全文获取类型
收费全文 | 443篇 |
免费 | 64篇 |
国内免费 | 154篇 |
专业分类
航空 | 241篇 |
航天技术 | 160篇 |
综合类 | 24篇 |
航天 | 236篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 7篇 |
2021年 | 22篇 |
2020年 | 34篇 |
2019年 | 11篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 26篇 |
2014年 | 40篇 |
2013年 | 31篇 |
2012年 | 38篇 |
2011年 | 30篇 |
2010年 | 35篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 33篇 |
2006年 | 66篇 |
2005年 | 29篇 |
2004年 | 9篇 |
2003年 | 23篇 |
2002年 | 15篇 |
2001年 | 1篇 |
2000年 | 7篇 |
1999年 | 25篇 |
1998年 | 14篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有661条查询结果,搜索用时 31 毫秒
471.
太阳能热动力系统吸热/蓄热器能量分析 总被引:4,自引:1,他引:4
空间太阳能热动力发电系统是一种新型的空间电力系统。吸热 /蓄热器是热动力发电系统关键部件之一。吸热 /蓄热器采用的蓄热方式是相变蓄热。通过对吸热 /蓄热器的能量分析 ,可以很好的了解吸热器的能量传递 ,以及相变材料的工作过程。建立了太阳能热动力发电系统吸热器腔体辐射模型 ,结合换热管的传热模型计算了吸热器的传热过程。得到了吸热器的能量损失、工质吸收能量、PCM的潜热储能和显热储能等重要指标 ,并且得到了换热管最大温度 ,工质出口温度等重要结果。计算结果可以用于吸热器的设计 相似文献
472.
Chian A.C.-L. Borotto F.A. Rempel E.L. Macau E.E.N. Rosa R.R. Christiansen F. 《Space Science Reviews》2003,107(1-2):447-461
Space plasmas are dominated by waves, instabilities and turbulence. Dynamical systems approach offers powerful mathematical
and computational techniques to probe the origin and nature of space environment turbulence. Using the nonlinear dynamics
tools such as the bifurcation diagram and Poincaré maps, we study the transition from order to chaos, from weak to strong
chaos, and the destruction of a chaotic attractor. The characterization of the complex system dynamics of the space environment,
such as the Alfvén turbulence, can improve the capability of monitoring Sun-Earth connections and prediction of space weather.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
473.
474.
H. Kunow W. Dröge B. Heber R. Müller-Mellin K. Röhrs H. Sierks G. Wibberenz R. Ducros P. Ferrando C. Rastoin A. Raviart C. Paizis 《Space Science Reviews》1995,72(1-2):397-402
Since June 1992 the Kiel Electron Telescope on board ULYSSES measures 26-day variations of the order of 6% in the fluxes of high energy H and He. In May 1993 ULYSSES entered into the unipolar region of the southern polar coronal hole, but continued to observe similar effects: increases in the MeV proton channels due to acceleration near the shocks of the corotating interaction region and decreases in the intensity of galactic nuclei associated with the same region. Amplitude variations are presented for different magnetic rigidities and the effects are discussed in view of corotating shock development in a 3-dimensional heliospheric structure. 相似文献
475.
The solar wind charge state and elemental compositions have been measured with the Solar Wind Ion Composition Spectrometers
(SWICS) on Ulysses and ACE for a combined period of about 25 years. This most extensive data set includes all varieties of
solar wind flows and extends over more than one solar cycle. With SWICS the abundances of all charge states of He, C, N, O,
Ne, Mg, Si, S, Ar and Fe can be reliably determined (when averaged over sufficiently long time periods) under any solar wind
flow conditions. Here we report on results of our detailed analysis of the elemental composition and ionization states of
the most unbiased solar wind from the polar coronal holes during solar minimum in 1994–1996, which includes new values for
the abundance S, Ca and Ar and a more accurate determination of the 20Ne abundance. We find that in the solar minimum polar coronal hole solar wind the average freezing-in temperature is ∼1.1×106 K, increasing slightly with the mass of the ion. Using an extrapolation method we derive photospheric abundances from solar
wind composition measurements. We suggest that our solar-wind-derived values should be used for the photospheric ratios of
Ne/Fe=1.26±0.28 and Ar/Fe=0.030±0.007. 相似文献
476.
Johannes Geiss is a world leader and foremost expert on measurements and interpretation of the composition of matter that
reveals the history, present state, and future of astronomical objects. With his Swiss team he was first to measure the composition
of the noble gases in the solar wind when in the late 1960s he flew the brilliant solar wind collecting foil experiments on
the five Apollo missions to the moon. Always at the forefront of the art of composition measurements, he with his colleagues
determined the isotopic and elemental composition of the solar wind using instruments characterized by innovative design that
have provided the most comprehensive record of the solar wind composition under all solar wind conditions at all helio-latitudes.
