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31.
太阳宇宙线在电离层D层中的电离 总被引:2,自引:0,他引:2
本文根据带电粒子对D层大气电离的理论,导出了太阳宇宙线在D层的电子产生率Q(h)的表达式,并计算了不同级别的太阳宇宙线事件、不同能谱参数下,Q(h)在极区随高度的分布。结果表明,不同级别、不同能谱的太阳宇宙线事件在极区产生的电离有显著的差别。同一级别,能谱指数γ越大,在较高的高度上电子产生率越大;能谱指数越小,在较低的高度上电子产生率越大。电子产生率的分布曲线出现明显的双峰,一个峰位于60公里左右,另一个峰位于85公里左右。前一个峰主要由太阳宇宙线中质子产生的,后一个峰主要是z≥2的重粒子成分产生的。本文所得结果明显好于Velinov等人的结果。 相似文献
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A global view of the ring current ions is presented using data acquired by the instrument MICS onboard the CRRES satellite during solar maximum. The variations of differential intensities, energy spectra, radial profile of the energetic particles and the origin of the magnetic local time (MLT) asymmetry of the ring current have been investigated in detail. O+ ions are an important contributor to the storm time ring current. Its abundance in terms of number density increases with increasing geomagnetic activity as well as its energy density. However, a saturation value for the energy density of O+ ions has been found. The low-energy H+ ions show a dramatic intensification and a rapid decay. However, its density ratio during the storm maximum is almost constant. On the other hand, high-energy H+ ions first exhibit a flux decrease followed by a delayed increase. Its density ratio shows an anti-correlation with the storm intensity. Both the positions of the maximum flux of O+ and He+ depend on storm activity: they move to lower altitudes in the early stage of a storm and move back to higher L-values during the recovery phase. Whereas the position of H+ and He++ show almost no dependence on the Dst index. The energy density distributions in radial distance and magnetic local time show drastic differences for different ion species. It demonstrates that the ring current asymmetry mainly comes from oxygen and helium ions, but not from protons. The outward motion of O+ around local noon may have some implications for oxygen bursts in the magnetosheath during IMF Bz negative conditions as observed by GEOTAIL. 相似文献
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灵巧壁面移动机器人运动学和动力学研究 总被引:3,自引:2,他引:1
灵巧壁面移动机器人是一个约束可变的系统,其可控性问题有待于证实.针对履带驱动方式具有非完整约束的性质,利用李群理论和微分几何的分析方法,对各种构型情况下灵巧壁面移动机器人运动学和动力学特性进行了研究,证明了灵巧壁面移动机器人的可控性,建立了机器人动力学方程,为机器人控制器的设计提供了理论指导. 相似文献
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Lijun Zong Jianjun Luo Mingming Wang Jianping Yuan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(8):1997-2009
This paper presents a novel obstacle avoidance constraint and a mixed integer predictive control (MIPC) method for space robots avoiding obstacles and satisfying physical limits during performing tasks. Firstly, a novel kind of obstacle avoidance constraint of space robots, which needs the assumption that the manipulator links and the obstacles can be represented by convex bodies, is proposed by limiting the relative velocity between two closest points which are on the manipulator and the obstacle, respectively. Furthermore, the logical variables are introduced into the obstacle avoidance constraint, which have realized the constraint form is automatically changed to satisfy different obstacle avoidance requirements in different distance intervals between the space robot and the obstacle. Afterwards, the obstacle avoidance constraint and other system physical limits, such as joint angle ranges, the amplitude boundaries of joint velocities and joint torques, are described as inequality constraints of a quadratic programming (QP) problem by using the model predictive control (MPC) method. To guarantee the feasibility of the obtained multi-constraint QP problem, the constraints are treated as soft constraints and assigned levels of priority based on the propositional logic theory, which can realize that the constraints with lower priorities are always firstly violated to recover the feasibility of the QP problem. Since the logical variables have been introduced, the optimization problem including obstacle avoidance and system physical limits as prioritized inequality constraints is termed as MIPC method of space robots, and its computational complexity as well as possible strategies for reducing calculation amount are analyzed. Simulations of the space robot unfolding its manipulator and tracking the end-effector’s desired trajectories with the existence of obstacles and physical limits are presented to demonstrate the effectiveness of the proposed obstacle avoidance strategy and MIPC control method of space robots. 相似文献
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宗光华 《北京航空航天大学学报》1990,(2):111-116
本文推导了一种气动人工肌肉系统的数学模型。探讨了用变结构系统理论实现人工肌肉夹持力控制的方法。给出了仿真和实验结果。人工肌肉既可以输出力(力矩),又可以调节刚性,是一种在柔顺运动控制中很有应用前途的新型作动器。 相似文献
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针对月壤剖面钻进成孔探测需求,提出一种锥型螺旋刃成孔钻头,建立其钻进排屑性能的理论模型,并以此开展钻头结构参数的优化设计。在此基础上,分析螺旋刃切削姿态及其切削参数,基于直线刃平面切削理论建立锥型螺旋刃成孔钻头钻进切削负载预估模型,开展锥型螺旋刃成孔钻头模拟月壤剖面钻进负载特性试验验证。研究结果表明,相比于直线刃钻头,锥型螺旋刃成孔钻头的钻进排屑性能更优,而且钻进切削负载模型与试验结果具有较好的吻合度。研究成果对我国拟实施的月面钻取采样工程具有重要的借鉴价值。 相似文献
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