全文获取类型
收费全文 | 704篇 |
免费 | 124篇 |
国内免费 | 36篇 |
专业分类
化学 | 570篇 |
晶体学 | 24篇 |
综合类 | 3篇 |
物理学 | 144篇 |
无线电 | 123篇 |
出版年
2024年 | 4篇 |
2023年 | 8篇 |
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 35篇 |
2018年 | 15篇 |
2017年 | 20篇 |
2016年 | 50篇 |
2015年 | 35篇 |
2014年 | 43篇 |
2013年 | 60篇 |
2012年 | 46篇 |
2011年 | 33篇 |
2010年 | 29篇 |
2009年 | 39篇 |
2008年 | 38篇 |
2007年 | 25篇 |
2006年 | 40篇 |
2005年 | 25篇 |
2004年 | 20篇 |
2003年 | 21篇 |
2002年 | 39篇 |
2001年 | 13篇 |
2000年 | 20篇 |
1999年 | 8篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 21篇 |
1995年 | 17篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有864条查询结果,搜索用时 15 毫秒
131.
Low dislocation density Ge wafers grown by a vertical gradient freeze (VGF) method used for the fabrication of multi-junction photovoltaic cells (MJC) have been studied by a whole wafer scale measurement of the lattice parameter, X-ray rocking curves, etch pit density (EPD), impurities concentration, minority carrier lifetime and residual stress. Impurity content in the VGF-Ge wafers, including that of B, is quite low although B2O3 encapsulation is used in the growth process. An obvious difference exists across the whole wafer regarding the distribution of etch pit density, lattice parameter, full width at half maximum (FWHM) of the X-ray rocking curve and residual stress measured by Raman spectra. These are in contrast to a reference Ge substrate wafer grown by the Cz method. The influence of the VGF-Ge substrate on the performance of the MJC is analyzed and evaluated by a comparison of the statistical results of cell parameters. 相似文献
132.
二氧化钒(VO2)作为一种长久以来备受关注的新型可逆相变材料,发展潜力巨大,其相变温度(TMIT)的调控一直是研究热点。本文主要利用锗离子作为掺杂离子探索其对VO2薄膜TMIT的影响,并尝试解释其内部作用机理。在约1 cm2大小抛光的氧化铝薄片上沉积了一系列含不同比例锗离子VO2薄膜。研究发现锗离子作为掺杂离子确实有利于TMIT的提高(本课题TMIT最大可达84.7 ℃)。TMIT提高的主要原因是锗离子的引入能够强化单斜态V-V二聚体的稳定性,进而增强单斜态的稳定性,使得低温单斜态向四方金红石态转变更加困难。 相似文献
133.
134.
Dominik Nied Wim Klopper Prof. Dr. Frank Breher Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(8):1411-1416
Ge, whiz! A detailed study of the synthesis, structure, redox chemistry, and bonding properties of pentagerma[1.1.1]propellane ( 1 , see picture) examines fundamental aspects of the interactions between the bridgehead germanium atoms. DFT and CASSCF calculations unravel the biradicaloid characteristics of 1 , and preliminary reactivity studies indicate that 1 features some radical‐type behavior.
135.
《Frontiers of Physics》2013,8(4):412
It is believed that weakly interacting massive particles (WIMPs) are candidates for dark matter (DM) in our universe which come from outer space and might interact with the standard model (SM) matter of our detectors on the earth. Many collaborations in the world are carrying out various experiments to directly detect DM particles. China Jinping underground Laboratory (CJPL) is the deepest underground laboratory in the world and provides a very promising environment for DM search. China Dark matter EXperiment (CDEX) is going to directly detect the WIMP flux with high sensitivity in the low WIMP-mass region. Both CJPL and CDEX have achieved a remarkable progress in recent three years. CDEX employs a point-contact germanium (PCGe) semi-conductor detector whose energy threshold is less than 300 eV. In this report we present the measurement results of muon flux, monitoring of radioactivity and radon concentration carried out in CJPL, as well describing the structure and performance of the 1 kg-PCGe detector in CDEX-1 and 10 kgPCGe detector array in CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of CDEX-1, CDEX-10 and the future CDEX-1T experiments. 相似文献
136.
137.
138.
139.
Kira M 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2012,88(5):167-191
Structure and properties of silicon-silicon doubly bonded compounds (disilenes) are shown to be remarkably different from those of alkenes. X-Ray structural analysis of a series of acyclic tetrakis(trialkylsilyl)disilenes has shown that the geometry of these disilenes is quite flexible, and planar, twist or trans-bent depending on the bulkiness and shape of the trialkylsilyl substituents. Thermal and photochemical interconversion between a cyclotetrasilene and the corresponding bicyclo[1.1.0]tetrasilane occurs via either 1,2-silyl migration or a concerted electrocyclic reaction depending on the ring substituents without intermediacy of the corresponding tetrasila-1,3-diene. Theoretical and spectroscopic studies of a stable spiropentasiladiene have revealed a unique feature of the spiroconjugation in this system. Starting with a stable dialkylsilylene, a number of elaborated disilenes including trisilaallene and its germanium congeners are synthesized. Unlike carbon allenes, the trisilaallene has remarkably bent and fluxional geometry, suggesting the importance of the π-σ* orbital mixing. 14-Electron three-coordinate disilene-palladium complexes are found to have much stronger π-complex character than related 16-electron tetracoordinate complexes. 相似文献
140.
A.R. Peaker V.P. Markevich I.D. Hawkins B. Hamilton K. Bonde Nielsen K. Gościński 《Physica B: Condensed Matter》2012,407(15):3026-3030
This paper is to commemorate the work of Leszek Dobaczewski1 who devoted much of his life to the development and application of high resolution DLTS. 相似文献