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191.
192.
杨振声 《北京航空航天大学学报》1993,(4):105-111
本文将一维三次样条函数推广到多维问题,它保留了三对角矩阵方程便于求解的特性,并能得到满意的插值、一阶和二阶偏导数。关于边界条件问题,若能给出边界节点处的一阶偏导数边界条件,则精度最高,但在大多数应用问题中,往往给不出此条件。为此,本文提出一种改进方法,即用拉格朗日三点插值法由域边附近的节点数据计算出边界节点处的一阶偏导数。算例表明,此法可改善精度。 相似文献
193.
利用1980年Nimbus-7卫星网络点资料(温度场)对中层大气行星波的空间结构进行诊断和分析后发现,行星波扰动主要集中于冬半球,夏半球及赤道地区上空的扰动则相对较弱,但也不可忽视.冬半球行星波扰动中的瞬变波部分可以跨过赤道向夏半球传播,且传播主要集中于20kin和70km两个高度层附近.波数1冬季以准定常行里波为主,夏季瞬变行星波与准定常行星波波幅相当.行星波扰动的波幅从冬到夏的衰减主要表现在波数1和波数2上,波数3变化不大. 相似文献
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对由AGV承载的工业机器人组成的AGV式移动制孔机器人的定位误差补偿方法进行了研究。在面向飞机装配的AGV式移动制孔机器人系统中,利用激光跟踪仪构建坐标系,提出了AGV式移动制孔机器人机座坐标系的换站方法,能更好地适应飞机制造多品种、小批量的特点。基于对AGV式移动制孔机器人定位误差源的分析,利用定位误差相似性,提出针对AGV式移动制孔机器人的基于反距离加权定位误差的空间插值与补偿方法,克服了现有技术对于AGV式移动制孔机器人定位误差补偿的局限性。以AGV搭载的KUKA KR480型工业机器人制孔系统作为试验对象,通过试验选取最优网格步长,补偿结果表明,能将系统综合定位误差平均值由补偿前的1.045 mm降低到0.227 mm,最大绝对定位误差由补偿前的2.727 mm降低到0.478 mm,降低了82.47%,该方法能有效提高AGV式移动制孔机器人的绝对定位精度。 相似文献
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D. Sudheer Reddy N. Gopal Reddy A.K. Anilkumar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The events that occurred after 2007 such as Chinese anti-satellite test, explosion of Briz-M upper stage, break up of cosmos-2421 and collision of cosmos-2251 with Iridium-33 satellites have completely changed the spatial density patterns in low earth orbits. This has increased the risk of collision between active satellites and debris created by them. Aftermath, the risk assessment of possible collisions called as conjunction analysis of working satellites from day to day has become more crucial. Spatial density models are useful in understanding the long-term likelihood of a collision in a particular region of space and helpful in pre-launch orbit planning. In this paper we present an algorithmic procedure for automatically estimating exact model parameters corresponding to the peak location and number of peaks using wavelets that will speed up the parameter estimation process for the models with peaks. 相似文献
199.
《中国航空学报》2020,33(10):2679-2693
In recent years, the Active Flutter Suppression (AFS) employing Linear Parameter-Varying (LPV) framework has become a hot spot in the research field. Nevertheless, the flutter suppression technique is facing two severe challenges. On the one hand, due to the fatal risk of flight test near critical airspeed, it is hard to obtain the accurate mathematical model of the aeroelastic system from the testing data. On the other hand, saturation of the actuator may degrade the closed-loop performance, which was often neglected in the past work. To tackle these two problems, a new active controller design procedure is proposed to suppress flutter in this paper. Firstly, with the aid of LPV model order reduction method and State-space Model Interpolation of Local Estimates (SMILE) technique, a set of high-fidelity Linear Time-Invariant (LTI) models which are usually derived from flight tests at different subcritical airspeeds are reduced and interpolated to construct an LPV model of an aeroelastic system. And then, the unstable aeroelastic dynamics beyond critical airspeed are ‘predicted’ by extrapolating the resulting LPV model. Secondly, based on the control-oriented LPV model, an AFS controller in LPV framework which is composed of a nominal LPV controller and an LPV anti-windup compensator is designed to suppress the aeroelastic vibration and overcome the performance degradation caused by actuator saturation. Although the nominal LPV controller may have superior performance in linear simulation in which the saturation effect is ignored, the results of the numerical simulations show that the nominal LPV controller fails to suppress the Body Freedom Flutter (BFF) when encountering the actuator saturation. However, the LPV anti-windup compensator not only enhances the nominal controller’s performance but also helps the nominal controller to stabilize the unstable aeroelastic system when encountering serious actuator saturation. 相似文献
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