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排序方式: 共有188条查询结果,搜索用时 187 毫秒
41.
Whipple防护屏弹道极限参数试验 总被引:10,自引:6,他引:10
在中国空气动力研究与发展中心FD-18A超高速碰撞靶上进行了Whipple防护屏的超高速撞击试验。弹丸为LY12铝球,撞击速度为4.5km/s,撞击角为0°。通过固定弹丸速度、变弹丸直径、寻找弹丸临界直径的办法获得了该Whipple防护屏在试验条件下的弹道极限参数。试验结果表明速度为4.5km/s时的弹丸临界直径为0.35cm,大于用Christiansen方程预测的0.27cm。 相似文献
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Asok K. Sen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009,44(11):1321-1325
We have used the Lempel–Ziv measure to describe the complexity in sunspot activity during the solar cycles 18–23. In particular, we examined the time series of daily sunspot numbers in the northern and southern hemispheres in each of the six cycles and calculated the Lempel–Ziv complexity (LZC) value for each time series. Our results indicate that in the even cycles, the LZC values of the sunspot numbers in the two hemispheres are very close to each other, whereas in the odd cycles they differ significantly between the two hemispheres. We also find that within each hemisphere the LZC varies from cycle to cycle. This even–odd cycle parity reflects the variations in inter-hemispheric strengths of the solar magnetic field leading to different temporal distributions of sunspots in the two hemispheres. The degree of complexity may influence the predictability of sunspot activity in the two hemispheres during the various cycles. Although the physical implication of the results is not clear, these results may stimulate new ideas into modeling the complex dynamics of the solar dynamo. 相似文献
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P. M. E. Décréau P. Fergeau V. Krannosels'kikh M. Lévêque Ph. Martin O. Randriamboarison F. X. Sené J. G. Trotignon P. Canu P. B. Mögensen 《Space Science Reviews》1997,79(1-2):157-193
The WHISPER sounder on the Cluster spacecraft is primarily designed to provide an absolute measurement of the total plasma density within the range 0.2–80 cm-3. This is achieved by means of a resonance sounding technique which has already proved successful in the regions to be explored. The wave analysis function of the instrument is provided by FFT calculation. Compared with the swept frequency wave analysis of previous sounders, this technique has several new capabilities. In particular, when used for natural wave measurements (which cover here the 2–80 kHz range), it offers a flexible trade-off between time and frequency resolutions. In the basic nominal operational mode, the density is measured every 28 s, the frequency and time resolution for the wave measurements are about 600 Hz and 2.2 s, respectively. Better resolutions can be obtained, especially when the spacecraft telemetry is in burst mode. Special attention has been paid to the coordination of WHISPER operations with the wave instruments, as well as with the low-energy particle counters. When operated from the multi-spacecraft Cluster, the WHISPER instrument is expected to contribute in particular to the study of plasma waves in the electron foreshock and solar wind, to investigations about small-scale structures via density and high-frequency emission signatures, and to the analysis of the non-thermal continuum in the magnetosphere. 相似文献
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某民用涡扇发动机飞行包线内吸雨量计算分析 总被引:2,自引:0,他引:2
分析吸雨对发动机工作性能的影响,首要的是确定能被发动机吸入的雨量。通过综合考虑适航规章要求的大气雨水分布、环境温度、飞行速度、发动机功率和聚集效应对发动机吸雨的影响,结合完整的推力调节计划,计算分析了某民用大涵道比涡扇发动机在不同推力等级下全飞行包线内风扇进口水气比(WAR)。结果表明:在同一马赫数下,风扇进口水气比在6 100m处达到最大;在该高度以下,水气比随着高度的增加而增大;在该高度以上,水气比随着高度的增加而减小;飞行马赫数越大、环境温度越高,水气比也越大;并且标准天空中慢车推力下的风扇进口水气比最大可达到7.38%。该计算方法可为民用涡扇发动机吸雨适航取证的关键点分析提供参考。 相似文献
47.
为评估燃烧加热设备对冲压发动机地面结果的影响,采用经典准一维方法,考虑燃烧可能存在的化学平衡过程,结合所发展的工作过程物理模型,研究了地面模拟飞行马赫数4~7实验中、氢气-空气加热器采用总焓模拟标准时,含水实验介质对发动机释热与面积匹配、性能潜力的影响规律。结果表明,在模拟总焓条件下,使用略大的燃烧室,燃料比冲数据和纯空气条件较为接近,Ma4~6条件下偏差不超过±1%,Ma7时不超过+3.1%,最大比冲对应的特征马赫数也和纯空气条件相同;但燃烧室所需扩张比、燃烧效率、空气比冲均大于纯空气条件,其中Ma4~7时空气比冲的最大偏差分别达到+2.2%,+4.5%,+8.3%,+14.4%,燃烧效率的偏差分别为+0.7%,+1.9%,+4.2%,+9.4%。这些数据的巧合与矛盾说明,需要在理解实验介质影响规律的基础上,建立纯空气应用时释热工作过程的再设计能力。 相似文献
48.
从理论和实验两个方面开展了基于PVDF(Polyvinylidene Fluoride)压电薄膜敏感器的空间碎片撞击航天器感知定位技术研究,分析了基于双曲线理论的定位方法,并在理论分析的基础上,利用气枪和超高速弹道靶分别开展了平面铝板、曲面铝板等单层结构和Whipple结构下的验证实验。弹丸速度范围100m/s-3km/s,实验靶材为2mm厚的单层铝板和铝板厚为1mm、前后间距为10cm的Whipple结构,靶材上安装了4个PVDF传感器。研究结果表明:基于PVDF传感器的感知定位技术可实现空间碎片撞击航天器的位置定位,是一种可应用于航天器在轨感知空间碎片撞击系统的可选技术。 相似文献
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Sheng-wei Lan Sen LiuAuthor VitaeYi LiAuthor Vitae Fa-wei KeAuthor VitaeJie HuangAuthor Vitae 《Acta Astronautica》2014
Cross-sectional area is an important parameter for spacecraft breakup debris as it is the directly measured data in space observation. It is significant for observing and analysing the spacecraft breakup event to accurately modelling the area distribution of the breakup debris. In this paper, experimental study has been performed on debris area distribution characteristics of spacecraft under hypervelocity impact. The tests are carried out at the ballistic ranges of CARDC. Aluminium projectiles are launched to normally impact the simulated spacecrafts at about 3.0 km/s. The simulated spacecrafts are made up of aluminium plates, filled with some simulated electronics boxes, each of which was installed with a circuit board. “Soft-catch” devices are used to recover the breakup fragments. The test results show that: 1) the relationship between the cross-sectional area and the characteristic length of debris, which can be obtained in the logarithmic coordinates by linear fitting, represents the debris shape characteristic in a certain extent; 2) the area-to-mass ratios of fragments show normal distributions in the logarithmic coordinates; 3) debris made of different materials can be distinguished by different peaks on the distribution curves; 4) the area-to-mass ratio distributions can be expressed by a linear superimposition of several normal functions which represent the main materials of the spacecraft. 相似文献