全文获取类型
收费全文 | 5410篇 |
免费 | 224篇 |
国内免费 | 105篇 |
专业分类
电工技术 | 105篇 |
综合类 | 247篇 |
化学工业 | 425篇 |
金属工艺 | 538篇 |
机械仪表 | 2384篇 |
建筑科学 | 236篇 |
矿业工程 | 158篇 |
能源动力 | 200篇 |
轻工业 | 125篇 |
水利工程 | 24篇 |
石油天然气 | 211篇 |
武器工业 | 21篇 |
无线电 | 118篇 |
一般工业技术 | 357篇 |
冶金工业 | 304篇 |
原子能技术 | 84篇 |
自动化技术 | 202篇 |
出版年
2024年 | 45篇 |
2023年 | 112篇 |
2022年 | 114篇 |
2021年 | 148篇 |
2020年 | 175篇 |
2019年 | 138篇 |
2018年 | 134篇 |
2017年 | 152篇 |
2016年 | 177篇 |
2015年 | 167篇 |
2014年 | 260篇 |
2013年 | 175篇 |
2012年 | 280篇 |
2011年 | 354篇 |
2010年 | 224篇 |
2009年 | 267篇 |
2008年 | 202篇 |
2007年 | 358篇 |
2006年 | 364篇 |
2005年 | 265篇 |
2004年 | 291篇 |
2003年 | 188篇 |
2002年 | 171篇 |
2001年 | 144篇 |
2000年 | 119篇 |
1999年 | 129篇 |
1998年 | 106篇 |
1997年 | 90篇 |
1996年 | 91篇 |
1995年 | 54篇 |
1994年 | 39篇 |
1993年 | 26篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 32篇 |
1989年 | 8篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 17篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有5739条查询结果,搜索用时 718 毫秒
1.
华治国 《混凝土与水泥制品》2020,(6):70-72
选择了几份典型的外墙外保温系统标准,通过对这几份标准中胶粘剂和抹面胶浆的成型和检测方法的比较,分析了现有检测技术的优劣,并结合工作实践提出了建议。 相似文献
2.
运用过程中各类相关因子的变化,会使得机车柴油机配气相位出现一定程度变化,采取某种措施调整或是处理可以解决动力不足的问题。 相似文献
3.
In this paper, limiting factors for increased use of biomethane as a transportation fuel are studied. The aim of this research is to recognize and estimate the limiting factors for biomethane utilization in the transportation sector. The limiting factors are studied by using calculation models from Life cycle perspective and literature reviews. According to the results, the main limiting factors can be classified into the following categories: production potential, technology, economy or policy. For biomethane utilization in Finland, the main limiting factors seem to be the lack of distribution infrastructure in northern parts of the country and the uncertain economical feasibility for agricultural biomass producers and for vehicle owners. From the political perspective, the external costs for petrol operated vehicles are higher than for biomethane operated vehicles. Reductions from the external costs could be used by political decisions as a base to support the growth of biomethane in the transportation sector which could lead to GHG emission reductions. A similar systematic approach can also be used to study limiting factors for other transportation energy systems. 相似文献
5.
6.
One of the new physical methods that provides much information about the processes going on in a friction contact zone in real time is acoustic emission (AE). Basic experimental results of AE in friction are presented and analysed. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surfaces in real time, sometimes about intensity of wear, changing of wear and friction regimes and so on. The influence of sliding velocity, load, roughness and some physical and mechanical properties of the body on the parameters of AE are also given. Some attention to the practical implementation of these techniques for control of capability for work of friction pairs in real conditions are given. Modern methods and devices enable condition monitoring of sliding and rolling bearings. 相似文献
7.
A lubrication-flow model for a free film in a corner is presented. The model, written in the hyperbolic coordinate system
ξ = x
2 −y
2, η = 2xy, applies to films that are thin in the η-direction. The lubrication approximation yields two coupled evolution equations
for the film thickness and the velocity field which, to lowest order, describes plug flow in the hyperbolic coordinates. A
free film in a corner evolving under surface tension and gravity is investigated. The rate of thinning of a free film is compared
to that of a film evolving over a solid substrate. Viscous shear and normal stresses are both captured in the model and are
computed for the entire flow domain. It is shown that normal stress dominates over shear stress in the far field, while shear
stress dominates close to the corner.
This revised version was published online in October 2005 with corrected page numbers. 相似文献
8.
The breakdown processes of oil films under quasi-static loading have been investigated by using a newly developed steel-oil-mercury system. The relationship between the thickness and breakdown ratio of a hexadecane film is represented by a single master curve independently of the indentation speed, indentation load, and temperature. The master curve shows that the breakdown process of hexadecane includes two stages; one is the decrement of the thickness without breakdown and the other is the decrement of the thickness with a drastic progress of breakdown. By solving a small amount of fatty acid in hexadecane, the thickness increases and the breakdown ratio decreases noticeably; a multilayer residual film supporting normal load is formed between two metal surfaces. Experiments at different temperatures reveal a negative relationship between the temperature and thickness of residual film, which indicates that the residual film is organized by physical interaction rather than chemical interaction. At least under a lower concentration, the residual film appears to consist of not only fatty acid molecules but also hexadecane molecules. 相似文献
9.
10.
冷成型模具低温锌系磷化 总被引:4,自引:1,他引:3
研制出适用于冷成型模具高硬度表面的低温锌系磷化工艺。其中磷化液含Zn(H2 PO4 ) 2 ·2H2 O 6 0g/L ,Zn(NO3) 2 ·6H2 O 90g/L ,NaNO2 1.5g/L ,稀土促进剂 0~ 1.0g/L ,游离酸度 4~ 6点 ,总酸度 70~ 75点。该磷化液在 4 0℃下 ,处理 30~ 4 0min后可获得厚约 10 μm的磷化膜。性能测试表明 ,其减摩、润滑性能良好 ,摩擦系数约降 0 .1,与未处理试样相比磨损量下降 96 % ,附着力 1级。 相似文献