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131.
Small (1–10 cm) debris in low Earth orbit (LEO) are extremely dangerous, because they spread the breakup cascade. Pulsed laser active debris removal using laser ablation jets on target is the most cost-effective way to re-enter the small debris. No other solutions address the whole problem of large (~100 cm, 1 t) as well as small debris. Physical removal of small debris (by nets, tethers and so on) is uneconomical because of the energy cost of matching orbits. In this paper, we present a completely new proposal relative to our earlier work. This new approach uses rapid, head-on interaction in 10–40 s rather than 4 minutes, using 20–40 kW bursts of 100 ps, 355 nm UV pulses from a 1.5 m diameter aperture on a space-based station in LEO. The station employs “heat-capacity” laser mode with low duty cycle to create an adaptable, robust, dual-mode system which can lower or raise large derelict objects into less dangerous orbits, as well as clear out the small debris in a 400-km thick LEO band. Time-average laser optical power is less than 15 kW. The combination of short pulses and UV wavelength gives lower required fluence on target as well as higher momentum coupling coefficient. An orbiting system can have short range because of high interaction rate deriving from its velocity through the debris field. This leads to much smaller mirrors and lower average power than the ground-based systems we have considered previously. Our system also permits strong defense of specific assets. Analysis gives an estimated cost less than $1 k each to re-enter most small debris in a few months, and about 280 k$ each to raise or lower 1-ton objects by 40 km. We believe it can do this for 2000 such large objects in about four years. Laser ablation is one of the few interactions in nature that propel a distant object without any significant reaction on the source. 相似文献
132.
Kangkang Liu Guozhu Li Baiqi Ning 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(11):3612-3620
The small-scale wave-like structure (SSWS) of F region bottomside plasma density was proposed to be an important seeding for equatorial plasma bubble (EPB) generation, and employed in theoretical simulations of EPBs in recent years. The seeding role of SSWS, however, is waiting to be demonstrated by observation. Here we present two cases of SSWS and EPB observed by the Fuke all-sky airglow imager (19.3°N, 109.1°E; dip latitude 14.3°N). For each case, the results show that two large-scale wave-like structures (LSWSs) initially appeared around sunset in the longitude regions separated by 3–4°, but EPB irregularities were only generated in one of the LSWSs where SSWSs were seen riding on LSWS. For the other LSWS, no SSWS and EPB irregularities were seen. Considering that the two LSWSs were situated closely in longitude where the amplitude of pre-reversal enhancement of background eastward electric field should be similar, the observation that EPB was only generated in the longitude with simultaneous LSWS and SSWS could provide supporting evidence for SSWS seeding of EPB. 相似文献
133.
134.
We analyzed UVCS/SOHO data and compared the H I Lyα (121.6 nm) and O VI (103.2 nm, 103.7 nm) emission in the polar and equatorial
coronal holes. We found that the emission lines have similar characteristics in these two types of coronal holes. Both types
show evidence for superradially diverging boundaries. The latitudinal distribution of the O VI line ratio may indicate that
the equatorial coronal hole has O+5 outflow velocities lower than in the polar coronal holes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
135.
利用高阶矩统计分析方法对AUREOL-3卫星观测数据进行分析处理,所涉及的信号分别为ELF频率范围内的电场扰动Eh(t)和等离子体密度波动δNe/ne(t),处理结果表明:利用高阶矩谱分析方法可以很好地识别空间等离了波-粒相互作用过程中的非线性成分 相似文献
136.
用于合成金刚石薄膜的微波等离子体CVD系统 总被引:2,自引:0,他引:2
研制了一套功率容量大、结构合理、工作稳定的微波等离子体CVD系统。描述了系统的基本结构和性能,讨论了它的特点。作者利用该系统,在单晶Si等衬底材料上成功地合成了金刚石薄膜。 相似文献
137.
138.
Geotail卫星的电场数据被用于分析近地磁尾等离子体片中电场在磁扰动(Dst<-25nT)和磁静时(Dst>-25 nT的统计分布.结果表明,伴随着地向高速离子流,在X>-16Re以内区域出现强电场(高达 5—8 mV/m).磁扰动期间强电场的幅值较磁静时大,并且出现在更靠近地球的位置.较强和较靠近地球的强电场与磁扰动时更薄的等离子体片和更接近地球的等离子体片内边界相联系.观测结果意味着磁扰动期间的亚暴可能更有效地将高能粒子注射到环电流中.这对磁暴和亚暴的关系问题的解决有重要意义. 相似文献
139.
J.K. Shi M.N.S. Qureshi S.Z. Ma L.D. Xia J.S. Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1842-1851
Considering the KuaFu mission, state of the energy release of substorm and storm is simply presented and it’s improvements by KuaFu mission are investigated. The KuaFu mission will provide us an opportunity to improve our understanding of the energy release during the storm and the substorms. The two KuaFu-B satellites flying in 180° phase-lagged formation in a polar orbit will allow synoptic observations of the auroral oval, central plasma sheet, ring current and other regions. It can monitor the polar region 24/7 continuously. The advantage of the KuaFu mission is to provide the data during all phases of storm and substorm time that can be used to study the global energy release during all phases continuously. The data from auroral imager and other in-situ instruments on board KuaFu-B can be used to study the auroral dynamics and Joule heating during a storm and substorm. The data from the neutral atom imager instrument can be used to study the dynamics and the energy release in the ring current region from sudden commencement to complete storm recovery. Furthermore the data from KuaFu-A, which is around L1 point, can be used to study the interplanetary conditions along with the data from the plasma sheet to study the triggering process and energy release during a substorm. So, KuaFu mission with its continuous time monitoring facilities would enable us to make much progress towards solving the underlying problems. 相似文献
140.
NS-DBD激励控制非细长三角翼前缘涡仿真研究 总被引:2,自引:1,他引:1
通过在三角翼前缘施加纳秒脉冲介质阻挡放电(NS-DBD)激励唯象学模型,进行了47°后掠角钝前缘三角翼流动控制的仿真。分析了不同迎角下升力和阻力系数的变化、流场结构的变化、以及激励诱导旋涡的演化过程。研究表明:施加无量纲激励频率F+=1.44的NS-DBD激励后,可明显提高三角翼失速前后的升力系数;同时阻力系数也有所增加,变化趋势与实验结果一致。激励在前缘分离剪切层处诱导产生流向涡,改变了前缘剪切层结构,使其向内卷吸;激励后时均流场形成了明显的负压峰值,前缘涡附着线外移,吸力面回流区减小。 相似文献