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1.
Characterization of the non-stoichiometric and isomorphic hydration and solvation in FK041 clathrate
Hisashi Mimura Satoshi Kitamura Teruyuki Kitagawa Shigetaka Kohda 《Colloids and surfaces. B, Biointerfaces》2002,26(4):397-406
FK041 crystallizes as a non-stoichiometric hydrate or as solvated hydrates which were characterized as isomorphic clathrates by powder X-ray diffractometry. Moisture and organic solvent vapor sorption studies, differential scanning calorimetry and thermogravimetric analysis revealed that FK041 monohydrate forms a physically stable host crystal, which has lattice channels for guest water and/or organic solvent molecules. The hydration state varies non-stoichiometrically between dihydrate and tetrahydrate depending on the relative humidity and the mol content of the co-existing organic solvent, that is 2-propanol, ethanol, or acetone. These organic solvents are thought to replace a part of originally present water with a mol ratio of 1:3. 2-Propanol exhibited the most stable solvation, indicating that the size and shape of 2-propanol are the most preferable to the lattice channels. 相似文献
2.
Weihua Di Xiaoxia Zhao Shaozhe Lu Haifeng Zhao 《Journal of solid state chemistry》2007,180(9):2478-2484
In this work, we used the solution precipitation route to synthesize Eu3+-doped YPO4·nH2O nanowires. The structure, morphology, composition, thermal behavior, and photoluminescence of as-synthesized product were characterized by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopic (FE-SEM) and photoluminescence (PL) spectra. The dependence of the structure, morphology, composition and luminescent properties on the thermal treatment was investigated. The results indicate that the aqueous synthesis has a better control on the structure, morphology, composition of the products, and that the heat treatment induces the transitions of the structure, composition, and luminescent properties. 相似文献
3.
NH4MIIPO4·H2O (MII = Mg, Mn0.5Mg0.5, Co0.5Mg0.5) were synthesized by direct-precipitating method. The olivine-like LiMIIPO4 were successfully generated through the solid state reaction between the synthesized NH4MIIPO4·H2O precursors and two different Li-sources (Li2CO3 or LiOH·H2O). The NH4MIIPO4·H2O and LiMIIPO4 compounds were confirmed by TG/DTG/DTA, AAS/AES, FTIR and XRD methods. The structural and morphological properties of LiMIIPO4 compounds were studied by XRD and SEM, respectively. The XRD reflection shifts of olivine-like LiMIIPO4 from the Li-source of Li2CO3 revealed changing toward higher diffraction angles than that of LiMIIPO4 from the Li-source of LiOH·H2O. The XRD shifts of LiM0.5Mg0.5PO4 (M = Mn or Co) compounds confirmed the formation of the single phase of isodivalent doping of Mn2+ and Co2+ ions according to the change in the lattice parameters and cell volumes. The morphological investigations of the LiMIIPO4 obtained from Li2CO3 system illustrated the grain-like shape particles having smaller size of about 150–400 nm on account of the sequential transformations of types: deammoniation, dehydration, polycondensation and decarbonization. Conversely, the larger size particles (300–700 nm) of the LiMIIPO4 obtained from LiOH·H2O were observed due to the shorter transformation path through the reactions of types: deammoniation and dehydration without polycondensation and decarbonization. 相似文献
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An efficient synthetic method for 3-aryl-5-dichloromethyl-2-isoxazolines has been established. Reactions between anhydrous chloral and acetophenones in hot acetic acid lead to 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones (chloralacetophenones), which provided 1-aryl-4,4-dichlorobut-3-en-1-ones (2,2-dichlorovinylacetophenones) by dehydration and subsequent electrochemical reduction. These β,γ-unsaturated enones reacted with hydroxylamine yielding oxime intermediates whose treatment with aqueous sodium hydroxide gave novel 3-aryl-5-dichloromethyl-2-isoxazolines in fair to high yields. The molecular structure of a member of this family of compounds, 5-dichoromethy1-3-(4-methoxyphenyl)-2-isoxazoline, was determined by X-ray crystallography. 相似文献
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8.
Magnesium dicyanamide tetrahydrate Mg[N(CN)2]2 · 4 H2O was synthesized by aqueous ion exchange starting from Na[N(CN)2] and Mg(NO3)2 · 6 H2O. The crystal structure was solved and refined on the basis of powder X‐ray diffraction data (P21/c, Z = 2, a = 737.50(2), b = 732.17(1), c = 971.67(2) pm, β = 98.074(1)°, wRp = 0.059, Rp = 0.046, RF = 0.075). In the crystal there are neutral complexes [Mg[N(CN)2]2(H2O)4] which are only connected via hydrogen bonds. Above 40 °C the tetrahydrate decomposes into anhydrous Mg[N(CN)2]2. 相似文献
9.
Dr. Radu Custelcean Neil J. Williams Charles A. Seipp 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(36):10671-10675
An effective approach to sulfate separation from aqueous solutions is based on the crystallization of extended [SO4(H2O)52−]n sulfate–water clusters with a bis(guanidinium) ligand. The ligand was generated in situ by hydrazone condensation in water, thereby bypassing the need for elaborate syntheses, tedious purifications, and organic solvents. Crystallization of sulfate–water clusters represents an alternative approach to the now established sulfate separation strategies that involve encapsulation of the “naked” anion. 相似文献
10.
This paper describes two analytic models for the heat-transfer-controlled lateral growth of a clathrate-hydrate film along a planar interface between liquid water and an immiscible hydrate-forming fluid (or guest fluid), such as methane or carbon dioxide. The two models are different from each other only regarding the assumption of the film-front geometry. Either model assumes the film to be uniform and constant in thickness, ignoring possible changes in the thickness on a time scale relevant to its lateral growth. Another fundamental assumption employed in the model is that the film's hydrate-forming front is maintained at the hydrate/guest/water three-phase equilibrium temperature, thereby forming a two-dimensional temperature distribution in the surrounding three-phase space. Based on these assumptions, the transient, two-dimensional conductive heat transfer from the film front into the three phases is formulated and numerically solved to give the instantaneous rate of lateral film growth (i.e., the linear speed of the film-front) along the water/guest-fluid interface, while the film thickness is arbitrarily assumed as a fitting parameter. By comparing the predicted rates of film growth with the corresponding experimental data obtained with methane or carbon dioxide as the guest fluid, we estimated the film thickness to be about 10–20 μm for the methane hydrate at a pressure of 9.06 MPa and about 0.5 μm for the carbon-dioxide hydrate at a pressure of 5 MPa. 相似文献