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排序方式: 共有204条查询结果,搜索用时 31 毫秒
1.
Effect of Mode of Drying on Microstructure of Potato 总被引:2,自引:0,他引:2
Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se. 相似文献
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ABSTRACTFreeze-drying (FD) and solvent evaporation (SE) were used to prepare solid dispersions (SDs) of meloxicam (MX) in polyvinylpyrrolidone K-30 (PVP). The SDs were prepared at different ratios, namely 1:1, 1:3, and 1:5 MX:PVP weight ratio. Differential scanning calorimetry (DSC), infrared absorption spectroscopy (IR), and x-ray powder diffractometry (XPD) were utilized to characterize the physicochemical properties of the SDs. Meloxicam (MX) in the solid dispersions appeared with less crystallinity form and was present in a complete amorphous form at higher PVP ratio. Dissolution rates of MX as a pure drug, physical mixtures (PMs), and SDs indicated a marked increase of the dissolution rate of MX in presence of PVP. The increase in the dissolution rate was dependent on the ratio of PVP and the method of preparation. In addition, the permeability of the drug through standard cellophane membrane and hairless mouse skin was also evaluated. The permeation rate of MX was significantly increased in the case of SDs and was dependent on the ratio of PVP. The results were primarily due to increase wettability, the solubilization of the drug by the carrier, and formation of MX amorphous form. 相似文献
4.
《Drug development and industrial pharmacy》2013,39(4):399-407
Microcapsules of methoxybutropate solid particles or of an oily saturated solution of the same drug were prepared by complex coacervation between gelatin and acacia and dried with three different methods: isopropanol addition, spray-drying, and freeze-drying. Successively, microparticles were analyzed by infrared thermobalance, ultraviolet (UV) spectroscopy, optical and scanning electron microscopy, and sieves to find out parameters such as yield, moisture content, encapsulation percentage, morphology of solid particles, and particle size. Results highlighted that the most appropriate drying method for industrial purposes was spray-drying, particularly for oil-containing microcapsule formulations. 相似文献
5.
《Measurement》2016
Many pharmaceutical products are obtained via freeze-drying of liquid solutions to obtain stable long lasting preparations. The freeze-dry process produces porous cakes whose structure strongly depends on the freezing phase, so that monitoring and optimizing this phase can help both reducing the product cost and insuring its constant quality. Nowadays the optimization is usually performed by determining the cake mass transfer coefficient via a costly process in pilot plants, while the quality is assured only by controlling the process conditions. This paper describes an alternative way of approximately estimating the mass transfer coefficient, which is based on the observation of the product structure by a simple electron microscope followed by a frequency domain imaging process. While the process has been designed and characterized specifically for pharmaceutical products, the proposed approach can be used in several other fields where the characteristics of porous material have to be monitored. 相似文献
6.
M. Y. Gonzalez-Castro M. J. Oruña-Concha J. Lopez-Hernandez J. Simal-Lozano A. Ganza-Gonzalez 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1996,203(4):370-373
GC-FID was used to monitor changes over time in palmitic, stearic, arachidic, oleic, linoleic and linoleic acid contents of green beans subjected to various preservation treatments. In beans stored in polyethylene bags at –22°C without prior blanching, all fatty acid contents dropped appreciably within the first month of storage, regardless of whether the beans had been hand- or vacuum-packed. In beans which had been freeze-dried then stored at room temperature in an airtight container, polyunsaturated fatty acid contents dropped appreciably only after 2 months. 相似文献
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Mathematical modeling of the primary and secondary vacuum freeze drying of random solids at microwave heating 总被引:2,自引:0,他引:2
This paper presents a complex model of the primary and secondary vacuum freeze-drying stages at microwave heating. The simulation of the process was performed for typical adsorbents which were chosen as ideal representatives of random solids having particle and bed porosity. One-dimensional two-region model of the primary freeze-drying at microwave heating was formulated and then solved numerically using the finite-difference MacCormack method. Varying during the process sublimation front temperature Ts(t) was taken into account. Simulated drying curves were compared with experimental results giving fairly good agreement. A mathematical model of the secondary freeze-drying at microwave heating was developed and solved using the numerical method of lines. Pressure drop in the material was taken into account and calculated using Ergun equation. As a result of the model solution, the moisture content and the temperature distributions in drying material were obtained. In both mathematical models steady internal heat source capacity was calculated as a function of material temperature. 相似文献
9.
A novel freeze-drying protocol has been explored to render fast and cost-effective freeze drying of hyperamylase producing Bacillus subtilis MTCC2396 employing a tungsten halogen lamp radiator (THLR) as a heat source. Response surface methodology assessed the maximum reduction in moisture content (96.07%) and minimum reduction in α-amylase (EC 3.2.1.1) activity (1.02%) in 4 h drying time at 42.5°C radiation temperature. α-amylase activity (0.046 U) and final moisture content (3.93%) of the optimally freeze-dried bacterial strain appeared satisfactory. The freeze-drying time using THLR (4 h) is remarkably lower compared to that under a conventional conductive plate heater (CPH) (10 h) at otherwise identical conditions. The higher effective moisture diffusivity of 0.0052 to 0.0078 m 2/s under THLR compared to 0.00084 to 0.0015 m 2/s under CPH (corresponding to 20–50°C) advocated the superiority of the THLR heating protocol. The higher efficacy of THLR was also evidenced through lower activation energy (8.42 kJ/mol) of moisture diffusion compared to that (12.051 kJ/mol) of CPH. The optimally freeze-dried bacteria demonstrated the same growth rate in addition to exhibiting excellent retention of bioremedial (Hg2+ removal) activity to that of the control. 相似文献
10.
介绍了冷冻干燥技术的基本原理和特点,简要综述冷冻干燥技术在国内外材料制备领域的研究进展,并对冷冻干燥技术在材料制备领域的发展方向做出预测。 相似文献