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61.
Hastings HM Sobel SG Lemus A Yuen F Peralta C Cammalleri C Chabrel J Chaterpaul S Frank C Hilaire C Lang D Ravinovitch D Zaharakis A 《The Journal of chemical physics》2005,123(6):64502
The prototype experimental example of "spontaneous" pattern formation in an unstirred chemical medium is the oscillatory Belousov-Zhabotinsky (BZ) reaction: target patterns of outward-moving concentric rings are readily observed when the reaction is run in a thin layer in a Petri dish. In many experimental runs, new target centers appeared to form closer to pre-existing target centers than expected in a randomized model. Here we describe a simple direct test for the presence of temporal order in the spatiotemporal dynamics of target nucleation, and apply this test to detect significant temporal order in target formation in the ferroin-catalyzed BZ reaction. We also describe how mixing heterogeneity can generate temporal order, even in the absence of heterogeneous physical nucleating centers. 相似文献
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Blewitt G LoSecco JM Bionta RM Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,55(20):2114-2117
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Radiative transitions in the proton-hydrogen atom system are theoretically analyzed over a wide range of wavelengths and temperatures of equilibrium hydrogen plasma. The light absorption at T~1500–3500 K due to photodissociation and transitions in the H 2 + ion continuum is shown to make a contribution that is comparable with the photoabsorption in the electron-hydrogen atom system near the maximum of the Planck distribution. 相似文献
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Arrays of polymer-coated surface acoustic wave microsensors are used in conjunction with a variety of signal-processing algorithms known as artificial neural networks (ANN). This format of data analysis has the capability to characterize complex mixtures of volatile and semi-volatile organic compounds commonly found in base flavors. The approach described, which minimizes the number of training sets while retaining the robustness of an ANN, utilizes a 2D bitmap matrix. The matrix is obtained by converting the time domain kinetics of sensor response into a bitmap. The high data throughput of this approach enables quantitation on the order of ppm of common base flavor adulterants. 相似文献
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Hastings HM Sobel SG Field RJ Bongiovi D Burke B Richford D Finzel K Garuthara M 《The journal of physical chemistry. A》2008,112(21):4715-4718
The unstirred, ferroin (Fe(phen)3(2+)) catalyzed Belousov-Zhabotinsky (BZ) reaction is the prototype oscillatory chemical system. Reaction media with added Br(-) appear red (reduced, low [Fe(phen)3(3+)]) during an induction period of several minutes, followed by the "spontaneous" formation of "pacemaker" sites, which oscillate between a blue, oxidized state (high [Fe(phen)3(3+)]) and the red, reduced state and generate target patterns of concentric, outwardly moving waves of oxidation (blue). Auto-oscillatory behavior is also seen in the Oregonator model of Field, Koros and Noyes (FKN), a robust, reduced model that captures qualitative BZ kinetics in the auto-oscillatory regime. However, the Oregonator model predicts a blue (oxidized) induction phase. Here we develop a generalized Oregonator-like model with no explicit bifurcation parameter that yields the observed transition from a red initial state to oscillatory dynamics, and displays a new bifurcation mechanism not seen in the original Oregonator. 相似文献
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A form of the weak temperature gradient (WTG) approximation, in which the temperature tendency and advection terms are neglected in the temperature equation so that the equation reduces to a diagnostic balance between heating and vertical motion, is applied to a two-dimensional nonlinear shallow-water model with the heating (mass source) parameterized as a Newtonian relaxation on the temperature (layer thickness) towards a prescribed function of latitude and longitude, containing an isolated maximum or minimum, as in the classic linear Gill problem. In this model, temperature variations are retained in the Newtonian heating term, so that it is not a pure WTG system. It contains no free unbalanced modes, but reduces to the Gill model in the steady linear limit, so that steady solutions may be thought of as containing components corresponding to unbalanced modes in the same sense as the latter. The equations are solved numerically and are compared with full shallow-water solutions in which the WTG approximation is not made. Several external parameters are varied, including the strength, location, sign, and horizontal scale of the mass source, the Rayleigh friction coefficient, and the time scale for the relaxation on the mass field. Indices of the Walker and Hadley circulations are examined as functions of these external parameters. Differences between the WTG solutions and those from the full shallow-water system are small over most of the parameter regime studied, which includes time-dependent as well as steady solutions. 相似文献