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101.
Production of anhydrous potassium tetraborate from potassium tetraborate tetrahydrate (PTT) was investigated in a controlled fluidized bed calcinatory (FBC). Single step calcination gives a puffed product with very low bulk density and the calcination of potassium tetraborate tetrahydrate is incomplete since agglomeration starts at temperature higher than 250 °C. Effect of the temperature on the bulk density of the product obtained at the end of single step is given and compared with theoretical calculation. In order to obtain anhydrous potassium tetraborate, dehydration should be carried out at least two stages. The most important step dominating the final bulk density is the first step. Dehydration of potassium tetraborate tetrahydrate up to 85% K2B4O7 content and temperature lower than 150 °C in the first step gives commercial available product at final stage. As a result, both puffed and denser anhydrous potassium tetraborate of 99.5% purity with bulk density around 0.4 and 0.7 g cm−3 has been produced by two and three stage calcinations. 相似文献
102.
T. Zmijewski Barbara Pacewska J. Pysiak 《Journal of Thermal Analysis and Calorimetry》1995,43(1):113-122
The influence of calcination conditions on changes in phase composition and porous structure was studied for hydrous aluminium oxide, obtained by leaching out potassium salts from the products of roasting basic aluminium-potassium sulfate in hydrogen atmosphere at 600°C. The product of calcination at 350°C in vacuum has the most developed porous structure with most pores of internal radius within 10–60 Å. Calcination in air atmosphere at temperatures 700, 800, 900, or 1000°C resulted in decrease of specific surface of aluminium oxide and increase of the share of pores with internal radius above 60 Å in the overall porosity of the samples. The reconstruction of the porous structure proceeds mainly as a result of coalescent sintering. 相似文献
103.
YUAN Song-Yue ZHAO Zhen Changchun institute of Applied Chemistry Academia Sinica Changchun. Jilin YU Zuo-LongChengdu Institute of Organic Chemistry Academia Sinica Chengdu Sichuan 《天然气化学杂志》1995,(4)
The correlations of the calcination temperature.structure and catalvtic activity of the LiLa_(0.5)Ti_(0.5)O_(2-(?)) catalvsts with main phase and major active phase of perovskite-type trmary complex oxide LaTi_(l-y)Li_yO_(3-λ)m the Oxidative coupling of methane(OCM)have been studied The surface and bulk structures of the catalysts were characterized by means of XRD,XPS. IR.BFT and so on. The results clearly indicated that the effect of calcination temperature on the activity for the oxidative coupling of methaneis twofold On one hand.high calcination temperature is favoragble for Lisubstitution for Ti~(3 )into the lattice of LaTiO_3 and the production of moreoxygen vacancies at which active oxygen species are formed However,excessivelv high calcmation temperature makes Li~ substitution for Ti~(3 )less due to a httle change of structure or phases of the catalvst On the otherhand,the conversion of CH_4 drops because of the decrease of surface area,when the calcination temperature is raised. 相似文献
104.
以不同焙烧温度和Ce负载量的CeY分子筛为研究对象,运用XRD及N_2吸附表征其织构性质;运用吡啶吸附红外光谱法剖析了分子筛中活性位的化学属性;采用固定床评价其对噻吩模拟油的吸附脱硫性能及芳烃和烯烃对噻吩脱除的影响;并结合红外光谱和GC-SCD技术分析了其脱硫机制。结果表明,CeY样品经150℃焙烧后,其超笼中具备高含量的B酸和Ce羟基化物种活性位,两者协同增强了噻吩低聚反应能力,进而提高了其吸附穿透硫容量(18.45 mg (S)/g);而提升焙烧温度和Ce负载量会严重降低其有效活性位的数量,削弱了噻吩低聚反应能力,其吸附穿透硫容量显著减小(4.03 mg (S)/g)。当加入烯烃和芳烃后,CeY-12.3-150吸附剂对含低浓度(质量分数)1-己烯(1.0%)和苯(0.1%)的噻吩模拟油依旧保持较高吸附穿透硫容量;但随两者含量的持续增加,其硫容量急剧下降。其主要分别归因于噻吩烷基化反应的发生及“S-H”键的作用模式。 相似文献
105.
106.
A variety of fluoroalkyl end‐capped N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomer [RF‐(DOBAA)n‐ RF]/silica nanocomposites, in which the oligomer contents are 18–96%, were prepared by reactions of the corresponding fluorinated oligomer with tetraethoxysilane and silica nanoparticles under alkaline conditions. Each fluorinated oligomer/silica composite thus obtained is nanometer size‐controlled very fine particles (22–68 nm) possessing a good dispersibility and stability in a variety of solvents including water. Interestingly, the weight loss of RF‐(DOBAA)n‐RF/silica nanocomposites, in which the oligomer contents are 18–72%, were not observed at all even at 800°C, as well as the original silica nanoparticles, although the corresponding sub‐micrometer size‐controlled RF‐ (DOBAA)n‐RF/silica composites (particle size: 359 nm) decomposed completely at 800°C to afford the weight loss in proportion to the content of RF‐(DOBAA)n‐RF oligomer in composites. On the other hand, a slight weight loss of RF‐(DOBAA)n‐RF/silica nanocomposites, in which the oligomer contents are 75–94%, was observed at 800°C compared to that of the original silica nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
107.
