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排序方式: 共有81条查询结果,搜索用时 15 毫秒
1.
Xianghui Wang Pengda Zhao Jianwei Chen Huizhong Zhao Kai He 《Ceramics International》2018,44(11):12162-12168
Al–Cr slag is the solid waste generated by the smelting of Cr metal. It presents a range of environmental hazards. This study addressed the corrosion resistance of Al–Cr slag containing chromium–corundum refractories to slags with different basicity. Herein, we provide suggestions for the use of Cr–corundum of different basicity in kilns. Al–Cr slag, brown fused Al2O3, and chrome green were used as the raw materials, with pure calcium aluminate cement being used as a binder. The brick samples, prepared using different blends of chrome green and corundum, were fired at 1600?°C, and subsequently subjected to a slag corrosion test. After corrosion by slag of different basicity, the phase composition and microstructure of the sample were analyzed by X-ray diffraction, energy dispersive spectrometer and scanning electron microscopy. There were two major findings. First, Cr–corundum brick made from Al–Cr slag has a better slag corrosion resistance than that made from Cr2O3 and brown fused Al2O3. Second, Cr–corundum brick made from Al–Cr slag has superior corrosion resistance to slag with a CaO:SiO2 ratio of 2:1. 相似文献
2.
3.
Further evidence was delivered that certain impurities, which could be contained in MgO samples, might be responsible for observed variability in MgO basicity and catalytic performance in oxidative coupling of methane. The surface basicity/base strength distribution of a series of MgO samples containing or not containing Ca and Na impurities was determined by a temperature-programmed desorption of CO2. It was revealed that samples containing Ca and Na impurities have much more medium, strong and very strong basic sites. The surface basicity of MgO samples containing added alkali or alkaline earth compounds or water was characterized by a test reaction of transformation of 2-butanol. It was confirmed that the introduction of these compounds to a pure MgO enhanced both its basicity and activity in oxidative coupling of methane. 相似文献
4.
高碱度渣精炼对轴承钢夹杂物的影响 总被引:4,自引:2,他引:4
对国内外几家特钢厂生产的GCr15轴承钢中夹杂物进行了试验分析 ,结果表明 ,在炉渣碱度较高 (CaO SiO2 =3~ 4 5 )的精炼条件下 ,低氧含量 (≤ 7× 10 - 6 )的轴承钢中夹杂物主要为 :含Cr、Fe的复合MnS夹杂 ,TiN型夹杂 ,具有不同MgO含量的镁铝尖晶石 (MgO·Al2 O3)夹杂 ;未发现单独存在的铝酸钙型 (CaO·Al2 O3)球状夹杂物。随渣碱度提高和钢中氧含量降低 ,镁铝尖晶石夹杂物中的MgO含量增加 ;当渣系碱度CaO SiO2 达 4 5时 ,镁铝尖晶石夹杂物中含有CaO。 相似文献
5.
Three novel alkaline guanidine ionic liquids as amphiphilic catalysts have been successfully synthesized for two-phase transesterification, which can efficiently improve the catalytic activity for the synthesis of biodiesel. They were characterized by a series of techniques including 1H NMR, thermal stability, electronegativity (DFT calculation), basicity and conductivity. It was demonstrated that 1,1,3,3-trimethyl-2-octyl-guanidine hydroxide(IL3) exhibited better catalytic activity compared with other base guanidine ionic liquid catalysts, which was related to the better basicity and electronegativity of the ILs. The experimental results indicated that catalytic performance was relative to both enough alkaline center and conductivity of ionic liquid catalysts, but the former was a main factor in the catalytic system. The catalytic performance also revealed that optimum catalyst dosage was about 6 wt.%, the appropriate reaction temperature was about 55 °C, the optimum n(Methanol)/n(Soybean Oil) for the biodiesel synthesis was about 15:1 and the suitable reaction time was 4 h on the basis of biodiesel yield of 97%. In addition, the reaction mechanism of the amphiphilic catalyst was illuminated by the interaction between the methoxyl group and the carbonyl group of the triglyceride after activating for two-phase transesterification. 相似文献
6.
对氢氧化物酸碱性强度的规律论述甚多,但大都为经验规则,本文对一些计算pK_1的经验规则进行了分类、比较和评述,指出了一些经验规则的适用范围及其存在问题,着重分析了适用性较广且有统一衡量标度即N,φ_w和φ′的三个计算公式,还进一步探讨了一些经验规则中所出现的重要经验常数5的物理意义,它可认为主要是中心离子(水合)φ_w值递变的结果,且是一个平均值,随着周期数的增大或中心离子半径的增大而递变。 相似文献
7.
