全文获取类型
收费全文 | 144篇 |
免费 | 22篇 |
国内免费 | 21篇 |
专业分类
航空 | 106篇 |
航天技术 | 27篇 |
综合类 | 17篇 |
航天 | 37篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 13篇 |
2016年 | 10篇 |
2015年 | 2篇 |
2014年 | 10篇 |
2013年 | 6篇 |
2012年 | 15篇 |
2011年 | 12篇 |
2010年 | 13篇 |
2009年 | 8篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 15 毫秒
111.
112.
113.
114.
针对某型航空发动机空中降转故障,从改变燃油流量调节器的供油特性方面分析其发生的主要原因,提出了核心排故途径,即改变膜盒组件相关设计参数。 相似文献
115.
新一代运载火箭动力系统试验台首次承担某型号动力系统试验任务,在发动机燃料头腔(燃气腔)吹除调试过程中发现吹除压力偏低,难以满足试验要求.介绍了吹除系统组成及利用孔板模拟发动机吹除路背压的调试方案,分析了引起吹除路压力偏低可能原因是孔板模拟的额定吹除流量或供气管路的阻力系数偏大.因此,通过模拟孔板流量系数标定和管路流阻特性计算,最终确定供气管路阻力系数偏大是引起吹除压力值偏低的主要影响因素,并通过制定加大供气管路内径、减少系统阀门数量等针对性改进措施,优化了地面配气工艺系统.经试验验证:吹除压力偏低的原因分析是正确性的,采取改进措施后供气管路的流阻损失降低了47%.同时确定了试前气源的容积及充气压力,保证了试验的顺利进行. 相似文献
116.
REALIZATION OF FUZZY-FILTER CONTROL ON A BRUSHLESS AC GENERATOR 总被引:5,自引:0,他引:5
CHEN Zhi-hui 《中国航空学报》2000,13(3):172-176
AC generators have adopted transistor volt-age regulators widely traditionally.The researchon the digital voltage regulators has arousedstrong interest[1~ 3] .The digital voltage regula-tors have some advantages on the transistor reg-ulators[4 ] : ( 1 ) They can realize advanced control algo-rithm; ( 2 ) They have communication function; ( 3) They have data record function. Recently,the DSPs ( Digital Signal Proces-sors) have been widely applied in digital controlarea with… 相似文献
117.
The electro-hydrostatic actuator (EHA) is a kind of power-by-wire (PBW) actuator that converts the electrical power into localized hydraulic power for flight control. By removing the central hydraulic power supply together with hydraulic pipes, an EHA's reliability and efficiency are greatly improved but its frequency width and stiffness decreased. To overcome the drawback, this article proposes a novel structure of EHA associated with a power regulator. Composed of a high-pressure accumulator and a proportional valve, it can store and harness the hydraulic power flexibly according to the changing control requirements. The concept of transferred volume is put forward to estimate the capability of the power regulator. The actuator output position can be kept fixed with a hydraulic lock. The compounded control is specially developed to ensure the actuator system to operate in a correct manner. The simulation results indicate that the new-brand actuator results in efficient expanding of the system frequency width with an optimal power supply. 相似文献
118.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013,52(12):2067-2079
In this study the gravitational perturbations of the Sun and other planets are modeled on the dynamics near the Earth–Moon Lagrange points and optimal continuous and discrete station-keeping maneuvers are found to maintain spacecraft about these points. The most critical perturbation effect near the L1 and L2 Lagrange points of the Earth–Moon is the ellipticity of the Moon’s orbit and the Sun’s gravity, respectively. These perturbations deviate the spacecraft from its nominal orbit and have been modeled through a restricted five-body problem (R5BP) formulation compatible with circular restricted three-body problem (CR3BP). The continuous control or impulsive maneuvers can compensate the deviation and keep the spacecraft on the closed orbit about the Lagrange point. The continuous control has been computed using linear quadratic regulator (LQR) and is compared with nonlinear programming (NP). The multiple shooting (MS) has been used for the computation of impulsive maneuvers to keep the trajectory closed and subsequently an optimized MS (OMS) method and multiple impulses optimization (MIO) method have been introduced, which minimize the summation of multiple impulses. In these two methods the spacecraft is allowed to deviate from the nominal orbit; however, the spacecraft trajectory should close itself. In this manner, some closed or nearly closed trajectories around the Earth–Moon Lagrange points are found that need almost zero station-keeping maneuver. 相似文献
119.
杨守环 《中国民航学院学报》1989,(4)
当同步发电机输出电流大小与功率因数改变时,其电枢反应与内阻抗压降将改变,则发电机输出电压也将改变。为使发电机输出电压保持额定值,通常都有自动电压调节器与发电机配套工作。本文较详细地分析了MD-80飞机使用的AVR403型电压调节器各部分电路的工作原理,以及整机调压的工作过程,并阐述了该调压器的特点。 相似文献
120.
具有频域指标约束的BTT导弹自动驾驶仪二次型法设计 总被引:6,自引:1,他引:6
本文研究了线性二次型最优控制系统的加权阵与频域指标间的对应关系,基于回路成形理论给出了加权阵选择方法,并将其应用于BTT导弹的自动驾驶仪设计。在建立了无静差控制模型的基础上,获得了满足预定频域指标的设计结果,并通过自动驾驶仪系统的非线性仿真验证了设计方法的有效性。 相似文献