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661.
Nicholas W. Watkins Daniel Credgington Bogdan Hnat Sandra C. Chapman Mervyn P. Freeman John Greenhough 《Space Science Reviews》2005,121(1-4):271-284
Mandelbrot introduced the concept of fractals to describe the non-Euclidean shape of many aspects of the natural world. In
the time series context, he proposed the use of fractional Brownian motion (fBm) to model non-negligible temporal persistence,
the ‘Joseph Effect’; and Lévy flights to quantify large discontinuities, the ‘Noah Effect’. In space physics, both effects
are manifested in the intermittency and long-range correlation which are by now well-established features of geomagnetic indices
and their solar wind drivers. In order to capture and quantify the Noah and Joseph effects in one compact model, we propose
the application of the ‘bridging’ fractional Lévy motion (fLm) to space physics. We perform an initial evaluation of some
previous scaling results in this paradigm, and show how fLm can model the previously observed exponents. We suggest some new
directions for the future. 相似文献
662.
I.V. Chashei A.I. Efimov L.N. Samoznaev D. Plettemeier M.K. Bird 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,35(12):2195-2198
Measurements of the motion of plasma density inhomogeneities in the inner solar wind are presented. The speeds were estimated using a cross-correlation analysis of radio frequency fluctuations of the Galileo spacecraft measured simultaneously at widely spaced ground stations. The radial projections of the correlation baselines on the pattern plane were of the order of several thousand kilometers. For cross-correlation functions calculated with comparatively short averaging times, we find that a pronounced two-velocity configuration is occasionally observed over the range of heliocentric distances 20 R < R < 40 R. The typical mean speed for such observations is about 300–400 km/s and the difference between the two predominant speeds is about 150–200 km/s. These results may indicate that the density fluctuations are associated with slow magnetosonic waves propagating in opposite directions at the local speed of sound in the reference frame moving with the mean solar wind speed. Quite reasonable estimates of the solar wind speed and speed of sound are obtained from this model. Another possible explanation of the two-velocity structures is that two independent solar wind streams are present simultaneously along different segments of the radio ray path. 相似文献
663.
We briefly discuss the strong intermittent nature of the interplanetary magnetic field, observing that similarity between
its statistical properties and the passive scalar ones exists, and may arise from different dynamical mechanisms. 相似文献
664.
665.
《中国航空学报》2016,(2):512-519
Air transport network, or airport network, is a complex network involving numerous airports. Effective management of the air transport system requires an in-depth understanding of the roles of airports in the network. Whereas knowledge on air transport network properties has been improved greatly, methods to find critical airports in the network are still lacking. In this paper, we present methods to investigate network properties and to identify critical airports in the network. A novel network model is proposed with airports as nodes and the correlations between traffic flow of airports as edges. Spectral clustering algorithm is developed to classify airports. Spatial distribution characteristics and intraclass correlation of different categories of airports are carefully analyzed. The analyses based on the fluctuation trend of distance-correlation and power spectrum of time series are performed to examine the self-organized criticality of the network. The results indicate that there is one category of airports which dominates the self-organized critical state of the network. Six airports in this category are found to be the most important ones in the Chinese air transport network. The flights delay occurred in these six airports can propagate to the other airports, having huge impact on the operation characteristics of the entire network. The methods proposed here taking traffic dynamics into account are capable of identifying critical airports in the whole air transport network. 相似文献
666.
667.
李奇 《中国民航学院学报》1991,(3)
装在波音747—400飞机上的中央维护计算机系统(CMCS)收集和显示飞机有关系统的故障信息,并提出报告。CMC 还可以使众多的飞机系统完成地面试验。本文叙述了 CMC 系统、信息处理、地面起始试验以及 CMC 的其他功能。 相似文献
668.
Theintensiveresearchonthesubjectofsweptshockwave/turbulentboundarylayerinteractionshasbeenconductedandsupportedformanyyearsb... 相似文献
669.
Recent developments of the physics of complexity in space plasmas are briefly reviewed. The definition of dynamical complexity
is provided. Concepts of probability distribution functions, wavelet transforms, intermittent turbulence, multifractal processes
and extreme events are described. Future directions for this emerging field are discussed. 相似文献
670.
This article investigates the near-field dynamics in a particle-laden round turbulent jet in a large-eddy simulation (LES). A point-force two-way coupling model is adopted in the simulation to reveal the particle modulation of turbulence. The particles mainly excite the initial instability of the jet and bring about the earlier breakup of vortex rings in the near-field. The flow fluctuating intensity either in the axial or in the radial directions is hence increased by particles. The article also describes the mean velocity modulated by particles. The changing statistical velocity induced by particle modulation implies the effects of modulation of the local flow structures. This study is expected to be useful to the control of two-phase turbulent jets. 相似文献