全文获取类型
收费全文 | 172篇 |
免费 | 14篇 |
国内免费 | 19篇 |
专业分类
航空 | 136篇 |
航天技术 | 58篇 |
综合类 | 8篇 |
航天 | 3篇 |
出版年
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 7篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 22篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 17篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 3篇 |
排序方式: 共有205条查询结果,搜索用时 265 毫秒
151.
对边界层内小孔气水多相流场下射流问题开展数值仿真及定常水洞试验研究,建立了适用于边界层内压差驱动下小孔向气腔射流多相流场问题研究的数值仿真计算模型,针对典型孔参数及气水流场条件,对比分析了仿真试验数据,验证了数值仿真模型的正确性及模型计算精度。结合流体质点受力及运动模型及平板边界层理论,分析了气水域压力场特征及水域流动规律对小孔射流过程的作用机理及影响规律,开展了孔参数对射流多相流场特征及射流量的影响研究。获得了小孔射流量估算方法,为航行体上防水装置设计提供数据支撑。 相似文献
152.
采用含有0~4排气膜孔的薄壁平板试样模拟镍基单晶冷却叶片,研究了气膜孔排布对镍基单晶冷却叶片高温持久性的影响,并基于晶体塑性理论建立单晶材料蠕变数值计算模型,将其编入Abaqus用户子程序中,对不同气膜孔排布的薄壁平板试件进行有限元分析。试验结果表明,在气膜孔数相同的情况下,随着气膜孔排数的逐渐增多,冷却叶片高温持久寿命不断降低,且下降趋势逐渐加剧。文中提出了基于有限元数据的高温持久寿命预测幂函数模型,在对应孔排布、应力、温度条件下,其相对误差均小于3%,有限元分析得到的应力场分布结果与试样的断口形貌相吻合。 相似文献
153.
离散孔结构超声速气膜冷却数值模拟 总被引:1,自引:1,他引:0
为了得到气膜入口结构对气膜冷却效率的影响规律,并为工程应用提供参考,针对不同形状气膜入口结构的离散孔超声速气膜冷却展开了三维数值模拟。结果表明:气膜入口结构对气膜冷却效率影响明显,轴对称孔入口收敛段结构的流量系数直接影响冷却效果,计算工况下流量系数降低013下游冷却效率约降低005,应该防止收敛段剧烈收缩;同时,离散孔扩张段面积变化速率越小越有利于冷却,变化过快会使得冷却剂得不到充分发展,垂直主流方向的速度分量大,使得气膜往两侧流动而中心区域冷却效果变差;在非轴对称离散孔出口增加平直段能使射流更集中,可以有效防止气膜在上游被穿透造成冷却恶化现象。 相似文献
154.
L. van Driel-Gesztelyi C.P. Goff P. Démoulin J.L. Culhane S.A. Matthews L.K. Harra C.H. Mandrini K.-L. Klein H. Kurokawa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
A series of three flares of GOES class M, M and C, and a CME were observed on 20 January 2004 occurring in close succession in NOAA 10540. Types II, III, and N radio bursts were associated. We use the combined observations from TRACE, EIT, Hα images from Kwasan Observatory, MDI magnetograms, GOES, and radio observations from Culgoora and Wind/ WAVES to understand the complex development of this event. We reach three main conclusions. First, we link the first two impulsive flares to tether-cutting reconnections and the launch of the CME. This complex observation shows that impulsive quadrupolar flares can be eruptive. Second, we relate the last of the flares, an LDE, to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines, when reconnection reverses and restores some of the pre-eruption magnetic connectivities. Finally, we show that reconnection with the magnetic structure of a previous CME launched about 8 h earlier injects electrons into open field lines having a local dip and apex (located at about six solar radii height). This is observed as an N-burst at decametre radio wavelengths. The dipped shape of these field lines is due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer. This particular situation explains why this is the first N-burst ever observed at long radio wavelengths. 相似文献
155.
