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排序方式: 共有58条查询结果,搜索用时 15 毫秒
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D. Verdi C.J. MúnezF. Sevillano P. Poza 《Journal of Materials Processing Technology》2013,213(11):1825-1834
The aim of this work is modify the surface composition of a Gr22 ferritic steel component with Ni(Al) using a high-power diode laser (HPDL). Two different combinations of parameters were used to obtain a superficial alloy modification macroscopically homogenous, with low porosity and low presence of cracks. From a microscopically point of view the surface presents a band structure due to the rapid cooling process. Isothermal oxidation tests at 640 °C were performed to evaluate the performance of the solution at high temperature. The introduction of Ni(Al) with this technique has allowed to reduce the degradation of the components, without modifying the ferritic structure of the steel. 相似文献
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There is no analytical method currently available in Spain to determine elapsed time in wine aging. The only control used is based on the levels of esters and other secondary metabolites as important indicators related to wine quality. The main goal of this work was to establish a useful method to differentiate among young, “crianza”, “reserva” and “gran reserva” wines based on the study of the enzymatic decay of different hydrolases present in the wines and also to determine which enzyme(s) may be applicable in fraud detection as regards time and storage conditions of the wine. We elaborated red wine based on “Tempranillo” grapes from the Rioja Alta Alavesa and fermented with Saccharomyces cerevisiae USC 013, followed by malolactic fermentation by Oenococcus oeni CECT 630 in order to evaluate the different enzymes. One of the enzymes present, i.e., invertase, which is resistant to inactivation, could be a useful marker of wine aging. 相似文献
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The microstructure and tensile properties of an 8090 Al−Li alloy reinforced with 15 vol pet SiC particles were investigated,
together with those of the unreinforced alloy processed following the same route. Two different heat treatments (naturally
aged at ambient temperature and artificially aged at elevated temperature to the peak strength) were chosen because they lead
to very different behaviors. Special emphasis was given to the analysis of the differences and similarities in the microstructure
and in the deformation and failure mechanisms between the composite and the unreinforced alloy. It was found that the dispersion
of the SiC particles restrained the formation of elongated grains during extrusion and inhibited the precipitation of Al3Li at ambient temperature. The deformation processes in the peak-aged materials were controlled by the S′ precipitates, which acted as barriers for dislocation motion and homogenized the slip. Homogeneous slip was also observed
in the naturally aged composite, but not in the unreinforced alloy, where plastic deformation was concentrated in slip bands.
The most notorious differences between the alloy and the composite were found in the fracture mechanisms. The naturally aged
unreinforced alloy failed by transgranular shear, while the failure of the peak-aged alloy was induced by grain-boundary fracture.
The fracture of the composite in both tempers was, however, precipitated by the progressive fracture of the SiC reinforcements
during deformation, which led to the early failure at the onset of plastic instability. 相似文献
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Fluorescein thiocarbamoyl-kappa-casein assay for the specific testing of milk-clotting proteases 总被引:1,自引:0,他引:1
Milk-clotting proteases, which are widely used in the cheese-making industry, are enzymes that use soluble caseins as their preferential substrates. Here, we propose a modification to a method previously described for the specific determination of milk-clotting proteases by using κ-casein labeled with fluorescein isothiocyanate as substrate. Validation of the modified method was confirmed using natural bacterial, fungal, plant, and animal milk-clotting proteases, as well as a milk-clotting enzyme of recombinant origin. The new modified method described here allowed specific quantification of the activity of milk-clotting proteases in a very sensitive way and permitted determination of the appropriate kinetic parameters of all the enzymes tested, consistent with their origin and degree of purity. 相似文献
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T. Gómez-del Río P. Poza J. Rodríguez M.C. García-Gutiérrez J.J. Hernández T.A. Ezquerra 《Composites Science and Technology》2010
Poly(ethylene terephthalate) (PET) is one of the most extensively used thermoplastic polyesters out on the market, and it has been implemented in many forms. There has been limited work in the area of PET reinforced with single-walled carbon nanotubes (SWCNT) in mechanical properties. Nanocomposites based on PET with small contents of SWCNT were prepared by in situ polymerization. Elastic constants were determined by tensile tests performed on specimens instrumented with strain gauges. Assuming random orientation distribution of nanotubes, experimental Young’s modulus and Poisson’s ratio values were compared to some micromechanical models (Cox and Krenchel, Halpin–Tsai and Mori–Tanaka) which take into account orientation and aspect ratio of the nanotubes. However, the waviness of the nanotubes is a factor that influences the reinforcing efficiency. 相似文献
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The failure mechanisms in tension and fatigue of three Al alloys reinforced with ceramic particulates were studied by means of optical and scanning electron microscopy. Damage was concentrated in the reinforcements, which failed in a brittle fashion during deformation, leading to the specimen fracture when a critical fraction of broken particulates was reached in a given section of the specimen. This critical fraction was measured on polished longitudinal sections of broken specimens for each composite, temper, and loading condition, and was mainly dependent on the matrix alloy. It was also found that the reinforcement fracture probability was controlled by the particulate size and aspect ratio: large and elongated particulates oriented in the loading direction were more prone to fail than small, equiaxed ones. Finally, a significant fraction of the reinforcements in the cast materials was broken prior to testing. They were shattered during extrusion rather than fractured, and associated with clusters of particulates formed during solidification. 相似文献