全文获取类型
收费全文 | 1164篇 |
免费 | 112篇 |
国内免费 | 46篇 |
专业分类
航空 | 216篇 |
航天技术 | 929篇 |
综合类 | 21篇 |
航天 | 156篇 |
出版年
2024年 | 3篇 |
2023年 | 38篇 |
2022年 | 15篇 |
2021年 | 65篇 |
2020年 | 37篇 |
2019年 | 42篇 |
2018年 | 40篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 19篇 |
2014年 | 86篇 |
2013年 | 65篇 |
2012年 | 66篇 |
2011年 | 88篇 |
2010年 | 73篇 |
2009年 | 94篇 |
2008年 | 98篇 |
2007年 | 55篇 |
2006年 | 28篇 |
2005年 | 84篇 |
2004年 | 34篇 |
2003年 | 15篇 |
2002年 | 24篇 |
2001年 | 22篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 29篇 |
1997年 | 29篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 32篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1987年 | 1篇 |
排序方式: 共有1322条查询结果,搜索用时 15 毫秒
931.
932.
933.
利用Helios2飞船的数据,对太阳风速度分布中质子束流部分与整个质子的密度之比随日心距离的变化做了分析.为了排除碰撞因素的影响,有针对性地分析了太阳风高速流(600相似文献
934.
"神舟3号"运行高度上大气密度的变化 总被引:4,自引:2,他引:4
"神舟3号"(SZ-3)大气密度探测器搭载在SZ-3留轨舱上于2002年3月发射入轨,在轨运行期间获得了轨道舱运行高度范围(330-410km)内的大气密度数据.数据分析表明,无明显太阳和地磁扰动时,热层大气密度的主要变化之一是日照和阴影区域之间的涨落变化,最大涨落变化比约为3.0,变化比与太阳和地磁活动程度有关.在2002-04-17和2002-04-19的强地磁扰动时,全球热层大气密度上涨,同时在磁扰峰期探测获得30°N-40°N区域出现密度扰动异常现象.对强地磁扰动在运行轨道高度上大气密度最大涨幅约为60%左右,响应过程在时间上要比地磁扰动过程滞后6-7h,日照和阴影区域中大气密度的响应变化程度明显不同.在太阳活动程度发生变化时,热层大气密度会呈现出明显的正相关变化关系. 相似文献
935.
936.
Y. Hanaoka T. Sakurai M. Noguchi K. Ichimoto 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2753
The Hα observation is a powerful tool to study the high-energy aspect of solar flares. Spiky brightenings of flare kernels at the Hα center reflect the rapid fluctuation in particle acceleration; linear polarization of Hα emission might be evidence of accelerated protons; red-shifts of the Hα line are caused by the chromospheric evaporation. To study the spiky brightenings of flare kernels with high-cadence imaging at the Hα center, a high-speed Hα camera for the Solar Flare Telescope at Mitaka, NAOJ, had been developed and it started the regular observation in 2001 July. However, the polarimetry and the Dopplermetry are also important and they are required to be carried out in parallel with the high-cadence imaging at the Hα center. Then, we upgraded the original high-speed Hα camera to a new Hα camera system for the multi-aspect Hα observations, which performs all of the high-cadence imaging, the linear polarization measurements, and the off-band imaging for velocity measurements. The new system started the observation in 2002 July. In this paper, the multi-aspect Hα imaging system is described and sample Hα images are presented. 相似文献
937.
E. Valtonen T. Laitinen K. Huttunen-Heikinmaa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2295-2302
We have studied statistically associations of moderate and intense geomagnetic storms with coronal mass ejections (CMEs) and energetic particle events. The goal was to identify specific energetic particle signatures, which could be used to improve the predictions of the geoeffectiveness of full and partial halo CMEs. Protons in the range 1–110 MeV from the ERNE experiment onboard SOHO are used in the analysis. The study covers the time period from August 1996 to July 2000. We demonstrate the feasibility of energetic particle observations as an additional source of information in evaluating the geoeffectiveness of full and partial halo CMEs. Based on the observed onset times of solar energetic particle (SEP) events and energetic storm particle (ESP) events, we derive a proxy for the transit times of shocks driven by the interplanetary counterparts of coronal mass ejections from the Sun to the Earth. For a limited number of geomagnetic storms which can be associated to both SEP and ESP signatures, we found that this transit time correlates with the strength of geomagnetic storms. 相似文献
938.
A.I. Efimov M.K. Bird V.K. Rudash V.E. Andreev I.V. Chashei D. Plettemeier P. Edenhofer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,35(12):2189-2194
Measurements of solar wind velocity have been derived from simultaneous coronal sounding observations of radio amplitude scintillations at both S-band and X-band during the solar conjunction of the Ulysses spacecraft in August 1991. The signal amplitude was recorded with an averaging time of 1 s. A cross-correlation analysis between S- and X-band amplitude fluctuations shows that the fluctuation signature at S-band appears to be shifted to earlier times with respect to the X-band recording. The time difference is proportional to the coronal separation of the ray paths and inversely proportional to the apparent velocity of plasma inhomogeneities across the ray paths. Preliminary estimates of solar wind speed obtained using model calculations of the differential refraction are found to lie near the expected transition from subsonic to supersonic velocities at solar offset distances of the order of 6–8 R. As a byproduct of the investigation, we find that the transition from weak to saturated scintillation occurs at about 16 R for S-band and 7 R for X-band. 相似文献
939.
940.
The Warm-Hot Intergalactic Medium (WHIM) arises from shock-heated gas collapsing in large-scale filaments and probably harbours
a substantial fraction of the baryons in the local Universe. Absorption-line measurements in the ultraviolet (UV) and in the
X-ray band currently represent the best method to study the WHIM at low redshifts. We here describe the physical properties
of the WHIM and the concepts behind WHIM absorption line measurements of H i and high ions such as O vi, O vii, and O viii in the far-ultraviolet and X-ray band. We review results of recent WHIM absorption line studies carried out with UV and X-ray
satellites such as FUSE, HST, Chandra, and XMM-Newton and discuss their implications for our knowledge of the WHIM. 相似文献