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121.
《中国航空学报》2020,33(12):3306-3317
The application of helicopter emergency rescue is becoming increasingly widespread, but the flight crew training in this area is still difficult due to high cost and risk. Nevertheless, with the development of Virtual Reality (VR) technology, virtual simulation has become a significant role in crew training of helicopter rescue. During the implementation of VR-based training, how to transform complex real tasks into VR scenarios and how to evaluate the performance of crew are of great importance. To address these issues, a novel VR-based R-E-A-D (Report, Evaluate, Agree, Do) evaluation model for training is proposed, which is suitable for complex missions with multiple tasks, multiple scenarios, and multiple people. Then, a mapping method of VR scenarios is put forward, which can transform the real tasks into virtual scenarios to serve the virtual simulation training. Finally, an experiment is carried out to verify the feasibility of the evaluation method and virtual scenario mapping method. 相似文献
122.
Saeedeh Hosseini Gholam Reza Lashkaripour Naser Hafezi Moghadas Mohammad Ghafoori Amin Beiranvand Pour 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(2):871-885
The present study describes a remote sensing approach for preparing lineament map that subsequently indicates the influence of lineament density in the severity of weathering development. In this study, SPOT-5 data, the integration of SPOT-ASTER and Digital Elevation Model (DEM) data were used and processed. The existence of an active fault system in the south of Mashhad city, NE Iran and presence of schistose rocks in this area result in the development of numerous lineament features. This region was selected for this research. Lineament features including fractures, bedding plane, cleavage, shear zones and schistosity were mapped in the study area. The results indicate that the highest concentration of lineaments occurred in the central-western and south-eastern parts of the study area, which coincide with metamorphic outcrops and NW-SE trending fault system. A comparison of lineament statistical analysis and field survey demonstrated that the structural discontinuities have a significant effect on forming and distribution of weathering profiles. It was observed that increasing the number, length and density of structural discontinuities led to strong severity in weathering, which can produce deep residual soils susceptible to landslide occurrence. The remote sensing approach developed in this study can be applicable for preparing lineament maps and evaluating the severity of weathering development in other active fault zones around the world. 相似文献
123.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(9):2184-2202
This study presents the continuation of our previous analysis of variations of atmospheric and space weather parameters above Iberian Peninsula along two years near the 24th solar cycle maximum. In the previous paper (Morozova et al., 2017) we mainly discussed the first mode of principal component analysis of tropospheric and lower stratospheric temperature and pressure fields, which was shown to be correlated with lower stratospheric ozone and anti-correlated with cosmic ray flux. Now we extend the investigation to the second mode, which suggests a coupling between the stratosphere and the ionosphere.This second mode, located in the low and middle stratosphere (and explaining ~7% of temperature and ~3% of geopotential height variations), showed to be statistically significantly correlated with variations of the middle stratosphere ozone content and anti-correlated with variations of ionospheric total electron content. Similar co-variability of these stratospheric and ionospheric parameters was also obtained with the wavelet cross-coherence analysis.To investigate the role of atmospheric circulation dynamics and the causal nature of the found correlations, we applied the convergent cross mapping (CCM) analysis to our series. Strong evidence for the stratosphere-ionosphere coupling were obtained for the winter 2012–2013 that is characterized by the easterly QBO phase (quasi-biennial oscillations of the direction of the stratospheric zonal winds) and a strong SSW (sudden stratospheric warming event). Further analysis (for the three-year time interval 2012–2015) hint that SSWs events play main role in emphasizing the stratosphere-ionosphere coupling. 相似文献
124.
