全文获取类型
收费全文 | 2453篇 |
免费 | 265篇 |
国内免费 | 540篇 |
专业分类
电工技术 | 16篇 |
综合类 | 124篇 |
化学工业 | 87篇 |
金属工艺 | 1542篇 |
机械仪表 | 152篇 |
建筑科学 | 32篇 |
矿业工程 | 17篇 |
能源动力 | 28篇 |
轻工业 | 11篇 |
水利工程 | 5篇 |
石油天然气 | 20篇 |
武器工业 | 22篇 |
无线电 | 93篇 |
一般工业技术 | 672篇 |
冶金工业 | 322篇 |
原子能技术 | 24篇 |
自动化技术 | 91篇 |
出版年
2024年 | 38篇 |
2023年 | 75篇 |
2022年 | 119篇 |
2021年 | 135篇 |
2020年 | 96篇 |
2019年 | 102篇 |
2018年 | 118篇 |
2017年 | 106篇 |
2016年 | 79篇 |
2015年 | 96篇 |
2014年 | 119篇 |
2013年 | 148篇 |
2012年 | 163篇 |
2011年 | 176篇 |
2010年 | 105篇 |
2009年 | 127篇 |
2008年 | 100篇 |
2007年 | 126篇 |
2006年 | 158篇 |
2005年 | 110篇 |
2004年 | 87篇 |
2003年 | 104篇 |
2002年 | 117篇 |
2001年 | 85篇 |
2000年 | 79篇 |
1999年 | 96篇 |
1998年 | 76篇 |
1997年 | 49篇 |
1996年 | 54篇 |
1995年 | 27篇 |
1994年 | 27篇 |
1993年 | 42篇 |
1992年 | 22篇 |
1991年 | 14篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有3258条查询结果,搜索用时 15 毫秒
991.
M. Okazaki M. Okamoto & Y. Harada 《Fatigue & Fracture of Engineering Materials & Structures》2001,24(12):855-865
It is important to control the interface strength of coatings and composite materials; a feature that has been noted for many years. However, how can interface strength be evaluated and controlled? In order to explore this aspect, subcritical fatigue crack growth behaviour was investigated along the interface of a CoNiCrAlY coated Ni‐Base superalloy. According to the traditional fatigue test methodology, fatigue crack propagation tests were carried out, using double cantilever beam specimens. The resistance to the fatigue crack propagation was successfully evaluated by a fracture mechanics approach. Particular attention was given to the effects of surface finish of the substrate as a coating parameter, the test temperature, and long‐term thermal ageing after the coating. 相似文献
992.
Y. Itoh M. Saitoh K. Takaki & K. Fujiyama 《Fatigue & Fracture of Engineering Materials & Structures》2001,24(12):843-854
This study concerns MCrAlY coatings (M is Ni, Co or both) sprayed by a vacuum plasma spraying process for protection against high-temperature corrosion and oxidation of gas turbine components, such as turbine blades and duct segments. The effect of high-temperature protective coatings on fatigue lives of nickel-based superalloys were investigated at high temperature under push–pull loading and rotary bending and then compared with uncoated superalloys, such as equiaxed IN738LC, unidirectional solidified CM247LC and single-crystal CMSX-2. The high-cycle fatigue lives of MCrAlY-coated superalloys at high temperature under push–pull loading showed an inferior performance when compared with the uncoated superalloys. This was because the crack initiation site was different. The high-cycle fatigue cracks of nickel-based superalloys initiated at casting cavities which were exposed on the specimen surface, whereas the high-cycle fatigue cracks of MCrAlY-coated specimens initiated at interface defects, such as small pores and grid residue, between the MCrAlY coating and the substrate and grew into the MCrAlY coating, and then into the substrate. Similarly, the rotary bending fatigue properties of MCrAlY-coated superalloys at high temperature showed an inferior performance when compared with the uncoated superalloys. This is because of a high stress due to the higher Young's modulus of the MCrAlY coating (in comparison with the substrate) being induced at the MCrAlY coating surface. The crack initiation site was on the specimen surface in both cases of the nickel-based superalloys and the MCrAlY-coated superalloys, respectively. As a result, it was considered that, for rotary bending tests, the fatigue life reduction was due to the high stress that originated from the difference of elastic constants between the MCrAlY coating and the superalloy. Consequently, in fatigue life design it is necessary to take account of the stress levels in a coating layer. 相似文献
993.
