全文获取类型
收费全文 | 67篇 |
免费 | 1篇 |
专业分类
化学 | 39篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 13篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 9篇 |
2009年 | 1篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
1998年 | 1篇 |
1992年 | 2篇 |
1985年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有68条查询结果,搜索用时 779 毫秒
51.
Farouq Ahmed Ryuji Muira Hideyuki Tsuboi Akira Endou Momoji Kubo 《Applied Surface Science》2010,256(24):7643-10513
Ultra accelerated quantum chemical molecular dynamics method (UA-QCMD) was used to study the dynamics of the hydrogen spillover process on Pt/CeO2 catalyst surface for the first time. The direct observation of dissociative adsorption of hydrogen on Pt/CeO2 catalyst surface as well as the diffusion of dissociative hydrogen from the Pt/CeO2 catalyst surface was simulated. The diffusion of the hydrogen atom in the gas phase explains the high reactivity observed in the hydrogen spillover process. Chemical changes, change of adsorption states and structural changes were investigated. It was observed that parallel adsorption of hydrogen facilitates the dissociative adsorption leading to hydrogen desorption. Impact with perpendicular adsorption of hydrogen causes the molecular adsorption on the surface, which decelerates the hydrogen spillover. The present study also indicates that the CeO2 support has strong interaction with Pt catalyst, which may cause an increase in Pt activity as well as enhancement of the metal catalyst dispersions and hence increasing the rate of hydrogen spillover reaction. 相似文献
52.
This paper deals with a new generalization of the linear exponential distribution. This distribution is called the generalized linear exponential distribution (GLED). Some statistical properties such as moments, modes and quantiles are derived. The failure rate function and the mean residual lifetime are also discussed. The maximum likelihood estimators of the parameters are obtained using a simulation study. Real data are used to determine whether the GLED is better than other well-known distributions in modeling lifetime data or not. 相似文献
53.
Markarian SA Gabrielian LS Bonora S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(5):1296-1304
FTIR and Raman spectra analysis of pure dipropylsulfoxide (DPSO), binary mixtures of DPSO/CCl(4), and DPSO/water has been first performed. The complex pattern of spectra has been explained on the basis of molecular interactions between DPSO and other molecules and, in the aqueous solutions, the role of both hydrophilic and hydrophobic interactions have been discussed depending on the concentrations. The changes in the intensities and in the frequencies of DPSO bands on concentration have been considered. The curve fitting procedure has been performed for both SO and C-H stretching region, and, on the basis of deconvolution results different type of molecular interactions have been considered. Density function theory DFT/(B3LYP) method has been used to determine the optimized geometry for free DPSO and for 1 DPSO:1 water complex. On the basis of the 6-31+G(d) quality sets parameters, the DFT calculated bond parameters and harmonic vibrations are in a very good agreement with experimental data. 相似文献
54.
The computational complexity of linear and nonlinear programming problems depends on the number of objective functions and constraints involved and solving a large problem often becomes a difficult task. Redundancy detection and elimination provides a suitable tool for reducing this complexity and simplifying a linear or nonlinear programming problem while maintaining the essential properties of the original system. Although a large number of redundancy detection methods have been proposed to simplify linear and nonlinear stochastic programming problems, very little research has been developed for fuzzy stochastic (FS) fractional programming problems. We propose an algorithm that allows to simultaneously detect both redundant objective function(s) and redundant constraint(s) in FS multi-objective linear fractional programming problems. More precisely, our algorithm reduces the number of linear fuzzy fractional objective functions by transforming them in probabilistic–possibilistic constraints characterized by predetermined confidence levels. We present two numerical examples to demonstrate the applicability of the proposed algorithm and exhibit its efficacy. 相似文献
55.
Mohammad Hossein Aboonasr Shiraz Mehran Rezaei Fereshteh Meshkani 《Research on Chemical Intermediates》2016,42(8):6627-6642
Mesoporous nano-crystalline γ-Al2O3 with high surface area prepared by a microemulsion (ME) method was employed as carrier for nickel catalysts in dry reforming of methane for syngas production. The structural properties of the catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, temperature programmed reduction and oxidation and scanning electron microscopy techniques. Microemulsion showed it to be a promising way for the production of nano-crystalline aluminum oxide, and the nickel catalysts prepared with this support have significant features and properties to use in the dry reforming reaction. The results revealed that the prepared γ-Al2O3 exhibited a nano-crystalline structure (crystal size: c.4.8 nm) with a high specific surface area (308 m2 g?1). In addition, the catalysts with different nickel contents exhibited high catalytic activity in the dry reforming reaction. The results also showed that an increase in Ni loading from 5 to 15 wt% caused a decrease in the specific surface area and nickel dispersion. 相似文献
56.
57.
58.
59.
60.
Markarian SA Gabrielian LS Bonora S Fagnano C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(3):575-588
FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO- and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3-21G* levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole-dipole and hydrogen bonding mechanisms. 相似文献