He discovered heavy interstellar pickup ions, from which the composition of the neutral gas of the Local Interstellar Cloud
is determined, and the “Inner Source” of pickup ions. Johannes Geiss played a key role both in the in-situ measurements and
modeling of molecular ions in comets, and the interpretation of these data. He and co-workers measured the composition of
plasmas in the magnetospheres of Earth and Jupiter. Here we highlight Johannes Geiss’ many discoveries and seminal contributions
to our knowledge of the composition of matter of the Sun, solar wind, interstellar gas, early universe, comets and magnetospheres. 相似文献
477.
R. A. Mewaldt C. M. S. Cohen G. M. Mason D. K. Haggerty M. I. Desai 《Space Science Reviews》2007,130(1-4):323-328
Data from ACE and GOES have been used to measure Solar Energetic Particle (SEP) fluence spectra for H, He, O, and Fe, over
the period from October 1997 to December 2005. The measurements were made by four instruments on ACE and the EPS sensor on
three GOES satellites and extend in energy from ∼0.1 MeV/nuc to ∼100 MeV/nuc. Fluence spectra for each species were fit by
conventional forms and used to investigate how the intensities, composition, and spectral shapes vary from year to year. 相似文献
478.
A. Milillo P. Wurz S. Orsini D. Delcourt E. Kallio R. M. KILLEN H. Lammer S. Massetti A. Mura S. Barabash G. Cremonese I. A. Daglis E. De Angelis A. M. Di Lellis S. Livi V. Mangano K. Torkar 《Space Science Reviews》2005,117(3-4):397-443
Mercury is a poorly known planet, since the only space-based information comes from the three fly-bys performed in 1974 by
the Mariner 10 spacecraft. Ground-based observations also provided some interesting results, but they are particularly difficult
to obtain due to the planet’s proximity to the Sun. Nevertheless, the fact that the planet’s orbit is so close to the Sun
makes Mercury a particularly interesting subject for extreme environmental conditions. Among a number of crucial scientific
topics to be addressed, Mercury’s exosphere, its interaction with the solar wind and its origin from the surface of the planet,
can provide important clues about planetary evolution. In fact, the Hermean exosphere is continuously eroded and refilled
by these interactions, so that it would be more proper to consider the Hermean environment as a single, unified system – surface-exosphere-magnetosphere.
These three parts are indeed strongly linked to each other. In recent years, the two missions scheduled to explore the iron
planet, the NASA MESSENGER mission (launched in March 2004) and the ESA cornerstone mission (jointly with JAXA) BepiColombo
(to be launched in 2012), have stimulated new interest in the many unresolved mysteries related to it. New ground-based observations,
made possible by new technologies, have been obtained, and new simulation studies have been performed. In this paper some
old as well as the very latest observations and studies related to the surface-exosphere-magnetosphere system are reviewed,
outlining the investigations achievable by the planned space-based observations. This review intends to support the studies,
in preparation of future data, and the definition of specific instrumentation. 相似文献
479.
L. A. Mcfadden M. K. Rountree-Brown E. M. Warner S. A. M Claughlin J. M. Behne J. D. Ristvey S. Baird-Wilkerson D. K. Duncan S. D. Gillam G. H. Walker K. J. Meech 《Space Science Reviews》2005,117(1-2):373-396
The Deep Impact mission’s Education and Public Outreach (E/PO) program brings the principles of physics relating to the properties
of matter, motions and forces and transfer of energy to school-aged and public audiences. Materials and information on the
project web site convey the excitement of the mission, the principles of the process of scientific inquiry and science in
a personal and social perspective. Members of the E/PO team and project scientists and engineers, share their experiences
in public presentations and via interviews on the web. Programs and opportunities to observe the comet before, during and
after impact contribute scientific data to the mission and engage audiences in the mission, which is truly an experiment. 相似文献
480.
Leon Ofman 《Space Science Reviews》2005,120(1-2):67-94
Coronal holes have been identified as source regions of the fast solar wind, and MHD wave activity has been detected in coronal
holes by remote sensing, and in situ in fast solar wind streams. I review some of the most suggestive wave observations, and
discuss the theoretical aspects of MHD wave heating and solar wind acceleration in coronal holes. I review the results of
single fluid 2.5D MHD, as well as multi-fluid 2.5D MHD models of waves in coronal holes, the heating, and the acceleration
of the solar wind be these waves. 相似文献