全文获取类型
收费全文 | 267373篇 |
免费 | 1818篇 |
国内免费 | 528篇 |
专业分类
化学 | 120320篇 |
晶体学 | 4340篇 |
力学 | 14001篇 |
综合类 | 3篇 |
数学 | 43583篇 |
物理学 | 87472篇 |
出版年
2020年 | 1409篇 |
2019年 | 1567篇 |
2018年 | 10681篇 |
2017年 | 11586篇 |
2016年 | 7180篇 |
2015年 | 2743篇 |
2014年 | 3247篇 |
2013年 | 7797篇 |
2012年 | 9955篇 |
2011年 | 19076篇 |
2010年 | 12056篇 |
2009年 | 12117篇 |
2008年 | 16923篇 |
2007年 | 20333篇 |
2006年 | 6288篇 |
2005年 | 12080篇 |
2004年 | 8444篇 |
2003年 | 7945篇 |
2002年 | 5840篇 |
2001年 | 5381篇 |
2000年 | 4177篇 |
1999年 | 3006篇 |
1998年 | 2526篇 |
1997年 | 2405篇 |
1996年 | 2412篇 |
1995年 | 2221篇 |
1994年 | 2183篇 |
1993年 | 2081篇 |
1992年 | 2378篇 |
1991年 | 2323篇 |
1990年 | 2269篇 |
1989年 | 2201篇 |
1988年 | 2209篇 |
1987年 | 2210篇 |
1986年 | 2099篇 |
1985年 | 2721篇 |
1984年 | 2788篇 |
1983年 | 2476篇 |
1982年 | 2582篇 |
1981年 | 2395篇 |
1980年 | 2380篇 |
1979年 | 2538篇 |
1978年 | 2576篇 |
1977年 | 2416篇 |
1976年 | 2507篇 |
1975年 | 2413篇 |
1974年 | 2379篇 |
1973年 | 2588篇 |
1972年 | 1641篇 |
1971年 | 1348篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
951.
Photoinduced optical and second-order non-linear optical effects in the interfaces separating In2O3–SiON (O/N ratio equals 1) films doped with A1, Sn and glass substrates were investigated using the photoinduced optical second harmonic generation. The photoinduced effective second-order optical susceptibility deff (at λ=1.76 μm) shows a good correlation with the linear optical susceptibility, particularly with the shift of the absorption edge. The maximal response of the photoinduced optical response signal was observed for the pump–probe delaying time of 34 ps. The performed experimental measurements indicate that the observed effects are mainly caused by the interface potential gradients on the border glass–In2O3–SiON film and by additional polarization due to insertion of the Al and Sn atoms. The observed phenomenon may be proposed as a sensitive tool for investigation of thin semiconducting interfacial layers and simultaneously such films may be used as materials for non-linear optical devices. 相似文献
952.
A. V. Burenin 《Optics and Spectroscopy》2004,97(6):867-875
A noninvariant geometrical group characterizing the internal dynamics of the tetrahydrofuran molecule C4H8O with allowance for the clearly pronounced pseudorotation effect is constructed. On this basis, some qualitative features of the energy spectrum of the molecule following from the analysis of high-resolution spectroscopic data are explained. 相似文献
953.
The Kα to Lα and Kβ to Lβ intensity ratios of seven elements have been measured following photoionization at 59.5 keV by using a Si (Li) detector
(FWHM=155 eV at 5.96 keV). The intensity ratios were determined by measuring K and L x-rays emitted from a standard target of a given element. The theoretical values of the Kα to Lα and Kβ to Lβ intensity ratios were calculated using theoretically tabulated values of shell/subshell photoionization cross sections,
fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates for ηKLi≠ and ηKLi=0. The measured values are in good agreement with theoretical results.
From Optika i Spektroskopiya, Vol. 97, No. 2, 2004, pp. 186–189.
Original English Text Copyright ? 2004 by A. Kü?ük?nder, S?ğüt, E. Kü?ük?nder, Büyükkasap.
This article was submitted by the authors in English. 相似文献
954.
The kinetics of decay of a phase hologram in a semiconductor CdF2 crystal with bistable In centers is studied. Kinetic constants of the hologram decay are found, and the potential relief of the bistable center is plotted. The resolving power of the crystal is evaluated and recording of a transparency is demonstrated. 相似文献
955.
Processes of electronic excitation energy transfer (EEET) in H2O+D2O solutions within reversed micelles with different degrees of hydration were studied. It is ascertained that the structure of solutions forms a cluster distribution of interacting molecules having a fractal dimensionality. As a result, in regions with a locally high concentration of the dye molecules, an increase in the EEET efficiency is observed. Solubilization by reversed micelles leads to destruction of the cluster structure of the water system, with the dependence of the EEET efficiency on the degree of hydration being nonmonotonic. As the degree of hydration increases, the inhomogeneities of the structure inherent in bulk water are restored. 相似文献
956.
The cross section of absorption of electromagnetic radiation by an inhomogeneous spherical particle is calculated. The general case of an arbitrary value of the ratio of the particle radius to the radius of the dielectric core is considered. The condition of diffuse reflection of electrons from the inner and outer surfaces of the metal layer of the particle is taken as the boundary condition of the problem. The limiting cases are considered and the results obtained are discussed. 相似文献
957.
Computer processing of electronic absorption spectra of rare-earth elements in inorganic laser media
Algorithms and program modules are developed for calculation of the Judd-Ofelt parameters on modern computers. These programs can be used to perform numerical analysis of the energy absorption by rareearth ions in laser media. 相似文献
958.
959.
We complete our previous(1, 2) demonstration that there is a family of new solutions to the photon and Dirac equations using spatial and temporal circles and four-vector behaviour of the Dirac bispinor. We analyse one solution for a bound state, which is equivalent to the attractive two-body interaction between a charged point particle and a second, which remains at rest. We show this yields energy and angular momentum eigenvalues that are identical to those found by the usual method of solving of the Dirac equation,(4) including fine structure. We complete our previous derivation(2) of QED from a set of rules for the two-body interaction and generalise these. We show that QED may be decomposed into a two-body interaction at every point in spacetime. 相似文献
960.