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31.
This first in a series of articles characterized the different varieties of Indian silk for their macrostructural parameters, such as filament length, degumming loss, denier, cross section, moisture regain, and intrinsic viscosity, for example. The results of amino acid analysis using a reverse‐phase technique were also reported. Five Indian silk varieties—two mulberry (bivoltine and crossbreed) and three nonmulberry (tasar, muga, and eri)—were investigated. The differences existing between the different varieties and the extent of lengthwise variations within a cocoon in the dimensional and macrostructural parameters were discussed. It was observed that denier of the filament decreases considerably from the outer to the inner layers, whereas density showed an increasing trend in all the varieties. Both the mulberry silks demonstrated lower moisture regain. Electron micrographs of all the nonmulberry varieties showed microvoids in their cross section. Fraction studies showed the development of mushroom structure on the tips. In both types of mulberry silk, glycine, alanine, and serine constitute about 82% of the amino acids present. On the other hand, in nonmulberry silks, these constitute about 73% with a high proportion of alanine. The nonmulberry varieties showed a substantial proportion of amino acids with bulky side groups. Similarly, the higher hydrophilic to hydrophobic amino acid ratio (9.06–9.85) for nonmulberry silks, compared against that of the mulberry varieties (5.29–6.22), was shown to be responsible for the higher moisture content of nonmulberry silks. Cystine and methionine were present in all the varieties. The higher intrinsic viscosity of nonmulberry varieties suggested their higher molecular weight. Through amino acid analysis, it was shown that there is no difference in chemical architecture between the outer and the inner layers of cocoons. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1080–1097, 2004 相似文献
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针对生产的神龙凸轮轴与进口法国KD件对应两凸轮间轴颈断口形貌存在的差异,对原凸轮轴材质、工艺进行研究,通过重新选择化学成分、炉料配比、采用热分析仪快速测定碳、硅含量及铁液过冷度、严格控制过热温度和保温时间等措施,显著改善过渡区轴颈组织,提高凸轮轴的抗断裂性能,各项性能达到了KD件同等质量水平. 相似文献
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采用粉煤灰、赤泥等类粘土质的工业固废制备建筑陶瓷是其生态高值化利用的有效途径.本文研究了陶瓷坯体主要成分粉煤灰和赤泥配比为3:2时优化的烧成温度、保温时间等工艺参数,研究了成孔剂含量对陶瓷体积密度、孔隙率及微观组织结构的影响,研究了与该坯体相适宜的釉料配方及涂布方式对坯釉结合性能的影响,并重点探讨了具有自保温性能的陶瓷坯釉一次干压成型和一次烧成的制备工艺.研究结果表明,较优化的烧成温度为1100℃,保温时间为2h;适宜的成孔剂含量为5%,釉料配方和涂布工艺对坯釉结合性能和釉层质量具有决定性作用,坯釉一次干压成型是解决坯釉适应性和提高结合强度的有效技术途径;陶瓷基体中加入成孔剂并不会对釉质层的质量造成影响,且坯釉一次干压成型和一次烧成的制备工艺可实现以粉煤灰、赤泥为主要原料的陶瓷的一体化生产,具有显著的生态、节能和经济性. 相似文献
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A volume average solidification model is extended to incorporate fragmentation as the source of equiaxed crystals during mixed columnar-equiaxed solidification. This study is to use this model to analyze the role of fragmentation in the formation of as-cast structure. Test simulations are made for the solidification of a model alloy(Sn-10wt.%Pb) with two different geometries. The first one is a 2D rectangular domain(50 × 60 mm~2) as cooled from the top boundary. Solidification starts unidirectionally as columnar structure from the top. The solute(Pb) enriched interdendritic melt is heavier than the bulk melt, and sinks downwards, hence leads to solutal convection. Fragmentation phenomenon occurs near the columnar tip front. The fragments are transported out of the columnar region, and they continue to grow and sink, and finally settle down and pile up at the bottom. The growing columnar structure from the top and pile-up of equiaxed crystals from the bottom finally lead to a mixed columnar-equiaxed structure, in turn leading to a columnar-to-equiaxed transition(CET). The second geometry is a 3D plate, 100 × 60 ×10 mm~3, as cooled laterally from one side. It was cast experimentally and analyzed for the as-cast structure. The equiaxed fragments are produced in the solidification front and transported into the bulk melt, leading to a special pattern of as-cast structure: columnar structure in the cool wall side and equiaxed structure in the upper left corner near the hot wall side, extending downwards to the middle bottom region. Numerically calculated as-cast structures agree with the experiment results. 相似文献
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李维钺 《冶金标准化与质量》1999,(3)
分析介绍了钢的低倍组织及缺陷酸蚀检验法、缺陷评级级图等有关标准的现状,提出标准中存在的一些问题和解决思路,对有关标准今后的修订提出建议。 相似文献
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李维钺 《冶金标准化与质量》2003,41(4):37-38
根据生产实践 ,对结构钢低倍组织缺陷评级图进行了分析和探讨 ,提出新标准中一些问题的同时 ,还提出一些建议内容。 相似文献