全文获取类型
收费全文 | 3029篇 |
免费 | 110篇 |
国内免费 | 6篇 |
专业分类
化学 | 2000篇 |
晶体学 | 179篇 |
力学 | 29篇 |
数学 | 410篇 |
物理学 | 440篇 |
无线电 | 87篇 |
出版年
2023年 | 21篇 |
2021年 | 37篇 |
2020年 | 59篇 |
2019年 | 51篇 |
2017年 | 26篇 |
2016年 | 59篇 |
2015年 | 58篇 |
2014年 | 47篇 |
2013年 | 98篇 |
2012年 | 115篇 |
2011年 | 134篇 |
2010年 | 71篇 |
2009年 | 78篇 |
2008年 | 112篇 |
2007年 | 108篇 |
2006年 | 115篇 |
2005年 | 89篇 |
2004年 | 86篇 |
2003年 | 78篇 |
2002年 | 59篇 |
2001年 | 47篇 |
2000年 | 36篇 |
1999年 | 36篇 |
1998年 | 31篇 |
1997年 | 30篇 |
1996年 | 38篇 |
1995年 | 30篇 |
1994年 | 40篇 |
1993年 | 41篇 |
1992年 | 28篇 |
1991年 | 36篇 |
1989年 | 36篇 |
1988年 | 23篇 |
1987年 | 33篇 |
1985年 | 39篇 |
1984年 | 23篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 42篇 |
1979年 | 29篇 |
1978年 | 33篇 |
1977年 | 27篇 |
1975年 | 25篇 |
1959年 | 69篇 |
1958年 | 65篇 |
1957年 | 44篇 |
1956年 | 80篇 |
1955年 | 57篇 |
1954年 | 89篇 |
排序方式: 共有3145条查询结果,搜索用时 26 毫秒
131.
Epitaxial layers of AgGaSe2 with thicknesses in the range from 50 to 70 nm were deposited onto (111)A-oriented semi-insulating GaAs substrates by flash-evaporation in the substrate temperature range TS = 825 … 900 K. Films grown at TS ≦ 850 K are n-type conducting whereas p-type conductivity was observed at TS ≧ 875 K. In the p-type samples two acceptor states with ionization energies of 60 and 410 meV were found from an analysis of the electrical measurements. 相似文献
132.
H. Neumann B. Perlt N.A.K. Abdul-Hussein R.D. Tomlinson A.E. Hill 《Crystal Research and Technology》1982,17(4):469-474
The optical absorption of r.f. sputtered CuInSe2 thin films was studied in the photon energy range from 1 to 3 eV. The gap energy and the spin-orbit splitting are found to be (1.01 ± 0.01) eV and (0.24 ± 0.02) eV, respectively. From the photon energy dependence of the absorption coefficient it is concluded that the heavy and light hole bands are parabolic whilst the split-off band contains terms linear in the wavevector. The optical transition probability for valence band- to- conduction band transitions is estimated to be (10.8 ± 1.0) eV which yields an admixture of copper d states to the valence band of (30 ± 8) %. 相似文献
133.
Wilhelm P. Neumann 《Nachrichten aus der Chemie》1982,30(3):190-194
134.
H. Neumann 《Crystal Research and Technology》1982,17(11):1388-1388
135.
Vapour phase epitaxial layers of InP were deposited onto (111)A-, (111)B-, (001)-, and (110)-oriented GaAs substrates in the InP/PCl3/H2 system using a close-space technique. It is shown that the dependence of the layer quality on the substrate orientation is due to differences in the initial growth stages. Results on the growth rates and the electrical properties of the layers are reported. 相似文献
136.
H. Neumann 《Crystal Research and Technology》1993,28(1):73-82
Theoretical relations are derived for the amplitude of the photoacoustic signal of a gas-coupled cell for thick semiconductor samples including the influence of multiple reflections of light within the sample. It is shown that in the range of low absorption coefficients characteristic of impurity absorption spectra the sensitivity of the cell can be enhanced by using a highly reflecting metal as backing material. Numerical estimates for CuInSe2 are given to illustrate this effect. 相似文献
137.
138.
Infrared reflectivity spectra of PbGa2S4 single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm−1 for the polarization directions E ∥ c and E ∥ b. The frequencies of 13 B1u modes and 11 B2u modes are derived from the spectra. The results are compared with previous studies and with lattice vibration data of ternary chalcopyrite and defect-chalcopyrite compounds. 相似文献
139.
M. V. Yakushev A. Zegadi H. Neumann P. A. Jones A. E. Hill R. D. Pilkington M. A. Slifkin R. D. Tomlinson 《Crystal Research and Technology》1994,29(3):427-437
The defect properties of p-type CuInSe2 single crystals hydrogenated by diffusion from a plasma source are investigated using the Rutherford backscattering/channeling technique and photoacoustic spectroscopy. Plasma hydrogenation is found to produce severe lattice damage, to affect the intrinsic defect equilibrium in the near surface region of the crystals and to create an additional donor. A defect formation model including both defect passivation by hydrogen and damage induced defect creation is proposed to explain the experimental data. The thermal stability of the property modifications is limited to temperatures below about 100 °C. 相似文献
140.
H. Neumann 《Crystal Research and Technology》1994,29(7):985-994
Based on simple approximations the backscattering minimum yield is estimated for axial ion channeling in perfect crystals of six CuBIIIC chalcopyrite compounds. The results obtained for CuInSe2 are compared with experimental channeling spectra. Point defect concentrations up to about 1021 cm−3 are estimated for CuInSe2 single crystals grown by the vertical Bridgman method. A simple power law is found for the fluence dependence of the damage density in oxygen implanted CuInSe2 single crystals. 相似文献