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971.
Terrestrial planets are accreted in a disk orbiting a central star. The basic challenge of their formation consists of assembling
micron-sized or smaller dust grains to bodies with over 104 km in diameter. This formation process, ultimately based on collisions, occurs in three very different physical regimes depending
upon the size of the bodies present: 1) Early on, micron- to mm-sized dust grains, chondrules and chondrites are strongly
coupled to the gas. 2) As they grow larger, gravity increases the collisional cross section allowing runaway growth to occur.
3) After this runaway phase stops from exhaustion of matter in the immediate surroundings of the protoplanets, further growth
occurs on timescales typical of mutual gravitational perturbations. The emphasis of this book is on the timescales corresponding
to these formation phases as well as the characteristic chemical and isotopic composition of the bodies involved.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
972.
D. Kucharski G. Kirchner H.-C. Lim F. Koidl 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The nanosatellite BLITS (Ball Lens In The Space) demonstrates a successful design of the new spherical lens type satellite for Satellite Laser Ranging (SLR). The spin parameters of the satellite were calculated from more than 1000 days of SLR data collected from 6 High Repetition Rate (HRR) systems: Beijing, Changchun, Graz, Herstmonceux, Potsdam, Shanghai. 相似文献
973.
AnalyticalredundancytechniquessuchasextendedKalmanfilter,componentstrackingfilterandsooncandetect,isolateandacommodatefailur... 相似文献
974.
A. G. Demekhov 《Space Science Reviews》2012,168(1-4):595-609
We discuss the electromagnetic processes in the ULF range which are important for the coupling between the atmosphere, ionosphere, and magnetosphere (AIM). The main attention is given to the Pc1–2 frequency ranges (f≈0.1–10 Hz) where some natural resonances in the AIM system are located. In particular, we consider the resonant structures in the spectra of the magnetic background noise related to the Alfvén resonances in the ionosphere as a possible diagnostic tool for studies of the ionospheric parameters. We also discuss the self-excitation of Alfvén waves in the ionosphere due to the AIM coupling and the role of such waves in the acceleration of electrons in the upper ionosphere and magnetosphere. Precipitation of magnetospheric ions due to their interaction with the ion-cyclotron waves is analyzed in relation to the ionospheric current systems, formation of partial ring current, and the influence of the ionosphere-magnetosphere feedback on the generation of such waves. 相似文献
975.
Space Science Reviews - 相似文献
976.
During recent years, defense budgets have been cut across all services while the cost of maintaining current standards has risen. The Aircraft Stores Interface Manual (ASIM) Program Office found that maintaining a staff for paper updates was no longer feasible and was tasked by the North Atlantic Treaty Organization (NATO) Air Armament Working Party (AAWP) to digitize the ASIM manuals. Converting this information from paper to electronic media presented several challenges which are discussed. Adopting Paperless Information Technology and replacing “Snail Mail” with the World Wide Web is presented 相似文献
977.
The coupling between the ionised plasma and the neutral thermospheric particles plays an important role for the dynamics of the upper atmosphere. Significant progress in understanding the related processes has been achieved thanks to the availability of continuous accurate measurements of thermospheric parameters like mass density and wind by high resolution accelerometers on board the satellites CHAMP and GRACE. Here we present some examples of ionosphere-thermosphere coupling where CHAMP observations contributed considerably to their interpretation. We start with the derived properties of the thermosphere at altitudes around 400 km. A new aspect is the significant control of the geomagnetic field geometry on thermospheric features. Phenomena discussed in some depths are the equatorial mass density anomaly, the cusp-related mass density enhancement and the thermospheric response to magnetospheric substorms. Here we consider both the effect on the density and on the wind. A?long predicted process is the wind-driven ionospheric F region dynamo. The high-resolution magnetic field measurements of CHAMP enabled for the first time a systematic study of that phenomenon considering longitudinal, local time, seasonal and solar flux dependences. Some open issues that require further investigations are mentioned at the end. 相似文献
978.
Jürgen Blum 《Space Science Reviews》2000,92(1-2):265-278
For a better understanding of the processes which lead to the formation of planetesimals in the early solar nebula, we performed
an extensive series of laboratory experiments. We find that the capture velocities in collisions between spherical grains
are more than one order of magnitude higher than predicted by Chokshi et al (1993). In contrast, irregular grains have no
capture threshold and can be better described by a sticking probability which is typically a few 10%, even for velocities
exceeding 10 m/s. However, adhesion forces between spherical, micron-sized particles match the theoretical predictions very
well, although contact areas and deformations are of the order of inter-atomic distances only. Aggregation experiments in
rarefied turbulent gases reveal the fractal nature of dust aggregates. Mass distribution functions are bell-shaped. Similar
behaviour can be found in aggregation experiments with sedimenting particles. Experiments on collision-induced aggregate compaction
and fragmentation match the numerical simulations by Dominik and Tielens (1997) very well if revised experimental values of
the break-up energy (from our impact experiments) and the rolling-friction force (from our AFM measurements on particle chains)
are used.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
979.
Benjamin S. Schwarz Adrian R.L. Tatnall Hugh G. Lewis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Coastal salinity is characterised by large and variable salinity contrasts on relatively small scales. Measurements of salinity at a resolution compatible with these coastal regions on a regular basis would provide a rich source of information that could be used for a number of applications that have a fundamental bearing on the world’s lifestyle. Doppler radiometry offers an approach to capture such measurements, as it reduces the number of required antennas needed to form an image, compared with an Interferometer type instrument. 相似文献
980.
T.P. Dachev B.T. Tomov Yu.N. Matviichuk P.S. Dimitrov S.V. Vadawale J.N. Goswami G. De Angelis V. Girish 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The RADiatiOn Monitor (RADOM) is a miniature dosimeter-spectrometer that flew onboard the Chandrayaan-1 lunar mission in order to monitor the local radiation environment. Primary objective of the RADOM experiment was to measure the total absorbed dose, flux of surrounding energetic particles and spectrum of the deposited energy from high energy particles both en-route and in lunar orbit. RADOM was the first experiment to be switched on after the launch of Chandrayaan-1 and was operational until the end of the mission. This paper summarizes the observations carried out by RADOM during the entire life time (22 October 2008–31 August 2009) of the Chandrayaan-1 mission and compares the measurement by RADOM with the radiation belt models such as AP-8, AE-8 and CRRESS. 相似文献