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361.
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我国空间引力波探测"太极计划"将打开中低频段(0.1 mHz~1 Hz)的引力波观测窗口,为人类研究宇宙起源与演化、黑洞起源与演化、引力本质、暗能量和暗物质等提供全新的方法和手段。由于空间引力波探测涉及一系列关键技术,太极计划提出了"单星""双星"和"三星"3步走的发展路线图。目前"单星"计划——"太极1号"发射成功,并圆满完成了第一阶段的在轨测试。本文将简要介绍空间引力波探测的科学价值、国内外背景和关键技术分解,重点对太极计划及其3步走发展规划进行分析,并提出后续工作的一些设想和发展建议。 相似文献
363.
Bobby Kazeminejad David H. Atkinson Jean-Pierre Lebreton 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The European Space Agency’s Huygens probe separated from the NASA Cassini spacecraft on 25 December 2004, after having been attached for a 7-year interplanetary journey and three orbits around Saturn. The probe reached the predefined NASA/ESA interface point on 14 January 2005 at 09:05:52.523 (UTC). It performed a successful entry and descent sequence and softly landed on Titan’s surface on the same day at 11:38:10.77 (UTC) with a speed of about 4.54 m/s. Since the publication of the official project entry and descent trajectory reconstruction effort by the Descent Trajectory Working Group in 2007 (referred to as DTWG#4) various other efforts have been performed and published. This paper presents an overview of the most relevant reconstructions and compares their methodologies and results. Furthermore, the results of a new reconstruction effort (DTWG#5) are presented, which is based on the same methodology as DTWG#4 but takes into account new estimates of Titan’s pole coordinates which were derived from radar images of different Cassini Titan flybys. It can be shown that the primary effect can be observed in the meridional direction which is represented by a stark southward shift of the trajectory by about 0.3 deg. A much smaller effect is seen in the zonal direction (i.e., less than 0.01 deg in the west to east direction). The revised probe landing coordinates are 192.335 deg W and 10.573 deg S. A comparison of these coordinates with results of recent landing site investigations using visual and radar images of the Cassini VIMS instrument shows excellent agreement of the two independently derived landing coordinates, i.e., longitude and latitude residuals of respectively 0.035 deg and 0.007 deg. 相似文献
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从试验手段能力角度引入了可信度的定义,针对可信度改进了贝叶斯算法,同时把试验阶段内所有试验同等对待,推导出了多源数据融合算法,有效解决了大样本验前信息压制小子样现场试验的问题。 相似文献
366.
Fast solar sail rendezvous mission to near Earth asteroids 总被引:1,自引:0,他引:1
The concept of fast solar sail rendezvous missions to near Earth asteroids is presented by considering the hyperbolic launch excess velocity as a design parameter. After introducing an initial constraint on the hyperbolic excess velocity, a time optimal control framework is derived and solved by using an indirect method. The coplanar circular orbit rendezvous scenario is investigated first to evaluate the variational trend of the transfer time with respect to different hyperbolic excess velocities and solar sail characteristic accelerations. The influence of the asteroid orbital inclination and eccentricity on the transfer time is studied in a parametric way. The optimal direction and magnitude of the hyperbolic excess velocity are identified via numerical simulations. The found results for coplanar circular scenarios are compared in terms of fuel consumption to the corresponding bi-impulsive transfer of the same flight time, but without using a solar sail. The fuel consumption tradeoff between the required hyperbolic excess velocity and the achievable flight time is discussed. The required total launch mass for a particular solar sail is derived in analytical form. A practical mission application is proposed to rendezvous with the asteroid 99942 Apophis by using a solar sail in combination with the provided hyperbolic excess velocity. 相似文献
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基于改进的Gauss伪谱法,研究了探月返回器跳跃式再入轨迹优化设计问题.首先给出了探月返回器再入轨迹优化问题的三维模型.然后针对探月返回器配平攻角飞行的特点,考虑到实际倾侧角反转机动不可能瞬时完成,对单一控制变量倾侧角的变化范围进行合理限制,并以总吸热量为性能指标,设计了满足过载和驻点热流约束的小升力体大航程跳跃式再入轨迹.最后基于该优化算法,将返回器在各相同初始条件下发生跳跃和不发生跳跃时的最大航程进行比较,并求解得到在不同升阻比和存在不同程度大气密度偏差时不发生跳跃的再入轨迹最大航程和过载峰值,以分析跳跃式轨迹在扩大小升力体再入航程方面的优势. 相似文献
370.
地球同步轨道卫星多阶段任务可靠性建模 总被引:1,自引:0,他引:1
在分析地球同步轨道卫星首次变轨任务剖面的基础上,以模块化的思路进行卫星多阶段任务系统(phased-mission systems,PMS)建模,采用基于二元决策图(binary decision diagram,BDD)的静态多阶段任务可靠性分析方法和基于马尔可夫模型的动态多阶段任务分析方法来计算地球同步轨道卫星转移轨道段首次变轨的可靠性。经与传统非任务剖面可靠性分析方法的计算结果比对可知,基于任务剖面的可靠性建模分析方法可得到较为真实和精细的结果,有助于卫星的轻量化设计和研制效益提高。 相似文献