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21.
Elton A. S. Castro Ricardo Gargano João B. L. Martins 《International journal of quantum chemistry》2012,112(16):2828-2831
In this work, we present a theoretical study of interaction of benzene with kaolinite and an analysis of the vibrational spectra, electrostatic potential maps, and self consistent field (SCF) orbitals. B3LYP and MP2 benzene–kaolinite results indicate a preferential interaction of benzene on kaolinite octahedral surface. Population analysis indicates that the atoms modified their charges when the monoaromatic molecule and clay mineral are close to tetrahedral and octahedral surface of kaolinite, which suggests that the adsorbed molecule becomes slightly positive. Infrared vibrational data show the reduction in the band frequencies related to the kaolinite external hydroxyls, indicating a weak interaction of benzene with clay mineral. It also was verified, from the potential electrostatic maps, a change in electron density in both benzene and kaolinite. Electron localization function analysis was also carried out for this interaction. © 2011 Wiley Periodicals, Inc. 相似文献
22.
Understanding adsorption phenomena involving humic acids and clays is a difficult challenge owing to their complex nature.
Thus, to progress in the study of such systems, attempts were made to replace natural systems by polyacids and oxides of simpler
chemical and morphological structure. Since the present investigation was dedicated to determine some characteristics of acidic
soils which contain traces of aluminium ions, these ions were added to the adsorbent/polyacid systems as trace constituents.
Phenomena related to the interactions of humic or polyacrylic acid with aluminium oxide and kaolinite clay have been investigated
and the well-differentiated interfacial behaviour of the oxide and kaolinite was determined and discussed. The results of
electrophoretic mobility measurements demonstrated the huge time-dependent effect of polymeric layers adsorbed on oxides and
modified clays.
Received: 24 July 2000 Accepted: 20 December 2000 相似文献
23.
Influence of the Degree of Dehydroxylation of Kaolinite on the Properties of Aluminosilicate Glasses
The degree of dehydroxylation of kaolinite, DTG and DIR, respectively, is characterized by thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FTIR). The
relation between DTG and DIR based on the infrared absorptions at 3600–3700, 915, 810, and 540 cm−1 is established. Three regions can clearly be distinguished: the dehydroxylation region (DTG<0.9), the metakaolinite region (0.9<DTG<1) and the ‘spinel’ region(DTG=1). The effect of the degree of dehydroxylation of kaolinite on the amount of reactive material is measured by the reaction
enthalpy, ΔH, of the low-temperature reaction of the dehydroxylated kaolinite with a potassium silicate solution using differential scanning
calorimetry (DSC). |ΔH| increases almost linearly with DTG in the dehydroxylation region. In the metakaolinite region, ΔH and thus the amount of reactive material, becomes constant. |ΔH| is sharply decreasing when metakaolinite transforms into other phases in the ‘spinel’ region. No significant differences
in the reactivity of the dehydroxylates is detected with DSC. According to FTIR, the use of partially dehydroxylated kaolinite
is not influencing the molecular structure of the low-temperature synthesized aluminosilicates, but residual kaolinite is
retrieved as an additive.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
24.
Thermoanalytical Investigation of Formamide Intercalated Kaolinites Under Quasi-isothermal Conditions 总被引:1,自引:0,他引:1
J. Kristóf E. Horváth R. L. Frost J. T. Kloprogge 《Journal of Thermal Analysis and Calorimetry》2001,63(1):279-289
The thermal behaviour of fully and partially expanded kaolinites intercalated with formamide has been investigated in nitrogen atmosphere under quasi-isothermal heating conditions at a constant, pre-set decomposition rate of 0.20 mg min–1 . With this technique it is possible to distinguish between loosely bonded (surface bonded) and strongly bonded (intercalated) formamide. Loosely bonded formamide is liberated in an equilibrium reaction under quasi-isothermal conditions at 118°C, while the strongly bonded (intercalated) portion is lost in an equilibrium, but non-isothermal process between 130 and 200°C. The presence of water in the intercalation solution can influence the amount of adsorbed formamide, but has no effect on the amount of the intercalated reagent. When the kaolinite is fully expanded, the amount of formamide hydrogen bonded to the inner surface of the mineral is 0.25 mol formamide/mol inner surface OH group. While the amount of surface bonded formamide is decreasing with time, no change can be observed in the amount of the intercalated reagent. With this technique the mass loss stages belonging to adsorbed and intercalated formamide can be resolved thereby providing a complex containing only one type of bonded (intercalated) formamide.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
25.
