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831.
Kenjiro Iida John Pierman Thabet Tolaymat Timothy Townsend Chang-Yu Wu 《Canadian Metallurgical Quarterly》2004,130(2):184-192
Chromated copper arsenate (CCA) has been the predominant wood preservative used in North America in recent years. The emission of volatile metals and leaching from the combustion ash of CCA-treated wood pose serious concerns. In this work, mineral sorbents were evaluated for their capabilities to control both problems. Results of thermodynamic analyses suggested that alkali and alkaline earth metal-based sorbents can potentially react with the metals during combustion. Experiments were conducted by mixing and burning mineral sorbents including lime and soda ash with CCA-treated wood in a fixed bed. Calcium-based sorbents showed great increase in the retention of arsenic (from 60 to 85%) and chromium (from 55 to 80%) and reduction in the leaching of arsenic (from 200 down to 0.1 mg/L) and copper (from 100 down to 1 mg/L). Sodium-based sorbents successfully retained metals in the ash below 750°C, but the products were highly leachable (over 1000 mg/L). The speciation of the products plays a critical role in determining the fate of the metals. 相似文献
832.
A new approach is presented for modeling multicomponent volatile organic compound (VOC) sorption equilibrium in ultra- and supernanoporous activated carbons. The model uses “Dubinin–Astakhov thermal equation of equilibrium adsorption” (DA-TEEA) for single-component adsorption thermodynamics and “ideal/real adsorbed solution theories” (IAST/RAST) for the multicomponent mixing rules. Use of the Henry’s Law adsorption isotherm resolves the singularity of DA-TEEA at zero-coverage conditions. The introduced method predicts multicomponent adsorption equilibria of VOCs based on equilibrium data of only one similar component. Single and binary adsorption equilibria of acetone and benzene vapors in Kynol ACFC-5092-20 activated-carbon-fiber-cloth adsorbents are predicted with the presented models and compared with modeled and measured characterization data available in the literature. The Wilson model for nonideal binary solution mixtures is used to predict the activity coefficients needed in DA-TEEA/RAST. Modeled results are compared against measured characterization data. The selected Henry’s Law upper-bound pressure (HUBP) is found to be an important factor controlling the accuracy of the multicomponent equilibrium models. An optimum HUBP can generate highly accurate results from both DA-TEEA/IAST and DA-TEEA/RAST. The accuracy realized by applying this method to acetone–benzene mixtures is sufficient for engineering design and development purposes. 相似文献
833.
Heavy metal migration through compacted, saturated sand and bentonite/soil admixtures were investigated using kinetic, batch sorption tests, and column tests. Sorption of Pb, Zn, and Cd at pH 5 by bentonite is found to be 411.2, 163.4, and 71.8 mL/g, respectively. The permeability of the compacted sand (8×10?4?cm/s) is found to be 6 orders of magniture higher than that of bentonite/soil admixture (about 8×10?10?cm/s) when permeated with metal solutions under an effective stress of 34.5 kPa (5 psi). The permeation of metal solutions into bentonite/soil admixture columns does not result in a significant increase in permeability. Experimental results of batch sorption and hydraulic conductivity tests were also analyzed with a computer-based simulation model, POLLUTE, to determine the transport parameters (effective porosity, dispersion coefficient, retardation) of chloride ions and heavy metals in a homogeneous compacted sand and bentonite/soil admixture using a curve fitting technique. 相似文献
834.
Bonnie Sjoberg Dobchuk S. Lee Barbour Jian Zhou 《Canadian Metallurgical Quarterly》2004,130(3):293-302
Evaporative losses from the surface of barren waste rock piles in arid environments occur as a result of water vapor diffusion. Water vapor diffusion is accompanied by adsorption of water vapor. A review of the literature found that adsorption of water vapor is commonly described as a sigmoidal function of suction with a predominant linear portion when plotted against the log of suction. Laboratory column tests were conducted with glass beads and waste rock to study water vapor diffusion. A monitoring system was developed for measuring relative humidity and temperature through the column. Water vapor fluxes and relative humidity profiles through the column were measured under steady-state conditions to establish the method of estimating the water vapor diffusion coefficient. Transient water vapor fluxes and relative humidity profiles were measured and a numerical model was developed to simulate the laboratory observations. The numerical model demonstrated the importance of water sorption in controlling the transient water vapor flux. Sorption described as a log–linear function of suction gave reasonable results for the numerical modeling of the glass beads and waste rock. 相似文献
835.
