全文获取类型
收费全文 | 81507篇 |
免费 | 8296篇 |
国内免费 | 5602篇 |
专业分类
电工技术 | 5812篇 |
技术理论 | 3篇 |
综合类 | 8201篇 |
化学工业 | 11844篇 |
金属工艺 | 4868篇 |
机械仪表 | 5047篇 |
建筑科学 | 6958篇 |
矿业工程 | 3033篇 |
能源动力 | 2480篇 |
轻工业 | 7420篇 |
水利工程 | 1886篇 |
石油天然气 | 3616篇 |
武器工业 | 762篇 |
无线电 | 8859篇 |
一般工业技术 | 8258篇 |
冶金工业 | 3402篇 |
原子能技术 | 1063篇 |
自动化技术 | 11893篇 |
出版年
2024年 | 435篇 |
2023年 | 1426篇 |
2022年 | 2640篇 |
2021年 | 3587篇 |
2020年 | 2757篇 |
2019年 | 2377篇 |
2018年 | 2422篇 |
2017年 | 2621篇 |
2016年 | 2314篇 |
2015年 | 3394篇 |
2014年 | 4051篇 |
2013年 | 4671篇 |
2012年 | 5273篇 |
2011年 | 5571篇 |
2010年 | 5160篇 |
2009年 | 4881篇 |
2008年 | 4831篇 |
2007年 | 4690篇 |
2006年 | 4404篇 |
2005年 | 3495篇 |
2004年 | 3216篇 |
2003年 | 3808篇 |
2002年 | 5244篇 |
2001年 | 4388篇 |
2000年 | 2268篇 |
1999年 | 1489篇 |
1998年 | 706篇 |
1997年 | 629篇 |
1996年 | 596篇 |
1995年 | 477篇 |
1994年 | 402篇 |
1993年 | 269篇 |
1992年 | 232篇 |
1991年 | 140篇 |
1990年 | 119篇 |
1989年 | 96篇 |
1988年 | 79篇 |
1987年 | 45篇 |
1986年 | 41篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1965年 | 1篇 |
1959年 | 11篇 |
1957年 | 1篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
比较了几种长距离传动方式的特点与适用场合,重点探讨了实现长距离精密传动的技术要点。结合实际工程,完成了长距离钢带精密传动的应用,并指出张紧机构的设计与应用是钢带实现长距离精密传动的关键。为此文中对钢带传动的典型张紧机构进行了比较,并分析了这几类张紧机构的应用情况,有参考和应用价值。 相似文献
23.
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
24.
已建成的兰州重离子加速器的真空室是一个大型整体结构的超高真空容器,直径约10m,高4.5m,重65000kg,内表面积211m~2,容积100m~3,工作真空度为5×10~(-5)Pa。采用有限单元法在计算机上用SAP-5C程序对真空室受力分析进行了计算。真空室结构材料选用瑞典Uddeholm钢厂生产的316 L 超低碳不锈钢。承制此大型容器的是航天工业部风华机器厂。由于结构庞大,首先将真空室分成八大块和几小块在工厂制造,然后运至现场焊制成一整体容器并进行机械加工。所有密封焊缝均用着色渗透液,X-射线探伤和氦质谱探漏仪进行检查和探漏。 相似文献
25.
Effect of boron on the low-cycle fatigue behavior and deformation structure of INCONEL 718 at 650 °C
L. Xiao M. C. Chaturvedi D. L. Chen 《Metallurgical and Materials Transactions A》2004,35(11):3477-3487
Symmetrical push-pull low-cycle fatigue (LCF) tests were performed on INCONEL 718 (IN718) containing 12, 29, 60, and 100 ppm
B at 650 °C. The results showed that all the alloys experienced a relatively short period of initial cyclic hardening at low
strain amplitudes, followed by a regime of saturation or slightly continuous cyclic softening. The initial cyclic hardening
phase decreased with increasing strain amplitudes, and disappeared at the high strain amplitudes. A serrated flow was observed
in the plastic regions of cyclic stress-strain hysteresis loops. The saturated cyclic stress amplitude at a given strain amplitude
was highest for the alloy with 60 ppm B, and lowest for the alloy with 12 ppm B. The LCF lifetime increased with increasing
B concentration up to 60 ppm, and then decreased as the B content increased from 60 to 100 ppm. Fractographic analysis suggested
that the fracture mode changed from intergranular to transgranular cracking as the B concentration increased. The characteristic
deformation microstructures produced by LCF tests at 650 °C, examined via transmission electron microscopy, were regularly spaced arrays of planar deformation bands on {111} slip planes in all four
alloys. A ladderlike structure was observed in some local regions in the alloy with 12 ppm B. Heavily deformed planar deformation
bands were observed in the fatigued specimens with 100 ppm B. The mechanism of improvement in the LCF life of IN718 due to
B addition is discussed. 相似文献
26.
27.
28.
Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles. 相似文献
29.
本文分析了QC小组活动与企业文化的特点与共同点,提出开展QC小组活动与企业文化建设是互相促进,互相补充的,两者可以互相结合。 相似文献
30.