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281.
为量化分析Crab脉冲星X射线波段光子到达时间(TOA)测量误差和自转频率误差对脉冲TOA估计的影响,仿真生成了13 200组带有不同光子TOA测量误差的光子TOA数据。采用含有不同大小自转频率误差的Crab脉冲星星历,通过历元折叠建立积分脉冲轮廓,与标准脉冲轮廓作互相关运算获得各组仿真观测的脉冲TOA测量误差,进一步计算出各误差参数组的仿真观测脉冲TOA测量误差均方根(RMS)。仿真结果表明,为使Crab脉冲星脉冲TOA短期测量精度达到30 ~300 μs量级的要求,有效面积为6 000 cm2和30 cm2的探测器脉冲星自转频率误差均应小于3×10-6 Hz,30 cm2的探测器光子TOA的偶然误差同时应控制在500 μs以内。 相似文献
282.
在组合导航系统中Kalman滤波技术的应用 总被引:1,自引:0,他引:1
在导航系统中引入Kalman滤波技术,主要是为了减小导航定时的参数误差并提高系统的定位精度,以INS/GPS组合导航系统为背景,设计位置速度组合模式的卡尔曼滤波器,并对组合导航系统进行仿真研究,结果表明组合导航系统在导航精度和稳定性方面较单一的导航系统都有提高。 相似文献
283.
飞船返回地球时再入速度很大,过大的过载和气动加热率尤其对载人飞船带来安全性问题。如果利用航天器在大气层外及其边缘处多次再入运动,可降低速度、耗散热量。文章主要分析了载人飞船在大气层外多次再入飞行时的各主要参数对飞船轨道和轨道终点的影响。在分析过程中,首先建立了飞船在大气层外飞行的数学模型,进而通过大量的数值仿真得到一条基准轨道,在此基础上分别改变轨道起始点参数(倾角、偏航角和飞行速度)的初始值,分析轨道的特性及轨道的终点误差。最后根据起始点参数值和对应的轨道终点误差值的关系,得到了飞船在大气层外飞行时的起始参数对飞行轨道及轨道终点影响的敏感度,从而为工程上轨道的设计提供一个有效的参考依据。 相似文献
284.
Experimental study of ice accretion effects on aerodynamic performance of an NACA 23012 airfoil 总被引:1,自引:1,他引:1
《中国航空学报》2016,(3):585-595
In this paper,the effects of icing on an NACA 23012 airfoil have been studied.Experiments were applied on the clean airfoil,runback ice,horn ice,and spanwise ridge ice at a Reynolds number of 0.6 106 over angles of attack from 8° to 20°,and then results are compared.Generally,it is found that ice accretion on the airfoil can contribute to formation of a flow separation bubble on the upper surface downstream from the leading edge.In addition,it is made clear that spanwise ridge ice provides the greatest negative effect on the aerodynamic performance of the airfoil.In this case,the stall angle drops about 10° and the maximum lift coefficient reduces about50% which is hazardous for an airplane.While horn ice leads to a stall angle drop of about 4° and a maximum lift coefficient reduction to 21%,runback ice has the least effect on the flow pattern around the airfoil and the aerodynamic coefficients so as the stall angle decreases 2° and the maximum lift reduces about 8%. 相似文献
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287.
This paper proposes a generic high-performance and low-time-overhead software control flow checking solution, graph-tree-based control flow checking (GTCFC) for space-borne commercial- off-the-shelf (COTS) processors. A graph tree data structure with a topology similar to common trees is introduced to transform the control flow graphs of target programs. This together with design of IDs and signatures of its vertices and edges allows for an easy check of legality of actual branching during target program execution. As a result, the algorithm not only is capable of detecting all single and multiple branching errors with low latency and time overheads along with a linear-complexity space overhead, but also remains generic among arbitrary instruction sets and independent of any specific hardware. Tests of the algorithm using a COTS-processor-based onboard computer (OBC) of in-service ZDPS-1A pico-satellite products show that GTCFC can detect over 90% of the randomly injected and all-pattern-covering branching errors for different types of target programs, with performance and overheads consistent with the theoretical analysis; and beats well-established preeminent control flow checking algorithms in these dimensions. Furthermore, it is validated that GTCGC not only can be accommodated in pico-satellites conveniently with still sufficient system margins left, but also has the ability to minimize the risk of control flow errors being undetected in their space missions. Therefore, due to its effectiveness, efficiency, and compatibility, the GTCFC solution is ready for applications on COTS processors on pico-satellites in their real space missions. 相似文献
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289.
《中国航空学报》2021,34(5):504-509
The interaction length induced by Shock Wave/Turbulent Boundary-Layer Interactions (SWTBLIs) in the hypersonic flow was investigated using a scaling analysis, in which the interaction length normalized by the displacement thickness of boundary layer was correlated with a corrected non-dimensional separation criterion across the interaction after accounting for the wall temperature effects. A large number of hypersonic SWTBLIs were compiled to examine the scaling analysis over a wide range of Mach numbers, Reynolds numbers, and wall temperatures. The results indicate that the hypersonic SWTBLIs with low Reynolds numbers collapse on the supersonic SWTBLIs, while the hypersonic cases with high Reynolds numbers show a more rapid growth of the interaction length than that with low Reynolds numbers. Thus, two scaling relationships are identified according to different Reynolds numbers for the hypersonic SWTBLIs. The scaling analysis provides valuable guidelines for engineering prediction of the interaction length, and thus, enriches the knowledge of hypersonic SWTBLIs. 相似文献
290.
由于雷达跟踪测量数据总存在误差,而目前采用的误差处理算法修正效果并不理想,为了有效估计数据中的未知误差,提高数据处理的精度,提出了一种基于希尔伯特-黄算法的雷达误差残差诊断方法,利用得到的内蕴模态函数拟合出误差残差的特征,准确分离出设备的误差信息。通过对某雷达的实测数据分析证明该方法较其他方法对解决该类问题更为有效,且在事后高精度数据处理中具有较好的实用性。 相似文献