |
1992年 | 2452篇 |
1991年 | 2404篇 |
1990年 | 2127篇 |
1989年 | 2101篇 |
1988年 | 2149篇 |
1987年 | 2058篇 |
1986年 | 1973篇 |
1985年 | 2904篇 |
1984年 | 2904篇 |
1983年 | 2325篇 |
1982年 | 2508篇 |
1981年 | 2405篇 |
1980年 | 2356篇 |
1979年 | 2314篇 |
1978年 | 2399篇 |
1977年 | 2268篇 |
1976年 | 2250篇 |
1975年 | 2199篇 |
1974年 | 2090篇 |
1973年 | 2216篇 |
1972年 | 1240篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
D. Chithrani R. L. Williams J. Lefebvre P. J. Poole G. C. Aers 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):290
We discuss the preparation and spectroscopic characterisation of a single InAs/InP quantum dot suitable for long-distance quantum key distribution applications around λ=1.55 μm. The dot is prepared using a site-selective growth technique which allows a single dot to be deposited in isolation at a controlled spatial location. Micro-photoluminescence measurements as a function of exciton occupation are used to determine the electronic structure of the dot. Biexciton emission, shell filling and many-body re-normalization effects are observed for the first time in single InAs/InP quantum dots. 相似文献
992.
J. Wang J. Kono A. Oiwa H. Munekata C. J. Stanton 《Superlattices and Microstructures》2003,34(3-6):563
We have carried out an ultrafast time-resolved differential reflectivity study of a ferromagnetic semiconductor InGaMnAs and made a systematic comparison with low-temperature grown and high-temperature grown InGaAs reference films. Very short carrier lifetimes (2 ps) were observed in InGaMnAs and the low-temperature grown InGaAs film, but not in the high-temperature grown InGaAs film. We attribute the short lifetimes to carrier trapping by mid-gap states introduced during low-temperature MBE growth. Furthermore, at long times, we observed periodic oscillations in the differential reflectivity signal with period 20 ps, which we interpret as coherent acoustic phonons. 相似文献
993.
994.
The logarithmic decrement and shear modulus of a bulk amorphous Zr52.5Ti5Cu17.9Ni14.6Al10 alloy were studied with an inverse torsion pendulum in the range from room temperature to the crystallization temperature and in the frequency range 5–40 Hz. The activation energy spectra of reversible and irreversible structural relaxation were estimated. The results obtained are discussed in the context of a two-energy-level model. 相似文献
995.
996.
V. A. Reznikov 《Technical Physics》2003,48(9):1216-1218
A shell model that describes the formation of molecular complexes around a C60 molecule upon the solid-phase interaction of the powders is considered. From the absorption spectra, it follows that a reacting
particle is a fullerene dimer. 相似文献
997.
998.
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
999.
R. Weidmann 《Archiv der Mathematik》2003,81(5):589-595
We describe a family of graph manifolds that have 2-generated
fundamental group but do not admit a Heegaard splitting of genus 2. They are
closely related to the examples provided by Boileau and Zieschang if these are
considered as (non-proper) graph manifolds.Received: 14 August 2002 相似文献
1000.
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