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91.
92.
Daniel T. Rooney Louis Gullo Dongji Xie N. Todd Castello Dongkai Shangguan 《Microelectronics Reliability》2007,47(12):2152-2160
This paper presents a study of the optimization of the gold plating thickness for the use of both wire bonding and soldered interconnects on a flexible printed circuit board sample module. Wire bondability is typically better, when the gold plating thickness is greater than 30 μin.; however, the risk of problems with solder joint embrittlement becomes a concern with thick gold plating. In order to better understand the effect of the gold plating thickness on wire bondability and solder joint embrittlement, an evaluation was performed on samples with three ranges of gold plating thicknesses (10–20 μin., 20–30 μin., and 30–45 μin.), on flexible printed circuit board (PCB), substrates. Mechanical shear testing and metallurgical analyses were conducted on chip component solder joints in this three thickness gold study. Thermal shock and drop testing were conducted to evaluate the reliability of the sample modules. Drop testing is especially critical for determining the reliability of the sample modules, which are used in portable consumer electronics products. Reliability testing and metallurgical analyses have been performed to characterize the effect of gold embrittlement on the mechanical integrity of the solder joints with a gold content ranging from 1 to 4 wt.%. 相似文献
93.
Caolong Li Jian YuanBingyan Han Wenfeng Shangguan 《International Journal of Hydrogen Energy》2011,36(7):4271-4279
Novel CdS nanomaterials were synthesized by a simple “one-pot” hydrothermal biomolecule-assisted method using glutathione (GSH) as the sulfur source and structure-directing reagent. Various morphologies of CdS photocatalysts, such as solid nanospheres (s-CdS), hollow nanospheres (h-CdS) and nanorods (r-CdS), were obtained by controlling only the hydrothermal temperatures. The X-ray diffraction patterns confirmed that all of the samples were typical hexagonal wurtzite CdS. It was found that the absorption edge of s-CdS was at 465 nm with a greater blue shift compared to that of h-CdS and r-CdS. The photocatalytic activity of s-CdS was superior to that of h-CdS and r-CdS under visible light. Photoluminescence measurements revealed their different photogenerated electron/hole recombination ability, which was in accordance with the order of s-CdS < h-CdS < r-CdS. The excellent photocatalytic activity of s-CdS was ascribed to the small sizes of sub-nanocrystallites, which make it easy for photoinduced electrons and holes on the solid sphere to migrate to the surface and react with water and the sacrificial agent quickly. It was crucial to control the temperature for preparing CdS photocatalysts via hydrothermal methods. The formation mechanism of different morphology might be due to complexation, S-C bond rupture, spherical aggregation and Ostwald ripening processes. 相似文献
94.
95.
忻州市现有五座中型水库不同程度地存在防洪标准低,坝体填筑质量差,坝基、坝肩渗漏严重,观测、管理配套孕施不健全等问题,结合除险加固工程实践,通过对水库病险成因的分析,阐述了相应的加固措施。 相似文献
96.
The effect of oxygen concentration on the catalytic reaction of NOx with soot over BaAl2O4 has been studied by Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS). The introduction of O2 into the NO flow can result in a reactant mixture of NO/NO2/O2. Increasing the O2 concentration from 2 % to 5 % in the NO‐containing flow promotes the formation of NO2 from the gas phase oxidation of NO. The reactant mixture with high O2/NO flow, allows for the formation of greater amounts of nitrate species than that with low O2/NO flow, which further promotes the reaction of soot with NOx and leads to a high conversion efficiency of NOx into N2 and N2O. In the absence of O2, N2O is not observed since the N2O produced at high temperatures has reacted with soot before it can be detected. 相似文献
97.
丙烯腈装置用25%乙二醇溶液(盐水)作为载冷刺,将装置产生的热量带走.运行18年至今,局部盐水管线出现腐蚀渗漏.分析了乙二醇的性质,并针对腐蚀部位从吸氧腐蚀和电偶腐蚀两方面分析了盐水管线产生腐蚀的原因,并提出应对措施. 相似文献
98.
Shangguan Hao-long Kang Jin-wu Yi Ji-hao Deng Cheng-yang Hu Yong-yi Huang Tao 《中国铸造》2018,15(3):210-215
3D printing technology has been used for sand molding and core printing, but they simply substitute the traditional molding and core making method without changing the shape or size of the sand mold(core) and their dense structure. In this study, a new type of hollow mold based on 3D printing is presented. The new type of mold is a rib reinforced thickness-varying shell mold. This mold design can realize the controlled cooling of castings, i.e., different cooling rates at different areas, and improve the temperature uniformity of a casting after its solidifi cation. Therefore, the performance of castings can be improved and their residual stress and deformation can be reduced. This kind of new mold was applied to a stress frame of A356 aluminum alloy. The 3D printed rib reinforced thickness-varying shell mold was compared with the traditional dense mold, and the castings obtained by these two kinds of molds were also compared. The experimental results showed that the rib reinforced shell mold increased the cooling rate of the casting by 30%, tensile strength by 17%, yield strength by 11%, elongation by 67%, and decreased its deformation by 43%, while sand consumption was greatly reduced by 90%. 相似文献
99.
基于BP神经网络,以挤压速度、挤压道次和挤压方式为输入层参数,以抗拉强度为输出层参数,构建了BP神经网络模型用于分析ECAP强变形对Cu-3Cr合金性能影响,并进行了试验验证以及金相组织和SEM分析。结果表明,BP神经网络输出的抗拉强度预测值与试验值之间的相对误差均小于2%,平均预测误差为1.4%,模型的预测精度高、实用性强。从改善合金抗拉强度出发,Cu-3Cr合金的最佳ECAP工艺参数:挤压速度为5mm/s、挤压道次为4次、挤压方式为每次挤压后旋转180°再进入下一道次。 相似文献
100.
MgO-CaO陶瓷抗热震稳定性研究 总被引:1,自引:0,他引:1
采用应力设计及热膨胀失配的原理,从微观结构入手,通过调整颗粒配比(粗颗粒的临界粒径、熟料细粉含量及中间颗粒含量)制备MgO-CaO陶瓷试样;探讨了颗粒配比、显气孔率等因素对试样体积密度、抗热冲击性能及热冲击对试样抗折强度的影响.实验结果表明:适当的颗粒级配使得MgO-CaO陶瓷中,颗粒与基质之间存在一定的残余应力,基质与气孔中气体之间存在热膨胀系数差异;当热震损伤产生的裂纹遇到颗粒及气孔时会发生偏转、分岔和钉扎,从而有效地改善MgO-CaO陶瓷的抗热震稳定性能. 相似文献