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261.
The solar upper atmosphere (SUA) is defined as the volume above the photosphere occupied by plasmas with electron temperatures, T
e, above 2×104 K. Until the Skylab era, only little was known about the morphology of the SUA, while the quality of the spectroscopic observations was continually improving. A spherically symmetric atmosphere was assumed at that time, in which the temperature increased with height. With advances in the observational techniques, it became apparent that the morphology of the SUA was very complex even during the minimum of the magnetic activity cycle. In particular, spectroscopic measurements with high spectral and spatial resolution, which were made in the light of ultraviolet emission lines representing a variety of temperatures, led to the conclusion that most of the radiation from the solar transition region could not be explained by assuming a continuous chromosphere-corona interface, but rather by a region of unresolved fine structures. Recent observational results obtained by modern instruments, such as the Extreme-ultraviolet Imaging Telescope (EIT), the Large Angle Spectroscopic Coronagraph (LASCO), and the Solar Ultraviolet Measurements of (SUMER) spectrograph on the Solar and Heliospheric Observatory (SOHO), as well as the Transition Region and Coronal Explorer (TRACE), and their interpretations will be presented in this review of our understanding of the morphology of the SUA. 相似文献
262.
263.
Chiu M.C. Von-Mehlem U.I. Willey C.E. Betenbaugh T.M. Maynard J.J. Krein J.A. Conde R.F. Gray W.T. Hunt J.W. Mosher L.E. McCullough M.G. Panneton P.E. Staiger J.P. Rodberg E.H. 《Space Science Reviews》1998,86(1-4):257-284
The Johns Hopkins University Applied Physics Laboratory (JHU/APL) was responsible for the design and fabrication of the ACE
spacecraft to accommodate the ACE Mission requirements and for the integration, test, and launch support for the entire ACE
Observatory. The primary ACE Mission includes a significant number of science instruments - nine - whose diverse requirements
had to be factored into the overall spacecraft bus design. Secondary missions for monitoring space weather and measuring launch
vibration environments were also accommodated within the spacecraft design. Substantial coordination and cooperation were
required between the spacecraft and instrument engineers, and all requirements were met. Overall, the spacecraft was kept
as simple as possible in meeting requirements to achieve a highly reliable and low-cost design.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
264.
M. Golombek M. Grott G. Kargl J. Andrade J. Marshall N. Warner N. A. Teanby V. Ansan E. Hauber J. Voigt R. Lichtenheldt B. Knapmeyer-Endrun I. J. Daubar D. Kipp N. Muller P. Lognonné C. Schmelzbach D. Banfield A. Trebi-Ollennu J. Maki S. Kedar D. Mimoun N. Murdoch S. Piqueux P. Delage W. T. Pike C. Charalambous R. Lorenz L. Fayon A. Lucas S. Rodriguez P. Morgan A. Spiga M. Panning T. Spohn S. Smrekar T. Gudkova R. Garcia D. Giardini U. Christensen T. Nicollier D. Sollberger J. Robertsson K. Ali B. Kenda W. B. Banerdt 《Space Science Reviews》2018,214(5):84
Although not the prime focus of the InSight mission, the near-surface geology and physical properties investigations provide critical information for both placing the instruments (seismometer and heat flow probe with mole) on the surface and for understanding the nature of the shallow subsurface and its effect on recorded seismic waves. Two color cameras on the lander will obtain multiple stereo images of the surface and its interaction with the spacecraft. Images will be used to identify the geologic materials and features present, quantify their areal coverage, help determine the basic geologic evolution of the area, and provide ground truth for orbital remote sensing data. A radiometer will measure the hourly temperature of the surface in two spots, which will determine the thermal inertia of the surface materials present and their particle size and/or cohesion. Continuous measurements of wind speed and direction offer a unique opportunity to correlate dust devils and high winds with eolian changes imaged at the surface and to determine the threshold friction wind stress for grain motion on Mars. During the first two weeks after landing, these investigations will support the selection of instrument placement locations that are relatively smooth, flat, free of small rocks and load bearing. Soil mechanics parameters and elastic properties of near surface materials will be determined from mole penetration and thermal conductivity measurements from the surface to 3–5 m depth, the measurement of seismic waves during mole hammering, passive monitoring of seismic waves, and experiments with the arm and scoop of the lander (indentations, scraping and trenching). These investigations will determine and test the presence and mechanical properties of the expected 3–17 m thick fragmented regolith (and underlying fractured material) built up by impact and eolian processes on top of Hesperian lava flows and determine its seismic properties for the seismic investigation of Mars’ interior. 相似文献
265.
