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301.
302.
This paper proposes a novel landing gear for spacecraft that allows a weight reduction due to using deformable crash legs. Numerical simulation of the landing process was performed. 相似文献
303.
G. S. Anufriev 《Cosmic Research》2010,48(1):101-107
The isotopic composition and concentrations of helium are investigated in 9 samples taken from different depths of a soil
column delivered by the Luna-24 mission. It is demonstrated that, with allowance made for random errors, the isotopic composition of helium remains invariable.
The concentrations of helium are subject to considerable variations, the increases and decreases relative to the average value
reaching a factor of 1.5–2. Assuming that the full length of the soil column was formed due to long-term accumulation of lunar
clastic rocks (regolith), based on measurements of cosmogenic isotopes, a method of determining the rate of regolith accumulation
has been developed, as well as a method of determining the age of the column soil samples. It is found that the rate of regolith
accumulation is variable, and it changes over the column length within the limits (0.2–0.8 cm)/106 years. The range of the time for formation of the investigated part of the column is 100–600 million years. The observed
decreases of concentration (at 250 and 600 million years) can be associated with both solar and lunar processes. In particular,
a possibility of diffusion losses of helium due to the mechanism of jump-like diffusion is discussed, and diffusion parameters
are found. A comparison of time periods of the observed variations in the solar wind with paleontological epochs and periods
is made. 相似文献
304.
Pascal Willis Hervé Fagard Pascale Ferrage Frank G. Lemoine Carey E. Noll Ron Noomen Michiel Otten John C. Ries Markus Rothacher Laurent Soudarin Gilles Tavernier Jean-Jacques Valette 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing System (GGOS), particularly to maintain and disseminate the Terrestrial Reference Frame as determined by International Earth rotation and Reference frame Service (IERS). A few years ago, under the umbrella of the International Association of Geodesy, a DORIS International Service (IDS) was created in order to foster international cooperation and to provide new scientific products. This paper addresses the organizational aspects of the IDS and presents some recent DORIS scientific results. It is for the first time that, in preparation of the ITRF2008, seven Analysis Centers (AC’s) contributed to derive long-term time series of DORIS stations positions. These solutions were then combined into a homogeneous time series IDS-2 for which a precision of less than 10 mm was obtained. Orbit comparisons between the various AC’s showed an excellent agreement in the radial component, both for the SPOT satellites (e.g. 0.5–2.1 cm RMS for SPOT-2) and Envisat (0.9–2.1 cm RMS), using different software packages, models, corrections and analysis strategies. There is now a wide international participation within IDS that should lead to future improvements in DORIS analysis strategies and DORIS-derived geodetic products. 相似文献
305.
I. Antonenko G.R. Osinski M. Battler M. Beauchamp L. Cupelli A. Chanou R. Francis M.M. Mader C. Marion E. McCullough A.E. Pickersgill L.J. Preston B. Shankar T. Unrau D. Veillette 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Remote robotic data provides different information than that obtained from immersion in the field. This significantly affects the geological situational awareness experienced by members of a mission control science team. In order to optimize science return from planetary robotic missions, these limitations must be understood and their effects mitigated to fully leverage the field experience of scientists at mission control. 相似文献
306.
G.L. Smith K.J. Priestley N.G. Loeb B.A. Wielicki T.P. Charlock P. Minnis D.R. Doelling D.A. Rutan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The Clouds and Earth Radiant Energy System (CERES) project’s objectives are to measure the reflected solar radiance (shortwave) and Earth-emitted (longwave) radiances and from these measurements to compute the shortwave and longwave radiation fluxes at the top of the atmosphere (TOA) and the surface and radiation divergence within the atmosphere. The fluxes at TOA are to be retrieved to an accuracy of 2%. Improved bidirectional reflectance distribution functions (BRDFs) have been developed to compute the fluxes at TOA from the measured radiances with errors reduced from ERBE by a factor of two or more. Instruments aboard the Terra and Aqua spacecraft provide sampling at four local times. In order to further reduce temporal sampling errors, data are used from the geostationary meteorological satellites to account for changes of scenes between observations by the CERES radiometers. 相似文献
307.
I. A. Krivosheev A. G. Godovanyuk V. S. Fatikov G. I. Pogorelov 《Russian Aeronautics (Iz VUZ)》2010,53(1):57-62
A technique for linear interpolation of the multidimensional characteristics of a coaxial propeller fan with opposite rotation
propellers is proposed; the technique makes it possible to simulate the turbofan engine operation in the entire range of flight
conditions and reduce expenses for fullscale tests. The mathematical models obtained meet the requirements imposed in the
semi-full-scale simulation. 相似文献
308.