V. Calvino-Casilda A. J. Lpez-Peinado J. L. G. Fierro R. M. Martín-Aranda 《Applied Catalysis A: General》2003,240(1-2):287-293
Two basic activated carbons (Na+ and Cs+-Norit) have been used as catalysts in the synthesis of N-propargyl imidazole. The effect of the microwave irradiation has been studied. Under the experimental conditions used higher yields and selectivities of N-propargyl imidazole than those obtained using other basic media were reached. The carbons were characterized by thermal analysis, nitrogen adsorption and X-ray photoelectron spectroscopy. Most of the basic sites in the promoted carbons have 13.3≤pKa≤16.5. The order or basicity is Na+-Norit+-Norit. The basicity enhancement is directly connected with the size of the alkaline cation. The yield of the N-propargyl imidazole presents a maximum for 0.04 g of Cs+-Norit at 300 W in only 3 min of microwave irradiation. 相似文献
8.
The role of MCM-41 composition in the creation of basicity by alkali metal impregnation 总被引:3,自引:0,他引:3
Aleksandra Michalska Marco Daturi Jacques Saussey Izabela Nowak Maria Ziolek 《Microporous and mesoporous materials》2006,90(1-3):362-369
Three types of mesoporous molecular sieves (silicate MCM-41, niobosilicate NbMCM-41, and aluminosilicate AlMCM-41) were impregnated with alkali metal acetates. The textural stability of the samples was estimated on the basis of XRD measurements and nitrogen adsorption/desorption methods. The acidic–basic properties of the obtained materials were tested in the cyclization of acetonylacetone and studied by FTIR spectroscopy after adsorption of methylacetylene (propyne) and pyridine. Two types of chemical reactions between mesoporous matrix and alkali metal salt/oxide were observed: the reaction between alkali metal salt and silica/silicate and the reaction between basic oxide and silanol groups or Na+ cations. In the first one the alkali metal silicate formation decreases from Li to Cs species and leads to the destruction of the material. The second reaction places alkali metal cations in extra framework positions, which increases from Li to Cs species and is only observed in the case of AlMCM-41 and NbMCM-41 materials. As a result of the second reaction Lewis acidity is generated. The average effect of these two interactions leads to the volcanic curve for basicity of M/AlMCM-41 and M/NbMCM-41 with the maximum for K-samples. In contrast, basicity of M/MCM-41 systematically increases from Li to Cs form since the second type of interaction does not occur for these samples. 相似文献
9.
Soon Young Min Sanjeev Maken Jin-Won Park Ankur Gaur Jang Soo Hyun 《Korean Journal of Chemical Engineering》2008,25(2):323-328
In this study, we melted four types of waste asbestos containing material such as spread asbestos, plasterboard asbestos,
slate asbestos and asbestos 99 wt%, in a melting furnace at 1,450–1,550 that uses a mixture of hydrogen and oxygen (Brown’s
gas) as a fuel. More volatile components (CaO, K2O) are enriched in spread asbestos, plasterboard asbestos, and slate asbestos, while less volatile compounds (SiO2, Fe2O3, MgO) remain in asbestos 99%. Through basicity of raw materials, spread asbestos, plasterboard asbestos, and slate asbestos
were found to have more alkalinity, and asbestos 99% was found more acidic. SEM and EDX results revealed that all raw materials
had various kinds of asbestos fiber. Spread asbestos, plasterboard asbestos, and slate asbestos were considered as tremolite
asbestos, whereas asbestos 99% was considered as chrysotile asbestos. It was further confirmed by SEM and XRD studies that
all waste materials contained some crystalline structures which transformed into amorphous glassy structure on melting. Also,
in case of added glass cullet during the melting of spread asbestos, it transformed the raw material into a perfect vitrified
product having more glassy surface and amorphous in nature 相似文献
10.
Katarzyna Świrk Paulina Summa Dominik Wierzbicki Monika Motak Patrick Da Costa 《International Journal of Hydrogen Energy》2021,46(34):17776-17783
A series of V-promoted hydrotalcite-derived nickel catalysts (1.0, 2.0, and 4.0 wt%) were tested in CO2 methanation. Ni–I–V2.0 with 2.0 wt% vanadium loading showed the highest catalytic activity, achieving 74.7% of CO2 conversion and 100% of CH4 selectivity at 300 °C. XRD and XANES analyses showed that the smallest Ni0 particles in Ni–I–V2.0 were consistent with the improved textural features observed for this catalyst. Moreover, CO2-TPD revealed the highest sum of weak and medium basic sites in Ni–I–V2.0 that can positively influence catalytic behavior. For the studied catalysts, a clear correlation was demonstrated between the catalytic activity and specific surface area, as well as the basic properties. 相似文献