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排序方式: 共有1203条查询结果,搜索用时 187 毫秒
1.
Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献
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Diffusion induced grain boundary migration (DIGM) was observed to occur in a Ni-48.5 wt pct Cu alloy during oxidation at 450
°C, 500 °C, 600 °C, and 707 °C in air. The DIGM zones are Cu enriched. A Ni depleted zone, consisting of small recrystallized
grains, formed in the matrix beneath the metal-oxide interface during oxidation at 600 °C and 707 °C. This process is referred
to as oxidation-induced recrystallization (OIR). Growth of the small OIR grains was observed to be associated with Cu-rich
DIGM. No Cu-rich DIGM was found in the same alloy when annealed in Ar at 707 °C. Oxidation of this alloy in air resulted in
the formation of a duplex oxide: an inner NiO layer and an outer CuO layer. The NiO layer was observed to grow at a faster
rate than the CuO layer. The occurrence of Cu-rich DIGM is interpreted in terms of this preferential oxidation of Ni. 相似文献
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Hans-Joachim Kleebe Gabriela Hilz Günter Ziegler 《Journal of the American Ceramic Society》1996,79(10):2592-2600
Sol-gel-derived mullite ceramics were processed by pressureless sintering at 1600°, 1650°, and 1700°C for 4 h. Microstructural and microchemical characterization of the mullite materials was performed using transmission electron microscopy, in conjunction with energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy (EELS). Apart from mullite grain diameter and triplepocket size, no major microstructural changes were observed with increasing sintering temperature. Residual glass was present at triple pockets and along two-grain junctions. Not all grain boundaries revealed the presence of a continuous amorphous intergranular film. Clean interfaces were observed only at boundaries with one grain parallel to the [001] orientation (low-energy configuration). Quantitative EELS analysis of mullite grains and glass pockets revealed only small changes in composition with increasing sintering temperature; i.e., the alumina:silica ratio slightly increased for mullite and glass. The analysis implied that mullite with this relatively high aluminum content would not be stable adjacent to residual glass. However, a stable glass-mullite system has been proposed, because impurity cations were detected within glass pockets, which suggested a slight shift of the subsolidus line (glass-mullite/ mullite) to a higher amount of alumina. Energy-loss nearedge structure studies of the Si- L 2,3 edge revealed a similar near-edge structure for the mullite, residual glass, and quartz. Thus, SiO4 tetrahedra were thought to be the main building units of the glass contained in sintered mullite. 相似文献
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The GKSS-Forschungszentrum has simulated within an extensive PSS (Pressure Suppression System) program small break LOCA situations in a large scale multivent PSS test arrangement. The gained experimental information indicates that the simulated small break LOCA in a BWR-PSS which initiates steam condensation in the wetwell pool at the vent pipe outlets, gives strong cyclic pressure pulses from chugging events over a long time period. 相似文献
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Angelika Elsner G. Mieth W. Engst L. Aust H.-J. Leverenz 《European Journal of Lipid Science and Technology》1991,93(8):290-293
Sucrose carboxylic acid polyesters are in dependence of the degree of acylation and fatty acid composition more or less undigestible or emulsifying fat substitutes and functional additives for foods. In this connection the relationships between their molecular parameters and functional properties are discussed. New procedures of the solvent-free synthesis are presented. Furthermore, open biochemical and toxicological problems of pinocytosis and accumulation of intact polyesters in organs and tissue being still under investigations are considered. 相似文献
10.
Gina‐Gabriela Bumbu Cornelia Vasile Maria Cristina Popescu Hristea Darie Gabrielle Charlotte Chianu Gheorghe Singurel Adrian Carpov 《应用聚合物科学杂志》2003,88(11):2585-2597
The compatibility of the hydroxypropyl cellulose (HPC) with maleic acid–vinyl acetate copolymer in the solid state was studied by thermogravimetry, thermo‐optical analysis, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and optical microscopy. It was established that physical interactions are prevalent in blends with a high content of HPC, whereas chemical interactions predominate in blends with a medium and low content of HPC. By increasing the temperature, the thermochemical reactions are favored. Thermal properties are dependent on the mixing ratio of the components. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2585–2597, 2003 相似文献