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101.
《Comptes Rendus Chimie》2016,19(10):1254-1265
Recent progress in catalytic direct NO decomposition is overviewed, focusing on metal oxide-based catalysts. Since the discovery of the Cu-ZSM-5 catalyst in the early 1990s, various kinds of catalytic materials such as perovskites, C-type cubic rare earth oxides, and alkaline earth based oxides have been reported to effectively catalyze direct NO decomposition. Although the activities of conventional catalysts are poor in the presence of coexisting O2 and CO2, some of the catalysts reviewed in this article possess significant tolerance toward these coexisting gases. The active sites for direct NO decomposition are different depending on the types of metal oxide-based catalysts. In the case of perovskite type oxides, oxide anion vacancies act as catalytically active sites on which NO molecules are adsorbed. C-type cubic rare earth oxides contain oxide anion vacancies with large cavity space, enabling easy access of NO molecules and their subsequent adsorption. Surface basic sites on alkaline earth based oxides participate in NO decomposition as active sites on which NO molecules are adsorbed as NO2− species. The reaction mechanisms of direct NO decomposition are also discussed. 相似文献
102.
以尿素为沉淀剂,采用均匀沉淀法制备了CexZr1-xO2(0≤x≤1)固溶体,并以其为载体制备了负载型Pd/CexZr1-xO2催化剂。利用XRD、N2物理吸附、CO脉冲化学吸附、CO2-TPD、原位漫反射红外光谱(in situ DRIFTS)等技术考察了载体表面碱性强弱对Pd/CexZr1-xO2催化剂中Pd烧结行为的影响。结果表明,载体的弱碱性位能有效抑制Pd的烧结,其中Pd/Ce0.75Zr0.25O2催化剂其载体具有更多的弱碱性位,活性组分钯的分散度较高,催化剂的热稳定性较好。 相似文献
103.
采用液相沉积方法分别制备了聚乙烯亚胺功能化和聚4-乙烯基吡啶功能化的碳纳米管催化剂,利用N2吸附/脱附、透射电子显微镜(TEM)、热重分析(TG)以及酸碱滴定等方法对所得催化剂的结构和碱性进行了表征,测试了其对于苯甲醛和丙二腈的Knoevenagel缩合反应的催化性能。结果发现,聚乙烯亚胺功能化的碳纳米管具有比聚4-乙烯基吡啶功能化的催化剂更高的碱催化能力。对碳纳米管进行强酸预处理可增加其与修饰剂的相互作用,虽然会降低其碱催化活性,但却可使其稳定性大大提高。 相似文献
104.
The reaction of aminomethylated polystyrene (PSCH2-NH2) and 2-hydroxyacetanilide in DMF results in the formation of polystyrene-anchored monobasic bidentate Schiff base, PSCH2-LH (I). On the other hand, the reaction of chloromethylated polystyrene (PSCH2-Cl), 3-formylsalicylic acid, ethylenediamine and acetylacetone in DMF in presence of ethyl acetate (EA) and triethylamine
(TEA) produces another polystyrene-anchored dibasic tetradentate Schiff base, PSCH2-L′H2 (II). BothI andII react with a number of di-, tri-and hexavalent metal ions like Co, Ni, Cu, Zn and Cd to form polystyreneanchored coordination
compounds, and these have been characterized and discussed. 相似文献
105.
Donghong Yin Liangsheng Qin Jianfu Liu Chengyong Li Yong Jin 《Journal of molecular catalysis. A, Chemical》2005,240(1-2):40-48
Three kinds of mesoporous alumina (denoted as meso-Al2O3-x (x = a, b, c)) supports with different surface basicity were synthesized by different structure-direct agent and different assembly pathway, respectively. The surface basicity of the meso-Al2O3-x and the commercial γ-Al2O3 was measured by means of CO2-TPD and IR spectroscopy. The profiles of CO2-TPD and IR spectra indicated that the mesoporous alumina owned more abundant surface basic sites than that of γ-Al2O3. Au nanoparticles deposited on the above supports via the method of homogeneous deposition precipitation (HDP) using urea as the precipitation agent. The supported Au catalysts were characterized by N2 adsorption–desorption isotherms, TEM, XPS and testing the catalytic performances in the epoxidation of styrene. The dispersion and average size of the gold particles are dependent of the number of surface basic sites on the supports. Transmission electron microscopy (TEM) observations show a homogeneous distribution of gold particles lower than 4 nm on meso-Al2O3-b and meso-Al2O3-c, which owned more basic sites on the surface. XPS spectra reveal that only metallic state of Au is presented on the supports, which is independent of surface properties. The different Al2O3 supported Au catalysts were employed as highly active/selective and reusable catalysts for the epoxidation of styrene by anhydrous t-butyl hydroperoxide (TBHP). Au nanoparticles as well as the surface basic sites of the support are responsible for the epoxidation. 相似文献
106.
