全文获取类型
收费全文 | 2803篇 |
免费 | 183篇 |
国内免费 | 101篇 |
专业分类
电工技术 | 109篇 |
综合类 | 273篇 |
化学工业 | 295篇 |
金属工艺 | 166篇 |
机械仪表 | 595篇 |
建筑科学 | 159篇 |
矿业工程 | 207篇 |
能源动力 | 125篇 |
轻工业 | 31篇 |
水利工程 | 16篇 |
石油天然气 | 32篇 |
武器工业 | 23篇 |
无线电 | 201篇 |
一般工业技术 | 237篇 |
冶金工业 | 187篇 |
原子能技术 | 8篇 |
自动化技术 | 423篇 |
出版年
2024年 | 2篇 |
2023年 | 21篇 |
2022年 | 45篇 |
2021年 | 70篇 |
2020年 | 79篇 |
2019年 | 34篇 |
2018年 | 38篇 |
2017年 | 84篇 |
2016年 | 103篇 |
2015年 | 116篇 |
2014年 | 272篇 |
2013年 | 181篇 |
2012年 | 323篇 |
2011年 | 301篇 |
2010年 | 180篇 |
2009年 | 166篇 |
2008年 | 143篇 |
2007年 | 133篇 |
2006年 | 135篇 |
2005年 | 116篇 |
2004年 | 97篇 |
2003年 | 107篇 |
2002年 | 76篇 |
2001年 | 69篇 |
2000年 | 48篇 |
1999年 | 41篇 |
1998年 | 36篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1961年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有3087条查询结果,搜索用时 140 毫秒
51.
High-quality industrial processes, characterized by a low fraction of non-conforming items, require paying special attention to the statistical control methods employed since traditional Shewhart's control charts are no longer suitable. In this article, CCC-r charts are considered based on the cumulative count of conforming items inspected until r non-conforming items are observed. However, even though these charts have shown to be useful for high-quality processes, they are characterized by a biased average run length (ARL). In order to help engineers interested in this control methodology to select the best option, a computational study of statistical validation was performed to compare the two most outstanding procedures for the cases r = 2, 3, and 4. The performance was evaluated based on the ARL under control. The application of the CCC-r chart to a real process is shown with data from an automobile parts plant. Finally, analysis and discussion of the results are presented. 相似文献
52.
Concerns about air quality and global warming have led to numerous initiatives to reduce emissions. In general, emissions are proportional to the amount of fuel consumed, and the amount of fuel consumed is a function of speed, distance, acceleration, and weight of the vehicle. In urban areas, vehicles must often travel at the speed of traffic, and congestion can impact this speed particularly at certain times of day. Further, for any given time of day, the observations of speeds on an arc can exhibit significant variability. Because of the nonlinearity of emissions curves, optimizing emissions in an urban area requires explicit consideration of the variability in the speed of traffic on arcs in the network. We introduce a shortest path algorithm that incorporates sampling to both account for variability in travel speeds and to estimate arrival time distributions at nodes on a path. We also suggest a method for transforming speed data into time-dependent emissions values thus converting the problem into a time-dependent, but deterministic shortest path problem. Our results demonstrate the effectiveness of the proposed approaches in reducing emissions relative to the use of minimum distance and time-dependent paths. In this paper, we also identify some of the challenges associated with using large data sets. 相似文献
53.
The efficient utilization of expensive rolling-stock has become imperative for all railroads. In this paper, we study the combined empty and loaded train-scheduling problem for the upcoming dedicated freight corridors in India. Existing optimization models either do not consider the simultaneous optimization of the loaded and empty flows or are not solvable for large railroads. Our model is the first of its kind to incorporate link capacity constraints in an IP formulation for this operational level problem. A simulated annealing algorithm hybridized with a constructive heuristic is proposed as the solution method. The computational experiments show that the proposed heuristic performs well both in terms of runtime and solution quality. 相似文献
54.
为满足客户日新月异的技术及运营需求,对车联网服务能力进行完善,发掘4G在新一代车联网应用中牵引作用,面向前装市场推出以云管端一体化为核心的和车连产品,引导车联网行业新变革. 相似文献
55.
车辆段含油废水需进行处理后,才能排至市政废水或者雨水管网。本文对南京某车辆段含油废水处理工艺进行了分析和介绍,并提出了自己的见解。 相似文献
56.
Cold rich bypass to the stripper in CO2 capture by alkanolamines will usually reduce the total heat duty. Bypass reduces the stripping steam in the overhead vapor and balances the temperature approach in the main cross exchanger. This process improvement reduces the energy requirement of any configuration, but it is most beneficial when the overhead vapor is not already countercurrently contacted with incoming rich solution. Therefore, the 2‐stage flash configuration was evaluated in this work, and it had an improvement of 11 % over the no bypass case. Its improvement was better than what was observed with a simple stripper and interheated column. An optimized cool rich bypass for a pilot scale 2‐stage reduces the equivalent work. 相似文献
57.
概括K18DG、K18DF和K18AT等煤炭漏斗车的易发故障,分析故障原因,指出设计制造方面的不足,并提出了在检修中的改进措施及注意事项、车辆采购及管理措施。 相似文献
58.
Giulio Vialetto Marco Noro Masoud Rokni 《International Journal of Hydrogen Energy》2017,42(15):10285-10297
In recent years, Denmark boosted investments in renewable energy and electrification of transportation. The Danish Agenda proposed that all primary energy consumption will be covered by renewable sources such as wind, biomass and solar by 2050. These changes require significant investment and re-thinking of entire energy infrastructures and types of consumption. The Agenda also suggested, among other things, improving the efficiency of energy systems.In this paper, the interactions between charging an electric car and an innovative cogeneration system for household application (micro-solid oxide fuel cell with an integrated heating system) are investigated. The charge of the electric car by the cogenerator produces waste heat that can be used to partially cover the heat demand of the house. In this way it may be possible to increase overall efficiency and decrease total energy costs. Different innovative strategies are proposed and analyzed to manage charging an electric car and efficiently using the waste heat available. The aims of this study are to make the system grid-independent, to decrease the thermal stress of SOFCs and to determine the nominal power of an integrated heating system. The results show energy efficiency and economic profitability of the system, even if subsidies are not included. 相似文献
59.
Experimental investigation of convective heat transfer coefficient of Al2O3/water nanofluid at lower concentrations in a car radiator 下载免费PDF全文
For many years, water and ethylene glycol were used as conventional coolants in automotive car radiators, but these coolants offer lower thermal conductivity than is required. This study is focused on the application of water‐based Al2O3 nanofluid at lower concentrations in a car radiator. The Al2O3 nanoparticles with an average diameter of 50 nm are dispersed in demineralized water at four different volume concentrations (0.1 vol. % to 0.4 vol. %) without any dispersant or stabilizer. Flow rate is varied in the range of 2 l/min to 5 l/min and inlet coolant temperature to the radiator is set to 50 °C, 60 °C, and 70 °C. The results show that the heat transfer coefficient increases with an increase in particle concentration, flow rate, and inlet temperature of coolant and the maximum increase in heat transfer coefficient is 45.87 % compared to pure water. However, the Nusselt number increases with the increase in particle concentration, Reynolds number, and inlet temperature of the coolant. In addition with the experimental study, a regression analysis is performed by using the ANOVA method and generates a correlation for the convective heat transfer coefficient. 相似文献
60.
介绍了适合国内焦化企业振动式压浮煤机构的研制过程,该设备不仅能够均匀压实和刮平煤饼、减轻工人劳动强度,而且提高了装煤车的工作自动化,给厂家带来一定的经济效益。 相似文献