全文获取类型
收费全文 | 108887篇 |
免费 | 7979篇 |
国内免费 | 4490篇 |
专业分类
电工技术 | 1722篇 |
技术理论 | 5篇 |
综合类 | 10667篇 |
化学工业 | 6283篇 |
金属工艺 | 18799篇 |
机械仪表 | 3642篇 |
建筑科学 | 39055篇 |
矿业工程 | 2105篇 |
能源动力 | 1542篇 |
轻工业 | 1286篇 |
水利工程 | 5675篇 |
石油天然气 | 2210篇 |
武器工业 | 554篇 |
无线电 | 545篇 |
一般工业技术 | 10405篇 |
冶金工业 | 15662篇 |
原子能技术 | 490篇 |
自动化技术 | 709篇 |
出版年
2024年 | 258篇 |
2023年 | 967篇 |
2022年 | 2398篇 |
2021年 | 2728篇 |
2020年 | 2910篇 |
2019年 | 2116篇 |
2018年 | 2010篇 |
2017年 | 3045篇 |
2016年 | 3207篇 |
2015年 | 3802篇 |
2014年 | 7010篇 |
2013年 | 5456篇 |
2012年 | 7648篇 |
2011年 | 8732篇 |
2010年 | 6768篇 |
2009年 | 7455篇 |
2008年 | 6415篇 |
2007年 | 8044篇 |
2006年 | 7002篇 |
2005年 | 5942篇 |
2004年 | 4790篇 |
2003年 | 4156篇 |
2002年 | 3571篇 |
2001年 | 2875篇 |
2000年 | 2463篇 |
1999年 | 1952篇 |
1998年 | 1463篇 |
1997年 | 1327篇 |
1996年 | 1112篇 |
1995年 | 834篇 |
1994年 | 738篇 |
1993年 | 509篇 |
1992年 | 437篇 |
1991年 | 287篇 |
1990年 | 228篇 |
1989年 | 207篇 |
1988年 | 139篇 |
1987年 | 82篇 |
1986年 | 42篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 31篇 |
1982年 | 34篇 |
1981年 | 16篇 |
1980年 | 55篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1975年 | 5篇 |
1964年 | 4篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
IntroductionSLlperalloyandheat-resistingsteelarenowwidelyusedasstructurematerialsinaerospace,a\-lationalldshipbuildingindustries.Nickel-basesuperalloywasfirstlyrevealedasanengineeringmaterialduringtheearly1960swhenitwasrecognizedasbeingsuitableforllledium-temperaturegasturbinel'l.Now.nickel-basesuperalloyhasbeenpracticallyusedinhigheffectiveturbinestosatisfytheincreasingdemandsforhighertemperatureenvironmentsIZI.Insomeaerospaceengines,theimpellersshouldserveattemperatureof1000C~1100C,andala… 相似文献
52.
Zinc Coated Steel/Epoxy Adhesive Systems: Investigation of the Interfacial Zone by FTIR Spectroscopy
The present study takes advantage of the ability of Fourier Transform Infrared Spectroscopy (FTIR) for the analysis of ultrathin organic films on metals. FTIR in the reflection mode (IRRAS) is used in order to study the interaction of ultrathin films of dicyandiamide (hardener of most one-pack epoxy resins) with various substrates, model ones such as gold or zinc and industrial ones such as steel and zinc-coated steels.
Pure zinc surfaces and, to a lesser extent, zinc-coated steels are shown to react with dicyandiamide after heating at 180°C, as evidenced by the frequency shift of the absorption band (at about 2200 cm-1) characteristic for nitrile groups. As real systems consist of thick layers of a fully formulated adhesive cured onto a metallic substrate, the direct investigation of such a buried interphase is no longer possible by FTIR and by most of the known spectroscopies. Some mechanically tested specimens are then analysed, after failure, by FTIR microspectrometry. The spectra obtained, corresponding to the fracture initiation zone which is about 100 μm in diameter, advocate for the presence of an ultrathin layer of modified polymer still covering the substrate. 相似文献
Pure zinc surfaces and, to a lesser extent, zinc-coated steels are shown to react with dicyandiamide after heating at 180°C, as evidenced by the frequency shift of the absorption band (at about 2200 cm-1) characteristic for nitrile groups. As real systems consist of thick layers of a fully formulated adhesive cured onto a metallic substrate, the direct investigation of such a buried interphase is no longer possible by FTIR and by most of the known spectroscopies. Some mechanically tested specimens are then analysed, after failure, by FTIR microspectrometry. The spectra obtained, corresponding to the fracture initiation zone which is about 100 μm in diameter, advocate for the presence of an ultrathin layer of modified polymer still covering the substrate. 相似文献
53.
列举了业主规定的压型钢板的涂装配套及膜厚要求,介绍了锌加的涂装工艺、安全与环保、质量检验。 相似文献
54.
55.
56.
57.
碳钢贮热水箱长期在30~80°C温变的热水环境中工作,易受到热水及水中杂质的腐蚀。研究了不同温度下Q235钢在自来水及含100μg/mLNaCl的自来水中的腐蚀速率。对裸钢及其涂覆相同厚度的不同涂层──酚醛环氧(自制)、钛纳米聚合物和改性聚乙烯后在70°C自来水中的极化曲线进行了比较。采用动电位扫描极化曲线测量和电化学交流阻抗谱法(EIS)分别对涂覆不同涂层的Q235钢进行了耐蚀性能研究。结果表明,3种防腐涂层均具有较佳的抗热水性,耐蚀能力较强,适宜对Q235钢贮热水箱进行防护。 相似文献
58.
The corrosion and inhibition behavior of mild steel in 1 M HCl in the presence of poly(4-vinylpyridine)(P4VP) and potassium iodide (KI) was investigated using weight loss measurements, potentiodynamic polarization studies and impedance measurements. The inhibition efficiency increased with increasing P4VP concentration. The inhibiting action of P4VP is considerably enhanced by the addition of potassium iodide. The adsorption of this compound either alone or in combination with iodide ions on the metal surface is found to obey Lamgmir's adsorption isotherm. The experimental results suggest that the presence of iodide ions in the solution increases the surface coverage and, therefore, indicate the joint adsorption of P4VP and iodide ions. On the other hand, it was found that the inhibiting effect of P4VP and (P4VP + KI) increased with increasing temperature of the corrosion medium. The presence of these species in the solution decreases the double layer capacitance and increases the charge transfer resistance, both derived from Nyquist plots obtained from a.c. impedance studies. The variation of charge transfer resistance with time suggests that the inhibitive action of (P4VP + KI) depends mainly on the protective inhibitor film formed on the steel surface. 相似文献
59.
60.
Polyaniline emeraldine base/epoxy resin (EB/ER) coating was investigated for corrosion protection of mild steel coupled with copper in 3.5% NaCl solution. EB/ER coating with 5-10 wt% EB had long-term corrosion resistance on both uncoupled steel and copper due to the passivation effect of EB on the metal surfaces. During the 150 immersion days, the impedance at 0.1 Hz for the coating increased in the first 1-40 days and subsequently remained constant above 109 Ω cm2, whereas that for pure ER coating fell below 106 Ω cm2 after only 30 or 40 days. Immersion tests on coated steel-copper galvanic couple showed that EB/ER coating offered 100 times more protection than ER coating against steel dissolution and coating delamination on copper, which was mainly attributed to the passive metal oxide films formed by EB blocking both the anodic and cathodic reactions. Salt spray tests showed that 100 μm EB/ER coating protected steel-copper couple for at least 2000 h. 相似文献