全文获取类型
收费全文 | 20136篇 |
免费 | 1605篇 |
国内免费 | 750篇 |
专业分类
电工技术 | 477篇 |
综合类 | 1755篇 |
化学工业 | 2102篇 |
金属工艺 | 719篇 |
机械仪表 | 2355篇 |
建筑科学 | 1223篇 |
矿业工程 | 374篇 |
能源动力 | 6096篇 |
轻工业 | 209篇 |
水利工程 | 267篇 |
石油天然气 | 1679篇 |
武器工业 | 754篇 |
无线电 | 485篇 |
一般工业技术 | 936篇 |
冶金工业 | 415篇 |
原子能技术 | 101篇 |
自动化技术 | 2544篇 |
出版年
2024年 | 24篇 |
2023年 | 183篇 |
2022年 | 459篇 |
2021年 | 487篇 |
2020年 | 490篇 |
2019年 | 383篇 |
2018年 | 391篇 |
2017年 | 493篇 |
2016年 | 506篇 |
2015年 | 544篇 |
2014年 | 1127篇 |
2013年 | 921篇 |
2012年 | 1511篇 |
2011年 | 1750篇 |
2010年 | 1245篇 |
2009年 | 1210篇 |
2008年 | 977篇 |
2007年 | 1424篇 |
2006年 | 1365篇 |
2005年 | 1103篇 |
2004年 | 1045篇 |
2003年 | 840篇 |
2002年 | 731篇 |
2001年 | 641篇 |
2000年 | 578篇 |
1999年 | 459篇 |
1998年 | 328篇 |
1997年 | 328篇 |
1996年 | 212篇 |
1995年 | 173篇 |
1994年 | 119篇 |
1993年 | 111篇 |
1992年 | 92篇 |
1991年 | 66篇 |
1990年 | 37篇 |
1989年 | 56篇 |
1988年 | 31篇 |
1987年 | 24篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(8):5609-5626
The demand for clean energy use has been increasing worldwide, and hydrogen has attracted attention as an alternative energy source. The efficient transport of hydrogen must be established such that hydrogen may be used as an energy source. In this study, we considered the influences of various parameters in the transportation of liquefied hydrogen using type C tanks in shipping vessels. The sloshing and thermal flows were considered in the transportation of liquefied hydrogen, which exists as a cryogenic liquid at ?253 °C. In this study, the sloshing flow was analyzed using a numerical approach. A multiphase sloshing simulation was performed using the volume of fluid method for the observation and analysis of the internal flow. First, a sloshing experiment according to the gas-liquid density ratio performed by other researchers was utilized to verify the simulation technique and investigate the characteristics of liquefied hydrogen. Based on the results of this experiment, a sloshing simulation was then performed for a type C cargo tank for liquefied hydrogen carriers under three different filling level conditions. The sloshing impact pressure inside of the tank was measured via simulation and subjected to statistical analysis. In addition, the influence of sloshing flow on the appendages installed inside of the type C tank (stiffened ring and swash bulkhead) was quantitatively evaluated. In particular, the influence of the sloshing flow inside of the type C tank on the appendages can be utilized as an important indicator at the design stage. Furthermore, if such sloshing impact forces are repeatedly experienced over an extended period of time under cryogenic conditions, the behavior of the tank and appendages must be analyzed in terms of fatigue and brittle failure to ensure the safety of the transportation operation. 相似文献
2.
3.
