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61.
混沌时序的噪声降低技术研究 总被引:2,自引:0,他引:2
介绍了噪声对混沌时序分析的影响,回顾了混沌时序噪声降低方法的研究情况。在此基础上将Tak-ens的嵌入理论拓展应用到具有噪声干扰的时间序列,并结合非线性信号处理和非线性近似函数技术,提出了一种把重构相空间同降低噪声干扰相结合的理论方法和处理技术,并以受噪声污染的Henon 映象时间序列为例,说明了有关概念和应用结果。 相似文献
62.
建立了外环轴水平放置的重力对称陀螺仪的运动方程.并将陀螺仪转子的质心位置作为扰动, 在一定条件下, 首先研究了自由陀螺仪的运动, 并给出力学意义解释; 然后利用Melnikov方法和KAM理论研究了非自由陀螺仪的运动.研究结果表明: 在陀螺仪转子的质心与支架中心不重合且充分接近, 或陀螺仪能量充分大时, 陀螺仪的运动出现Smale马蹄意义下的混沌; 同时它的Hamiltonian流存在KAM不变环面和不变闭曲线. 相似文献
63.
以三种典型细高结构为研究对象,采用全仿弹性模型,进行了外形、质量分布、雷诺数和风结构等不同参数条件下的风洞实验。用应变仪测量了每种模型根部弯矩,通过计算,分析了模型风振响应的基本特性以及风振过程的混沌特性。 相似文献
64.
K. Stasiewicz 《Space Science Reviews》1993,65(3-4):221-252
This article reviews theories and observations related to effects produced by finite (and large) Larmor radii of charged particles in the magnetosphere. The FLR effects depend on =r
H
/L, wherer
H
is the Larmor radius andL is the spatial scale for field/plasma inhomogeneity. The parameter is a basic expansion parameter for most equations describing plasma dynamics in the magnetosphere. The FLR effects enter naturally the drift approximation for particle motion and represent also non-ideal MHD terms in the fluid formalism. The linear and higher order terms in lead to charge separation, energization of particles, and produce viscosity without collisions. The FLR effects introduce also important corrections to the dispersion relations for MHD waves and drift instabilities. Expansion of plasma into magnetic field leads to filamentation of the plasma boundary and to creation of structures with thickness less than an ion gyroradius. Large Larmor radius effects (1) in curved magnetic field geometry lead to stochastic behaviour of particle trajectories and to deterministic chaos. The tiny scale of the electron and ion gyroradii does not necessarily mean that FLR/LLR phenomena have negligible effect on the macroscopic dynamics and energetics of the whole magnetosphere. On the contrary, the small scale gyro-effects may provide the physical mechanism for gyroviscous coupling between the solar wind and the magnetosphere, the mechanism for triggering disruption of the magnetotail current layer, and the mechanism for parallel electric field that accelerate auroral particles. 相似文献
65.
Ch. Hubaux A.-S. Libert N. Delsate T. Carletti 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Solar radiation pressure affects the evolution of high area-to-mass geostationary space debris. In this work, we extend the stability study of Valk et al. (2009) by considering the influence of Earth’s shadows on the short- and long-term time evolutions of space debris. To assess the orbits stability, we use the Mean Exponential Growth factor of Nearby Orbits (MEGNO), which is an efficient numerical tool to distinguish between regular and chaotic behaviors. To reliably compute long-term space debris motion, we resort to the Global Symplectic Integrator (GSI) of Libert et al. (2011) which consists in the symplectic integration of both Hamiltonian equations of motion and variational equations. We show how to efficiently compute the MEGNO indicator in a complete symplectic framework, and we also discuss the choice of a symplectic integrator, since propagators adapted to the structure of the Hamiltonian equations of motion are not necessarily suited for the associated variational equations. The performances of our method are illustrated and validated through the study of the Arnold diffusion problem. We then analyze the effects of Earth’s shadows, using the adapted conical and cylindrical Earth’s shadowing models introduced by Hubaux et al. (2012) as the smooth shadow function deriving from these models can be easily included into the variational equations. Our stability study shows that Earth’s shadows greatly affect the global behaviour of space debris orbits by increasing the size of chaotic regions around the geostationary altitude. We also emphasize the differences in the results given by conical or cylindrical Earth’s shadowing models. Finally, such results are compared with a non-symplectic integration scheme. 相似文献
66.
67.
In a driven/damped drift-wave system a steady wave induces nonlinear variation of the dispersion of a perturbation wave (PW).
Competition between the nonlinear dispersion with self-nonlinearity of the PW results in rich wave dynamic behaviors. In particular,
a steady wave at the negative tangency slope of a hysteresis becomes unstable due to a saddle instability. It is found that
such saddle steady wave (SSW) plays an important role in the discontinuous transition from a spatially coherent state to spatiotemporal
chaos (STC). The transition is caused by a crisis due to a collision of the PW attactor to an unstable orbit of the SSW. In
the time evolution, it is a ‘pattern resonance’ of the realized wave with the virtual SSW that triggers the crisis. The transition
also displays as a critical phenomenon in parameter space, which is related to the change in the symmetry property of the
motion of master mode (k = 1) of the PW with respect to that of SSW. In the spatially coherent state the former is trapped by the SSW partial wave,
while in the STC it can become free from the latter, its trajectory crosses two unstable orbits of the SSW frequently, causing
very turbulent behavior.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
68.
69.
70.
周向阳 《西安航空技术高等专科学校学报》2006,24(2):30-32
以人为本的管理作为新型的管理理念受到社会的推案。党中央提出;坚持以人为本,树立全面、协调、可持续的科学发展观。社会发展的目标是要达到人与社会、人与自然的高度和谐。在学校后勤管理工作中,要树立新型的以人为本的管理理念,调动职工的积极性,搞好学校各项服务工作。 相似文献