全文获取类型
收费全文 | 16914篇 |
免费 | 1077篇 |
国内免费 | 841篇 |
专业分类
电工技术 | 1059篇 |
综合类 | 787篇 |
化学工业 | 5341篇 |
金属工艺 | 1636篇 |
机械仪表 | 626篇 |
建筑科学 | 926篇 |
矿业工程 | 175篇 |
能源动力 | 250篇 |
轻工业 | 947篇 |
水利工程 | 58篇 |
石油天然气 | 475篇 |
武器工业 | 109篇 |
无线电 | 1478篇 |
一般工业技术 | 1976篇 |
冶金工业 | 536篇 |
原子能技术 | 301篇 |
自动化技术 | 2152篇 |
出版年
2024年 | 58篇 |
2023年 | 241篇 |
2022年 | 557篇 |
2021年 | 599篇 |
2020年 | 445篇 |
2019年 | 399篇 |
2018年 | 320篇 |
2017年 | 402篇 |
2016年 | 518篇 |
2015年 | 532篇 |
2014年 | 760篇 |
2013年 | 953篇 |
2012年 | 990篇 |
2011年 | 1257篇 |
2010年 | 990篇 |
2009年 | 1078篇 |
2008年 | 989篇 |
2007年 | 1174篇 |
2006年 | 1080篇 |
2005年 | 830篇 |
2004年 | 683篇 |
2003年 | 606篇 |
2002年 | 532篇 |
2001年 | 411篇 |
2000年 | 356篇 |
1999年 | 288篇 |
1998年 | 229篇 |
1997年 | 181篇 |
1996年 | 164篇 |
1995年 | 109篇 |
1994年 | 94篇 |
1993年 | 108篇 |
1992年 | 85篇 |
1991年 | 74篇 |
1990年 | 64篇 |
1989年 | 64篇 |
1988年 | 45篇 |
1987年 | 41篇 |
1986年 | 54篇 |
1985年 | 56篇 |
1984年 | 46篇 |
1983年 | 39篇 |
1982年 | 35篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1978年 | 35篇 |
1977年 | 39篇 |
1976年 | 43篇 |
1975年 | 48篇 |
1974年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Effects of austenitizing treatment temperatures on aqueous corrosion properties of martensitic stainless steels were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy), and surface analyses (optical microscopy and XRD). The results of potentiodynamic test revealed that the breakdown potential increased with the increased austenitizing temperature, indicating increased relative resistance to initiation of localized corrosion. EIS measurements showed that MSS3 (1030 °C) exhibits larger polarization resistance value than MSS1 (970 °C) and MSS2 (1000 °C) at passive and breakdown states. This was caused by decreasing the amount of Cr-rich M23C6 carbide which acts as preferential sites for pitting corrosion. 相似文献
22.
介绍了在Window系统中设计兼容IPv4及IPv6的网络程序的方法,并给出了用WinsockAPI编程的具体步骤。 相似文献
23.
Influence of Ni Interlayers on the Mechanical Properties of Ti6Al4V/(WC-Co) Friction Welds 总被引:2,自引:0,他引:2
M. Shamanian M. Salehi A. Saatchi T. H. North 《Materials and Manufacturing Processes》2003,18(4):581-598
Ni interlayers were introduced prior to dissimilar friction welding of Ti6Al4V base material to three cemented carbide substrates. The fracture strength of Ti6Al4V/(WC-6 wt% Co) welds were poor and were markedly improved when 20-µm thick Ni interlayers were introduced prior to dissimilar friction welding. These results were only produced when the (WC-6 wt% Co) cermet was electroplated prior to friction welding. When the Ti6Al4V alloy was electroplated prior to friction welding, fractured WC particles and cracking were observed in the (WC-Co) carbide substrate. The fracture strengths of Ti6Al4V/(WC-11 wt% Co) and Ti6Al4V/(WC-24 wt% Co) welds were not improved when 20-µm thick Ni interlayers were introduced prior to friction welding. During mechanical testing, the Ni layer retained at the dissimilar joint interface created a region of weakness. 相似文献
24.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献
25.
26.
27.
2,6-二甲基萘生产技术进展 总被引:2,自引:0,他引:2
许杰 《精细石油化工进展》2003,4(2):44-47
概述了国外2,6-二甲基萘生产技术现状,详细介绍了ExxonMobil公司2,6-二甲基萘的工艺路线和日本神户制钢所的提纯方法,指出了实现我国2,6-二甲基萘工业化生产应注意的问题。 相似文献
28.
29.
S. J. Pearton K. P. Lee M. E. Overberg C. R. Abernathy N. Theodoropoulou A. F. Hebard R. G. Wilson S. N. G. Chu J. M. Zavada 《Journal of Electronic Materials》2002,31(5):336-339
High concentrations (0.1–5 at.%) of Mn or Fe were introduced into the near-surface region (≤2000 Å) of 6H-SiC substrates by direct implantation at ~300°C. After annealing at temperatures up to 1000°C, the structural properties were examined by transmission electron microscopy (TEM) and selected-area diffraction pattern (SADP) analysis. The magnetic properties were examined by SQUID magnetometry. While the Mn-implanted samples were paramagnetic over the entire dose range investigated, the Fe-implanted material displayed a ferromagnetic contribution present at <175 K for the highest dose conditions. No secondary phases were detected, at least not to the sensitivity of TEM or SADP. 相似文献
30.
从催化裂化柴油中分离高纯度2,6-二甲基萘 总被引:3,自引:0,他引:3
以大庆石油化工总厂炼油厂催化柴油为原料 ,通过精馏分离得到二甲基萘 (DMN)窄馏分 (2 5 8~ 2 70℃ ) ,经糠醛溶剂抽提 ,减压蒸馏后 ,在 -10~ -2 5℃冷冻 2~ 5h ,离心分离制得纯度约 80 %的粗 2 ,6 DMN ,再经无水乙醇在 -10~ -2 5℃重结晶 ,得到纯度大于等于 98%的 2 ,6 DMN。 相似文献