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991.
The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly. The suitable mechanism was supposed. 相似文献
992.
Ante Juki? 《European Polymer Journal》2006,42(5):1105-1112
The miscibility and intermolecular interactions between polystyrene (PS) and poly(ethylene-co-propylene) (EPC), as well as between PS and long-chain poly(alkyl methacrylates) (PAMA), namely, poly(dodecyl methacrylate) (PDDMA) and poly(octadecyl methacrylate) (PODMA), in dilute xylene solutions at 30 °C were studied. Investigated polymers are widely used as rheology modifiers, i.e. viscosity index improvers and pour point depressants for lubricating mineral oils. The specific and reduced viscosities of two- and three-component polymer solutions as well as intrinsic viscosities and Huggins’ parameter values were determined as functions of the polymer mixture composition and overall polymer concentration. The reduced viscosity was found to be linearly dependent on the overall polymer concentration. The observed viscosities of polymer mixtures were intermediate to those of the mixture constituents; the values decrease in the order: EPC > PS > PAMA. The specific viscosities of all the polymer mixtures obtained as the experimental results and calculated applying the Catsiff-Hewett and Krigbaum-Wall theoretical equations were considered. Since all the polymer/polymer pairs showed the negative viscometric interaction parameter values (Δb12 < 0), the PS/EPC and EPC/PAMA mixtures were found to be immiscible. The observed repulsive molecular interactions originate from the differences in polymer composition and molar masses. This conclusion was supported by calculations employing the group contribution approach of Coleman, Graf and Painter. The calculated values of interaction parameters for (co)polymer blends, Λ12, were 5.47, 6.42 and 13.1 J cm−3 for PS/PDDMA, PS/PODMA and PS/EPC, respectively. 相似文献
993.
The reduction of diphenyl ditelluride by the Sm/CrCl3(cat.) system led to a telluride anion.This species reacted with acid chlorides,alkyl halides,and α,β-unsaturated enoates or α,β-unsaturated ene nitriles to afford telluroesters and unsymmetrical phenyltellurides,respectively,in moderate to good yields under mild and neutral conditions. 相似文献
994.
The adsorption of codeine from aqueous solution onto colloidal silica and silica surface-modified with chemiadsorbed octadecyl dimethyl silane (ODDMS) or dimethyl silane (DMS) groups was studied in the presence of neutral electrolytes at different pH values. From codeine-hydrochloride solutions codeine cations are strongly bound to negatively charged silica surfaces. Inorganic salts (NaCl, NaNO3) reduce the adsorption of the organic cation. On silica modified by ODDMS (10% of surface silanol groups are occupied), codeine cations are adsorbed to a higher extent at pH 6, while at pH 8 the adsorbed amounts are lower than on the bare silica surface. Neutral electrolytes reduce codeine adsorption on the ODDMS modified silica. On the hydrophobic silica, completely covered by DMS groups, codeine adsorption is considerably lower than on the bare silica, but neutral salts increase the adsorption. The adsorption of codeine is compared with the adsorption of aggregating surfactant ions. Common and different features of their interactions with silica surfaces are outlined. 相似文献
995.
Preparation and 13C NMR identification of 1,2-diethyl-3-(trimethylsilyl)cyclopropenylium hexachloroantimonate (4) is described. The assignment of the NMR data was corroborated by calculating 13C NMR chemical shifts of the corresponding model ion 4M. The total stabilization of the parent cyclopropenylium ion 1 substituted by the silyl and the two methyl groups is found to be only slightly lower than stabilization of the trimethyl derivative. The computed NICS(1) parameters reveal that all of the examined ions possess substantial aromatic character. 相似文献
996.
997.
Novel alkyl thiophosphoramidate derivatives of nucleosde analogues(5) have been prepared by phosphochloridothioate chemistry.O-Isopropyl 2‘,3‘-O-isopropylidene uridine-5‘-yl N-thiophosphoryl threonine and serine methyl esters(5a and 5b )underwent the intramolecular catalyzed hydrolysis reaction. 相似文献
998.
V. Yu. Petukhova Yu. A. Strelenko K. A. Lyssenko N. N. Makhova 《Russian Chemical Bulletin》2007,56(8):1550-1554
A method for the synthesis of 1-[ω-(3,3-dialkyldiaziridin-1-yl)alkyl]-3,3-dialkyldiaziridines based on the reaction of ketoxime
O-arenesulfonates with alkylenediamines was developed. Diastrereomers (the racemic and meso forms) of 1-[2-(3,3-dimethyldiaziridin-1-yl)ethyl]-3,3-dimethyldiaziridine were isolated. The structure of the meso form was confirmed by X-ray diffraction analysis.
Dedicated to Academician V. A. Tartakovsky on his 75th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1491–1495, August, 2007. 相似文献
999.
Kouki Matsubara Hiromi Okazaki Misako Senju 《Journal of organometallic chemistry》2006,691(17):3693-3699
Palladium-catalyzed α-arylation of ketones, which can efficiently give coupling products by using appropriate ligands and bases, could be applied to a polycondensation reaction. Stable N-heterocyclic carbenes (NHC) were used as favorable ligands coordinating the Pd catalysts, which were generated in situ from commercially available palladium compounds such as Pd(OAc)2 and Pd2(dba)3 as suitable catalyst precursors in this polymerization. Using small amounts of binary catalysts, poly(aryl alkyl ketone)s were afforded in high yields from haloarylketones in the presence of a base. A primarily prepared palladium catalyst having an NHC ligand, [Pd(OAc)2(NHC)], also efficiently catalyzed the polycondensation, whereas a palladium compound bearing two carbene ligands, [PdX2(NHC)2], did not. 相似文献
1000.
(Vinyl acetate)/(ethyl acrylate) (V/E) and (vinyl acetate)/(butyl acrylate) (V/B) copolymers were prepared by free radical solution polymerization. 1H-NMR spectra of copolymers were used for calculation of copolymer composition. The copolymer composition data were used for determining reactivity ratios for the copolymerization of vinyl acetate with ethyl acrylate and butyl acrylate by Kelen-Tudos (KT) and nonlinear Error in Variables methods (EVM). The reactivity ratios obtained are rv = 0.03 ± 0.03, rE = 4.68 ± 1.70 (KT method); rv = 0.03 ± 0.01, rE = 4.60 ± 0.65 (EV method) for (V/E) copolymers and rv ? 0.03 ± 0.01, rB ? 6.67 ± 2.17 (KT method); rv = 0.03 ± 0.01, rB = 7.43 ± 0.71 (EV method) for (V/B) copolymers. Microstructure was obtained in terms of the distribution of V- and E-centered triads and V- and B-centered triads for (V/E) and (V/B) copolymers respectively. Homonuclear 1H 2D-COSY NMR spectra were also recorded to ascertain the existence of coupling between protons in (V/E) as well as (V/B) copolymers. © 1995 John Wiley & Sons, Inc. 相似文献