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61.
62.
Interference-free biosensor based on screen-printing technology and sol-gel immobilization for determination of acetaldehyde in wine 总被引:1,自引:0,他引:1
Noguer T Tencaliec A Calas-Blanchard C Avramescu A Marty JL 《Journal of AOAC International》2002,85(6):1382-1389
A monoenzymatic amperometric biosensor was developed for the detection of acetaldehyde. The sensor is based on the association of screen-printed carbon electrodes and aldehyde dehydrogenase immobilized by a sol-gel entrapment method. Modification of screen-printed carbon electrodes with Reinecke salt of Meldola's Blue (MBRS) resulted in highly sensitive and interference-free nicotinamide-adenine dinucleotide (NADH) detectors. Based on MBRS-mediated oxidation of NADH at -150 mV versus pseudo Ag/AgCl, acetaldehyde was determined in the range 10-260 microM, compatible with wine quality monitoring. The method of immobilization based on sol-gel entrapment was optimized to obtain the best compromise between sensitivity and operational stability. The sensor response was stable for 40 consecutive assays with methyltrimethoxysilane used as alkoxide precursor, thus allowing a possible calibration of the sensor before each measurement. The biosensors were used to analyze French wines. The method was validated with a commercially available enzymatic kit based on a standard spectrophotometric method. 相似文献
63.
Kesson T Albrow MG Almehed S Benary O Boggild H Botner O Breuker H Brody H Burkert V Callen B Carter AA Carter JR Cecil P Choi Y Cleland WE Dam P Dagan S Dahl-Jensen E Dahl-Jensen I Damgaard G Evans WM Fabjan CW Frandsen P Frankel S Frati W Gordon H Goerlach U Hansen KH Hedberg V Hooper JE Jarlskog G Kessler G Killian T Kroeger R Kulka K v d Lans J Lissauer D Lörstad B Ludlam T McCubbin NA Möller R Molzon W Nielsen BS Olsen LH Oren Y Rosso E Rudge A Specht H Stumer I Thompson JA Thorstensen G 《Physical review letters》1985,55(23):2535-2538
64.
A. Rotaru Anca Moanta I. Sălăgeanu P. Budrugeac E. Segal 《Journal of Thermal Analysis and Calorimetry》2007,87(2):395-400
The non-isothermal kinetic parameters corresponding to the decomposition
of 4-[(4-chlorobenzyl)oxy]-4’-nitro-azobenzene were evaluated. The kinetic
analysis was performed by means of different multi-heating rates methods:
isoconversional (‘model-free’) methods (Flynn–Wall–Ozawa)
and invariant kinetic parameters method (IKP) associated with the criterion
of the independence of activation parameters on the heating rate. The values
of the obtained non-isothermal kinetic parameters are in satisfactory agreement. 相似文献
65.
66.
Iulia Matei Anca Nicolae Mihaela Hillebrand 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):597-601
The complex formed by the inclusion of the polarity-sensitive fluorescent probe 2-[2′-quinoxalinyl]-phenoxathiin (QP) into
β-cyclodextrin (β-CD) was investigated by steady-state fluorescence spectroscopy in order to confirm the previously stated intramolecular charge
transfer nature of the first excited singlet state of QP. A decrease in the emission intensity in the presence of β-CD was observed and explained on this basis. The 1:1 stoichiometry of the inclusion complex and its association constant
of 2,223 M−1 were computed. The QP–β-CD complex was further studied by molecular mechanics (MM+ force field), in order to determine its structure and the type
of interactions between QP and β-CD. All possible ways QP could penetrate the β-CD cavity were considered and several structures were generated and optimized. The interaction, binding (van der Waals and
electrostatic contributions) and perturbation energies were also calculated. The results have showed that the β-CD cavity incorporates the central part of QP and that complexation is mainly due to van der Waals host–guest interactions. 相似文献
67.
Bassil BS Kortz U Tigan AS Clemente-Juan JM Keita B de Oliveira P Nadjo L 《Inorganic chemistry》2005,44(25):9360-9368
The 6-cobalt-substituted [{Co3(B-beta-SiW9O33(OH))(B-beta-SiW8O29(OH)2)}2]22- has been characterized by IR and UV-vis spectroscopy, elemental analysis, magnetic studies, electrochemistry, and gel filtration chromatography. A single-crystal X-ray analysis was carried out on K10Na12[{Co3(B-beta-SiW9O33(OH))(B-beta-SiW8O29(OH)2)}2].49H2O (KNa-1), which crystallizes in the monoclinic system, space group P2(1)/n, with a=19.9466(8) A, b=24.6607(10) A, c=34.0978(13) A, beta=102.175(1) degrees, and Z=2. Polyanion 1 represents a novel class of asymmetric sandwich-type polyanions. It contains three cobalt ions, which are encapsulated between an unprecedented (B-beta-SiW9O34) fragment and a (B-beta-SiW8O31) unit. Polyanion 1 is composed of two sandwich species via two Co-O-W bridges in the solid state and almost certainly in solution as well based on gel filtration chromatography. UV-visible spectroscopy and cyclic voltammetry also confirmed its stability. Two well-separated groups of waves appeared in the voltammetric pattern: the wave observed in the negative potential range versus a saturated calomel electrode features the redox processes of WVI centers; the two reversible redox couples observed in the positive potential domain are attributed to the redox processes of Co2+ centers and indicated that the two types of Co2+ centers in the structure are oxidized in separate waves. Such reversibility of Co2+ centers within multi-Co-substituted polyoxometalates is uncommon. The magnetic properties of KNa-1 are also discussed. The ferromagnetic ground state has been studied by magnetic susceptibility and magnetization measurements and fitted according to an anisotropic exchange model. 相似文献
68.
Buica George-Octavian Soare Maria-Laura Inel Georgiana Anca Razus Alexandru C. Birzan Liviu Oprisanu Alexandra Ungureanu Eleonora-Mihaela 《Journal of Solid State Electrochemistry》2016,20(11):3151-3164
Journal of Solid State Electrochemistry - The electrochemical behavior of substituted 1-phenylselanyl azulenes has been established by cyclic, differential pulse, and rotating disk electrode... 相似文献
69.
Dragulescu-Andrasi A Rapireddy S Frezza BM Gayathri C Gil RR Ly DH 《Journal of the American Chemical Society》2006,128(31):10258-10267
Peptide nucleic acid (PNA) is a synthetic analogue of DNA and RNA, developed more than a decade ago in which the naturally occurring sugar phosphate backbone has been replaced by the N-(2-aminoethyl) glycine units. Unlike DNA or RNA in the unhybridized state (single strand) which can adopt a helical structure through base-stacking, although highly flexible, PNA does not have a well-defined conformational folding in solution. Herein, we show that a simple backbone modification at the gamma-position of the N-(2-aminoethyl) glycine unit can transform a randomly folded PNA into a helical structure. Spectroscopic studies showed that helical induction occurs in the C- to N-terminal direction and is sterically driven. This finding has important implication not only on the future design of nucleic acid mimics but also on the design of novel materials, where molecular organization and efficient electronic coupling are desired. 相似文献
70.
Dragulescu-Andrasi A Rapireddy S He G Bhattacharya B Hyldig-Nielsen JJ Zon G Ly DH 《Journal of the American Chemical Society》2006,128(50):16104-16112