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791.
民用飞机融合式翼梢小翼优化设计   总被引:2,自引:0,他引:2  
民用飞机性能的提高将在很大程度上依赖于降低空气阻力。在巡航状态下,如果能减小机翼的诱导阻力,则全机的减阻效果将会得到很明显的提高。因此,本文以民用飞机机翼为设计平台,通过加装融合式翼梢小翼来减阻,并在设计了初始小翼的基础上,将减阻作为设计目标,对翼梢小翼的平面几何形状进行优化,并对结果进行了流动机理分析。  相似文献   
792.
针对空中运动目标的识别和跟踪,提出图像匹配算法和连通域算法相结合的方法。该方法主要用图像匹配算法获得目标的位置信息,当图像匹配算法失效时,则采用连通域算法重新捕获目标、获得图像模板。同时,为提高跟踪的实时性,采用最小二乘线性预测法来预测目标的运动轨迹。在实验室的目标跟踪系统平台上,该方法能够对运动目标进行稳定的识别和跟踪。  相似文献   
793.
The elliptical cross-section spiral equal-channel extrusion (ECSEE) process is simulated by using Deform-3D finite element software. The ratio m of major-axis to minor-axis length for ellipse-cross-section, the torsion angle u, the round-ellipse cross-section transitional channel L1, the elliptical rotation cross-section transitional channel L2 and the ellipse-round cross-section transitional channel L3 are destined for the extrusion process parameters. The average effective strain eave on cross-section of blank, the deformation uniformity coefficient a and the value of maximum damage dmax are chosen to be the optimize indexes, and the virtual orthogonal experiment of L16 (45) is designed. The correlation degree of the process factors affecting eave, a and dmax is analyzed by the numerical simulation results using the weights and grey association model. The process parameters are optimized by introducing the grey situation decision theory and the ECSEE optimal combination of process parameters is obtained: u of 120 , m of 1.55, L1 of 7 mm, L2 of 10 mm, and L3 of 10 mm. Simulation and experimental results show that the material can be refined with the optimized structural parameters of die. Therefore, the optimization results are satisfactory.  相似文献   
794.
Approaching control is a key mission for the tethered space robot to perform the task of removing space debris. But the uncertainties of the TSR such as the change of model parameter have an important effect on the approaching mission. Considering the space tether and the attitude of the gripper, the dynamic model of the TSR is derived using Lagrange method. Then a disturbance observer is designed to estimate the uncertainty based on STW control method. Using the disturbance observer, a controller is designed, and the performance is compared with the dynamic inverse controller which turns out that the proposed controller performs better. Numerical simulation validates the feasibility of the proposed controller on the position and attitude tracking of the TSR.  相似文献   
795.
针对模拟电路故障不易被检测、不易被精确定位且现场情况复杂的特点,本文以基本共射放大电路为例重点研究了基于BP神经网络的模拟电路故障诊断方法。首先,提取待测电路特征值,对可能出现的电路故障编号,随机测量多组电路正常情况下和各故障状态下的电路特性,包括输入、输出电阻,上限、下限截止频率,增益等。随后,将测量得到的多组电路特征值用于故障检测模型的训练。接着,根据模型输出值与目标值的误差,调整模型参数,直至误差满足要求。最后,将模型参数固化于诊断系统微控制器的Flash中。经实验验证,依据该方法设计的便携式故障诊断系统具有较高准确率和较低的成本,切合社会生产实际。另外,由于其结合了深度学习算法和电子线路分析方法,也可用于电子信息类本科教育课程实践。  相似文献   
796.
The two line elements(TLEs),released by the North American Aerospace Defense Command(NORAD),are chosen for CubeSats' mission operators.Unfortunately,they have errors and other accompanied problems,which cause large deviations in the in-track component.When a TLE value is available at a certain epoch,the dominant error is the angular error.It is proposed to correct the angular error by solving-for the mean argument of latitude at the desired epoch.A batch least squares technique and range rate measurements are used for the correction process.With the assistance of satellite tool kit(STK)software and Matlab,a simulation to verify the orbit determination(OD)technique is implemented.This paper provides an angular correction low cost OD method and presents a complete analysis for various test cases.This approach maintains high accuracy in cross-track and radial and makes great improvement in in-track at the same time,but it is exclusive for circular orbits.When it is applied to an elliptical orbit,the error will be unacceptable.Therefore,the angular error is corrected using the longitude of periapsis which totally mitigates the error at the epoch under consideration.For inclinations less than 20 o,the mean longitude is preferred for the angular correction as it provides more accuracy compared with the mean argument of latitude.  相似文献   
797.
798.
The APOD (Atmospheric density detection and Precise Orbit Determination) is the first LEO (Low Earth Orbit) satellite in orbit co-located with a dual-frequency GNSS (GPS/BD) receiver, an SLR reflector, and a VLBI X/S dual band beacon. From the overlap statistics between consecutive solution arcs and the independent validation by SLR measurements, the orbit position deviation was below 10?cm before the on-board GNSS receiver got partially operational. In this paper, the focus is on the VLBI observations to the LEO satellite from multiple geodetic VLBI radio telescopes, since this is the first implementation of a dedicated VLBI transmitter in low Earth orbit. The practical problems of tracking a fast moving spacecraft with current VLBI ground infrastructure were solved and strong interferometric fringes were obtained by cross-correlation of APOD carrier and DOR (Differential One-way Ranging) signals. The precision in X-band time delay derived from 0.1?s integration time of the correlator output is on the level of 0.1?ns. The APOD observations demonstrate encouraging prospects of co-location of multiple space geodetic techniques in space, as a first prototype.  相似文献   
799.
800.
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