采用超声分散法制备出氧化铝、高岭土、氧化硅/聚四氟乙烯复合材料, 使用线性往复摩擦磨损试验机对比三种复合材料的摩擦学性能. 结果表明 质量分数10%的氧化铝、高岭土能将聚四氟乙烯的磨损率降低约4个数量级, 而氧化硅仅能降低约3个数量级. 对金属对偶表面形成的转移膜的形貌和化学成分进行分析发现 氧化铝、高岭土/聚四氟乙烯在金属对偶面上形成了高度羧酸盐化的转移膜. 用密度泛函理论对三种填料表面上碳氟分子吸附过程进行模拟, 结果显示氧化铝、高岭土表面的路易斯酸性位点促进了碳氟分子的脱氟过程, 产生了更多的羧酸螯合物的中间产物; 氧化硅缺少路易斯酸性位点, 因此不能促进高度羧酸盐化的转移膜形成. 相似文献
26.
27.
A. K. Chakravorty 《Journal of Thermal Analysis and Calorimetry》1993,39(3):289-299
TMA/DTMA with DTA studies on the thermal changes of kaolinite were performed with special emphasis on the crystallization behaviour of amorphous SiO2. The results of four different physical techniques (semiquantitative XRD, DTA, TMA and DTMA) were clearly in good agreement with the fact that the 1420°C exotherm in DTA is due to silica crystallization.Thanks to Dr. B. K. Sarkor, Director of the Institute for his kind permission to publish the paper and to Mr. D. K. Ahosh for his needful suggestions. 相似文献
28.
Clay such as kaolinite, is commonly used as an additive to modify the thermal properties of polymer. In this paper, the morphology, composition, shape and structure of kaolinite was characterized by various advanced techniques. The TEM/ EDX data showed that the kaolinite had a larger particle size and a Si/Al ratio of 1.8. The individual particle of kaolinite was a single crystalline. TEM also showed that these particles were always stacked together due to the presence of electrostatic cohesive energy and hydrogen bond between plaletes. The PAS-FTIR spectra showed that no absorbance of hydroxyl group for hydration water in hydrogen bond region or at 1650cm-1 was observed at room temperature. It meant a little ability to adsorb water for kaolinite particle. Kaolinite clay also showed no change for its PAS-FTIR spectra with increasing temperature. The TGA results revealed that kaolinite almost doesn′t lose weight at 60℃ due to loss of dehydration of absorbed water, however, it will decomposed around 510℃ and lose its hydroxyl functional group in the form of water (dehydroxylation). The result is consistent with that of PAS-FTIR analysis. This suggests that the structural hydroxyl group on the surface of individual kaolinite clay particle is very stable below 500℃, and the kaolinite composed polymer could be got by the reaction of its stable structural hydroxyl group with isocynate group of polyurethane prepolymer. 相似文献
29.
The structure default of kaolinites was characterized with 1H MAS NMR and Raman spectra. Although the HI indexes of Suzhou and Maoming kaolinite are similar, their 1H MAS NMR and Raman spectra are very different. 1H MAS NMR showed that the hydroxyl proton chemical shifts of Suzhou kaolinite are in the higher field and with larger different between the inner surface hydroxyls protons and inner hydroxyls proton chemical shifts than Maoming kaolinite. Raman spectra showed that the surface hydroxyls stretching vibration bands of Suzhou kaolinite are in the high frequency region, and the half height widths of the bands are 7.0~14 cm-1. The area ratio Sz/(Sz+SA), where SZ and SA are the areas of bands 3685 cm-1 and 3695 cm-1 respectively, is 0.23. But the surface hydroxyls stretching vibration bands of Maoming kaolinite are in the low frequency region, and the half height widths of the bands are 8.9~15.1 cm-1. The area ratio Sz/(Sz+SA) is 0.77. Those data proved that Suzhou kaolinite has lower structure default than Maoming kaolinite and 1H MAS NMR and Raman spectra are effective method for study of kaolinite structure default. 相似文献
30.