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排序方式: 共有2920条查询结果,搜索用时 15 毫秒
1.
The present study proposes an algorithm for fault detection in terms of condition‐based maintenance with data mining techniques. The proposed algorithm is applied on an aircraft turbofan engine using flight data and consists of two main sections. In the first section, the relationship between engine exhaust gas temperature (EGT) as the main engine health monitoring criterion and other operational and environmental parameters of the engine was modelled using the data‐driven models. In the second section, a data set including EGT residuals, that is, the difference between the actual EGT of the system and the EGT estimated by the developed model in the health conditions of the engine, was created. Finally, faults occurring in each flight were detected based on the identification of abnormal events by a one‐class support vector machine trained by the health condition EGT residual data set. The results indicated that the proposed algorithm was an effective approach for inspecting aircraft engine conditions and detecting faults, with no need for technical knowledge on the interior characteristics of the aircraft engine. 相似文献
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Lightweight flexible aircraft suffers from unwanted oscillatory vibrations during aircraft manoeuvres. A recently developed distributed-delay signal (DZV) shaper is therefore proposed to be applied as a feedforward controller to alleviate the manoeuvre loads, as an alternative to traditional structural filters used routinely in this context. Structural filters are essentially linear low-pass filters with bandwidth below the significant flexible modes, applied to control signals generated either by the pilot’s direct input or by the flight control system. It has been showed that if instead a properly tuned signal shaper is used, better performance can be achieved: first, the target modes are significantly attenuated while the responsiveness of the aircraft is less compromised and secondly, the oscillatory nature of the vibrations are reduced. The high fidelity simulation results on a full scaled dynamic model of a highly flexible blended wing–body (BWB) aircraft show that in comparison to traditional structural filters, signal shapers significantly reduce the wing root loading (forces and moments) which provides potential structural benefits. 相似文献
3.
Assessment of NOx emissions of the Scimitar engine at Mach 5 based on a thermodynamic cycle analysis
《International Journal of Hydrogen Energy》2020,45(5):3632-3640
The Scimitar engine is a new advanced propulsion system designed to propel the aircraft A2 of the LAPCAT project. It is a hybrid system that utilizes the features of turbofan, ramjet and air-turborocket. Hydrogen and air are used as the fuel and oxidant, respectively, while helium is used to transfer heat from the hot incoming air to the hydrogen in the engine. In this study, we present a thermodynamic cycle analysis of the Scimitar engine for the assessment of NOx emissions. The combustion of fuel is studied in detail with an equilibrium model taking into account various dissociation and formation reactions since high levels of temperatures are achieved in its combustion chamber. The NOx emissions of the engine at Mach 5 and the effects of fuel and air flow rates, cruise speed and altitude on these emissions are presented by solving a nonlinear system of equations formed through our novel thermodynamic model. The results show that the NO emissions of the engine can be diminished significantly by decreasing air flow rate, cruise speed and altitude and by increasing the fuel flow rate. The variations of NO2 emissions with these parameters are similar except the variation with altitude which has an inverse effect as compared to the variation of NO. 相似文献
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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
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Antonella Ingenito 《International Journal of Hydrogen Energy》2018,43(50):22694-22704
The promising opportunity to reach intercontinental long distances in a few hours is a remarkable issue for both private companies and public organizations: teams of scientists, technicians and researchers in Europe, USA, China, Russia and India are working at national and international programs on long range high speed civil transport. The Space X's CEO also announced, at the IAC 2017 conference, the growing interest in developing a 30-min transatlantic passenger flight by means of a 2-stage rocket-based vehicle. Meeting the dwell requirement of antipodal ranges and high speeds is realistic through a new era of hydrogen-fuelled hypersonic airbreathing vehicles. The interest in hydrogen as aviation fuel has recently increased not only due to the growth of worldwide air travel and time reduction requirements, also for the dramatic rise of common aviation fuel prices, and the continuously increasing restrictive environmental issues.In the light of these changes that have occurred in fuel prices, emissions reduction imperatives and the currently higher demand for supersonic airline travels, hydrogen-fuelled hypersonic airbreathing airliners are a valuable chance with respect to other means of transport (i.e., a rocked based passenger transport). In fact, hydrogen is one of the most environmental friendly fuels, since no particulate and carbon oxide emissions are produced. Past objections on hydrogen as fuel for civil transport, such as safety, liquefying and storing hydrogen are now overcame and its technological maturity opens a large worldwide market for hydrogen as “green” fuel. However, since the opportunity for hydrogen as fuel for future fleets of airline transport resides in its “green” peculiarity, the investigation of the impact of the H2/air hot exhausts on the ozone layer depletion is mandatory. In fact, a lot of hypersonic cruise vehicles fly at an altitude of 25000–30000 m that corresponds to the ozonosphere. In this region, the concentration of ozone is maximum and NOx emissions may catalyse the ozone destruction.In this context, the goal of this paper is to estimate the effect of the H2/air emissions (i.e., nitrogen oxides, hydroxide and water vapor) of a fleet of 200 hydrogen fuelled hypersonic airliners flying once a day for 360 days from Brussels to Sydney, on the ozone layer and on the global temperature increase. 相似文献
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在恶劣天气和机械故障等原因造成航班不能按照原计划执行时,航空公司需要采取相应的措施对航班进行恢复。本文基于经典的资源指派模型,综合考虑了调整时间、换机、联程拉直、取消航班和调机5种恢复策略,提出一种以最小化加权成本为优化目标的航班恢复模型,并设计一种迭代局部搜索算法。首先用构造-修复启发式方法构造可行解,然后从该初始解出发,在飞机路线对的邻域中进行局部搜索。当陷入局部最优后,对解进行扰动,然后从扰动后的解重新出发进行局部搜索。为了提高搜索效率,同时降低陷入局部最优解的概率,局部搜索过程采用模拟退火算法。实例结果表明,本文提出的模型及算法能够在短时间内对受到影响的大规模航班计划进行恢复。 相似文献
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本文针对典型高温气冷堆乏燃料厂房在双发商用飞机撞击载荷下的响应及结构完整性开展研究,并探讨结构特性对撞击损伤的影响。对乏燃料厂房及飞机分别建立有限元模型,通过弹体-目标相互作用分析模拟了飞机撞击过程,综合IAEA与NRC的评价准则对乏燃料厂房在飞机撞击下的损伤程度进行评估。数值结果表明:厂房上对应于机身及发动机的撞击位置发生可接受的局部损伤;乏燃料贮存井墙体对于提高构筑物抗飞机撞击能力有重要作用。此外,构筑物外形对损伤有很大影响,圆柱形壳体的抗飞机撞击能力显著强于方形厂房,是核电厂厂房设计的优化方向之一。 相似文献