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581.
Kai Qin Lixin Wu Shuo Zheng Weiyu Ma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(5):1324-1331
In the process of exploring pre-earthquake thermal anomalies using satellite infrared data, Blackett et al. (2011) found that the previously reported anomalies before the 2001 Mw 7.7 Gujarat earthquake, in India, were related to positive biases caused by data gaps due to cloud cover and mosaicing of neighboring orbits of MODIS satellite data. They supposed that such effects could also be responsible for other cases. We noted a strip-shaped TIR anomaly on March 17th, 2010, 28?days before the Ms. 7.1 Yushu earthquake (Qin et al., 2011). Here we again investigate multi-year infrared satellite data in different bands to discriminate whether the anomaly is associated with the earthquake, or is only bias caused by the data gaps. From the water vapor images, we find lots of clouds that have TIR anomalies. However, on the cloudiness background, there is an obvious strip-shaped gap matching the tectonic faults almost perfectly. In particular, the animation loops of hourly water vapor images show that the cloud kept moving from west to east, while they never covered the strip-shaped gap. We consider that the cloud with this special spatial pattern should have implied the abnormal signals associated with the seismogenic process. Based on current physical models, the satellite IR anomalies both on TIR and water vapor bands can qualitatively be explained using synthetic mechanisms. 相似文献
582.
附加周期和神经网络补偿的实时钟差预报模型 总被引:1,自引:0,他引:1
考虑到多项式模型拟合残差中仍存在显著周期信号及其他系统误差影响,提出构建一种多项式结合周期项与BP神经网络的北斗(BDS)超快速钟差预报模型,并利用实测超快速钟差数据进行算法测试验证。数值算例结果显示:利用本文模型得到的北斗超快速钟差产品,相比国内iGMAS超快速钟差产品(ISU)与德国地学中心超快速钟差产品(GBU),预报精度在3 h,6 h,12 h和24 h四个方面分别提升了26.14%,16.46%,12.68%和 10.58% 及10.34%,13.85%,8.17%和14.41%。 相似文献
583.
基于层面结构的三维闭合地质区块构造算法 总被引:15,自引:2,他引:13
复杂地质体几何模型的建立是油气勘探开发领域的一项重要工作,在介绍目前地质体几何建模方法的同时,分析了表面建模方法与实体建模方法相互之间的融合趋势,提出了一种基于三角网格模型的整体建模过程,并在地质体层面三角网格模型的基础上,提出了一种改进的半边数据结构,给出了一种三维地质体闭合区块结构的构造算法,该算法为进一步的地质体实体模型的建立奠定了基础,并且可应用于地震正演模拟计算,射线追踪和三维地质模型可视化等领域. 相似文献
584.
基于遗传算法的定位布局优化新方法 总被引:1,自引:0,他引:1
在夹具设计过程中,建立了一种定位元件布局确定的新方法.该方法基于模糊评判,考虑候选表面特征类型、表面面积、位置公差等影响因素,确定定位参考面和定位点的数量.以定位误差最小为优化目标通过遗传算法确定定位点的具体位置.最后,通过实例验证该方法优于检验设计,并且能有效提高定性精度. 相似文献
585.
以甲基三乙氧基硅烷为前驱体,通过溶胶-凝胶法和超临界干燥制备块状柔性SiO2气凝胶.研究了前驱体浓度对材料化学组成、微观结构及柔韧性、热稳定性的影响.结果表明,甲基的存在降低了分子网络的交联密度,赋予了材料柔韧性.随着前驱体浓度降低,微观结构中颗粒堆积紧密程度下降,材料的柔韧性增强;同时分子中硅羟基增多,热稳定性提高. 相似文献
586.
Among a variety of design requirements, reducing the drag and aeroheating on hypersonic vehicles is the most crucial one. Unfortunately, these two objectives are often conflicting. On one hand, sharp slender forebodies design reduces the drag and ensures longer ranges and more economic flights. However, they are more vulnerable to aerodynamic heating. On the other hand, blunt forebodies produce more drag, however, they are preferred as far as aeroheating is concerned. In addition, in the context of hypersonic vehicles, blunt geometries are preferred over slender ones for practical implications such as higher volumetric efficiency, better accommodation of crew or on-board equipment.In principle, a blunt vehicle flying at hypersonic speeds generates a strong bow shock wave ahead of its nose, which is responsible for the high drag and aeroheating levels. There have been a number of efforts devoted towards reducing both the drag and the aeroheating by modifying the flowfield ahead of the vehicle's nose. Of these techniques, using spikes is the simplest and the most reliable technique. A spike is simply a slender rod attached to the stagnation point of the vehicle's nose. The spike replaces the strong bow shock with a system of weaker shocks along with creating a zone of recirculating flow ahead of the forebody thus reducing both drag and aeroheating.Since their introduction to the high-speed vehicles domain in the late 1940s, spikes have been extensively studied using both experimental facilities and numerical simulation techniques. The present paper is devoted to surveying these studies and illustrating the contributions of the authors in this field. The paper also raises some of the areas in the field that need further investigations. 相似文献
587.
588.
秦健 《中国民航飞行学院学报》2011,(5):61-63,66
广州民航职业技术学院航空港安全检查专业从职业岗位工作任务分析入手,按完成工作任务的要求来设置课程和实训项目,系统设计了以职业能力和综合素质培养为主体、突出能力目标和安检岗位工作要求的、基于工作过程与行业标准的"课证一体"型的专业课程体系,努力实现知识与应用、理论与实践的有机结合,有效地提高了人才培养的质量。 相似文献
589.
590.
直升机海面悬停时精确高度的维纳滤波提取法 总被引:2,自引:0,他引:2
研究了直升机作海面低高度(15m)悬停时获取精确高度的维纳滤波组合系统。高度量测来自捷联垂直加速度计和无线电高度表。维纳滤波器根据海浪、无线电高度表噪声和加速度计噪声三种随机干扰的功率谱采用伯特一香农设计法获得。对组合系统作了五种环境下的滤波仿真,结果表明:该系统既能有效滤除上述三种干扰,又能准确跟踪悬停高度的变化。 相似文献