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61.
J. J. Blandin 《Materialwissenschaft und Werkstofftechnik》2014,45(9):793-798
Capacity to reach large deformation at high temperature is an important issue in many forming processes of metallic alloys. It is well known that a low value of the stress exponent (or a concomitant high value of the strain rate sensitivity parameter) is a key point for controlling resistance to necking. A first way for decreasing the stress exponent is to get superplastic properties but it frequently requires dealing with fine microstructures which can be difficult to produce and to preserve. Moreover, in the case of single phase alloys, like aluminum or magnesium alloys, superplastic deformation generally induces damage which can result in premature fracture or damaged components after forming. The aim of this paper is to give some guidelines for promoting high temperature deformation of metallic alloys, with a particular attention given to superplastic forming. The possibility to reduce the temperature of superplastic forming (SPF) for titanium alloys, the capacity to get a better understanding of the specificities of damage process in the case of superplastic deformation and the ability to get large strains to fracture avoiding the production of fine grains before strain are more specifically discussed. 相似文献
62.
A. V. Mikhaylovskaya A. D. Kotov V. S. Levchenko V. K. Portnoy 《Materialwissenschaft und Werkstofftechnik》2014,45(9):822-827
Al–Zn–Mg–Cu aluminum alloy contain 0.3% Zr and 4% Ni was processed by traditional hot and cold rolling with a total reduction from 0 to 80%. The relationship between superplastic behavior and reduction of cold deformation and casting cooling rate was analyzed. It is shown that the decrease in the reduction of cold rolling do not significantly influence on flow stress and elongation. Decrease in casting cooling rate leads to insignificantly decrease in superplastic indicators. Alloy exhibits advanced superplasticity: the elongation of 400–800% at the strain rates of (5 × 10–3–1 × 10–1) s–1. 相似文献
63.
采用实验方法研究国外广泛用于汽车车身板件冷冲压成形的工业牌号铝合金板材AA5182和6016的超塑性能,以及超塑变形中微观组织的演化特征。通过超塑性单向拉伸试验、材料变形前后的微观组织观察和自由胀形试验,揭示出铝合金AA5182具有一定的超塑性能,而铝合金6016的超塑性能很低。铝合金AA5182在温度为375℃、应变速率为1.67×10-3/s时,材料的延伸率达到210%,m值达到0.25;在温度为500℃、应变速率为1.67×10-2/s时,材料延伸率达到225%,m值达到0.35。 相似文献
64.
搅拌摩擦加工AZ31镁合金的超塑性 总被引:1,自引:0,他引:1
对搅拌摩擦加工AZ31镁合金的微观组织和拉伸力学行为进行了研究。结果表明,通过搅拌摩擦加工,热轧AZ31板材的平均晶粒尺寸由92.0μm细化到11.4μm。搅拌摩擦加工板材在高温下具有优异的塑性,伸长率在温度为723K和应变速率为5×10-4s-1的条件下达到1050%。该材料还具有高应变速率超塑性,在723K和1×10-2s-1的条件下伸长率达到268%。在相同实验条件下,母材由于晶粒尺寸粗大,没有显示出超塑性。 相似文献
65.
66.
《中国有色金属学会会刊》2007,17(A01):372-375
67.
68.
M. Vanderhasten L. Rabet B. Verlinden 《Journal of Materials Engineering and Performance》2007,16(2):208-212
A superplastic Ti-6Al-4V grade has been deformed at a strain rate of 5 × 10−4 s−1 and at temperatures up to 1050 °C. Structural mechanisms like grain boundary sliding, dynamic recrystallization, and dynamic
grain growth, occurring during deformation, have been investigated and mechanical properties such as flow stress, strain hardening,
and strain at rupture have been determined. Dynamic recrystallization (DRX) brings on a decrease in the grain size. This could
be of great interest because a smaller grain size allows a decrease in temperature for superplastic forming. For DRX, the
driving force present in the deformed microstructure must be high enough. This means the temperature must be sufficiently
low to ensure storing of enough dislocation energy but must also be high enough to provide the activation energy needed for
DRX and to allow superplastic deformation. The best compromise for the temperature was found to be situated at about 800 °C;
this is quite a bit lower than the 925 °C referenced in the literature as the optimum for the superplastic deformation. At
this medium temperature the engineering strain that could be reached exceeds 400%, a value high enough to ensure the industrial
production of complex parts by the way of the superplastic forming. Microstructural, EBSD, and mechanical investigations were
used to describe the observed mechanisms, some of which are concurrent.
This article was presented at the AeroMat Conference, International Symposium on Superplasticity and Superplastic Forming
(SPF) held in Seattle, WA, June 6-9, 2005. 相似文献
69.
陶瓷材料的超塑性研究 总被引:3,自引:0,他引:3
胡士康 《兵器材料科学与工程》1995,18(2):3-10
介绍了陶瓷材料超塑性研究的现状,陶瓷材料超塑性的主要工艺特点及参数,重点讨论了陶瓷材料超塑性的机理,并指出了其应用前景。 相似文献
70.
通过工艺试验发现,供应态的铍青铜(QBe2)经一定的预处理,可获得良好的超塑性。在550℃和ε=1.67×10~(-3)s~(-1)的应变速率拉伸,合金能呈现大于1000%的高延伸率。文中提出的淬火+时效;淬火+冷轧,淬火+时效+冷轧的三种预处理工艺都能使合金获得超塑性的组织状态。分析和讨论了预处理工艺参数和所需的最佳组织条件。 相似文献