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521.
We consider in detail the intense Pc5 pulsations of the magnetic field, riometric absorption, and electron fluxes occurred
on the recovery phase of the strong magnetic storm on November 21, 2003. The global structure of these disturbances is studied
using the world network of magnetometers and riometers supplemented by the data of particle detectors onboard the LANL geosynchronous satellites. The local spatial structure is investigated according to data of the regional network of Finnish
vertical riometers and of stations of the IMAGE magnetic network. Though a certain similarity is observed in the frequency
composition and time evolution of the variations of magnetic field and riometric absorption, the local spatial structure of
these oscillations turns out to be different. It is suggested that these variations can be manifestations of oscillatory properties
of two weakly connected systems: the magnetospheric MHD waveguide/resonator and the system cyclotron noise + electrons. The
recorded Pc5 oscillations are, presumably, a result of excitation of the magnetospheric waveguide on the morning and evening
flanks of the magnetosphere. At high velocities of the solar wind this waveguide can appear in a metastable state. Not only
jumps in the solar wind density, but injection of electrons into the magnetosphere as well, can serve as a trigger for the
waveguide excitation. 相似文献
522.
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
523.
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
524.
Dynamics of planets around other stars that demonstrate a variety of possible characteristics is of interest from the point
of view of realization of new scenarios of evolution which have not been realized in the Solar System. We consider the rotational
evolution of exoplanets under the action of gravitational perturbations and magnetic disturbances using the methods of quality
analysis and theory of bifurcation of multiparametric differential equations that describe evolution of non-resonant rotation
of a dynamically symmetric planet magnetized along its symmetry axis. We analyze 64 phase portraits describing the evolution
of angular momentum vector L for all possible values of planet parameters. The values of parameters are determined for the case when the direct rotation
of a planet is changed for its retrograde rotation. 相似文献
525.
Shlomi Ziskin Nir J. Shaviv 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The 20th century temperature anomaly record is reproduced using an energy balance model, with a diffusive deep ocean. The model takes into account all the standard radiative forcings, and in addition the possibility of a non-thermal solar component. The model is parameterized and then optimized to produce the most likely values for the climate parameters and radiative forcings which reproduce the 20th century global warming. We find that the best fit is obtained with a negligible net feedback. We also show that a non-thermal solar component is necessarily present, indicating that the total solar contribution to the 20th century global warming, of ΔTsolar = 0.27 ± 0.07 °C, is much larger than can be expected from variation in the total solar irradiance alone. However, we also find that the largest contribution to the 20th century warming comes from anthropogenic sources, with ΔTman = 0.42 ± 0.11 °C. 相似文献
526.
A. S. Meshchanov 《Russian Aeronautics (Iz VUZ)》2010,53(4):382-393
The results obtained for the systems with a linear stationary object and scalar control of sliding and switching modes [1]
are further developed. The methods of forming five modes of system operation with discontinuous and linear vector control
at nominal and uncertain limited disturbances are suggested. The necessary quality of transient processes with regard to the
speed of response and zero stationary error at all five modes and also controlled oscillation frequency and amplitude of control
signals at the sliding modes are provided. The effective sequence of switching the modes mentioned during the finite and unlimited
time intervals is proposed. The results are useful for qualitative tracking of programmed motion for flight vehicles, robot
manipulators, and other technical and production systems. 相似文献
527.
Vitali Braun A. LüpkenS. Flegel J. GelhausM. Möckel C. KebschullC. Wiedemann P. Vörsmann 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Today’s space debris environment shows major concentrations of objects within distinct orbital regions for nearly all size regimes. The most critical region is found at orbital altitudes near 800 km with high declinations. Within this region many satellites are operated in so called sun-synchronous orbits (SSO). Among those, there are Earth observation, communication and weather satellites. Due to the orbital geometry in SSO, head-on encounters with relative velocities of about 15 km/s are most probable and would thus result in highly energetic collisions, which are often referred to as catastrophic collisions, leading to the complete fragmentation of the participating objects. So called feedback collisions can then be triggered by the newly generated fragments, thus leading to a further population increase in the affected orbital region. This effect is known as the Kessler syndrome. 相似文献
528.
J.K. Hargreaves 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The paper summarises key facts and figures about the phenomenon of auroral radio absorption which are relevant to the problem of predicting its occurrence and intensity. The regions most affected are well known in terms of magnetic latitude (or L-value) and local time. The greater difficulty comes from its highly variable character. Exact predictions are never likely to be possible, but statistical forecasts, which would give the likelihood that some critical level will be reached or exceeded, may well be possible. At the present time it is suggested that they might be based on magnetic indices, since their prediction is already well established. Direct measurements of the solar wind, now available in real time, offer another possibility, perhaps to be considered in parallel. The substorm character of the absorption might also be applied, using the observed duration of absorption events and their known dynamics over the Earth’s surface, as an early warning. A comprehensive reference list is included. 相似文献
529.
530.
Three experiments are reported that used an interference paradigm to test the extent to which perceptual orientation to a task environment interfered with retrieval from long-term spatial memory. Visual and spatial sources of interference were tested. The findings were consistent with a spatial locus of interference and showed that orientation to the task environment disrupted the accessibility of relative direction under two retrieval conditions: when the imagined viewpoint was 180 degrees misaligned with the actual viewpoint and when the actual body location was anterior to the imagined body location. While the former finding replicates previous reports of interference in perspective-taking tasks, the latter finding is new and difficult for current models of spatial long-term memory retrieval to explain. More research is needed to articulate further the constraints that perceptual orientation to the task environment place on spatial retrieval and their implications for models of spatial memory. 相似文献