J. H. Hoffman G. M. Keating H. Niemann V. Oyama J. Pollack A. Seiff A. I. Stewart U. Von Zahn 《Space Science Reviews》1977,20(3):307-327
Although in recent years much has been learned about the atmospheric composition and structure of Venus, there are many key questions which remain unanswered. The Pioneer Venus set of experiments is designed to provide information both individually and collectively to help understand and explain first of all the present state of the atmosphere (the composition and distribution in both the lower and upper parts, the state property profiles, the cloud compositions, the role of phase in the thermal structure, the planet's surface and interior composition, the high surface temperature, the stability of CO2, the ionosphere — its chemistry and thermal structure, the existence of superrotation, the response of the upper atmosphere to changes in solar EUV and the solar wind) and secondly the origin and evolution of the atmosphere. This paper discusses these questions and the degree to which the Pioneer Venus instruments will respond to them. 相似文献
266.
A. Pedersen R. Grard K. Knott D. Jones A. Gonpalone U. Fahleson 《Space Science Reviews》1978,22(4):333-346
Quasi-static electric fields have been measured with two spherical probes supported by cable booms providing a baseline of 42 m for the measurement. The performance of the experiment is outlined to demonstrate that electric fields can be measured with accuracies of ±0.7 mV m-1 and ±1.0 mV m-1 in the dawn-dusk and satellite-sun directions respectively. These uncertainties can be considerably reduced under favourable plasma conditions. Examples of typical observations are described.
- The average electric field is always characterized by an irregular structure with time scales 0.5–5 min and with amplitudes of a few mV m-1.
- During substorms dawn-dusk electric fields up to 20–30 mV m-1 have been observed over intervals of 30–60 s.
- Oscillating electric fields with peak-to-peak amplitudes up to 10 mV m-1 and periods of 3–10 min have been observed following magnetospheric disturbances.
267.
H. U. Auster I. Apathy G. Berghofer A. Remizov R. Roll K. H. Fornacon K. H. Glassmeier G. Haerendel I. Hejja E. Kührt W. Magnes D. Moehlmann U. Motschmann I. Richter H. Rosenbauer C. T. Russell J. Rustenbach K. Sauer K. Schwingenschuh I. Szemerey R. Waesch 《Space Science Reviews》2007,128(1-4):221-240
The scientific objectives, design and capabilities of the Rosetta Lander’s ROMAP instrument are presented. ROMAP’s main scientific
goals are longterm magnetic field and plasma measurements of the surface of Comet 67P/Churyumov-Gerasimenko in order to study
cometary activity as a function of heliocentric distance, and measurements during the Lander’s descent to investigate the
structure of the comet’s remanent magnetisation. The ROMAP fluxgate magnetometer, electrostatic analyser and Faraday cup measure
the magnetic field from 0 to 32 Hz, ions of up to 8000 keV and electrons of up to 4200 keV. Additional two types of pressure
sensors – Penning and Minipirani – cover a pressure range from 10−8 to 101 mbar. ROMAP’s sensors and electronics are highly integrated, as required by a combined field/plasma instrument with less
than 1 W power consumption and 1 kg mass. 相似文献
268.
The THEMIS Magnetic Cleanliness Program 总被引:1,自引:0,他引:1
M. Ludlam V. Angelopoulos E. Taylor R. C. Snare J. D. Means Y. S. Ge P. Narvaez H. U. Auster O. Le Contel D. Larson T. Moreau 《Space Science Reviews》2008,141(1-4):171-184
The five identical THEMIS Spacecraft, launched in February 2007, carry two magnetometers on each probe, one DC fluxgate (FGM) and one AC search coil (SCM). Due to the small size of the THEMIS probes, and the short length of the magnetometer booms, magnetic cleanliness was a particularly complex task for this medium sized mission. The requirements leveled on the spacecraft and instrument design required a detailed approach, but one that did not hamper the development of the probes during their short design, production and testing phase. In this paper we describe the magnetic cleanliness program’s requirements, design guidelines, program implementation, mission integration and test philosophy and present test results, and mission on-orbit performance. 相似文献
269.
运用ANSYS CFX 11.0和home-code程序对AI222发动机风扇流路气动参数进行了3维CFD(Computational Fluid Dynamics)计算;通过3维建模,实现了风扇主要积分特性和局部参数计算。通过与风扇进行大量试验结果的对比,验证了计算结果,并找出了产生差别的原因,得到了风扇总特性以及气流径向参数的计算值与试验值的吻合度。结果表明:通过运用3维建模计算方法简化了风扇设计过程,缩短了风扇从设计到试验的时间,降低了航空发动机部件的设计成本。 相似文献
270.
At the ISSI Workshop 'The Origin and Composition of Cometary Material' a short questionnaire was devised by the 'Critical
Measurements for the Future' Working Group and distributed to the attendees. The aim was to find out what they thought were
the 'critical questions' and the key measurements needed to find answers. Results from the 15 respondents are collated and
summarized.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献