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991.
992.
993.
Görgen JJ Comfort JR Tinsley JR Averett T DeKorse J Franklin B Ritchie BG Kyle G Klein A Berman B Burleson G Cranston K Faucett JA Jarmer JJ Knudson JN Penttilä S Tanaka N Brinkmöller B Dehnhard D Yen YF Hoibråten S Breuer H Flanders BS Khandaker MA Naples DL Zhang D Barlett ML Hoffmann GW Purcell M 《Physical review letters》1991,66(17):2193-2196
994.
T. ?kesson S. Almehed A. L. S. Angelis H. Atherton P. Aubry H. W. Bartels G. Beaudoin J. M. Beaulieu H. Beker O. Benary et al. 《Zeitschrift fur Physik C Particles and Fields》1991,49(3):355-366
Diffractive dissociation of nuclei (Be, Al, W) in collisions with 450 GeV/c protons,pApX, has been measured with the HELIOS spectrometer at the CERN Super Proton synchrotron. The dependence of the single-diffraction cross-section on the nuclear massA can be parametrized as SD mb×A
0.35±0.02, showing the peripheral nature of the process. The differential cross-section dSD=(3.8±0.3)mb ×A
0.35±0.02, is exponential with the slope parameter, increasing from 6.2±0.4 (GeV/c)–2 for beryllium to 7.9±0.5 (GeV/c)–2 for tungsten. The slope parameter also increases with increasing massM
X
of the diffractively produced state. The rapidity, multiplicity, and transverse-momentum distributions of the particles of the diffractively produced stateX show a longitudinal phase-space population and are remarkably insensitive to the nuclear mass. This, together with theA
1/3 dependence of SD, suggests that the dominant process of nuclear diffractive excitation is the dissociation of single nucleons.Deceased 相似文献
995.
R. ?obiński J. A. C. Broekaert P. Tsch?pel G. T?lg 《Fresenius' Journal of Analytical Chemistry》1992,342(7):569-580
Four independent procedures including one using slurry nebulization ICP-AES were developed for the trace analysis of ZrO2 powders. They were evaluated with respect to detection limits, blank values, interferences, accuracy and precision. For the procedures I–III ZrO2 powder was decomposed by fusion with a 10-fold excess of NH4HSO4 and subsequent dissolution of the melt in either water or, after evaporation of NH4HSO4, in diluted HNO3. In procedure I the solution was directly analyzed by ICP-AES, which was optimized with the aid of a simplex algorithm. In procedure II Zr was separated by extraction from 6 mol/l HNO3 with a 0.5 mol/l solution of 2-thenoyltrifluoroacetone (TTA) in xylene. More than 99.5% of the Zr was removed and more than 95% of the trace elements retained. In procedure III the matrix was separated by its precipitation as ZrOCl2·8 H2O from a (1:4) HCl-acetone medium. More than 98% of Zr were removed and more than 90% of the trace elements were retained. In procedure IV the ZrO2 powder was dispersed by ultrasonic treatment in water acidified with HCl (pH 2) and the slurry was directly analyzed by ICP-AES using a Babington nebulizer. The optimization and the analytical features of this procedure will be described in a subsequent paper. In all procedures the calibration was performed by standard addition and matrix matching was not necessary. The detection limits varied from 0.3 g/g (Ca) to 10 g/g (Al). The standard deviations obtained were 1–10% depending on the element and its concentration in the sample. The results of the procedures for 6 commercially available fine ZrO2 powders were found to agree for Al, Ca, Fe, Mg, Na, Ti and Y. A good agreement between the results of the procedures using matrix separation was also observed for Cu, Mn, V, but the concentrations of these elements found by methods without matrix separation were considerably higher. Except for Ca and Mg the blank values encountered were below the detection limits.On leave from Department of Analytical Chemistry, Technical University, PL-00-664 Warsaw, Poland 相似文献
996.
997.
998.
The electrochemical reduction of fenofibrate at a hanging mercury drop electrode (HMDE) was investigated by cyclic voltammetry, square-wave voltammetry, and chronoamperometry. Different buffer solutions were used over a wide pH range (3.0–10.0). The best definition of the analytical signals was found in borate buffer (pH 9.0)–tetrabutylammonium iodide mixture containing 12.5% (v/v) methanol at –1.2 V (versus Ag/AgCl). According to cyclic voltammetric studies, the reduction was irreversible and diffusion controlled. The diffusion coefficient was 2.38×10–6 cm2 s–1 as determined by chronoamperometry. Under optimized conditions of square-wave voltammetry, a linear relationship was obtained between 0.146–4.96 g mL–1 of fenofibrate with a limit of detection of 0.025 g mL–1. Validation parameters such as sensitivity, accuracy, precision, and recovery were evaluated. The proposed method was applied to the determination of fenofibrate in pharmaceutical formulations. The results were compared with those obtained by a published high-performance liquid chromatography method. No difference was found statistically. 相似文献
999.
A selective procedure is described for the determination of amitriptyline in plasma. The method involves extraction, separation of amitriptyline from its metabolites and subsequent oxidation by ceric sulphate in 5.4 M sulphuric acid. The oxidation product, anthraquinone, is determined by means of electron-capture gas chromatography. The metabolites were separated by a column chromatographic extraction technique. The choice of oxidation reagent, optimum conditions for the oxidation, and the electron-capture properties of anthraquinone are discussed. The method can be used to determine down to 2 ng of amitriptyline in a plasma sample; the relative standard deviation at the 50-ng level was 4.0% (n = 8). The levels of amitriptyline found in a series of plasma samples are compared with those obtained by gas chromatography with use of nitrogen-specific detection; the two techniques gave coincident results. 相似文献
1000.
Peter Schwendt Alena Oravcová Jarmila Tyršelová František Pavel?ík Jaromír Marek 《Polyhedron》1996,15(24):4507-4511
The vanadium(V) peroxo phosphato complex K7[V4O4(O2)8(PO4)]·9H2O has been obtained from the KVO3---KH2PO4---KOH---H2O2---H2O---C2H5OH system. The X-ray structural analysis revealed a tetranuclear anionic structure in which two dinuclear [V2O2(O)2)2(μ-η1 : η2-O2)2] units are connected by the μ4-PO4 group. 相似文献