全文获取类型
收费全文 | 62篇 |
免费 | 1篇 |
专业分类
化学 | 40篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 2篇 |
物理学 | 10篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有63条查询结果,搜索用时 0 毫秒
1.
2.
3.
The mass spectra of eleven 1,2,4-triazepines with oxo, thioxo, methoxy and methylmercapto groups in the 3 and 5 positions are reported and analysed. Each of the five structures of the triazepine ring present is characterized by a particular group of fragmentations. 相似文献
4.
We report here a one-step synthesis of the 4,5,6,7-tetrahydro-1H- 1,2,4,-triazolo[4,3-d][1,4]diazepine, 4-6, and 1,2,4-oxadiazolo[4,5-d][1,4]-diazepine, 7-10, by 1,3-dipolar cycloaddition of nitrile imines and nitrile oxides with 2,3-dihydro-H-1,4-diazepine, 1. In all cases these cycloaddition are peri- and regioselectives (the C ? N bond is sole affected) and occures with high yields. Structure and conformations of cycloadducts have been assigned by means of nmr analysis 相似文献
5.
The oxidation of aluminum single crystals is studied using molecular dynamics (MD) simulations with dynamic charge transfer between atoms. The simulations are performed on three aluminum low-index surfaces ((1 0 0), (1 1 0) and (1 1 1)) at room temperature. The results show that the oxide film growth kinetics is independent of the crystallographic orientation under the present conditions. Beyond a transition regime (100 ps) the growth kinetics follow a direct logarithmic law and present a limiting thickness of ∼3 nm. The obtained amorphous structure of the oxide film has initially Al excess (compared to the composition of Al2O3) and evolves, during the oxidation process, to an Al percentage of 45%. We observe also the presence of an important mobile porosity in the oxide. Analysis of atomistic processes allowed us to conclude that the growth proceeds by oxygen atom migration and, to a lesser extent, by aluminum atoms migration. In both cases a layer-by-layer growth mode is observed. The results are in good agreement with both experiments and earlier MD simulations. 相似文献
6.
Laminar natural convection heat transfer in inclined fluid layers divided by a partition with finite thickness and conductivity is studied analytically and numerically. The governing equations for the fluid layers are solved analytically in the limit of a thin layered system with constant flux boundary conditions. The study covers of the range of Ra from 103 to 107, from 0° to 180° and the thermal conductivity ratio of partition to fluid ratioK from 10–2 to 106. The Prandtl number was 0.72 (for air). Results are obtained in terms of an overall Nusselt number as a function of Rayleigh number, angle of inclination of the system, mid layer thickness, and mid layer thermal conductivity. The critical Rayleigh number for the onset of convection in a bottom-heated horizontal system is predicted. The results are compared with the numerical results obtained by solving the complete system of governing equations, using SIMPLER method, as well as with the limiting cases in the literature. 相似文献
7.
In this work, we present a numerical study of mixed convection coupled with radiation in an inclined channel with an aspect ratio B = L/H=10, and locally heated from one side. Convective, radiative and total Nusselt numbers, evaluated on the cold surface and at the exit of the channel, are presented for different combinations of the governing parameters namely, the surface emissivity (0 1), the Reynolds number (10 Re 50), the inclination of the channel with respect to the horizontal surface (0° 90°) and the Rayleigh number (Ra = 105). The ratio, R = QC/QE, of the heat quantities, leaving the channel through the cold wall, QC, and through the exit, QE, is presented to identify the most favorable issue to the heat transfer in the studied configuration. The results obtained show that the flow structure is significantly altered by radiation which contributes to reduce or to enhance the number of the solutions obtained. 相似文献
8.
M. Elaloui A. Laamouri J. Fabre C. Mathieu G. Vilarem B. Hasnaoui 《Natural product research》2015,29(1):94-97
Ziziphus jujuba pulps are very much appreciated by the inhabitants and have been recently exported. This article reports on the chemical composition (amino acids, polyphenols and sugars) of the pulps of four Z. jujuba ecotypes (Choutrana, Mahdia, Mahres and Sfax). The major amino acids identified were proline, aspartic acid and glutamic acid. Among these, proline was the most abundant amino acid (17.4 mol). Considerable differences in total phenolic contents (15.85 mg/L) were found. Predominant phenols identified by using HPLC were rutin (1.09 mg/L) and chlorogenic acid (2.57 mg/100 g). Sugars isolated from Ziziphus pulps were found at a rate of 43.52%. Using HPLC method, three sugars from the pulp extract were identified: glucose, galactose and sucrose. The Mahdia ecotype was the richest in these sugars with 0.45, 136.51 and 113.28 mg/L, respectively. 相似文献
9.
The methods used to prepare five types of 1,2,4-triazepines disubstituted by oxo, thioxo, methoxy or methylthio groups in the 3 and 5 positions are described. Thus eleven triazepines have been synthesized and their structure established from the spectral data. 相似文献
10.
R. Benelbaghdadi A. Benharref A. Hasnaoui J. P. Lavergne M. Pierrot F. Huet 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):e461-e462
The structure of the title compound, C24H25ClN2O6, has been established and the central seven‐membered ring is fused to chlorobenzo and oxazolino rings to form the core of the molecule. 相似文献