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61.
Saed Raji Yves Jannot Philippe Lagière Jean Rodolphe Puiggali 《Construction and Building Materials》2009,23(10):3189-3195
The experimental results obtained by the thermophysical characterization of a wall made of stacked laminated solid-wood planks are reported in this article. The interface between two logs is filled with a felt packing that is compressed under the weight of the upper plank. The characteristics which affect heat, air and water vapour transfers through the wall have been determined, i.e. the sorption isotherm, density, thermal conductivity and diffusivity, water vapour diffusion coefficient, and air permeability of the wall. The results achieved demonstrate the influence of the presence of the laminating adhesive on water vapour and air diffusion, and the influence of the presence of the felt packing on air permeability. The result is that the hygrothermal behaviour of the wall studied cannot be described properly by simply taking into account the properties of the solid wood, and it is thus necessary to determine the global properties of the composite wall. 相似文献
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Chlorine contents of 32 surface soils representing the four savanna zones in Nigeria, the major soil parent materials and the main agricultural fields were examined. Total chlorine contents varied from 47.2 to 296.5 mg kg-1 while the water-soluble chloride varied from 0.1 to 7.7 mg kg-1 in all the soils. Total Cl and water-soluble Cl- did not vary by either ecological zones or by soil parent material. However, according to the order of magnitude, the contents in the ecological zones may be arranged as follows: Southern Guinea > Sudan > Northern Guinea > Sahel while, with respect to parent material, the contents could be arranged as follows: Basement Complex > Basalt > Sedimentary > Aeolian. Preliminary results tend to indicate that over eighty percent of the Nigerian savanna soils may be deficient in Cl, though detailed study may be necessary. Lack of significant correlation between Cl and selected soil properties tends to indicate that neither texture, organic matter nor soil reaction has a controlling influence on Cl occurrence in the study area. 相似文献
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The present article reports numerical results of natural convection within an air filled square cavity with its horizontal walls submitted to different heating models. The temperature of the bottom horizontal surface (hot temperature) is maintained constant, while that of the opposite surface (cold temperature) is varied sinusoidally with time. The remaining vertical walls are considered adiabatic. The parameters governing the problem are the amplitude (0 ≤ a ≤ 0.8) and the period (τ ≥ 0.001) of the variable temperature, the Rayleigh number (103 ≤ Ra ≤ 7 × 106), and the Prandtl number (Pr = 0.71). In constant cooling conditions (a = 0), up to three different solutions (monocellular flow MF, bicellular vertical flow BVF, and bicellular horizontal flow BHF) are obtained. Their existence ranges are delineated and, in the limits of the existence range of each solution, the transitions observed are identified and described. In the variable cooling conditions, the effect of the amplitude and the period of the exciting temperature on fluid flow and heat transfer is examined in the case of the MF, and BHF for specific values of Ra. Results are presented in terms of Ψ max (t), Ψ min (t), Nu(t) and streamlines, heatlines, and isotherms during the evolutions of selected flow cycles. In comparison with the constant heating conditions, it is found that the variable cooling temperature could lead to a drastic change in the flow structure and the corresponding heat transfer, especially at specific low periods of the cold variable temperature. This leads to a resonance phenomenon characterized by an important increase in heat transfer by about 46.1% compared to the case of a constant cold temperature boundary condition. 相似文献
66.
In this study, silver nanoparticles were prepared using silver nitrate as the metal precursor, starch as protecting agent, and sodium borohydride (NaBH4) as a reducing agent by the chemical reduction method. The formation of the silver nanoparticles was monitored using ultraviolet-visible absorption spectroscopy, cyclic voltammetry, and particle size analyzer and characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD). Synthesis of nanoparticles were carried out by varying different parameters, such as reaction temperature, concentration of reducing agent, concentration of silver ion in feed solution, type and concentration of the stabilizing agent, and stirrer speed expressed in terms of particle size and size distribution. Dispersion destabilization of colloidal nanoparticles was detected by Turbiscan. It was observed that size of the starch stabilized silver nanoparticles were lower than 10 nm. The microbial activity of synthesized silver nanoparticles was examined by modified Kirby-Bauer disk diffusion method. Silver nanoparticles were tested for their antibacterial activity against Gram negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Gram positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis. High bacterial activity was observed at very low concentrations of silver (below 1.39 μg/ml). The antifungal activity of silver nanoparticles has been assayed against Candida albicans. 相似文献
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McCarthy D.K. Allnutt J.E. Salazar W.E. Omeata E.C. Owolabi B.R. Oladiran T. Ojeba E.B. Ajayi G.O. Raji T.I. Zaks C. 《Electronics letters》1994,30(17):1452-1453
Three experiments were set up within a joint African radiometric propagation measurement program to provide data at frequencies above 10 GHz for predictive modelling. The authors report the results of the second year of measurements in Ile-Ife, Nigeria. Compared with ITU-R (formerly CCIR) predictions, the rain measurements agree fairly well but the path attenuation results differ significantly 相似文献
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Ishaq Adeyanju Raji Muhammad Hisyam Lee Muhammad Riaz Mu'azu Ramat Abujiya Nasir Abbas 《Quality and Reliability Engineering International》2021,37(6):2665-2684
Lately, the multivariate setup of control charts, especially the memory-less chart has received less attention of researchers as compared to the univariate setup. However, the multivariate setup is of paramount importance in this big-data era. In this research work, we study the multivariate Shewhart chart for monitoring location parameter by examining the robustness of this scheme with the mean estimator. We also explored the scheme with some other robust parametric estimators in different process environments. The multivariate estimators such as median, midrange, tri-mean (TM), and Hodges–Lehmann (HL) estimators were examined under uncontaminated, location contaminated, variance contaminated, and both location–variance contaminated normal environments. Through a synthetic Monte Carlo simulation and application of the schemes on a real-life dataset, the findings suggest that the proposed estimators outperform the default estimator of the multivariate scheme (mean). The performance measures of comparing these estimators through the charts are the average run length, standard deviation run length, extra-quadratic loss, and relative average run length. The charts resulting from applying the schemes on real-life dataset recorded from glass manufacturing process also buttresses the simulation findings. 相似文献