《International Journal of Hydrogen Energy》2022,47(63):27199-27222
In this present work, the effect of lanthanum oxides (La2O3) on the thermal cycle behavior of TBC coatings and mechanical properties such as adhesion strength and microhardness of 8% Yttria Stabilized Zirconia (8YSZ) TBCs were investigated. CoNiCrAlY and aluminium alloy (Al–13%Si) were used as bond coat and substrate materials. 8YSZ and different wt % of La2O3 (10, 20, and 30%) top coatings were applied using the atmospheric plasma spray (APS) method. The thermal cycling test for TBC coated samples were conducted at 800 °C in the electric furnace. The XRD pattern shows that the La2O3 doped 8YSZ material transformed to cubic pyrochloric structured La2Zr2O7 during thermal cycling. Further, the Taguchi-based grey relation analysis (GRA) method was applied to optimize the TBC coating parameters to achieve better mechanical properties such as adhesion strength and microhardness. And the optimized La2O3/8YSZ TBC coating was coated on CRDI engine combustion chamber components. The engine was tested with microalgae biodiesel and hydrogen, and the results were promising for the TBC-coated engine. The engine performance increased while using La2O3/8YSZ coated components, and the emissions from engine exhaust gas such as CO, HC, and smoke reduced considerably. It was found that there was no separation crack and spallation of the coating layer in the microstructure. Ultimately, the microstructural analysis of the optimized TBC coated piston sample after 50 h of running in the diesel engine confirmed that the developed coating had a superior thermal insulation effect and longer life. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(18):10409-10419
The utilization of renewable gaseous fuels in the diesel engine has gained significant interest in recent years due to its clean-burning nature and higher availability. In this study, hydrogen-rich reformed biogas was used as a gaseous fuel in a common rail diesel engine with diesel as pilot fuel. The hydrogen-rich reformed gas was synthesized through dry-oxidative reforming. The experimentations were performed in the load range from 6 to 24 N m with two different flow rates of gaseous fuel (0.5 and 1.5 kg/h) at a constant speed of 1800 RPM. The effects on engine performance parameters (brake thermal efficiency, brake specific energy consumption, and brake specific diesel consumption), combustion parameters (rate of pressure rise and maximum heat release rate) and emission parameters (Unburnt hydrocarbons, nitrogen oxides, carbon monoxide, and carbon dioxide) were assessed. The induction of gaseous fuel led to an increase in brake thermal efficiency by 10.5%, reduction in brake specific energy consumption by 13.6%, and a reduction of 26.4% in brake specific diesel consumption with a flow rate of 0.5 kg/h when compared to diesel-only mode at 24 N m load. The HC, NOX and CO2 emissions were reduced by 18.2%, 7.4% and 1.4% with a flow rate of 0.5 kg/h when compared to diesel-only mode at 24 N m load due to lower availability of carbon content in the combustible mixture. The utilization of renewable fuel like hydrogen-rich reformed biogas has great potential for overcoming the issue related to both biogas and hydrogen in diesel engines. Moreover, the higher diesel substitution also demonstrates the potential for cost-saving and fossil fuel conservation. 相似文献
5.
为解决定距螺旋桨与船用主机在船舶运行工况的机桨匹配问题,结合船舶系泊和航行试验的相关标准,分析和归纳船舶运行数据,将实船测试与船机桨匹配理论计算相结合,得出运输船和拖轮在常用工况及特殊工况下定距螺旋桨对主机外特性的定量要求,为配套不同细分市场时船用主机的优化和开发提供参考依据。 相似文献
6.
This paper deals with the modelling and the identification of an electromechanical Diesel engine actuator. The studied Bosch GPA-S actuator is designed for swirl/tumble flaps to control the air amount entering into the cylinder. This study aims to design a complete simulator that reproduces, with sufficient accuracy, the actuator dynamics taking into account the effects of the friction phenomenon. Hence, an overview of the actuator structure and its operation principle is first given. Then, its mathematical model as well as the nonlinearity, related to its behaviour, is discussed. Next, three identification procedures, which allow estimating both the system parameters and the friction model coefficients, are introduced. Finally, simulation results, using MATLAB, and experimental results, using LabVIEW, are presented demonstrating the effectiveness of the proposed techniques. 相似文献
7.
针对在高太阳辐射地区,柴油车驾驶室内使用车载空调会增加车辆发动机的耗油量、降低柴油车经济效益的问题,搭建了一套由发动机尾气余热驱动的吸附式车载空调系统。系统由填充有氯化钙/氯化锰/硫化膨胀石墨复合吸附剂的吸附床、蒸发器、冷凝器、储液罐和阀门组成,使用氨作为制冷剂,利用车辆在行驶时接触到的自然风为吸附床冷却,在发动机尾气余热的驱动下,为驾驶室内提供连续的制冷效果。结合仿真和实验测试,对所设计系统的制冷性能进行了分析,仿真结果表明,系统最优循环时间为45 min,系统的理论平均制冷功率可达3.5 kW以上,系统COP处于0.2~0.25之间。实验结果表明,在230℃的尾气温度条件下,系统能产生3 kW的平均制冷量。在40℃环境温度条件下,系统在蒸发器进出口处的平均温差为6.5℃,平均制冷量为3.2 kW。 相似文献
8.
9.
实时数据管理系统是流程企业控制信息网络与管理信息网络平滑集成的基础,为两者的数据通讯提供桥梁。介绍了笔者在炼油化工C企业IMS建设中的实时数据管理引擎设计与开发,具有其先进性与实用性。 相似文献
10.
地理信息系统的应用越来越广泛,特别是基于网络的GIS的发展使地理空间信息通过网络被多用户所共享,因此必须考虑地理数据访问的安全性。文章以MapInfoSpatailWare空间数据引擎为研究对象,给出了基于此模式的数据访问安全性解决方案。 相似文献