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351.
Nilgün Yener Müşerref Önal Gökçe Üstünışık Y. Sarıkaya 《Journal of Thermal Analysis and Calorimetry》2007,88(3):813-817
An industrial raw material taken from Beypazarı (Ankara, Turkey) region was heated at different temperatures in the 100–1100°C
interval for 2 h. The volumetric percentage of particles having diameter below 2 μm in an aqueous suspension of the material
held 24 h were determined as 85% by the particle size distribution analysis. The mineralogical composition of the material
was obtained as mass% of 81% sepiolite, 15% dolomite, and 4% interparticle water by using the X-ray diffraction (XRD) and
thermal analysis (TG, DTA) data. The temperature ranges were determined for the dehydrations of the interparticle water and
the zeolitic water as 25–340°C, for the dehydration of the bound water as 340–580°C, and for the dehydroxylation of the hydroxyls
as 800–833°C in the sepiolite. The zig-zag changes in the specific surface area (S/m2 g−1) and specific micro-and mesopore volume (V/cm3 g−1) with the temperature increases were discussed according to the dehydrations and dehydroxylation of the sepiolite. 相似文献
352.
The dehydrated form of (Li,Na)-substituted analcime, Li1.30Na0.53[Al1.83Si4.17O12], has been prepared and investigated with single crystal X-ray diffraction: a = 32.167(6) Å, b = 18.551(2) Å, c = 11.693(2) Å; β = 90.06(1)°, V = 6978(1) Å3, Z = 24, space group C2. The structure was analyzed through considering the aluminosilicate framework as a system of tubes composed from corrugated 6-membered rings joint by triples of tetrahedra. Volume decrease by 6.5% and trigonal distortion of the structure are explained by the localization of the non-framework cations in new unusual positions. On dehydration of Li, Na-analcime, 67% of Na+ and 20% of Li+ migrated from the standard M-positions at the periphery of the tubes into essentially different positions NaW and LiL situated on the axes of the tubes. Among the total of the fixed tube positions— 12NaW and 16LiL — one half is aggregated in the tubes parallel to [001] and has a planar three-fold coordination by framework O-atoms. The configuration and cation population of the tubes in other directions follow the motif of the “basic” system. 相似文献
353.
Ezahri M. El Hadek M. Coffy G. Mentzen B. F. 《Journal of Thermal Analysis and Calorimetry》2002,68(1):207-213
The study of the dehydration/rehydration of ammonium tris-oxalato aluminate(III) (NH4)3Al(C2O4)3⋅3H2O in flowing dinitrogen saturated with water vapor at room temperature, using thermogravimetric analysis and X-ray diffraction
techniques, allowed the determination of the temperature stability domains of (NH4)3Al(C2O4)3⋅3H2O, (NH4)3Al(C2O4)3⋅2H2O and the anhydrous salt. The X-ray powder diffraction profiles are reported for each of the three phases.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
354.
By refluxing the anatase form of TiO2 powder in phosphoric acid, the surface acidity was observed to increase. The amount of acid was determined by n-butylamine titration in n-heptane media, and was found to be proportional to the reflux period in phosphoric acid. XRD patterns and IR spectra revealed that the products contained a mixture of the anatase form of TiO2 and titanium phosphate phases. Based on the calculated acid density on the surface, part of the titrant, n-butylamine penetrated into the titanium phosphate layers. Further investigations using TGA, FT-IR and TEM techniques along with surface area measurements indicated that the titanium phosphate phase was coated over the TiO2 phase. The surface acidity of the phosphoric acid treated anatase increased due to the substitution of Ti-OH groups by phosphate groups. Nevertheless, the chemical properties of the resultant surfaces were found to be influenced by the internal anatase phase. The kinetic data on the 2-propanol dehydration reaction, where the activation energies were found to decrease gradually with an increase in phosphate content, also support these conclusion. 相似文献
355.
