全文获取类型
收费全文 | 13477篇 |
免费 | 1266篇 |
国内免费 | 557篇 |
专业分类
电工技术 | 224篇 |
综合类 | 1343篇 |
化学工业 | 383篇 |
金属工艺 | 359篇 |
机械仪表 | 1962篇 |
建筑科学 | 298篇 |
矿业工程 | 236篇 |
能源动力 | 5780篇 |
轻工业 | 30篇 |
水利工程 | 12篇 |
石油天然气 | 672篇 |
武器工业 | 590篇 |
无线电 | 406篇 |
一般工业技术 | 565篇 |
冶金工业 | 121篇 |
原子能技术 | 28篇 |
自动化技术 | 2291篇 |
出版年
2024年 | 42篇 |
2023年 | 143篇 |
2022年 | 327篇 |
2021年 | 326篇 |
2020年 | 329篇 |
2019年 | 269篇 |
2018年 | 294篇 |
2017年 | 354篇 |
2016年 | 313篇 |
2015年 | 338篇 |
2014年 | 654篇 |
2013年 | 542篇 |
2012年 | 950篇 |
2011年 | 1184篇 |
2010年 | 851篇 |
2009年 | 856篇 |
2008年 | 690篇 |
2007年 | 1045篇 |
2006年 | 972篇 |
2005年 | 780篇 |
2004年 | 706篇 |
2003年 | 587篇 |
2002年 | 487篇 |
2001年 | 454篇 |
2000年 | 400篇 |
1999年 | 298篇 |
1998年 | 230篇 |
1997年 | 221篇 |
1996年 | 148篇 |
1995年 | 118篇 |
1994年 | 71篇 |
1993年 | 78篇 |
1992年 | 67篇 |
1991年 | 60篇 |
1990年 | 27篇 |
1989年 | 46篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
K-9曲拐质量不合格主要是由于热处理后,珠光体数量太少所引起。因此应用正交试验,合理地选择了热处理工艺参数,提高了出炉温度,增加了珠光体数量,解决了K-9曲拐的质量问题。 相似文献
42.
Thermal analysis of a ceramic coating diesel engine piston using 3-D finite element method 总被引:1,自引:0,他引:1
In this study, firstly, thermal analyses are investigated on a conventional (uncoated) diesel piston, made of aluminum silicon alloy and steel. Secondly, thermal analyses are performed on pistons, coated with MgO-ZrO2 material by means of using a commercial code, namely ANSYS. Finally, the results of four different pistons are compared with each other. The effects of coatings on the thermal behaviors of the pistons are investigated. It has been shown that the maximum surface temperature of the coated piston with material which has low thermal conductivity is improved approximately 48% for the AlSi alloy and 35% for the steel. 相似文献
43.
44.
45.
本文对超高增压柴油机与斯特林发动机的复合运行进行了初步的探讨,陈述了这种复合运行作为未来发动机技术发展方向之一的可能性。 相似文献
46.
将金属铜易与过氧化物发生氧化还原反应生成游离基的原理应用于厌氧胶,开发了针时金属零件表面微孔进行局部渗补的实用技术。在相关技术可靠性和工艺可行性得以论证的前提下。将局部渗补技术成功地应用于渗补发动机泄漏缸盖,减少了废品损失,取得了良好的经济效益。 相似文献
47.
48.
Fuel cell-based automobiles have gained attention in the last few years due to growing public concern about urban air pollution
and consequent environmental problems. From an analysis of the power and energy requirements of a modern car, it is estimated
that a base sustainable power ofca. 50 kW supplemented with short bursts up to 80 kW will suffice in most driving requirements. The energy demand depends greatly
on driving characteristics but under normal usage is expected to be 200 Wh/km. The advantages and disadvantages of candidate
fuel-cell systems and various fuels are considered together with the issue of whether the fuel should be converted directly
in the fuel cell or should be reformed to hydrogen onboard the vehicle. For fuel cell vehicles to compete successfully with
conventional internal-combustion engine vehicles, it appears that direct conversion fuel cells using probably hydrogen, but
possibly methanol, are the only realistic contenders for road transportation applications. Among the available fuel cell technologies,
polymer-electrolyte fuel cells directly fueled with hydrogen appear to be the best option for powering fuel cell vehicles
as there is every prospect that these will exceed the performance of the internal-combustion engine vehicles but for their
first cost. A target cost of $ 50/kW would be mandatory to make polymer-electrolyte fuel cells competitive with the internal
combustion engines and can only be achieved with design changes that would substantially reduce the quantity of materials
used. At present, prominent car manufacturers are deploying important research and development efforts to develop fuel cell
vehicles and are projecting to start production by 2005. 相似文献
49.
50.
In the first half of the paper, various types of processing pertaining to a polygon, using the 4×4 determinant theories are explained along with a new containment test algorithm of a point in a polygon. In the latter half of the paper, a general-purpose geometric processor, the POLYGON ENGINE, is presented which can deal with various types of interference problems, such as Boolean operations in solid modelling, hidden line and surface eliminations, ray tracing and so on. It is, a successor of the TRIANGLE PROCESSOR and is also based upon the 4×4 determinant theories [4–6]. While the TRIANGLE PROCESSOR processes a triangulated polygon on a triangle-by-triangle basis, the POLYGON ENGINE can treat a polygon without triangulation. The latter is expected to be more functional, more efficient and easier to use. 相似文献