首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   311篇
  免费   81篇
  国内免费   67篇
航空   168篇
航天技术   127篇
综合类   49篇
航天   115篇
  2024年   3篇
  2023年   13篇
  2022年   14篇
  2021年   17篇
  2020年   14篇
  2019年   27篇
  2018年   32篇
  2017年   23篇
  2016年   36篇
  2015年   22篇
  2014年   19篇
  2013年   17篇
  2012年   23篇
  2011年   20篇
  2010年   17篇
  2009年   16篇
  2008年   19篇
  2007年   23篇
  2006年   19篇
  2005年   9篇
  2004年   14篇
  2003年   6篇
  2002年   6篇
  2001年   6篇
  2000年   9篇
  1999年   7篇
  1998年   3篇
  1997年   5篇
  1996年   5篇
  1995年   2篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1990年   5篇
  1989年   3篇
排序方式: 共有459条查询结果,搜索用时 234 毫秒
451.
四足机器人灵巧运动技能的生成一直受到机器人研究者们的广泛关注,其中空中翻滚运动既能展现四足机器人运动的灵活性又具有一定的实用价值.近年来,深度强化学习方法为四足机器人的灵巧运动提供了新的实现思路,利用该方法得到的闭环神经网络控制器具有适应性强、稳定性高等特点.本文在绝影Lite机器人上使用基于模仿专家经验的深度强化学习方法,实现了仿真环境中四足机器人的后空翻动作学习,并进一步证明了设计的后空翻闭环神经网络控制器相比于开环传统位置控制器具有适应性更高的特点.  相似文献   
452.
《中国航空学报》2023,36(5):486-498
Imposing compressive residual stress field around a fastening hole serves as a universal method to enhance the hole fatigue strength in the aircraft assembly filed. Ultrasonic Peening Drilling (UPD) is a recently proposed hybrid hole making process, which can achieve an integration of strengthening and precision-machining with a one-shot-drilling operation. Due to the ironing effect of tool flank surface, UPD introduces large compressive residual stress filed in hole subsurface. In order to reveal the strengthening mechanism of UPD, the influence of ultrasonic vibration and tool dynamic relief angle on ironing coverage rate and its corresponding effect on surface integrity in UPD were analyzed. The experiments were conducted to verify the influence of ironing effect on surface integrity and fatigue behavior of Ti-6Al-4V hole in UPD. The results indicate that the specimen features smaller surface roughness, higher micro-hardness, plastic deformation degree and circumferential compress residual stress under higher ironing coverage rate. The fatigue life increases with the raise of ironing coverage rate, and the fatigue source site in UPD shifts from surface to subsurface comparing with that without vibration assistance. The results demonstrates that a better strengthening effect can be obtained by reasonably controlling the ironing coverage rate in UPD.  相似文献   
453.
工业机器人工作空间大、姿态灵活、可配置性高,且成本低,广泛应用于搬运、装配、喷涂和焊接等多个领域。但由于机器人末端轨迹精度不高,低速波动大,在电化学加工领域的应用很少。根据电化学加工低速、高轨迹精度特点,提出采用象限法设定电化学加工机器人工作区域,建立电化学加工机器人动力学优化函数,采用第三代非支配遗传算法NSGA-Ⅲ求解各设计参数最优Pareto解集,通过仿真和实验进行了动态性能测试验证。结果表明在设定工作区域内,电化学加工机器人直线轨迹精度可达0.073 mm,圆弧轨迹精度可达0.145 mm,低速工况下轨迹精度相比传统工业机器人提高近10倍。  相似文献   
454.
《中国航空学报》2023,36(2):350-362
A 2 m class robotic drill was sent to the Moon and successfully collected and returned regolith samples in late 2020 by China. It was a typical thick wall spiral drill (TWSD) with a hollow auger containing a complex coring system to retain subsurface regolith samples. Before the robotic drill was launched, a series of laboratory tests were carried out to investigate and predict the possible drilling loads it may encounter in the lunar environment. This work presents how the sampling performance of the TWSD is affected by the regolith compressibility. Experiments and analysis during the drilling and sampling process in a simulated lunar regolith environment were conducted. The compressibility of a typical lunar regolith simulant (LRS) was measured through uni-directional compression tests to study the relationship between its inner regolith stress and bulk density. A theoretical model was established to elucidate the cutting discharge behavior by auger flights based on the aforementioned relationship. Experiments were conducted with the LRS, and the results show that the sampling performance is greatly affected by the flux of the drilled cuttings into the spiral flight channels. This work helped in scheduling reasonable drilling parameters to promote the sampling performance of the robotic drill in the Chinese Chang'E 5 mission.  相似文献   
455.