The thermal dehydration and decomposition of M(IO3)2·2H2O (M 2+=Ni2+ and Zn2+) and their deuterates were investigated by DTA and DSC methods. The data obtained confirm their onestage dehydration and their decomposition to the respective oxides. Ni(IO3)2·2H2O and Ni(IO3)2·2D2O, were more stable than Zn(IO3)2·2H2O and Zn(IO3)2·2D2O. A considerable isotope effect was observed in relation toT deh for Ni(IO3)2·2H2O and Ni(IO3)2·2D2O, which was explained by the presence of structural changes well differentiated from the dehydration process for the deuterate. The data obtained for both pairs of dihydrates were used to determine ΔH f o for Ni(IO3)2·2H2O and Ni(IO3)2·2D2O. 相似文献
356.
Synthesis of (2R,3S,4S)-4-aryl-3-hydroxyprolinols has been established starting from 2-benzyloxymethylpyrrolidin-2-one framework, which is derived from commercially available trans-(2S,4R)-4-hydroxyproline. The single diastereomer having a trans–cis relative configuration with C2 and C3 and C3 and C4 is constructed in two one-pot functional group transformations of Grignard addition/dehydration and epoxidation/isomerization as the key steps in moderate yield. 相似文献
357.
P. G. Kislitsyn F. A. Kucherov L. N. Chukhrov S. G. Zlotin Z. A. Starikova F. M. Dolgushin 《Russian Chemical Bulletin》2004,53(4):916-924
A new procedure was developed for the synthesis of nitriles of vic-[alkyl(aryl)sulfonyl] derivatives of benzoic, anthraquinonecarboxylic, and 4-isothiazolecarboxylic acids by the reactions of the corresponding vic-[alkyl(aryl)thio]-substituted aromatic (heteroaromatic) carboxamides with chlorine in organic solvents containing 20—65% of water. Oxidative dehydration of 1-(butylthio)anthraquinone-2-carboxamide afforded 1-butyl-6,11-dihydro-3H-14-anthra[2,1-d]isothiazole-3,6,11-trione 1-oxide as a by-product. The structure of the latter was established by X-ray diffraction analysis. The reaction scheme involving the formation of S-chlorosulfonium chlorides followed by their hydrolysis was proposed. 相似文献
358.
E. Torres-Garcia J. Balmaseda L. F. del Castillo E. Reguera 《Journal of Thermal Analysis and Calorimetry》2006,86(2):371-377
Divalent transition metal nitroprussides form a family of microporous
materials which lose their crystallization water (coordinated and zeolitic)
below 100°C and then remain stable up to above 150°C. The dehydration
process of representative samples in their stable phases was studied by thermo-gravimetry
(TG) and differential scanning calorimetry (DSC). The copper complex dehydrates
in a single step through a practically irreversible process. For cadmium and
cobalt complexes the water evolution on heating takes place in two stages.
The first one, where only zeolitic waters are removed, is dominated by a diffusion
mechanism while, during the loss of the strongly bonded waters (second stage)
the material framework effect is added. The involved activation energy and
its dependence on the conversion degree were estimated evaluating the thermo-gravimetric
data according to an isoconversion model. 相似文献
359.
云母钛脱水脱硫过程的动力学研究 总被引:3,自引:0,他引:3
对强制水解硫酸钛制得的云母钛前驱体进行了TG分析,利用了Freeman-Carroll方法处理热重数据,得到云母钛热处理的动力学参数,脱水阶段:E=93.32kJ/mol,n=5.16,A=5.31×10^11min^-1脱硫阶段,E=149.25kJ/mol,n=5.13,A=2.75×10^11min^-1。相同条件下制得的水合氧化钛粉末的动力学参数表明,云母钛中水合氧化钛膜层的脱水,脱硫速率 相似文献
360.
The mechanism of the precursor dehydration route was revealed for the synthesis of NTE c-ZrW1.6Mo0.4O8. The hydrate precursor was dehydrated at 473 K and transformed to a NTE cubic compound above 800 K. A novel intermediate phase o-ZrWl.6Mo0.4O8 occurs between the temperature range of 573-800 K. The XRD pattern of novel intermediate was refined with the structural model of LT-ZrMo2O8 by using Rietveld method.The residuals are Rwp=7.80% and Rp=5.79%. The space group is Pmn21 and the lattice parameters are α=0.5917(4)nm, b=0.7273(4) nm, c =0.9148(6) nm, and Z=2. 相似文献