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171.
非线性三维自适应模糊变结构制导规律的研究 总被引:2,自引:0,他引:2
在三维球坐标系下建立了导弹与目标的相对运动模型,针对大机动目标提出了一种 基于零化导弹与目标视线角速度的三维自适应模糊变结构末制导律。所设计的制导律通过模 糊系统对非线性模型进行逼近,克服了模型不确 定性和外界干扰对制导系统的影响,并把目标加速度视为一类有界干扰,在线对目标加速度 的界进行估计。通过计算机数字仿真验证了导弹与目标的相对视线角速度最终趋向于零,验 证了制导规律的正确性和有效性。 相似文献
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《中国航空学报》2020,33(12):3112-3124
This paper presents a method to predict the pilot workload in helicopter landing after one engine failure. The landing procedure is simulated numerically via applying nonlinear optimal control method in the form of performance index, path constraints and boundary conditions based on an augmented six-degree-of-freedom rigid-body flight dynamics model, solved by collocation and numerical optimization method. UH-60A helicopter is taken as the sample for the demonstration of landing after one engine failure. The numerical simulation was conducted to find the trajectory of helicopter and the controls from pilot for landing after one engine failure with different performance index considering the factor of pilot workload. The reasonable performance index and corresponding landing trajectory and controls are obtained by making a comparison with those from the flight test data. Furthermore, the pilot workload is evaluated based on wavelet transform analysis of the pilot control activities. The workloads of pilot control activities for collective control, longitudinal and lateral cyclic controls and pedal control during the helicopter landing after one engine failure are examined and compared with those of flight test. The results show that when the performance index considers the factor of pilot workload properly, the characteristics of amplitudes and constituent frequencies of pilot control inputs in the optimal solution are consistent with those of the pilot control inputs in the flight test. Therefore, the proposed method provides a tool of predicting the pilot workload in helicopter landing after one engine failure. 相似文献
177.
In this paper, a new approach has been proposed to identify and model the dynamics of a highly maneuverable fighter aircraft through artificial neural networks(ANNs). In general, aircraft flight dynamics is considered as a nonlinear and coupled system whose modeling through ANNs, unlike classical approaches, does not require any aerodynamic or propulsion information and a few flight test data seem sufficient. In this study, for identification and modeling of the aircraft dynamics, two known structures of internal and external recurrent neural networks(RNNs) and a proposed structure called hybrid combined recurrent neural network have been used and compared.In order to improve the training process, an appropriate evolutionary method has been applied to simultaneously train and optimize the parameters of ANNs. In this research, it has been shown that six ANNs each with three inputs and one output, trained by flight test data, can model the dynamic behavior of the highly maneuverable aircraft with acceptable accuracy and without any priori knowledge about the system. 相似文献
178.
A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the two dimensional airfoil, the wing, and the full aircraft. Different non- linearities encountered in aeroelastic systems are discussed firstly, where the emphases is placed on new nonlinear model to describe tested nonlinear relationship. Research techniques, especially new theoretical methods and aeroelastic flutter control methods are investigated in detail. The route to chaos and the cause of chaotic motion of two-dimensional aeroelastic system are summarized. Var- ious structural modeling methods for the high-aspect-ratio wing with geometric nonlinearity are dis- cussed. Accordingly, aerodynamic modeling approaches have been developed for the aeroelastic modeling of nonlinear high-aspect-ratio wings. Nonlinear aeroelasticity about high-altitude long- endurance (HALE) and fight aircrafts are studied separately. Finally, conclusions and the chal- lenges of the development in nonlinear aeroelasticity are concluded. Nonlinear aeroelastic problems of morphing wing, energy harvesting, and flapping aircrafts are proposed as new directions in the future. 相似文献
179.
建立了考虑材料塑性强化的滚弯成形力学分析解析模型,推导出了应力应变、残余应力以及回弹半径计算公式.基于非线性有限元软件,对滚弯成形进行了动态模拟,对应力应变状态、塑性应变分布、残余应力以及回弹等进行了分析计算,结果表明:板料滚弯成形初始效应明显,下压点附近曲率不均匀;采用足够的滚弯时间后,中间段的曲率均匀度很好;成形半径与上辊下压量呈近似幂函数关系;多道次滚弯可以减小两端的曲率波动和最大应力应变.最后通过与滚弯成形试验数据的对比,分析和验证了解析模型与数值模型的适用性和精度. 相似文献
180.
G.S. Lakhina S.V. SinghA.P. Kakad 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A general model for the ion- and electron-acoustic solitons and double layers in a multi-component unmagnetized plasma consisting of background electrons, counter-streaming electron beams and ions is discussed. The model is based on the multi-fluid equations and the Poisson equation, and uses the Sagdeev pseudo-potential techniques. For identical counter-streaming electron beams and depending upon the plasma parameters, three types of solutions, namely, ion-acoustic, slow and fast electron-acoustic soliton/double layer, are possible. Generally, the ion acoustic solitons have positive potentials, slow-electron acoustic solitons have negative potentials and fast electron-acoustic solitons and double layers can have either positive or negative potentials depending on the core electron density. As beam speed is increased, first ion-acoustic and then slow electron-acoustic solitons disappear. At large beam speed, only fast electron-acoustic solitons/double layers survive. The results may be relevant to the observations of the electrostatic solitary waves (ESWs) observed in the Earth’s magnetosphere. 相似文献