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71.
29Si NMR rate studies of the bulk reaction of 1,4-bis(hydroxydimethylsilyl)benzene (BHB) with dichlorodimethylsilane, dichloromethylphenylsilane, and dichlorodiphenylsilane show a very rapid kinetic equilibrium giving aryl-SiMe2Cl groups in place of the aryl-SiMe2OH of the BHB and OH groups in place of Cl in the dichlorosilane. This is followed by a slow condensation polymerization of the 1,4-bis(chlorodimethylsilyl)benzene with the hydroxy terminated disilane groups. The very rapid initial rates could be followed with 29Si NMR using the INEPT pulse sequence despite the very long 29Si relaxation times. Condensation polymerization is complete within minutes for BHB + SiMe2Cl2, but hours and days are required for the SiMePhCl2 and SiPh2Cl2, respectively, at +22°C. Initial reaction kinetics in the presence of Cr(acac)3 are not identical to those obtained using the INEPT pulse sequence and no relaxation reagent. 相似文献
72.
X-ray photoelectron spectroscopy was used to study the effect of atomic oxygen on Ru(0 0 0 1), and the effect of dissociated ammonia on RuO2/Ru(0 0 0 1), in UHV conditions at ambient temperature. The Ru(0 0 0 1) surface was exposed, at ambient temperature, to a mixed flux of atomic and molecular oxygen generated by dissociation of O2 in a thermal catalytic cracker, with 45% dissociation efficiency. The detailed study of the XPS spectra shows the formation of a disordered multilayer oxide (RuO2). No formation of higher oxides of Ru was observed. The formation of RuO2 proceeded without saturation for total oxygen exposures of up to 105 Langmuir, at which point an average oxide thickness of 68 Å was observed. RuO2 formed by the reaction with atomic oxygen was exposed to a flux of NHx (x = 1, 2) + H generated by the cracker. The reduction of RuO2 to Ru metal was observed by XPS. An exposure of 3.6 × 102 L of NHx + H, resulted in the observation of adsorbed H2O and OH, but no evidence of lattice oxide. The chemisorbed species were removed by additional NHx + H exposure. No nitrogen adsorption was observed. 相似文献
73.
X. Fan S. Garai R.R. Gaddam P.V. Menezes D.P. Dubal Y. Yamauchi P.W. Menezes A.K. Nanjundan X.S. Zhao 《Materials Today Chemistry》2020
The giant wheel-shaped Na15{[Mo154O462H14(H2O)70]0.5[Mo152O457H14(H2O)68]0.5}·ca. 400 H2O (Mo154) is one of the fascinating clusters with the open host framework, which is designed by simple metal-oxygen fragment–linked coordination modes. The generation of structural vacancies (here referred to as defects), the substitution of ligands, and incorporation of heterometallic centers in Mo154 could offer several attractive possibilities to achieve good electrochemical performance such as high specific capacity and stability in multivalent batteries. Herein, we have introduced electronically rich giant nanowheel Mo154 as a potential cathode material in magnesium-rechargeable batteries (MRBs). The experimental evidence indicates that the Mo154 wheels offer a reversible capacity of ~150 mAh g?1 at 50 mA g?1 in MRBs, which was retained to about 55 mAh g?1 after a long cycling life (>500 cycles). Typically, the divalent alkali metals (Mg2+) suffer from diffusion and insertion reactions in host materials; however, the stable and high rate performance against cycling with good Coulombic efficiency was achieved for Mo154 electrodes. Thus, the work demonstrates that the complex inorganic clusters are promising cathode materials in multivalent ion batteries. 相似文献
74.
75.
Tomáš Remiš Jagan Mohan Dodda Martin Tomáš Pavel Novotný Petr Bělský 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(12):757-767
Composite membranes based on Nafion (N115) loaded with furfuryl alcohol (FA) were prepared by in situ acid-catalyzed polymerization technique, with the aim to improve the ionic conductivity of Nafion membranes. The functionalization, thermal stability, electrical properties and mechanical strength of N115-PFA composites was analyzed by means of Fourier transform infrared (FT-IR) attenuated total reflection (ATR) spectroscopy, small- and wide-angle X-ray scattering (SAXS/WAXS), thermogravimetric analysis (TGA), electrical impedance spectroscopy, dynamic vapor sorption (DVS) and dynamic mechanical analyser (DMA). The FA loading in the resultant composites had a positive correlation with the water uptake (Wu), water vapor uptake (Wvu), ionic conductivity and thermo-mechanical stability. At low polyfurfuryl alcohol (PFA) loading, these membranes displayed higher Wu and improved ionic and electrical properties. Further, the thermo-mechanical stability also gradually increased with the PFA loading. All the composites showed a well-defined glass transition temperature in DMA, which shifted to higher temperature with repeated PFA loading. Overall, the results indicate that the developed composite membrane are promising for low temperature polymer electrolyte membrane (PEM) fuel cells. 相似文献
76.
