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Vladimir D. Kiselev Helena A. Kashaeva Ilzida I. Shakirova Lubov’ N. Potapova Alexander I. Konovalov 《Journal of solution chemistry》2012,41(8):1375-1387
Enthalpies of solution and partial molar volumes of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate were determined in 15 solvents of different polarity. Very large differences of the enthalpies of solution (????sol H IL=38.9?kJ?mol?1) and partial molar volumes (??V IL=43 cm3?mol?1) are nearly the same as observed for lithium perchlorate solutions. These results clearly indicate that the low values of the macroscopic polarity parameters of [bmim]BF4 do not correspond with the large differences of the intermolecular interactions in IL solutions. The values of the partial molar volume of the cation, $V_{[\mathrm{bmim}]^{+}}$ , were estimated for the first time. The changes of the partial molar volumes, V IL, reflect mainly the changes of anion volume, $V_{\mathrm{BF}_{4}^{-}}$ . The rate of the Diels?CAlder reaction of 9,10-dimethylanthracene with maleic anhydride in the [bmim]BF4 medium was nearly the same as in common molecular solvents. 相似文献
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[reaction: see text] Lithium aminoborohydride (LAB) reagents promote the amination of 2-fluoropyridine under mild reaction conditions, providing 2-(dialkylamino)pyridines in excellent yield and purity. Treatment of 2-fluoropyridine with 1.1 equiv of lithium aminoborohydride at room temperature affords complete conversion after 1 h. This is the first general way by which 2-(dialkylamino)pyridines may be directly obtained from fluoropyridines under ambient reaction conditions. 2-Chloropyridine can also be converted to 2-(dialkylamino)pyridine by simply increasing the number of LAB equivalents and the reaction temperature. 相似文献
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Using Monte Carlo simulation, we study the metallization of DNA fragments via the templating of gold nanoparticles. To represent the interaction between metal entities, a nanoparticle-nanoparticle interaction potential was derived on the basis of the many-body Gupta potential. The aggregation of the nanoparticles on the template surface is due to the additive effect of electrostatic attraction between the positive charges on the Au particles and the negative charges of the phosphate groups of DNA molecule and the short-range attraction between the metallic nanoparticles. As a result, the assembly of a continuous nanowire can be templated. Depending on the nanoparticle size and charge, the metallic covering can be both continuous and discontinuous. The question of how size and charge of Au nanoparticles influence the structure of metallic coat is discussed in detail. Both monodisperse and polydisperse nanoparticles are considered. Dispersion in the nanoparticle size was found to have little effect on the calculated characteristics of the aggregate. 相似文献
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Pasumansky L Collins CJ Pratt LM Nguyên NV Ramachandran B Singaram B 《The Journal of organic chemistry》2007,72(3):971-976
The influence of temperature and solvent effects on the reduction and amination mechanisms of iodomethane by lithium N,N-diisopropylaminoborohydride (iPr-LAB) was examined in varying concentrations of THF and dioxane. The reactions of benzyl chloride and trimethylsilyl chloride with iPr-LAB in THF were also studied. The amination of iodomethane is favored over reduction at low and room temperatures in pure THF and with increasing the amount of dioxane in THF. At higher temperatures, the reduction reaction appears to compete with the amination. In dioxane solvent, however, iodomethane yields exclusively the amination product regardless of temperature. On the other hand, reduction by iPr-LAB to the aminoborane is the only product observed in THF when benzyl chloride and trimethylsilyl chloride are used. To understand the solvent effects on the product distribution, ab initio and density functional theory (DFT) calculations were used to examine the mechanisms of reduction and amination of chloromethane and bromomethane by lithium dimethylaminoborohydride (LAB) in THF and dioxane. The results of these calculations show that the relative reaction barrier heights are significantly affected by the nature of the coordinated solvent molecule and thus lend support to the experimental observations. 相似文献
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The kinetics of the formation of impurity clusters in subsurface nanopores in crystals is studied theoretically. A physical model of precipitation of the impurity phase in nanopores in a sample with sinks of various types is developed. This model forms the basis for the calculation of the annealing kinetics of copper containing subsurface pores and cobalt impurity atoms. The optimal annealing conditions are determined in which cobalt atoms diffuse predominantly into pores and form impurity clusters in them. 相似文献
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Vladimir D. Kiselev Alexander V. Bolotov Ilzida I. Shakirova Helen A. Kashaeva Lubov N. Potapova Alexander I. Konovalov 《Journal of solution chemistry》2012,41(3):525-535
In this article negative values of the activation volume in retro-Diels–Alder reactions are interpreted in terms of the different
possibilities of penetration of the solvent molecules into the sterically branched structures of the adduct and activated
complex. Empty spaces, inaccessible to penetration of solvent molecules, lead to increases of the molar volume of the screened
adducts in solution and, consequently, to a less negative value of the Diels–Alder reaction volume. The values of partial
molar volumes of anthracene, maleic anhydride and the adducts cyclopentadiene–maleic anhydride, anthracene–maleic anhydride
and anthracene–tetracyanoethylene, in several solvents, were calculated from the solution density data. 相似文献