全文获取类型
收费全文 | 13391篇 |
免费 | 1784篇 |
国内免费 | 486篇 |
专业分类
电工技术 | 402篇 |
综合类 | 778篇 |
化学工业 | 3221篇 |
金属工艺 | 2169篇 |
机械仪表 | 377篇 |
建筑科学 | 312篇 |
矿业工程 | 1587篇 |
能源动力 | 146篇 |
轻工业 | 390篇 |
水利工程 | 30篇 |
石油天然气 | 228篇 |
武器工业 | 89篇 |
无线电 | 715篇 |
一般工业技术 | 1273篇 |
冶金工业 | 3773篇 |
原子能技术 | 59篇 |
自动化技术 | 112篇 |
出版年
2024年 | 53篇 |
2023年 | 185篇 |
2022年 | 364篇 |
2021年 | 497篇 |
2020年 | 517篇 |
2019年 | 347篇 |
2018年 | 376篇 |
2017年 | 425篇 |
2016年 | 493篇 |
2015年 | 551篇 |
2014年 | 783篇 |
2013年 | 820篇 |
2012年 | 971篇 |
2011年 | 947篇 |
2010年 | 711篇 |
2009年 | 733篇 |
2008年 | 564篇 |
2007年 | 802篇 |
2006年 | 799篇 |
2005年 | 705篇 |
2004年 | 626篇 |
2003年 | 562篇 |
2002年 | 514篇 |
2001年 | 438篇 |
2000年 | 380篇 |
1999年 | 302篇 |
1998年 | 244篇 |
1997年 | 184篇 |
1996年 | 142篇 |
1995年 | 98篇 |
1994年 | 103篇 |
1993年 | 63篇 |
1992年 | 87篇 |
1991年 | 68篇 |
1990年 | 34篇 |
1989年 | 38篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 8篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Arthur J. Learn 《Journal of Electronic Materials》1974,3(2):531-552
An investigation of electromigration-induced failure in aluminum alloy films, with the major emphasis on aluminum-copper-silicon,
was conducted. Flash evaporation was utilized for alloy deposition and yielded aluminum-copper films having electromigration
resistance comparable to that of such films prepared by other techniques. Results for aluminum-copper-silicon and aluminum-copper
were similar indicating the passive role of silicon in the presence of copper. Additions of four weight percent copper resulted
in near-optimum electromigration resistance. In addition, hot-substrate deposition was beneficial in attaining greater lifetime.
For films deposited on unheated substrates, or having lower copper contents, heat treatment seriously degraded electromigration
resistance. Heat treatment effects were considered to be a consequence of copper redistribution. Lifetime decrease at large
copper contents and possible saturation at large thicknesses were interpreted in terms of clustering of CuAl2 precipitates. The superior reliability of copper-alloyed metallization when compared with aluminum or aluminum-silicon was
clearly demonstrated. Lifetime improvement could be accounted for by the increased activation energy for the failure process
in the aluminum-copper alloys. 相似文献
932.
闪速炼铜“高效反应区”的形成条件与应用效果 总被引:1,自引:0,他引:1
运用闪速炉反应塔“高效反应区”模型,研究闪速炉操作的优化与强化。结果表明,形成“高效反应区”的主要条件是高温、氧气和颗粒群的集中。“高效反应区”模型在生产中的初步应用获得了显著效果。“高效反应区”的形成有利于强化生产、降低油耗和烟尘率、延长反应塔寿命、提高氧利用率和铜直收率。 相似文献
933.
934.
The adhesive characteristics and the formation of phase boundaries in the Cr Cu system in a vacuum of (2-4)·10–3 Pa in the temperature range 1100-1300°C have been studied. The microstructure of composites (50:50 by mass) made by copper impregnation of porous samples of Cr electrolytic powders and Cr obtained by calcium hydride reduction. The effect of Cr, Fe, Co, Ni, Si additions on above characteristics has been investigated. 相似文献
935.
两步电镀铜对Cf/Cu复合材料的复合效果的影响 总被引:11,自引:1,他引:10
通过对碳纤维表面进行空气热氧化短处理,然后采用两步镀铜法对纤维表面进行电镀铜,有效的避免了普通镀铜方法中常见的“黑心”现象,使得纤维束内部单丝获得了均匀连续的镀铜层,而且纤维与镀铜层之间结合牢固.经两步镀铜处理后的碳纤维复合丝与铜基体复合后,碳纤维/铜复合材料中常见的严重纤维偏聚现象得到很大改善,获得了Cf/Cu界面结合良好,纤维分布均匀的铜基复合材料. 相似文献
936.
甘肃公婆泉铜矿化集中区火山岩的地球化学特征 总被引:2,自引:1,他引:1
公婆泉铜矿化集中区产出中性一基性和中酸性两大类型火山岩.前者稀土元素总量低,轻度富集轻稀土,弱铕亏损,轻、重稀土分馏均不明显,亲石元素的强不相容元素及Ce,Sm富集,而Nb,Ta亏损,Th/Yb,Hf/Th,La/Ta,Ti/Zr和K分别为0.7—1.4,1.3—1.6,33—50,34—83和14—20;后者稀土元素轻稀土富集,弱一强铕亏损,轻稀土分馏较明显而重稀土分馏不明显,强不相容元素富集,而Nb,P,Ti等亏损,Ti/Zr,Hf/Nb和K值分别为38—50,1.1—2.5和4.5—26.它们属于岛弧型钙碱性玄武岩一安山岩一流纹岩产出的构造环境,由地慢楔形源区玄武岩浆结晶分异演化形成.各类火山岩特别是钾质中酸性火山岩中成矿元素Cu及其主要伴生元素Au,Ag,Pb,Zn和As等富集,说明其受到了成岩后火山或次火山热液的叠加作用. 相似文献
937.
The three main methods for oxidation of metallic substrates, thermal, anodic and plasma have been applied to a copper, titanium, and zirconium alloy and its corresponding binaries (Cu–33Ti–33Zr, Cu–50Ti, Cu–50Zr and Ti–50Zr). Polished polycrystalline samples of these alloys were examined before treatment, after vacuum thermal annealing at 100°C and heating in 20 mTorr oxygen at 100, 200, and 300°C. ISS depth profiles were taken of selected samples. The least-noble component oxidizes first, but at high temperatures and with plasma oxidation the noble component segregates to the surface. A comparison of the resulting structures on the ternary and binary alloys with different oxidation methods is used to explore the physico-chemical processes during oxidation. Results from these three methods are discussed in terms of physical/chemical parameters that influence the chemical nature and structure of the resulting oxides. The electrochemical processes that occur during the materials reaction with a chosen environment are used to discuss the physical and chemical mechanisms involved. Intrinsic (thermal and plasma oxidation) and extrinsic (electrochemical oxidation) electric fields are shown to influence the chemical and structural nature of the resulting oxide structures. The influence of transport phenomena is discussed. 相似文献
938.
A method for predicting the optical constants and the radiative properties of metals and heat mirror films, by introducing an expression for the damping frequency in the Drude model, is described. The directional emissivity of aluminum predicted by this method agrees well with the classical experimental values given by Schmidt and Eckert. The prediction of the normal emissivity of indium–tin–oxide (ITO) heat mirror films is in agreement with our measured results. The directional emissivity of copper predicted using this method is reported. The calculated result of the spectrum normal emissivity of copper at 4 m and 20°C is also given, which supports the measured result. The values for the directional emissivity of aluminum calculated by using various methods based on the Hagen–Rubens relation are reported, and the values do not agree with the experimental results. 相似文献
939.
940.