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91.
Analitycal model for predicting the size of the Mach reflection wave configuration in steady flows has been improved (Azevedo
1989; Azevedo and Liu (1993)). Predictions based on the modified analytical model were compared to available experimental
results. The agreement was found to be better than that obtained by Azevedo (1989) and Azevedo and Liu (1993). The reason
for the better agreement is due to the fact that, unlike Azevedo's original model, downstream effects were not neglected in
the modified model which was developed in the course of this study.
Received 12 May 1996 / Accepted 15 January 1997 相似文献
92.
M. Ozer L. J. Graham 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):499-503
In a Hodgkin-Huxley neuron model driven just above threshold, external noise can increase both jitter and latency of the first
spike, an effect called “noise delayed decay” (NDD). This phenomenon is important when considering how neuronal information
is represented, thus by the precise timing of spikes or by their rate. We examine how NDD can be affected by network activity
by varying the model's membrane time constant, τm. We show that NDD is significant for small τm or high network activity, and decreases for large τm, or low network activity. Our results suggest that for inputs just above threshold, the activity of the network constrains
the neuronal coding strategy due to, at least in part, the NDD effect. 相似文献
93.
Arif B. Ozer Ahmet F. Oncel D. Keith Hollingsworth Larry C. Witte 《Experimental Thermal and Fluid Science》2011,35(8):1522-1529
A method is developed to capture the distribution of surface temperature while simultaneously imaging the bubble motions in diabatic flow boiling in a horizontal minichannel. Liquid crystal thermography is used to obtain highly resolved surface temperature measurements on the uniformly heated upper surface of the channel. High-speed images of the flow field are acquired simultaneously and are overlaid with the thermal images. The local surface temperature and heat transfer coefficient can be analyzed with the knowledge of the nucleation site density and location, and bubble motion and size evolution. The horizontal channel is 1.2 mm high × 23 mm wide × 357 mm long, and the working fluids are Novec 649 and R-11. Optical access is through a machined glass plate which forms the bottom of the channel. The top surface is an electrically heated 76 μm-thick Hastelloy foil held in place by a water-cooled aluminum and glass frame. The heat loss resulting from this construction is computed using a conduction model in Fluent. The model is driven by temperature measurements on the foil, glass plate and aluminum frame. This model produces a corrected value for the local surface heat flux and enables the computation of the bulk fluid temperature and heat transfer coefficient along the channel. The streamwise evolution of the heat transfer coefficient for single-phase laminar flow is compared to theoretical values for a uniform-flux boundary condition. Examples of the use of the facility for visualizing subcooled two-phase flows are presented. These examples include measurements of the surface temperature distribution around active nucleation sites and the construction of boiling curves for locations along the test surface. Points on the curve can be associated with specific image sequences so that the role of mechanisms such as nucleation and the sliding of confined bubbles may be discerned. 相似文献
94.
Elmali D Altindal A Ozkaya AR Salih B Bekaroğlu O 《Dalton transactions (Cambridge, England : 2003)》2011,40(3):651-660
Novel mononuclear Zn(ii) 4, Co(ii) 5 and Cu(ii) 6 metallophthalocyanines have been synthesized from 4,4'(ethane-1,1-p-phenol-2,2-p-phenoxy)phthalonitrile 3, which can be obtained by the reaction of 4-nitrophthalonitrile 1 with 1,1,2,2-tetrakis(p-hydroxy-phenyl)-ethane 2. The target water-soluble derivatives of 7-9 were acquired from a boiling suspension of the compounds in aqueous 20% KOH solution. The synthesized complexes have been characterized by UV-vis, IR, (1)H NMR and MALDI-TOF-mass spectroscopies. In addition, the geometric and electronic structures of 2-6 were investigated by ab initio/DFT quantum mechanical calculations using the Gaussian 03 program with HF theory at the B3LYP/3-21G level. The redox properties of the complexes 4-6 were examined by cyclic voltammetry on platinum in DMSO/TBAP. These complexes displayed one-electron metallophthalocyanine-based and multi-electron hydroxyphenyl-based redox processes. The effect of temperature on the d.c. conductivity and impedance spectra of spin coated films of compounds were investigated at the temperatures between 300-452 K and in the frequency range of 40-105 Hz. Thermally activated conductivity dependence on temperature was observed for all compounds. A.c. results indicated that conduction mechanism can be explained by classical hopping barriers mechanism for all films. 相似文献
95.
Ceyhan T Altindal A Ozkaya AR Erbil MK Salih B Bekaroğlu O 《Chemical communications (Cambridge, England)》2006,(3):320-322
1,3 dimethoxy-4-t-butylcalix[4]arene has been used to synthesize a novel ball-type dimeric zinc(II) phthalocyanine, [Zn2Pc2(tbca)4] that exhibits mixed-valence behaviour and non-Arrhenius type dependence of conductivity. 相似文献
96.
The paper describes a scheme which is based on the CIP scheme and modified to properly describe a gas/liquid interface without
smearing the density jump across the interface. This was achieved by calculating the density separately for each phase. The
density at each grid point was determined by using a density function in a similar fashion as CIP. As a result a sharp density
gradient was obtainable throughout the flow field and the scheme could handle properly gas/liquid interfaces having a large
density ratio. Shock wave interaction with a cylindrical water column was simulated. The numerical results were compared with
appropriate interferograms. Good agreement was found between the two. The results obtained for the cylindrical water column
were compared with a similar solid cylinder case. The comparison reveled that even 40 s after shock impingement some differences were found between a liquid column and the solid cylinder.
Received 11 July 2000 / Accepted 28 March 2001 相似文献