994.
995.
全导流95-Ⅱ型塔板上液层温度分布与板效率 总被引:1,自引:1,他引:0
引 言塔板是塔器中传质、传热最重要的元件之一 .近几十年来 ,开发大通量、高效率、低压降、低能耗的新型塔板一直是人们努力的方向 .在综合分析已有各种塔板结构性能的基础上 ,通过热力学熵增速率分析法[1] ,张志炳等开发出了 95 Ⅰ型大通量塔板[2 ] ,有关该塔板的详细介绍见文献 [3].为了进一步提高塔板效率 ,本文提出了一种全导流 95 Ⅱ型塔板结构 ,并对其进行性能实验 ,以得到板上液层的温度分布与板效率值 ,并且与 95 Ⅰ型塔板的板效率值进行了比较 .1 实验部分1 1 95 Ⅱ型塔板结构及其全导流板的设置95 Ⅱ型塔板的平面结构如… 相似文献
996.
CONTROL TECHNIQUES公司MENTOR II系列直流调速单元在很多行业获得应用,文章介绍运行在Windows 95环境的主机利用串行接口和直流驱动器的通讯程序设计。 相似文献
997.
The thermal fatigue behavior of a single crystal superalloy SRR99 was investigated.Specimens with V-type notch were tested at the peak temperatures of 900,1000,and 1100℃.The crack growth curves as a function of the number of cycles were plotted.With the increase of peak temperature,the crack initiation life was shortened dramatically.Through optical microscopy (OM) and scanning electron microscopy (SEM) observation,it was found that multiple small cracks nucleated at the notch tip region but only one or two of them continued to develop in the following thermal cycles.The primary cracks generally propagated along a preferential direction.Microstructure changes after thermal fatigue were also discussed on the basis of SEM observation. 相似文献
998.
研究了电场处理后的长期时效GH4199合金在不同应变速率下的拉伸变形行为.结果表明,随应变速率增加合金屈服强度升高,应变速率低于3.3×100 s-1时,应变速率敏感指数m值较低且随应变速率的增加无明显变化;当应变速率超过3.3×100 s-1时,m显著升高,当应变速率为3.3×101 s-1时,m达到0.16;随应变速率增加合金拉伸塑性呈下降趋势;在较低应变速率范围内变形时,电场处理后产生的退火孪晶是改善合金塑性的主要因素,随着应变速率的提高,晶内开动的滑移系数量增加,塑性变形能力随之提高,但存在于合金晶界处的连续分布的碳化物对晶界的弱化作用逐渐显露,晶界与晶内塑性变形能力差异增大,晶界成为断裂的主要途径,导致合金塑性降低. 相似文献
999.
热处理态NiCoCrAlY涂层的抗中性盐雾腐蚀性能 总被引:1,自引:0,他引:1
通过500 h中性盐雾试验研究了在低膨胀高温合金GH907上低压等离子喷涂(LPPS)的NiCoCrAlY涂层在热处理后的抗腐蚀性能,并与热处理态的LPPS制备的NiCr涂层的抗腐蚀性能进行了对比.结果表明,盐雾腐蚀500 h后,NiCoCrAlY涂层在扫描电镜下可以看到几个无破坏性作用的腐蚀坑,涂层表面仍保持较好的完整性和光洁性,对腐蚀产物的EDS面扫描表明腐蚀产物主要为Al的氧化物,涂层的腐蚀保护等级仅下降到9级;而NiCr涂层的表面出现了较多的腐蚀斑点,涂层的完整性和均匀性均已经被破坏,涂层表面产生了腐蚀裂纹,其腐蚀等级下降到4级.EDS分析表明腐蚀产物主要为Ni、Fe、Co等的氧化物.对比结果表明,NiCoCrAlY涂层表现出比NiCr涂层更强的抗中性盐雾腐蚀性能. 相似文献
1000.