全文获取类型
收费全文 | 125篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
化学 | 74篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 25篇 |
物理学 | 28篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有129条查询结果,搜索用时 187 毫秒
61.
N. Narasimha Rao I.V. Kityk V. Ravi Kumar P. Raghava Rao B.V. Raghavaiah P. Czaja P. Rakus N. Veeraiah 《Journal of Non》2012,358(3):702-710
Piezoelectric coefficients d33 as well as ultrasonic velocities and elastic coefficients of ZnF2–PbO–TeO2 glasses crystallized with different concentrations of TiO2 (0.5 to 2.0 wt.%) were measured. The contribution to the piezoelectric coefficients is attributed to presence of Pb5Ti3F19, PbTiO3 and PbTeO3 ferroelectric crystal phases. The piezoelectric coefficients show substantial sensitivity to presence of TiO2. The ultrasonic velocities and the related elastic coefficients in these glass ceramics as a functions of concentration of nucleating agent TiO2 exhibited minimal effect at 1.0 wt.%. This is ascribed to the larger presence of titanium ions in Ti3+ states which act as modifiers and finally de-polymerize glass ceramic network. The results have been further discussed quantitatively within a framework of different oxidation states of titanium ions and the nature of the crystal phases ingrained in the glass ceramic. 相似文献
62.
63.
64.
Walter Bartelmus Fakher Chaari Radoslaw Zimroz Mohamed Haddar 《European Journal of Mechanics - A/Solids》2010,29(4):637-646
Fault detection and diagnosis in mechanical systems during their time-varying nonstationary operation is one of the most challenging issues. In the last two decades or so researches have noticed that machines work in nonstationary load/speed conditions during their normal operation. Diagnostic features for gearboxes were found to be load dependent. This was experimentally confirmed by a smearing effect in the spectrum.In order to better understand the involved phenomena and to ensure agreement between simulation and experimental results, two models of gearboxes (a fixed-axis two-stage gearbox and a planetary gearbox) operating under varying load conditions are proposed. The models are based on two mechanical systems used in the mining industry, i.e. the belt conveyor and the bucket wheel excavator. An original transmission error function expressing changes in technical condition and load variation is presented.Energy based parameters (the signal RMS value or the arithmetic sum of the amplitudes of spectral gearmesh components) are adopted as the diagnostic features. Simulation results show a strong correlation between load values, changes in condition and the diagnostic features. The findings are key to condition monitoring. Thanks to the use of the models one can better understand the phenomena identified through an analysis of vibration signals captured from real machines. 相似文献
65.
Wójcik Kamil Czaja Tomasz Szostak Roman Grzeszczuk Maria 《Journal of Solid State Electrochemistry》2018,22(12):3933-3945
Journal of Solid State Electrochemistry - Silver(I) halide particles embodied in polypyrrole matrices are synthesized and further processed electrochemically to get nanoparticles of silver with... 相似文献
66.
Two broad luminescence bands in weakly hydrogenated (glow discharge) undoped amorphous silicon have been observed using time resolved spectroscopy on a nanosecond timescale. Whereas the luminescence decay of the low energy band has been found to be sample independent, the peak position of the luminescence does show a sample dependence. We propose an intrinsic origin of this luminescence. 相似文献
67.
68.
Theoretical and chemical studies of the reactivity of isoprekinamycin, the kinamycins, and the lomaiviticins support the proposal that these natural products exhibit enhanced diazonium salt character and may owe their antitumor antibiotic properties to their ability to act as electrophilic azo-coupling agents in vivo. 相似文献
69.
Khalimon AY Holland JP Kowalczyk RM McInnes EJ Green JC Mountford P Nikonov GI 《Inorganic chemistry》2008,47(3):999-1006
Reaction of Mo(NAr)2Cl2(DME) (Ar=2,6-C6H3iPr2, DME=1,2-dimethoxyethane) with NaBH4 and PMe3 in THF formed the paramagnetic Mo(V) d1 borohydride complex Mo(NAr)2(PMe3)2(eta2-BH4) (1). Compound 1, which was characterized by EPR spectroscopy and X-ray diffraction analysis, provides a rare example both of a paramagnetic bis(imido) group 6 compound and a structurally characterized molybdenum borohydride complex. Density functional theory calculations were used to determine the electronic structure and bonding parameters of 1 and showed that it is best viewed as a 19 valence electron compound (having a primarily metal-based SOMO) in which the BH4- ligand behaves as a sigma-only, 2-electron donor. 相似文献
70.
Ohne Zusammenfassung 相似文献