全文获取类型
收费全文 | 523篇 |
免费 | 40篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 22篇 |
综合类 | 21篇 |
化学工业 | 40篇 |
金属工艺 | 21篇 |
机械仪表 | 26篇 |
建筑科学 | 29篇 |
矿业工程 | 1篇 |
能源动力 | 137篇 |
轻工业 | 4篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
武器工业 | 3篇 |
无线电 | 137篇 |
一般工业技术 | 43篇 |
冶金工业 | 10篇 |
原子能技术 | 7篇 |
自动化技术 | 76篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 22篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 33篇 |
2013年 | 64篇 |
2012年 | 35篇 |
2011年 | 54篇 |
2010年 | 42篇 |
2009年 | 38篇 |
2008年 | 27篇 |
2007年 | 23篇 |
2006年 | 27篇 |
2005年 | 22篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
排序方式: 共有583条查询结果,搜索用时 15 毫秒
81.
82.
《International Journal of Cast Metals Research》2013,26(1-4):168-173
AbstractThe effects of different heating rates to a homogenisation temperature on the semisolid microstructure of Al–Mg–Si–Mn alloys are investigated. It is found that the size, morphology and distribution of the α-Al12Mn3Si2 intermetallic compound (Mn containing dispersoid) depend on the heating rate in the homogenisation process. Fine spherical and homogeneously distributed Mn containing dispersoid particles are found in the slow heated samples (0˙7°C min?1), while inhomogeneously distributed coarser particles with a rod-like shape are found in the rapid heated samples (110°C min?1). The homogenised sample is deformed by 60% cold rolling. It is found that the recrystallised and semisolid grain sizes of the rapid heated sample are smaller than those of the slow heated sample in all conditions. Compared with the M4 alloy (0˙4 mass-%Mn), the M7 alloy (0˙72 mass-%Mn) has much finer semisolid grain size and smaller values of the shape factor close to 1. The Mn containing dispersoid greatly affects the semisolid grain size of the alloys. The results in this work show that the rapid heating in the homogenisation process is useful to produce high quality semisolid products of the Al–Mg–Si–Mn alloys. 相似文献
83.
《International Journal of Cast Metals Research》2013,26(1-4):264-267
AbstractAn Fe–Mo–Cr–Mn–Si–C alloy was prepared in an induction furnace and was cast into cylindrical rod in a copper mould in castmatic equipment (low pressure casting). A single phase non-equilibrium featureless (no visible microstructures after deep etching) phase was observed over a certain range of thickness of the rod. In this present work, the extent of the featureless phase was studied with different concentrations of Mo (5–25 wt-%) for 5·5 mm diameter of cylindrical rod at a cooling rate of 1100 K s–1. Light optical microscopy, scanning electron Microscopy and Vickers hardness tests were used to analyse the samples. The amount of the featureless area varies as the Mo content changes and the maximum featureless area was obtained for 7 wt-% of Mo. This single phase featureless structure exhibits very high hardness (>1350 HV) which can be used in many interesting applications with or without suitable heat treatments. 相似文献
84.
《International Heat Treatment & Surface Engineering》2013,7(1):41-46
AbstractSpray forming offers the possibility of producing alloys with very fine, homogeneous microstructures. Even materials with high contents of intermetallic precipitates, which cannot be produced by casting because of the high solidification rates required, can be distributed homogeneously. Alloying aluminium with high contents of Mg and Si (>20 wt-%Mg2Si) gives an increase in stiffness plus a significant reduction in density, but a very fine distribution of the Mg2Si particles in the aluminium matrix is required. Therefore, such alloys are commonly produced by spray forming. Post-spraying processes such as forming and heat treatment are generally carried out to optimise properties. To examine the microstructure and hardness as a result of subsequent processing, aluminium alloys with high Mg2Si content (22–30 wt-%) have been produced under a variety of spray forming conditions. The duration and temperature of heating before extrusion were varied. In addition, some specimens were preheated without extrusion. The influence of subsequent heat treatment was investigated by varying the age hardening parameters. Hardness measurements were conducted and the distribution and size of the precipitates were evaluated by light microscopy. Image analysis was used to study the coarsening behaviour of primary Mg2Si. The results indicate that the subsequent processing conditions have a strong influence on the microstructure and hardness of the material. Further, a significant dependence of coarsening rate during subsequent processing on the initial state of the material after spray forming was observed. Knowledge of correlations between process parameters and microstructural development offers the possibility of optimising the hot extrusion and heat treatment parameters for high Mg2Si containing aluminium alloys. 相似文献
85.
Changwei Ji Chen LiangYongming Zhu Xiaolong LiuBinbin Gao 《Fuel Processing Technology》2012,94(1):94-100
Dimethyl ether (DME) and ethanol are thought to be alternative fuels for future internal combustion (IC) engines. The experiments in this paper were carried out at idle and stoichiometric conditions to investigate the effect of DME addition on the idle performance of a spark-ignited (SI) ethanol engine. The engine was modified to be fueled with the mixture of DME and ethanol which were injected into the engine intake ports simultaneously. A hybrid electronic control unit (HECU) was specially developed to control the injection timings and durations of ethanol and DME, accomplishing specified excess air ratios and DME addition fractions in the total ethanol-DME fuel mixture. The experimental results demonstrated that, the indicated thermal efficiency was increased by over 20% after DME blending and the flame development and propagation durations were shortened with the increase of DME addition fraction. Meanwhile, HC emissions were obviously decreased with the increasing fraction of DME addition, while NOx emissions were slightly increased. Therefore, DME addition is a potentially applicable method to improve the idle performance of SI ethanol engines. 相似文献
86.
Poly(γ‐methacryloxypropyltrimethoxysilane) (PMPTS)‐grafted silica hybrid nanoparticles were prepared by surface‐initiated atom transfer radical polymerization (SI‐ATRP). The resulting PMPTS‐grafted silica hybrid nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIRS), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), static water contact angle (WCA) measurement, and thermogravimetric analysis (TGA). Combined FTIRS, NMR, XPS, SEM, and TGA studies confirmed that these hybrid nanoparticles were successfully prepared by surface‐initiated ATRP. SEM and AFM studies revealed that the surfaces of the nanoparticles were rough at the nanoscale. In addition, the results of the static WCA measurements showed that the nanoparticles are of low surface energy and their surface energy reaches as low as 6.10 mN m?1. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
87.
为解决CAN总线与上位机或PC机的的通信问题,需要设计一个主节点作为转换接口,实现CAN数据转异步串口数据和异步串口数据转USB数据.选择MC9S1 2XS256和CP2101来设计主节点,简单介绍MC9S12XS256芯片和CP2101芯片的功能,设计了USB转UART串口的传输模块设计和CAN总线的传输模块,并通过调试验证了主节点设计方案是可行的. 相似文献
88.
89.
90.
Anand Prabu Kalaivanan 《国际自然能源杂志》2020,41(12):1404-1408
ABSTRACT The need for development of a more efficient IC engine is always on the rise which can be related to oil being a non-renewable resource and its increasing carbon foot print causing global warming. In addition to the CO2, there are more toxic pollutants such as NOx, CO and HC due to improper combustion. These demands have paved way for development of alternative fuel engines such as bio-diesel, bio-ethanol and hybrids. Still these engines need to optimise their combustion to get the best of both worlds. And for the purpose of optimisation there must be a means to measure and estimate the combustion characteristics. Thus analysing the combustion noise gives some insight into the performance of the engine. 相似文献