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981.
982.
Russell G Evans Oleksiy V Klymenko Paul D Price Stephen G Davies Christopher Hardacre Richard G Compton 《Chemphyschem》2005,6(3):526-533
Measurements on the diffusion coefficient of the neutral molecule N,N,N',N'-tetramethyl-para-phenylenediamine and the radical cation and dication generated by its one- and two-electron oxidation, respectively, are reported over the range 298-348 K in both acetonitrile and four room temperature ionic liquids (RTILs). Data were collected using single and double potential step chronoamperometry at a gold disk electrode of micrometer dimension, and analysed via fitting to the appropriate analytical expression or, where necessary, to simulation. The variation of diffusion coefficient with temperature was found to occur in an Arrhenius-type manner for all combinations of solute and solvent. For a given ionic liquid, the diffusional activation energies of each species were not only closely equivalent to each other, but also to the RTIL's activation energy of viscous flow. In acetonitrile supported with 0.1 M tetrabutylammonium perchlorate, the ratio in diffusion coefficients of the radical cation and dication to the neutral molecule were calculated as 0.89 +/- 0.05 and 0.51 +/- 0.03, respectively. In contrast, amongst the ionic liquids the same ratios were determined to be on average 0.53 +/- 0.04 and 0.33 +/- 0.03. The consequences of this dissimilarity are considered in terms of the modelling of voltammetric data gathered within ionic liquid solvents. 相似文献
983.
盛平兴 《应用数学与计算数学学报》1996,10(1):67-72
本文讨论两点边值问题解的存在性,在没有孤立性条件下,获得了不动点定理,作为应用实例,给出了反应扩散方程稳态解的存在性证明。 相似文献
984.
L. Rogovina Peiguang Zhou H. L. Frisch 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):515-519
We have studied the densities, kinetics, and equilibrium degree of swelling in a number of different solvents of poly(carbonate urethane)/poly(methyl methacrylate) and poly(carbonate urethane)/poly(vinyl pyridine) interpenetrating polymer networks (IPN's). The kinetics of solvent uptake are often anomalous. The equilibrium extent of swelling reflects, among other factors, the number of phases present. © 1993 John Wiley & Sons, Inc. 相似文献
985.
§1. IntroductionItiswellknownthatthedegreetheoryforak-set-contractoperatorhasmanyapplicationsontheexistenceofthesolutionsofsomeequations(see[1],[2],[3]).However,someopera-torsarenotk-set-contractoperators.Itisanewproblemthatweestablishadegreetheoryfo… 相似文献
986.
Rh-catalyzed π-facial selective intermolecular hydroacylations of norbornenes with salicylaldehyde have been attained. In the reaction with norbornylene, the exo-hydroacylated product was produced because of steric hindrance. In the case of norbornadiene, the endo-product was obtained because of chelation effect. Lastly, because of chelation and remote substituent effects, the product formed in the reaction of 7-tert-butoxynorbornadiene was the endo,syn-product. Deuterium-labeling experiments revealed that the hydroacylation stereoselectively proceeded via endo- and exo-intermediates. 相似文献
987.
Carlos Guerrero‐Sanchez Caroline Abeln Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2005,43(18):4151-4160
Anionic polymerization techniques have been implemented successfully in a commercial automated synthesizer. The main problems for a successful adaptation of the experimental technique in the automated synthesizer are addressed, as well as some simple potential applications, such as the anionic polymerization of styrene, isoprene, and methyl methacrylate. The obtained results were reproducible and in concordance with literature knowledge. The apparent rate constant of the anionic polymerization of styrene in cyclohexane initiated by sec‐butyllithium could be determined at two different concentrations of the monomer and initiator in a temperature range of 10–60 °C. All the synthesis and characterization experiments of the polymers were performed within a short time period. Moreover, the syntheses of poly(styrene‐b‐isoprene) and poly(styrene‐b‐methyl methacrylate) block copolymers were also successfully carried out within the automated synthesizer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4151–4160, 2005 相似文献
988.
989.
Tanveer M. Shaikh 《Tetrahedron letters》2005,46(33):5589-5592
NaIO4 oxidizes lithium bromide efficiently under acidic conditions to functionalize alkylbenzenes and alkanes and produce the corresponding bromo and acetoxy derivatives in excellent yields. The protocol also demonstrates the direct conversion of cyclohexane into trans-1,2-dibromocyclohexane in moderate yield. 相似文献
990.