因CFRP、TC4材料的物理性能差异较大,导致CFRP/TC4叠层构件切削性能匹配性较差,钻削过程中存在界面损伤、CFRP孔壁损伤难以调控的问题。针对上述问题,本文采用变参数啄式钻削工艺、变参数钻削工艺和恒参数钻削工艺对CFRP/TC4叠层结构进行了制孔实验,并对不同工艺条件下的轴向力、界面质量、TC4的切屑形态、CFRP层孔壁质量进行了对比分析。结果表明:相对于其他两种钻削工艺,在变参数啄式钻削工艺条件下,TC4材料层轴向力明显较高,产生短带状和短螺旋状切屑;CFRP层出口和入口处的孔径更接近于名义孔径,孔壁缺陷较少,表面粗糙度相对较小。  相似文献   
456.
利用热像仪对碳/环氧复合材料高速钻孔时的钻削温度及温度场分布进行了系统的试验研究。实验结果显示,钻削热主要是由刀具后刀面与已加工表面之间的摩擦产生的。转速越高,钻削温度赵高;进给量越大,钻削温度越低,但钻削温度一般不超过环氧树脂的玻璃化转变温度。  相似文献   
457.
《中国航空学报》2023,36(2):402-416
The use of space robots (SRs) for on-orbit services (OOSs) has been a hot research topic in recent years. However, the space unstructured environment (i.e.: confined spaces, multiple obstacles, and strong radiation interference) has greatly restricted the application of SRs. The coupled active-passive multilink cable-driven space robot (CAP-MCDSR) has the characteristics of slim body, flexible movement, and electromechanical separation, which is very suitable for extreme space environments. However, the dynamic and stiffness modeling of CAP-MCDSRs is challenging, due to the complex coupling among the active cables, passive cables, joints, and the end-effector. To deal with these problems, this paper proposes a workspace, stiffness analysis and design optimization method for such type of MCDSRs. Firstly, the multi-coupling kinematics relationships among the joint, cables and the end-effector are established. Based on hybrid series-parallel characteristics, the improved coupled active–passive (CAP) dynamic equation is derived. Then, the maximum workspace, the maximum stiffness, and the minimum cable tension are resolved, among them, the overall stiffness is the superposition of the stiffness produced by the active and the passive cable. Furthermore, the workspace, the stiffness, and the cable tension are analyzed by using the nonlinear optimization method (NOPM). Finally, an 8-DOF CAP-MCDSR experiment system is built to verify the proposed modeling and trajectory tracking methods. The proposed modeling and analysis results are very useful for practical space applications, such as designing a new CAP-MCDSR, or utilizing an existing CAP-MCDSR system.  相似文献   
458.
针对未来在轨服务过程中,可能遇到单个空间机器人难以独立胜任的应用场景,需要多个空间机器人协同操作,但目前针对多空间机器人协同工作空间的研究很少。考虑到解析法计算工作空间难度很大,提出了一种基于蒙特卡洛法的一般协同工作空间数值求解方法。再进一步针对空间机器人协同的特殊性,提出了广义协同工作空间的概念,并给出了数值求解方法。仿真结果表明,基座姿态约束会引起协同工作空间的缩小,同时广义协同工作空间的范围明显大于一般协同工作空间。所得结论可以为空间机器人任务设计与规划提供参考。  相似文献   
459.
为研究玻璃纤维复合材料钻削轴向力与分层特征,以电镀金刚石钻头和硬质合金麻花钻为钻削工具,对玻璃纤维复合材料进行正交钻削实验,研究钻头的几何形状、刀具材质以及钻削工艺参数对玻璃纤维复合材料钻削轴向力和钻削质量的影响.结果表明,钻削工艺参数直接影响玻璃纤维复合材料的钻削轴向力和钻削质量,高转速、低进给速度和合适的刀具结构、...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号