全文获取类型
收费全文 | 67657篇 |
免费 | 5095篇 |
国内免费 | 3476篇 |
专业分类
电工技术 | 1222篇 |
技术理论 | 5篇 |
综合类 | 5075篇 |
化学工业 | 3384篇 |
金属工艺 | 18095篇 |
机械仪表 | 3271篇 |
建筑科学 | 15801篇 |
矿业工程 | 1239篇 |
能源动力 | 1027篇 |
轻工业 | 1129篇 |
水利工程 | 817篇 |
石油天然气 | 2090篇 |
武器工业 | 439篇 |
无线电 | 421篇 |
一般工业技术 | 7019篇 |
冶金工业 | 14342篇 |
原子能技术 | 416篇 |
自动化技术 | 436篇 |
出版年
2024年 | 159篇 |
2023年 | 686篇 |
2022年 | 1668篇 |
2021年 | 1887篇 |
2020年 | 2042篇 |
2019年 | 1526篇 |
2018年 | 1277篇 |
2017年 | 2087篇 |
2016年 | 2153篇 |
2015年 | 2459篇 |
2014年 | 4294篇 |
2013年 | 3735篇 |
2012年 | 4901篇 |
2011年 | 5690篇 |
2010年 | 4300篇 |
2009年 | 4440篇 |
2008年 | 3538篇 |
2007年 | 4577篇 |
2006年 | 4076篇 |
2005年 | 3398篇 |
2004年 | 2828篇 |
2003年 | 2435篇 |
2002年 | 2087篇 |
2001年 | 1744篇 |
2000年 | 1525篇 |
1999年 | 1243篇 |
1998年 | 998篇 |
1997年 | 944篇 |
1996年 | 801篇 |
1995年 | 586篇 |
1994年 | 531篇 |
1993年 | 366篇 |
1992年 | 318篇 |
1991年 | 221篇 |
1990年 | 185篇 |
1989年 | 158篇 |
1988年 | 105篇 |
1987年 | 56篇 |
1986年 | 37篇 |
1985年 | 29篇 |
1984年 | 19篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 39篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1959年 | 10篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
Utilizing the existing properties of steel, a modern technological society has been constructed. While there are over 25,000
worldwide equivalent steels based on manipulating the eutectoid transformation, there exist only a handful of commercial nanostructured
steel alloys based on manipulating the more complex glass devitrification transformation. Thus, research on nanostructured
steels is in its infancy, and many further developments are expected with the demonstrated promise of developing new combinations
of superior properties. In this article, seven enabling metallurgical factors are presented that ultimately allow a variety
of nanostructured steel products to be produced in an ever-increasing array of industrial processing techniques. Additionally,
a case example of the formation of nanostructured steel are given showing how these factors can be harnessed on an industrial
scale. 相似文献
172.
DD—921钢铁常温发黑剂的研制和应用 总被引:4,自引:0,他引:4
研究了钢铁常温发黑过程的成膜机理,各组分之间的作用以及相互之间的影响,着重分析了常温发黑的优缺点,工艺控制参数以及经济性。 相似文献
174.
介绍了浮动芯棒、限动芯棒和三辊式限动芯棒连轧管工艺的发展历程。分析了各种型式连轧管机的适用条件;并认为,各种机型装备的发展与市场需求紧密相关,单纯从技术上考虑,而追求同一机型不能带来良好的经济效益 相似文献
175.
In this paper, the author dipped surface vapor oxidized H13 steel specimens into 700℃ molten aluminum liquid for a certain period of time. Analyze the intermetallic phases formed on the H13 samples surface with optical microscope and X-ray diffraction method. The observation of immersion test sample's cross-section shows that Fe3O4 film will protect die substrate from molten aluminum erosion. The identification of the intermetallic phases reveals that they consist of 2parts, which is named as the composite layer and the compact layer. Further investigations are made in order to know the phase constituents of the 2 layers, they are Al8Fe2Si (outer composite layer), (AlCuMg) and Al5Fe2 (compact layer),respectively. The experimental results show that on the same specimen, a convex surface with bigger radius of curvature is more likely to be molten and the melting loss speed is also faster than a flat and smooth surface. The thickness of compact layer on a smooth surface is much bigger than that of the convex surface. Therefore, the author supposes the compact layer is favorable in stabilizing the die surface material from further melting loss, as their formation on the die surface, the melting loss speed will decrease. 相似文献
176.
IntroductionSLlperalloyandheat-resistingsteelarenowwidelyusedasstructurematerialsinaerospace,a\-lationalldshipbuildingindustries.Nickel-basesuperalloywasfirstlyrevealedasanengineeringmaterialduringtheearly1960swhenitwasrecognizedasbeingsuitableforllledium-temperaturegasturbinel'l.Now.nickel-basesuperalloyhasbeenpracticallyusedinhigheffectiveturbinestosatisfytheincreasingdemandsforhighertemperatureenvironmentsIZI.Insomeaerospaceengines,theimpellersshouldserveattemperatureof1000C~1100C,andala… 相似文献
177.
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
178.
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
179.
实际运行的压力钢管可能存在腐蚀进而破裂、泄漏的隐患,因此需要开展在役的压力钢管实时安全监测方法研究,实现对泄漏的及时定位、报警。本文基于F-OTDR光纤干涉原理的振动监测方法,开展了模拟压力钢管泄漏的室内试验,系统研究不同泄流条件下的分布式光纤的检测结果。试验结果表明,随着泄流孔孔径的增加和泄流量的增加,泄漏引起的振动信号强度增加,但是由于系统初始扰动能量的存在,仅依据数据分析,难以判断极小泄流量引起的振动信号。本实验中,当泄流量大于1.00L/s时,分布式光纤检测效果较好。 相似文献
180.
考虑钢铁企业钢材生产受钢材需求和生产变动成本波动的双重影响,在预测基础上,建立钢材生产库存多期动态优化模型。由于模型涉及多种钢材及多个时段,属于大规模问题,求解困难,且为了避免粒子群算法陷入局部最优,提出采用模拟退火与粒子群组合智能算法对模型进行求解。最后通过钢铁企业L的案例,结果表明算法具有较强的收敛性和适用性,模型可用于解决钢铁企业多期生产实际问题。 相似文献