Jagan Mohan Rao Tingirikari Wesley Faria Gomes Sueli Rodrigues 《Applied biochemistry and biotechnology》2017,183(4):1265-1281
Dextransucrase from Leuconostoc mesenteroides NRRL B-512F was subjected to immobilization and co-immobilization with dextranase from Chaetomium erraticum. Immobilization has enhanced the operational and storage stability of dextransucrase. Two hundred milligrammes (2.4 IU/mg) of alginate beads (immobilized and co-immobilized) were found to be optimum for the production of gluco-oligosaccharides (GOS) in orange juice with a high degree of polymerization. The pulp of the orange juice did not interfere in the reaction. In the batch process, co-immobilized dextransucrase (41 g/L) produced a significantly higher amount of GOS than immobilized dextransucrase (37 g/L). Alginate entrapment enhanced the thermal stability of dextransucrase for up to 3 days in orange juice at 30 °C. The production of GOS in semi-continuous process was 39 g/L in co-immobilized dextransucrase and 33 g/L in immobilized dextransucrase. Thus, immobilization technology offers a great scope in terms of reusability and efficient production of a value added functional health drink. 相似文献
77.
Jagan Mohan Dodda Tomáš Remiš Martin Tomáš Pavel Novotný 《Journal of Macromolecular Science: Physics》2015,54(6):629-648
Polyimides (PI)s and Poly(amide imide)s (PAI)s containing di/tri-structural arrangements of monomer constituents were synthesized from 1,2,4,5 benzenetetracarboxylic anhydride/3,3′,4,4′ benzophenonetetracarboxylic dianhydride, diamines and trimellitic dianhydride chloride, i.e., a mixture of dianhydrides and diamines, using low-temperature solution polymerization. The majority of the resulting polymers were readily soluble in polar aprotic solvents such as dimethylformamide, dimethylsulfoxide, dimethylacetamide, etc. Thermal cycloimidization studies by thermogravimetic analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) revealed that the rate of cycloimidization was much faster during the initial 15 min, and then occurred at much slower rates till the completion. The activation energies (Ea) for thermal cycloimidization of poly(amic acid)s was calculated from the rate of mass loss of the polymer heated at different temperatures according to the Coats and Redfern method. PI and PAIs derived from diamines containing single cyclic/benzene ring structures, such as m-phenylenediamine and 1,3-cyclohexanebis(methylamine), showed less amount of char yield than those having two benzene rings and separated by methylene, sulfone, or ether linkages. The structure of both diamine and trimellitic chloride had a profound effect on the polymer chain mobility, as indicated by the big variation in the glass transition temperatures. Thermally stable polymers were developed into membranes and tested for their mechanical strength by dynamic mechanical analysis(DMA). 相似文献
78.
Venkatapuram Padmavathi Boggu Jagan Mohan Reddy Boreddy Chandra Obula Reddy Adivireddy Padmaja 《Journal of heterocyclic chemistry》2004,41(6):951-954
A new class of spiro‐pyrimidines, pyrazoles and isoxazoles are prepared by nucleophilic reaction of 3,5‐diaroyl‐2,6‐diaryl‐piperidine‐4,4‐dicarbonitrile (1), 3,5‐diaroyl‐2,6‐diaryl‐tetrahydropyran‐4,4‐dicarbonitrile (2) and 3,5‐diaroyl‐2,6‐diaryl‐tetrahydrothiopyran‐4,4‐dicarbonitrile (3) with urea, N,N'‐dimethyl urea, thiourea, hydrazine hydrate and hydroxylamine hydrochloride. 相似文献
79.
N. B. Gaddam S. F. Xavioir T. C. Goel 《Journal of polymer science. Part A, Polymer chemistry》1977,15(6):1473-1478
2-Hydroxypropyl methacrylate has been copolymerized with methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate in bulk at 60°C using benzoyl peroxide as initiator. The compositions of copolymers have been determined by the estimation of the hydroxyl group by acetylation process. The copolymerization parameters have been determined by conventional scheme of copolymerization. 相似文献
80.
Geetha Marpadga Gaddam S. Rajender Reddy Madhukar C. Ganorkar 《Transition Metal Chemistry》1996,21(2):101-104
Summary New complexes of NiII-containing dihydrazones derived from dehydroacetic acid as primary ligands and ammonia or pyridine as secondary ligand were prepared and characterized by elemental analysis, conductance, spectral and magnetic data. The dihydrazones react with NiCl2 in their enolic forms as bis-tridentate complexing agents, forming dinuclear dihydrazido-diamine-dinickel complexes with ammino co-ligands. The ammino complexes were treated with pyridine to give the pyridino complexes. Squareplanar geometries are proposed for all the complexes and preliminary studies show that they possess antifungal activity. 相似文献