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排序方式: 共有466条查询结果,搜索用时 15 毫秒
1.
《Materials and Manufacturing Processes》2007,22(1):5-8
The technological properties of the hot-work tool steels depend on their microstructural quality induced by the production process and the heat treatment. One of the frequently applied methods to improve microstructure is preheat treatment. The treatment of carbonitriding X37CrMoV5-1 steel has been investigated in fluidized bed furnaces. Thickness and phase composition have been conducted using optical microscopy Neophot 32 and scanning microscopy, JEOL 5400, after etching in nital. 相似文献
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The electroless nickel–phosphorous (Ni–P) coating was chosen as an interlayer to improve the properties of the CrN/mild steel (MS) composite. A hypophosphite-reduced acid solution was used to first deposit electroless Ni–P onto MS substrates, and then the CrN overlayer was deposited by reactive r.f. magnetron sputtering onto the electroless Ni–P modified substrate. The electroless Ni–P layer crystallizes with the precipitation of a Ni3P phase during r.f. sputtering, and thus a coating–substrate composite of CrN/Ni–Ni3P/MS is formed. The electroless Ni–P coating increases the surface hardness of the steel substrate to more than three times. The surface hardness of the CrN coating modified by an electroless Ni–P interlayer exhibits a hardness higher than 2000 HK0.015. The usual substrate effect on the microhardness of the coatings is nearly eliminated with the complex coating feature, and a significant enhancement of surface hardness in the coating assembly is achieved. The corrosion tests indicate that the Ni–Ni3P/MS configuration exhibits a more positive Ecorr value (i.e. less electronegative) than CrN/MS and the corresponding potential curve is shifted toward the low-current side, indicating a better anti-corrosion performance. Through comparison of the Ecorr values and the polarization curves, it is demonstrated that the CrN/Ni–Ni3P/MS composite exhibits significantly higher corrosion resistance than the Ni–Ni3P/MS and CrN/MS coating configurations. 相似文献
4.
Frank N. Jones Weidian Shen Stanley M. Smith Zhihua Huang Rose A. Ryntz 《Progress in Organic Coatings》1997,34(1-4):119-129
Scanning probe microscopy (SPM) is in a period of rapid development. It shows great promise for characterizing coating surfaces. This paper describes modification of an SPM so that it can be used to mar the surfaces of coatings under controlled conditions and to characterize the mars. Mar resistance of coatings is analyzed in terms of a ‘three response, two mechanism model.' The three responses (fracture, elastic, and plastic) can be measured quantitatively using the SPM. Of the three responses, only two (fracture and plastic deformation) are marring mechanisms – elastic deformations recover instantaneously. In some cases mars resulting from plastic deformation may recover slowly with time or with immersion in water; this phenomenon is attributed to viscoelastic creep. Microhardness is also measured with the modified SPM. Some thermoset coatings appear to be substantially harder near their surfaces than in the mass of material, and such materials may respond quite differently to stress applied at different levels near the surface. This finding has important implications for all coating properties that are strongly influenced by the surface. A quantity called ‘micro mar resistance' is defined. It may be useful for comparing different coatings under specified conditions of marring. However, there can be no single quantity that expresses ‘mar resistance' of a coating under all conditions. 相似文献
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Prabhu Ganesan 《Surface & coatings technology》2007,201(18):7896-7904
Compositionally modulated multilayer (CMM) Zn-Ni deposits were electrodeposited from single acidic bath (pH = 4.7) by using a potentiostatic sequence. The Zn and Ni composition in the alloy was tailored as a function of distance from the steel substrate. X-ray diffraction studies of the deposit showed the presence of γ-phase with a composition of Ni5Zn21. The corrosion properties of modulated multilayer coatings were studied in 5% NaCl solution using electrochemical corrosion techniques. The polarization resistance of the deposits varied as a function of Ni content between 1700 and 3440 Ω. CMM Zn-Ni with 20 wt% Ni exposed in ASTM B117 salt spray test did not show any red rust formation after 400 h. 相似文献
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针对5CrMnMo热作模具,选用D397和D337焊条作为堆焊材料,采用直流反接法对其进行手工电弧焊修复.并利用金相显微镜和显微硬度仪观察、测试并分析不同焊接工艺条件下堆焊层的组织形貌、性能和硬度,得出选用D397焊条,可以获得性能优良的焊接接头的结论. 相似文献
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采用非平衡磁控溅射技术在Q235钢基体上制备了TiAlN薄膜,通过精密电子天平、纳米力学探针、划痕测试仪及扫描电镜等测试分析,研究了薄膜氧化动力学行为、薄膜显微硬度和结合力的变化规律及不同温度下氧化后薄膜表面形貌演变规律,探讨了Ti AlN薄膜的抗高温氧化机制。结果表明,在700℃以上TiAlN薄膜的氧化动力学行为服从抛物线规律。随着氧化温度的升高,薄膜的显微硬度和结合力逐渐下降,当氧化温度升高到800℃时,薄膜具有较高的显微硬度和结合力,分别为19.3 GPa和32.1 N,表现出良好的抗高温氧化性能。当氧化温度升高到900℃时,薄膜表面出现了明显的鼓包和裂纹,此时薄膜发生了严重氧化,薄膜已失去对基体的保护作用。 相似文献
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The effects of friction stir processing (FSP) parameters such as rotational, traverse speeds and tool penetration depth on the formation of fine and defect free magnesium layers were investigated. The achieved microstructures were optically studied, and the microhardness profile of the optimised workpiece was measured. The results show that rotational and traverse speeds as well as their ratio play key roles in achieving a sound friction stir processed workpiece of pure Mg. In addition, at constant rotational and traverse speeds, when the penetration depth increases, the title angle must also increases in order to have a defect free workpiece. At optimum conditions, one pass FSP significantly refined the grain size from 3 mm in the as received magnesium to 14·6 μm in friction stir process layer. The microhardness of the fabricated layer reached to about 1·6 times that of the base metal. 相似文献
10.
The identification of welded tubes properties considering the weld bead and Heat Affected Zone (HAZ) is important for reliable and accurate finite element simulation of tubular plastic forming processes such as tube hydroforming and rotary draw bending processes. Therefore, a simplified method is proposed to extract the weld bead and HAZ properties. Full size standard tensile specimens cut from the welded tube and comprising the weld parallel to the load direction are extended to failure. Mechanical properties obtained from uniaxial tensile test are correlated with the microhardness data measured across the welded specimen and by using the rule of mixtures; the constitutive model parameters of weld bead and HAZ regions are identified. Accuracy of the proposed method is assessed by comparing finite element simulation predictions to experimental measurements obtained from two mechanical tests: the first one is the uniaxial tensile test performed on specimens comprising the weld line perpendicular to the loading direction and the second test is the free bulge hydroforming test achieved on seamed tubular samples. This investigation has shown that the presented method is practical in use and sufficiently accurate to extract the weld metal properties of seamed tubes. 相似文献