全文获取类型
收费全文 | 317篇 |
免费 | 22篇 |
国内免费 | 108篇 |
专业分类
航空 | 67篇 |
航天技术 | 190篇 |
综合类 | 19篇 |
航天 | 171篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 18篇 |
2019年 | 15篇 |
2018年 | 27篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 18篇 |
2014年 | 47篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 22篇 |
2010年 | 19篇 |
2009年 | 26篇 |
2008年 | 25篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 32篇 |
1999年 | 13篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有447条查询结果,搜索用时 218 毫秒
121.
122.
卫星在空间碎片撞击下的易损性分析方法研究 总被引:1,自引:0,他引:1
针对厘米/毫米级空间碎片对卫星的撞击风险评估,在对卫星部件的失效模式及影响分析(FMEA)的基础上,结合射线跟踪法和失效树分析法建立一种卫星目标的易损性分析方法,计算卫星在空间碎片撞击下导致不同损伤等级的系统失效概率PK/H。详细介绍了该易损性分析方法的总体思路和各项关键技术,并给出了应用实例。该方法可推广应用于载人航天器上,对于航天器的撞击风险评估和防护结构优化设计有重要意义。 相似文献
123.
124.
125.
I. Molotov V. Agapov V. Titenko Z. Khutorovsky Yu. Burtsev I. Guseva V. Rumyantsev M. Ibrahimov G. Kornienko A. Erofeeva V. Biryukov V. Vlasjuk R. Kiladze R. Zalles P. Sukhov R. Inasaridze G. Abdullaeva V. Rychalsky V. Kouprianov O. Rusakov E. Litvinenko E. Filippov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(7):1022-1028
A joint team of researchers under the auspices of the Center for Space Debris Information Collection, Processing and Analysis of the Russian Academy of Sciences collaborates with 15 observatories around the world to perform observations of space debris. For this purpose, 14 telescopes were equipped with charge-coupled device (CCD) cameras, Global Positioning System (GPS) receivers, CCD frame processing and ephemeris computation software, with the support of the European and Russian grants. Many of the observation campaigns were carried out in collaboration with the Astronomical Institute of the University of Bern (AIUB) team operating at the Zimmerwald observatory and conducting research for the European Space Agency (ESA), using the Tenerife/Teide telescope for searching and tracking of unknown objects in the geostationary region (GEO). More than 130,000 measurements of space objects along a GEO arc of 340.9°, collected and processed at Space Debris Data Base in the Ballistic Center of the Keldysh Institute of Applied Mathematics (KIAM) in 2005–2006, allowed us to find 288 GEO objects that are absent in the public orbital databases and to determine their orbital elements. Methods of discovering and tracking small space debris fragments at high orbits were developed and tested. About 40 of 150 detected unknown objects of magnitudes 15–20.5 were tracked during many months. A series of dedicated 22-cm telescopes with large field of view for GEO survey tasks is in process of construction. 7 60-cm telescopes will be modernized in 2007. 相似文献
126.
Jhonathan O. Murcia Piñeros Walter Abrahão dos Santos Antônio F.B.A. Prado 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(2):902-918
It is estimated that more than 22,300 human-made objects are in orbit around the Earth, with a total mass above 8,400,000 kg. Around 89% of these objects are non-operational and without control, which makes them to be considered orbital debris. These numbers consider only objects with dimensions larger than 10 cm. Besides those numbers, there are also about 2000 operational satellites in orbit nowadays. The space debris represents a hazard to operational satellites and to the space operations. A major concern is that this number is growing, due to new launches and particles generated by collisions. Another important point is that the development of CubeSats has increased exponentially in the last years, increasing the number of objects in space, mainly in the Low Earth Orbits (LEO). Due to the short operational time, CubeSats boost the debris population. One of the requirements for space debris mitigation in LEO is the limitation of the orbital lifetime of the satellites, which needs to be lower than 25 years. However, there are space debris with longer estimated decay time. In LEÓs, the influence of the atmospheric drag is the main orbital perturbation, and is used in maneuvers to increment the losses in the satellite orbital energy, to locate satellites in constellations and to accelerate the decay.The goal of the present research is to study the influence of aerodynamic rotational maneuver in the CubeSat?s orbital lifetime. The rotational axis is orthogonal to the orbital plane of the CubeSat, which generates variations in the ballistic coefficient along the trajectory. The maneuver is proposed to accelerate the decay and to mitigate orbital debris generated by non-operational CubeSats. The panel method is selected to determine the drag coefficient as a function of the flow incident angle and the spinning rate. The pressure distribution is integrated from the satellite faces at hypersonic rarefied flow to calculate the drag coefficient. The mathematical model considers the gravitational potential of the Earth and the deceleration due to drag. To analyze the effects of the rotation during the decay, multiple trajectories were propagated, comparing the results obtained assuming a constant drag coefficient with trajectories where the drag coefficient changes periodically. The initial perigees selected were lower than 400 km of altitude with eccentricities ranging from 0.00 to 0.02. Six values for the angular velocity were applied in the maneuver. The technique of rotating the spacecraft is an interesting solution to increase the orbit decay of a CubeSat without implementing additional de-orbit devices. Significant changes in the decay time are presented due to the increase of the mean drag coefficient calculated by the panel method, when the maneuver is applied, reducing the orbital lifetime, however the results are independent of the angular velocity of the satellite. 相似文献
127.
Sittiporn Channumsin Matteo Ceriotti Gianmarco Radice 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(4):1066-1096
A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body; however, these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth’s gravity field (J2), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100?days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time. 相似文献
128.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(11):2692-2710
The space environment around the Earth is populated by more than 130 million objects of 1 mm in size and larger, and future predictions shows that this amount is destined to increase, even if mitigation measures are implemented at a far better rate than today. These objects can hit and damage a spacecraft or its components. It is thus necessary to assess the risk level for a satellite during its mission lifetime. Few software packages perform this analysis, and most of them employ time-consuming ray-tracing methodology, where particles are randomly sampled from relevant distributions. In addition, they tend not to consider the risk associated with the secondary debris clouds. The paper presents the development of a vulnerability assessment model, which relies on a fully statistical procedure: the debris fluxes are directly used combining them with the concept of vulnerable zone, avoiding the random sampling the debris fluxes. A novel methodology is presented to predict damage on internal components. It models the interaction between the components and the secondary debris cloud through basic geometrical operations, considering mutual shielding and shadowing between internal components. The methodologies are tested against state-of-the-art software for relevant test cases, comparing results on external structures and internal components. 相似文献
129.
提出卫星解体碎片生成的数值模拟方法,对卫星模型解体实验问题进行了数值模拟研究。有限元重构方法是一种有限元与 SPH 方法的结合,能够模拟获得孤立碎片的特性数据。通过在 SPH 模拟结果中重构有限元单元,能够有效区分碎片云中的置信孤立碎片和非置信孤立碎片,结合图论方法能够获得每个孤立碎片的单元构成及其尺寸、速度矢量和质量等信息。进而通过数据统计能够获得碎片分布信息。解体碎片数值模拟数据与实验数据具有较好的一致性,表明了该方法的有效性。 相似文献
130.