Based on the acoustic mapping, a prediction model for the ground noise radiated from an in-flight helicopter is established. For the enhancement of calculation efficiency, a high-efficiency second-level acoustic radiation model capable of taking the influence of atmosphere absorption on noise into account is first developed by the combination of the point-source idea and the rotor noise radiation characteristics. The comparison between the present model and the direct computation method of noise is done and the high efficiency of the model is validated. Rotor free-wake analysis method and Ffowcs Williams-Hawkings (FW-H) equation are applied to the aerodynamics and noise prediction in the present model. Secondly, a database of noise spheres with the characteristic parameters of advance ratio and tip-path-plane angle is established by the helicopter trim model together with a parametric modeling approach. Furthermore, based on acoustic mapping, a method of rapid simulation for the ground noise radiated from an in-flight helicopter is developed. The noise footprint for AH-1 rotor is then calculated and the influence of some parameters including advance ratio and flight path angle on ground noise is deeply analyzed using the developed model. The results suggest that with the increase of advance ratio and flight path angle, the peak noise levels on the ground first increase and then decrease, in the meantime, the maximum Sound Exposure Level (SEL) noise on the ground shifts toward the advancing side of rotor. Besides, through the analysis of the effects of longitudinal forces on miss-distance and rotor Blade-Vortex Interaction (BVI) noise in descent flight, some meaningful results for reducing the BVI noise on the ground are obtained. 相似文献
125.
基于非结构背景网格的动网格方法研究 总被引:1,自引:0,他引:1
借鉴弹簧动网格方法和Delaunay背景图方法,提出一种基于非结构背景网格的动网格生成方法。先用少量的物面控制点生成相对较粗的非结构背景网格,再用弹簧法将动边界的变化量作用到该背景网格,然后利用计算网格与背景网格的映射关系插值生成对应的动网格,最后对物面网格点及其附近受影响的密网格点进行局部网格修正,获得最终计算所需的动网格。所提方法与直接弹簧法比较,由于弹簧法作用的背景网格远粗于实际的计算网格,提高了计算效率,此外,由于网格的运动受控于受弹簧法作用的背景网格,边界变形或运动能较为均匀地传递到内部网格上,使网格单元过渡光滑,提高了动网格的质量。给出若干算例,展示了方法的效率和可行性。 相似文献
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128.
The fluid–structure interaction and aerodynamic shape optimization usually involve the moving or deforming boundaries, thus the dynamic mesh techniques are the key techniques to cope with such deformation. A novel dynamic mesh method was developed based on the Delaunay graph in this paper. According to the Delaunay graph, the mesh points were divided into groups. In each group, a factor ranging from 0 to 1 was calculated based on the area/volume ratio. By introducing a proper function for this factor, this method can control the mesh quality with high efficiency. Several test cases were compared with other dynamic mesh methods regarding mesh quality and CPU time, such as radial basis function method and Delaunay graph mapping method. 相似文献
129.
针对目标权重选取的主观性问题,提出基于竞争博弈进行多目标可靠性优化设计的方法。首先,将各设计目标视为不同的博弈方,通过随机设计变量集映射(RDVSM)技术,将优化模型中的随机设计变量集分解为各博弈方所拥有的策略集;然后,各博弈方以自身收益为目标,结合性能测量方法在各自的策略集中进行单目标可靠性优化设计,并由所有的优化设计结果形成一轮博弈的策略组合;经过多轮博弈之后得博弈均衡解。压力容器和齿轮减速器2个案例的分析表明,所提方法有效避免了目标权重的选择,设计结果具有较高客观性。 相似文献
130.
一种基于约束框架的棱柱网格生成方法 总被引:1,自引:0,他引:1
提出了一种基于约束框架的棱柱网格生成方法,即利用物面网格节点与背景结构框架网格之间的单一映射关系线性插值生成棱柱网格。背景结构框架网格基于TFI方法生成。物面网格节点与背景框架网格之间的映射关系通过一种线性投影方法建立。然后通过V型槽、圆球、M6机翼和F6翼身组合体四种不同外形对该棱柱网格生成方法进行了测试,测试结果表明该方法能够避免棱柱网格生成中的网格交叉现象,保证棱柱网格的成功生成。该方法在棱柱网格质量控制、棱柱网格局部修改等方面具有较好的效率和优势,但背景框架网格的生成依然是该方法的一个瓶颈,需要进一步的研究。 相似文献