全文获取类型
收费全文 | 5603篇 |
免费 | 587篇 |
国内免费 | 375篇 |
专业分类
电工技术 | 86篇 |
综合类 | 281篇 |
化学工业 | 1457篇 |
金属工艺 | 1188篇 |
机械仪表 | 300篇 |
建筑科学 | 487篇 |
矿业工程 | 63篇 |
能源动力 | 50篇 |
轻工业 | 137篇 |
水利工程 | 47篇 |
石油天然气 | 83篇 |
武器工业 | 66篇 |
无线电 | 878篇 |
一般工业技术 | 1014篇 |
冶金工业 | 251篇 |
原子能技术 | 18篇 |
自动化技术 | 159篇 |
出版年
2024年 | 21篇 |
2023年 | 114篇 |
2022年 | 173篇 |
2021年 | 205篇 |
2020年 | 180篇 |
2019年 | 190篇 |
2018年 | 152篇 |
2017年 | 213篇 |
2016年 | 212篇 |
2015年 | 185篇 |
2014年 | 282篇 |
2013年 | 416篇 |
2012年 | 315篇 |
2011年 | 359篇 |
2010年 | 295篇 |
2009年 | 329篇 |
2008年 | 282篇 |
2007年 | 412篇 |
2006年 | 395篇 |
2005年 | 285篇 |
2004年 | 265篇 |
2003年 | 198篇 |
2002年 | 172篇 |
2001年 | 157篇 |
2000年 | 137篇 |
1999年 | 111篇 |
1998年 | 76篇 |
1997年 | 64篇 |
1996年 | 75篇 |
1995年 | 59篇 |
1994年 | 42篇 |
1993年 | 35篇 |
1992年 | 30篇 |
1991年 | 33篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有6565条查询结果,搜索用时 15 毫秒
1.
2.
The bonding of β'-Al2O3 and pyrex glass to Al matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope (SEM), energy dispersive X-ray fluorescence spectrometer (EDX). It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding. 相似文献
3.
Wang Xuegang Yan Fengjie Yan Qian Li Xingeng 《Frontiers of Materials Science in China》2007,1(2):225-227
An iron-based amorphous foil (FeNiCrSiB) was used as an interlayer for the amorphous diffusion bonding of low carbon steel
pipes under argon flux. The microstructure and mechanical properties of the joint were analyzed using an electron probe micro-analyzer
(EPMA), tensile test, bending test and impact test. The results show that the joint microstructure resembles that of the base
metal and no precipitates form at the joint. Melting point depressants (B, Si) diffuse far away from the joint and the base
metal element is homogenous across the joint. The joint impact toughness is greater than the base metal toughness and the
mechanical properties of the joint are similar around the pipe. 相似文献
4.
The structural properties and hydrogen bonding of undoped and phosphorous doped polycrystalline silicon produced by step-by-step laser dehydrogenation and crystallization technique were investigated using Raman spectroscopy and hydrogen effusion measurements. At low laser fluences, EL, a two-layer system is created. This is accompanied by the change in hydrogen bonding. The intensity of the Si–H vibration mode at 2000 decreases faster than the one at 2100 cm−1. This is even more pronounced in phosphorous-doped specimens. The laser crystallization results in an increase of the hydrogen binding energy by approximately 0.2–0.3 eV compared to the amorphous starting materials. 相似文献
5.
6.
通过对国内外大量石油套管螺纹参数的测量和全尺寸的模拟试验,以及对测量和试验数据的理论分析,找出了影响国产套管发生粘扣的原因,并在实际生产中实施验证。采取相应的措施改善了套管的抗粘结性能,同时套管的密封和抗滑脱性能并未下降。 相似文献
7.
We succeeded in the fabrication of bonded laser crystals composed of a neodymium-doped YVO4 laser crystal (Nd:YVO4) and its host crystals YVO4 by a newly developed dry etching technique using an argon ion beam. The optical distortion caused by the bonded interface of size 5 mm × 6 mm was estimated to be 0.05λ at 633 nm. From the comparison of laser performance pumped by a laser diode, the bonded crystals could increase the laser output power by nearly twice that of the non-bonded crystals with the same degree of polarization of 99.2%. To analyze the mechanism of the enhanced reduction of the thermal load in the bonded crystals, numerical simulations with a finite-element method were also performed. 相似文献
8.
通过正交试验研究了各工艺量数以钢/铝合金液固相复合性能的影响,最佳工艺条件为铝合金液体温度790℃,钢板表面处理为酸洗+钢刷+5%的氟钛酸钾助焊剂,复合压力为39.2MPa,组织观察表面界面脆性化合物的形成是导致结合强度降低的一个重要因素。 相似文献
9.
金属-橡胶硫化粘接过程中分子取向行为的间接证据 总被引:2,自引:1,他引:1
对金属-橡胶热硫化粘接复合体的剥离行为进行了研究,同一粘接试样的双向180°剥离试验显示出了巨大的差异。本文分析了弹性材料在硫化过程中的分子行为,并提出了相应的新假设,认为这是由于金属-橡胶在硫化粘接过程中分子取向交联行为所致。这种双向180°剥离破坏现象可被看作是金属-橡胶硫化粘接过程中分子取向行为的间接证据。 相似文献
10.