Muoi Tang Wei-Heng Huang Yan-Ping Chen 《Journal of the Chinese Institute of Chemical Engineers》2007,38(5-6):419-424
Diffusion and interaction of supercritical carbon dioxide (SCCO2) with polycarbonate (PC) and polysulfone (PSF) is investigated in this study. Experiments on the sorption of SCCO2 at 40 °C and 20 MPa into these polymers were carried out. Both the sorption amount of SCCO2 (Ms) and the desorption diffusivity (Dd) were determined by employing Fick's diffusion model. The Ms and Dd values for SCCO2 in PC were greater than those in PSF, owing to different interactions of SCCO2 with the polymers in the sorption process. The FTIR spectroscopy results for both polymers showed that CO2 desorbed faster from PSF than from PC. This indicated that the carbonyl group in PC had a stronger interaction with SCCO2. The plasticization effect of SCCO2 on these polymers was also investigated by comparing the DMA measurement results on pure and SCCO2 treated polymers. It is shown that PC had a larger shift in glass transition temperature than that of PSF after the SCCO2 treatment. This implied that there is a greater extent of plasticization on PC. 相似文献
836.
Giuliana GorrasiMariarosaria Tortora Vittoria Vittoria Dirk KaempferRolf Mülhaupt 《Polymer》2003,44(13):3679-3685
Syndiotactic polypropylene (sPP) nanocomposites were obtained by melt blending synthetic fluorohectorite modified octadecyl ammmonium ions (OLS), and maleic-anhydride-grafted isotactic polypropylene (iPP-g-MA) as compatibilizer. The composition of the inorganic material was varied between 5 and 20 w/w%. Films of the composites were obtained by hot press molding the pellets. Melt-direct polymer intercalation of sPP into the OLS gave rise to nanocomposites in which the silicate layers were delaminated at low clay contents, and ordered to intercalated structures at the highest clay content. The elastic modulus was higher than for the pure polymer in a wide temperature range and increased with the inorganic content. The transport properties were measured for dichloromethane and n-pentane. The sorption was reduced compared to pure sPP. There were not significative differences between the samples having different inorganic contents. The diffusion coefficient decreased with increasing clay content. Permeability (P) showed a strong decreasing dependence on the clay content. The improvement of the barrier properties was largely caused by the reduced diffusion. 相似文献
837.
《分离科学与技术》2012,47(12):1583-1597
Abstract The pervaporation of water/ethanol mixtures through an aromatic polyetherimide membrane was attempted. The membrane was laboratory prepared using the solution casting technique. The sorption characteristics in relation to pervaporation were also studied. It was found that the preferential sorption was altered when the liquid composition was changed, whereas the water component permeated through the membrane preferentially over the whole range of feed mixture compositions. The experimental results were analyzed in terms of sorption ratio and permeation ratio to characterize nonideality of sorption and pervaporation. The effects of some operating parameters, including temperature, feed concentration, and permeate pressure, on the pervaporation performance were also investigated. 相似文献
838.
Moisture adsorption isotherms of spray-dried yogurt powder were determined at 10, 25, and 40°C using the standard, static-gravimetric method. Experimental data were fitted to five mathematical models (Guggenheim-Anderson-de Boer [GAB], Brunauer-Emmett-Teller [BET], Halsey, modified Oswin, and modified Henderson). A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. The shelf-life of yogurt powder was predicted based on the relationship between permeability coefficient of the packaging material and moisture adsorbed by the powder determined by the GAB equation. Furthermore, the storage stability of spray-dried yogurt powder in terms of quality parameters including moisture content, water activity, color change, and thiobarbituric acid (TBA) value was studied in aluminum laminated polyethylene (ALPE) pouches under storage conditions of 25°C and 50% relative humidity (RH). 相似文献
839.
A rapid and novel approach for predicting sorption isotherms based on the Polanyi theory is proposed. This approach allows the prediction of the sorption isotherms at different temperatures from one experimental isotherm. The theoretical predictions of isotherms and isosteric heats were validated successfully using data from the literature for different meat types. This method allows total experimental time and operation costs to be reduced. 相似文献
840.