A. Ipiña G.M. Salum E. Crinó R.D. Piacentini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Intense fires were produced on the Paraná river delta islands, Argentina, during most part of 2008, by a combination of an exceptionally dry period and the farmers’ use of a fire land-cleaning technique. In April 2008, those fires significantly affected the nearby regions and their inhabitants, from Rosario city to Buenos Aires mega-city. In this work we present satellite as well as ground Aerosol Optical Depth (AOD) at 550 nm data obtained during the propagation of pollution clouds to the central zone of Argentina. The highest value (1.18) was registered at Buenos Aires by atmospheric remote sensing, using the satellite instrument MODIS/Terra on April 18th 2008 at 10:35 local time (= UT − 3 h). On the same day, ground air quality detectors also measured in this city the highest Total Suspended Particle (TSP) value of the month, 2.02 mg/m3. The AOD(550) daily variation at Rosario Astronomical Observatory, which is located near the Paraná riverside, was derived by combining solar ultraviolet erythemal irradiance data (measured with a YES biometre) with model calculations. On April 25th 2008, from 12:00 to 15:30 local time, a rather high and constant AOD(550) value was registered, with a mean value of (0.90 ± 0.21). Cities located on the side of the Rosario–Buenos Aires highway (San Nicolás, Baradero and San Pedro) were also affected, showing a mean AOD(550) between the Rosario and Buenos Aires values. The particulate matter was collected with gridded samplers placed on the Paraná river islands as well as at the Rosario Observatory. They were analysed with a Scanning Electron Microscope (SEM) and mainly showed a biological origin. Even if normally large particles travel small distances from the source, organic aerosol in the range of 40–100 μm and complex asymmetric structures were registered several kilometres away from the aerosol sources on the islands. Another event of intense UV index attenuation (98.6%) occurred on September 18th 2008, due to very dense smoke clouds that extended over the Rosario area for several hours. The clouds were driven away from the fires by East–northeast and East–southeast winds. The minimum value of this index measured around noon allows to derive a maximum AOD(550)max = (3.65 ± 0.90) at 12:45 local time. Soot clouds extended over the Paraná river, transporting Burned Biomass Debris (BBD) that deposited on Rosario. In particular, burned leaves and small branches with dimensions of 1–20 cm were collected. The mean (BBD) particles deposited on the ground from 7:00 to 19:00 local time were (0.92 ± 0.20) BBD/(m2 h). 相似文献
309.
The Lunar Gravity Ranging System for the Gravity Recovery and Interior Laboratory (GRAIL) Mission 总被引:1,自引:0,他引:1
William M. Klipstein Bradford W. Arnold Daphna G. Enzer Alberto A. Ruiz Jeffrey Y. Tien Rabi T. Wang Charles E. Dunn 《Space Science Reviews》2013,178(1):57-76
The Lunar Gravity Ranging System (LGRS) flying on NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission measures fluctuations in the separation between the two GRAIL orbiters with sensitivity below 0.6 microns/Hz1/2. GRAIL adapts the mission design and instrumentation from the Gravity Recovery and Climate Experiment (GRACE) to a make a precise gravitational map of Earth’s Moon. Phase measurements of Ka-band carrier signals transmitted between spacecraft with line-of-sight separations between 50 km to 225 km provide the primary observable. Measurements of time offsets between the orbiters, frequency calibrations, and precise orbit determination provided by the Global Positioning System on GRACE are replaced by an S-band time-transfer cross link and Deep Space Network Doppler tracking of an X-band radioscience beacon and the spacecraft telecommunications link. Lack of an atmosphere at the Moon allows use of a single-frequency link and elimination of the accelerometer compared to the GRACE instrumentation. This paper describes the implementation, testing and performance of the instrument complement flown on the two GRAIL orbiters. 相似文献
310.
J. B. Blake P. A. Carranza S. G. Claudepierre J. H. Clemmons W. R. Crain Jr. Y. Dotan J. F. Fennell F. H. Fuentes R. M. Galvan J. S. George M. G. Henderson M. Lalic A. Y. Lin M. D. Looper D. J. Mabry J. E. Mazur B. McCarthy C. Q. Nguyen T. P. O’Brien M. A. Perez M. T. Redding J. L. Roeder D. J. Salvaggio G. A. Sorensen H. E. Spence S. Yi M. P. Zakrzewski 《Space Science Reviews》2013,179(1-4):383-421
This paper describes the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the RBSP spacecraft from an instrumentation and engineering point of view. There are four magnetic spectrometers aboard each of the two spacecraft, one low-energy unit (20–240 keV), two medium-energy units (80–1200 keV), and a high-energy unit (800–4800 keV). The high unit also contains a proton telescope (55 keV–20 MeV). The magnetic spectrometers focus electrons within a selected energy pass band upon a focal plane of several silicon detectors where pulse-height analysis is used to determine if the energy of the incident electron is appropriate for the electron momentum selected by the magnet. Thus each event is a two-parameter analysis, an approach leading to a greatly reduced background. The physics of these instruments are described in detail followed by the engineering implementation. The data outputs are described, and examples of the calibration results and early flight data presented. 相似文献