采用二维裂纹扩展分析方法研究含孔边角裂纹平板中疲劳裂纹扩展速率和寿命。该方法假设孔边角裂纹两个主方向上裂纹扩展主要取决于两方向裂纹尖端的应力强度因子。并采用裂纹闭合特性修正。预测在常幅拉伸疲劳载荷情况下2124T851铝合金板和30CrMnSiN12A合金钢板中孔边角裂纹扩展速率和寿命。理论计算和实验结果较吻合。 相似文献
156.
157.
M. I. Desai G. M. Mason R. E. Gold S. M. Krimigis C. M. S. Cohen R. A. Mewaldt J. E. Mazur J. R. Dwyer 《Space Science Reviews》2007,130(1-4):243-253
Using high-resolution mass spectrometers on board the Advanced Composition Explorer (ACE), we surveyed the event-averaged
∼0.1–60 MeV/nuc heavy ion elemental composition in 64 large solar energetic particle (LSEP) events of cycle 23. Our results
show the following: (1) The Fe/O ratio decreases with increasing energy up to ∼10 MeV/nuc in ∼92% of the events and up to
∼60 MeV/nuc in ∼64% of the events. (2) The rare isotope 3He is greatly enhanced over the corona or the solar wind values in 46% of the events. (3) The heavy ion abundances are not
systematically organized by the ion’s M/Q ratio when compared with the solar wind values. (4) Heavy ion abundances from C–Fe exhibit systematic M/Q-dependent enhancements that are remarkably similar to those seen in 3He-rich SEP events and CME-driven interplanetary (IP) shock events. Taken together, these results confirm the role of shocks
in energizing particles up to ∼60 MeV/nuc in the majority of large SEP events of cycle 23, but also show that the seed population
is not dominated by ions originating from the ambient corona or the thermal solar wind, as previously believed. Rather, it
appears that the source material for CME-associated large SEP events originates predominantly from a suprathermal population
with a heavy ion enrichment pattern that is organized according to the ion’s mass-per-charge ratio. These new results indicate
that current LSEP models must include the routine production of this dynamic suprathermal seed population as a critical pre-cursor
to the CME shock acceleration process. 相似文献
158.
The heliospheric counterparts of coronal mass ejections (CMEs) at the Sun, interplanetary coronal mass ejections (ICMEs),
can be identified in situ based on a number of magnetic field, plasma, compositional and energetic particle signatures as
well as combinations thereof. We summarize these signatures and their implications for understanding the nature of these structures
and the physical properties of coronal mass ejections. We conclude that our understanding of ICMEs is far from complete and
formulate several challenges that, if addressed, would substantially improve our knowledge of the relationship between CMEs
at the Sun and in the heliosphere. 相似文献
159.
R. Schwenn 《Space Science Reviews》2006,124(1-4):51-76
In this paper I will briefly summarize the present status of our knowledge on the four different sorts of solar wind, their
sources and their short- and long-term variations. First: the fast solar wind in high-speed streams that emerges from coronal
hole regions. Second: the slow solar wind emerging from the non-active Sun near the global heliospheric current sheet above
helmet streamers and underlying active regions. Third: the slow solar wind filling most of the heliosphere during high solar
activity, emerging above active regions in a highly turbulent state, and fourth: the plasma expelled from the Sun during coronal
mass ejections. The coronal sources of these different flows vary dramatically with the solar activity cycle. 相似文献
160.
P. Lemaire K. Bocchialini V. Aletti D. Hassler K. Wilhelm 《Space Science Reviews》1999,87(1-2):249-252
The analysis of data taken by SUMER near disk center, where a small coronal hole is observed in EIT images, is performed.
From the measurements of Doppler non-thermal velocities and intensities, we search for the diagnostics and the signature of
small scale structures in the coronal hole using transition region lines. Transition region lines in the range of 7 × 104 K to 2.5 × 105 K have a non-thermal velocity excess of 4.0 to 5.5 km s-1 relative to the contiguous quiet Sun. While the average intensity is lower in the coronal hole than in the quiet area, this
result shows an increase of turbulence at the base of the high speed solar wind.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献