Naka H Kanase N Ueno M Kondo Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(17):5267-5274
Chiral bisphosphazides complexed with lithium salts efficiently catalyze the direct enantioselective 1,4-addition of dialkyl malonates to acyclic enones. Spectroscopic studies on the stoichiometry of the bisphosphazide and lithium salt have indicated the formation of a 1:1 species as the active enantioselective catalyst. It is suggested that the catalyst generates a complex of the protonated phosphazide and the chiral nucleophile as the key intermediate. The phosphazide moiety appears to be a promising dual basic functionality for stereo- and chemoselective catalytic transformations. 相似文献
107.
O. A. Ivashkevich Vadim E. Matulis P. N. Gaponik G. T. Sukhanov J. V. Filippova A. G. Sukhanova 《Chemistry of Heterocyclic Compounds》2008,44(12):1472-1482
Quantum-chemical calculations have been carried out on molecular electrostatic potentials, proton affinity in the gas phase,
gas phase basicity, and pK
BH+ values in aqueous solution for C-nitro- and N-alkyl-4(5)-nitro-1,2,3-triazoles, and the relative stability of the isomeric
N-alkyl-4(5)-nitrotriazoles (alkyl = Me, Et, i-Pr, t-Bu) in the gas phase and in aqueous solution. For all the studied substances in the gas phase the 2H-tautomer and the N(2)-isomers
were considerably more stable than the corresponding N(1) compounds, and the 3H-tautomer and N(3)-isomer were the least stable.
In aqueous solution 1- and 3-isomers had close values of energies, but in the case of C-nitro-1,2,3-triazole the 1H form became
even more stable than the 2H-form. It was established which ring nitrogen atoms of 1,2,3-triazoles are protonated in the gas
phase and in solution. The obtained data correlate well with the results of experimental investigations on the alkylation
of 1,2,3-triazoles in acidic and basic media and of the experimental investigation on the alkylation of C-nitro-1,2,3-triazoles
with diethyl sulfate carried out in the present work.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1816–1828, December, 2008. 相似文献
108.
Bagrat A. Shainyan Nina N. Chipanina Larisa P. Oznobikhina Vladimir I. Meshcheryakov 《Journal of Physical Organic Chemistry》2016,29(2):92-100
The effect of the electron–acceptor substituent CF3SO2 at the imine nitrogen atom on the basicity and the electron distribution in N,N‐alkylformamidines ( 1 , 2 , 3 , 4 , 5 ) was studied experimentally by the FTIR spectroscopy and theoretically at the DFT (B3LYP/6‐311+G(d,p)) level of theory, including the natural bond orbital (NBO) analysis. The calculated proton affinities of the imine nitrogen atom and the sulfonyl oxygen (PAN′ and PAO) depend on the atomic charges, the C?N′ and N′―S bond polarity and on the energy of interaction of the amine nitrogen and the oxygen lone pairs with antibonding π* and σ*‐orbitals. The basicity of the imine nitrogen atom is increased with the increase of the electron‐donating power of the substituent at the amine nitrogen atom due to stronger interaction nN → π*C?N′, but is decreased for the electron‐withdrawing groups MeSO2 and CF3SO2 at the imine nitrogen atom in spite of the increase of this conjugation. Protonation of ( 1 , 2 , 3 , 4 , 5 ) in CH2Cl2 solution in the presence of CF3SO3H occurs at the imine nitrogen atom, while the formation of hydrogen bonds with 4‐fluorophenol takes place at the sulfonyl oxygen atom, whose basicity is lower than that of N,N′‐dimethylmethanesulfonamide but higher than of N,N′‐dimethyltrifluoromethanesulfonamide. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
109.
110.
Aqueous pKA values for 15 hexa‐aqua transition metal complexes were computed using a combination of quantum chemical and electrostatic methods. Two different structure models were considered optimizing the isolated complexes in vacuum or in presence of explicit solvent using a QM/MM approach. They yield very good agreement with experimentally measured pKA values with an overall root mean square deviation of about 1 pH unit, excluding a single but different outlier for each of the two structure models. These outliers are hexa‐aqua Cr(III) for the vacuum and hexa‐aqua Mn(III) for the QM/MM structure model. Reasons leading to the deviations of the outlier complexes are partially explained. Compared to previous approaches from the same lab the precision of the method was systematically improved as discussed in this study. The refined methods to obtain the appropriate geometries of the complexes, developed in this work, may allow also the computation of accurate pKA values for multicore transition metal complexes in different oxidation states. © 2014 Wiley Periodicals, Inc. 相似文献