Sucrose chelated auto combustion synthesis of BiFeO3 nanoparticles: Magnetically recoverable catalyst for the one‐pot synthesis of polyhydroquinoline 下载免费PDF全文
Sucrose chelated Bismuth ferrite (BiFeO3) nanoparticles as a novel heterogeneous catalyst was synthesized by an auto combustion route. Different calcination temperatures (150 °C, 450 °C, 550 °C, 650 °C, 750 °C and 850 °C) have been employed to obtain single phased BiFeO3 nanoparticles. The perovskite structure formation and disappearance of organic phase (sucrose) was obtained by Fourier transform infrared spectroscopy (FT‐IR). Phase determination and structural characterization was carried out by powder X‐ray diffraction (XRD). The magnetic properties were analyzed by vibrating sample magnetometer (VSM) whereas surface area/pore volume was obtained by Brunauer–Emmett–Teller (BET). Transmission electron microscope (TEM) analyzed the particles size and morphology. Thermal stability was investigated by thermogravimetric analysis (TGA) and determination of constituent elements was carried out by X‐ray Photo‐Electron Spectroscopy (XPS). Raman spectroscopy confirmed the perovskite structure of the synthesized materials. The BiFeO3 nanoparticles so obtained were employed as heterogeneous catalyst for the synthesis of polyhydroquinoline derivatives. All the polyhydroquinoline derivatives were characterized by Fourier transform infrared spectroscopy (FT‐IR) and Nuclear magnetic resonance spectroscopy (1H NMR). For the very first time ever we have used BiFeO3 as a recyclable magnetic nanocatalyst in the one‐pot four component cyclization reaction of benzaldehyde, ethylacetoacetate/methylacetoacetate, dimedone/cyclohexane‐1,3‐dione, and ammonium acetate for the synthesis of polyhydroquinoline derivatives without solvent under refluxing conditions to provide excellent yields of products. BiFeO3 nanocatalyst (without any functionalization/surface coatings) shows easy magnetic separation, recyclability, reusability along with excellent yield of polyhydroquinoline derivatives in an economic and benign way. 相似文献
108.
α-Al2O3在耐火材料、电子材料等多个领域有着极其重要的应用。本文首先介绍了α-Al2O3在工业应用方面的评价指标和α-Al2O3的相变机理,接着分别从固相合成、液相合成、气相合成三个方面阐述了α-Al2O3制备的相关研究进展,对制备过程中影响α-Al2O3晶粒微观状态的若干因素,包括煅烧温度、矿化剂类型、pH值及预处理条件等进行讨论。最后指出了当前对α-A12O3成核生长机理研究缺乏的问题,表明明确的成核机理、高纯度α-A12O3的量产和形貌控制技术将会是该领域未来的研究重点和发展方向。 相似文献
109.
沉淀铁费托合成催化剂焙烧工艺的优化研究 《燃料化学学报》2017,45(2):235-242
通过DOE实验设计对沉淀铁费托合成催化剂焙烧过程进行了优化,并给出了焙烧过程的分子模拟与粒子长大模型。结果表明,随着焙烧温度的升高和焙烧时间的延长,催化剂的孔容减小,堆比及骨架密度增加,耐磨性改善。BET表面与磨耗的变化趋势一致,即比表面积越小磨耗越小;磨耗与密度成线性反比关系,密度越高磨耗越小。通过焙烧工艺的优化,可调变Cu、Si通过O原子与Fe原子的键合作用及催化剂的粒子粒径,得到较高F-T活性且稳定性好的沉淀铁催化剂。在该实验中,优化的焙烧温度为560℃。 相似文献
110.
TiO2 nanotubes (TiO2-NTs) were synthesized by the hydrothermal method. Co and Mo active components were supported on a series of the as-prepared TiO2-NTs samples which were calcined at different temperatures. The effects of support calcination temperature of CoMo/TiO2-NTs catalysts on their catalytic performance were investigated for selective hydrodesulfurization (HDS). The samples were characterized by means of the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy and H2 temperature-programmed reduction (H2-TPR). The experimental results revealed that TiO2-NTs support calcined under 500 °C can maintain the nanotubular structure with higher surface area and pore volume. Meanwhile, the obtained supported CoMo/TiO2-NTs catalysts exhibited weak metal-support interaction, more octahedral Mo6+ species and high catalytic performance in selective HDS. 相似文献