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861.
Summary This paper describes a novel process for the production of chemically bonded phases using fluidised bed technology. Hitherto
fluidisation of particles with the size range below 50 μm was considered impossible. In this study, particles with sizes as
small as 7 μm have been successfully fluidised and subsequently reacted to produce bonded phases. The operating parameters
of the fluidised bed system have been studied and their effect on the chromatographic properties of the products have been
investigated. Advantages of the process are thein situ removal of fines, high batch to batch repeatability andin situ chemical post-treatments (end-capping).
Studies of the chromatographic performance of the fluidised bed products show them to possess markedly superior retention
characteristics and good peak shapes. Comparisons were made with various C8 and C18 commercially available bonded phases and on bonded phases prepared by conventional method. Mass loading effects were also
investigated for preparative HPLC use. 相似文献
862.
863.
使用一种特殊的复合氧/气泡探头,对流化床燃烧器中气泡相和密相氧浓度进行了实验测定,并与以两相理论为基础所建立的燃烧模型的预测值进行了比较。燃烧模型较准确地预测了密相氧浓度随时间的变化。对于气泡相,模型值与实验值间存在着少许偏差。当从实验数据中扣除含有碳颗粒的低氧浓度气泡的影响后,气泡相的模型值与实验结果吻合良好。在本实验条件下,燃烧模型的唯一可调参数为煤焦与床层颗粒;司的温差值(20℃)。该温差值明显低于以往的报道值,其可能原因有三个:(1)当烧失过程趋于完成时,煤焦颗粒温度减小;(2)过去所测的煤焦温度可能偏向于煤焦在气泡内的温度值;(3)计算模型各参数时的微小误差也可能导致所得△T值偏低一些。 相似文献
864.
G.P. Raja Sekhar 《Applicable analysis》2013,92(6):833-848
We have used effective medium model for beds of circular cylindrical porous fibres in order to estimate the overall bed permeability (OBP). It is assumed that a representative circular porous cylindrical fibre is inside a fluid envelope beyond which effective medium is used. Both inside the cylindrical fibre and in the effective medium, Brinkman equation is used, however of different permeabilities and in the fluid envelope Stokes equation is used. The OBP corresponding to the porous fibres is estimated when the flow direction is perpendicular to the axis of the cylindrical fibres as well as parallel to the fibres. This in turn is used to estimate the OBP corresponding to a collection of porous cylindrical fibres that are randomly oriented. We have compared the results with some existing literature. 相似文献
865.
A mathematical model is presented to simulate the multiple heterogeneous reactions with complex set of physicochemical and
thermal phenomena in a moving bed of porous pellets. This model is based on both heat and mass transfer phenomena of gaseous
species in a porous medium including chemical reactions at interfaces whose areas vary during the conversion. This model accounts
for both the exothermic and endothermic reactions which can be equimolar or nonequimolar. Furthermore it considers simultaneously
the reactions in the nonisothermal transient condition. A powerful technique based upon finite volume fully implicit approach
has been implemented to solve the complicated governing equations numerically. The model has been validated by comparing with
various experimental and analytical results in two cases: the single pellet scale as well as the counter current moving bed
reactor.
相似文献
Yadollah SaboohiEmail: |
866.
In a packed-bed reactor a comparative study of bubble breakup and coalescence models has been investigated to study bubble size distributions as a function of the axial location. The bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of bubble breakup and coalescence models is examined under two inlet flow conditions: (1) predominant bubble breakup flow and (2) predominant bubble coalescence flow. The resulting bubble size distributions, breakup and coalescence rates estimated by individual models, are qualitatively compared to each other. The change of bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing bubble breakup and coalescence models do not agree with the experimental data, a new bubble breakup and coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor. 相似文献
867.
M.S.N. Murty K.V. RameshG. Prabhakar P. Venkateswarlu 《Experimental Thermal and Fluid Science》2011,35(2):338-346
Three-phase fluidized beds are found to have wide applications in process industries. The present investigation essentially comprises of the studies on gas holdup, liquid holdup and bed porosity in three-phase fluidized beds with coaxially placed disc promoter. Holdup data were obtained from bed expansion and pressure drop measurements. Analysis of the data was done to elucidate the effects of dynamic and geometric parameters on gas holdup, liquid holdup and bed porosity. Data were correlated and useful equations were obtained from empirical modeling. 相似文献
868.
Songbai Cheng Daisuke HiraharaYouhei Tanaka Yoji GondaiBin Zhang Tatsuya MatsumotoKoji Morita Kenji FukudaHidemasa Yamano Tohru SuzukiYoshiharu Tobita 《Experimental Thermal and Fluid Science》2011,35(2):405-415
A series of experiments on bubbling behavior in particle beds was performed to clarify three-phase flow dynamics in debris beds formed after core-disruptive accident (CDA) in sodium-cooled fast breeder reactors (FBRs). Although in the past, several experiments have been performed in packed beds to investigate flow patterns, most of these were under comparatively higher gas flow rate, which may be not expected during an early sodium boiling period in debris beds. The current experiments were conducted under two dimensional (2D) and three dimensional (3D) conditions separately, in which water was used as liquid phase, and bubbles were generated by injecting nitrogen gas from the bottom of the viewing tank. Various particle-bed parameters were varied, including particle-bed height (from 30 mm to 200 mm), particle diameter (from 0.4 mm to 6 mm) and particle type (beads made of acrylic, glass, alumina and zirconia). Under these experimental conditions, three kinds of bubbling behavior were observed for the first time using digital image analysis methods that were further verified by quantitative detailed analysis of bubbling properties including surface bubbling frequency and surface bubble size under both 2D and 3D conditions. This investigation, which hopefully provides fundamental data for a better understanding and an improved estimation of CDAs in FBRs, is expected to benefit future analysis and verification of computer models developed in advanced fast reactor safety analysis codes. 相似文献
869.
Mun S 《Journal of chromatography. A》2011,1218(44):8060-8074
The performance of a five-zone simulated moving bed (SMB) chromatographic process for ternary separation has been improved to a certain extent in previous researches by applying either a partial-feeding (PF) or a partial-closing of the extract-2 port (PCE(2)) to its operation. To make a further improvement, the strategy of applying both PF and PCE(2) simultaneously to the five-zone SMB operation was proposed in this study. The results from both equilibrium-theory analysis and detailed simulation proved that the proposed strategy, which was called PF-PCE(2) in this article, had the benefit of a synergy between the individual merits of PF and PCE(2) in the five-zone SMB performance. As a consequence, the PF-PCE(2) mode could surpass the PF and the PCE(2) modes by a wide margin and the standard mode by a much wider margin in the aspects of ternary-separation performance and throughput. For the separation system considered, the PF-PCE(2) mode was found to achieve more than 100% improvement, compared to the standard mode. Furthermore, such advantage of the PF-PCE(2) over all the other modes was greater as the selectivity between the intermediate-affinity and the highest-affinity components was reduced. 相似文献
870.