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221.
An Adaptive Extended Kalman Filter for Target Image Tracking 总被引:1,自引:0,他引:1
222.
A Detection Algorithm for Optical Targets in Clutter 总被引:2,自引:0,他引:2
There is active interest in the development of algorithms for detecting weak stationary optical and IR targets in a heavy opticalclutter background. Often only poor detectability of low signal-to-noise ratio (SNR) targets is achieved when the direct correlation method is used. In many cases, this is partly obviated by using detection with correlated reference scenes [1, 2].This paper uses the experimentally justified assumption that most optical clutter can be modeled as a whitened Gaussian randomprocess with a rapidly space-varying mean and a more slowlyvarying covariance [2]. With this assumption, a new constant falsealarm rate (CFAR) detector is developed as an application of the classical generalized maximum likelihood ratio test of Neyman and Pearson. The final CFAR test is a dimensionless ratio. This test exhibits the desirable property that its probability of a false alarm(PFA) is independent of the covariance matrix of the actual noiseencountered. When the underlying noise processes are complex intime, similar considerations can yield a sidelobe canceler CFARdetection criterion for radar and communications. Performance analyses based on the probability of detection (PD)versus signal-to-noise ratio for several given fixed false alarm probabilities are presented. Finally these performance curves are validated by computer simulations of the detection process which use real image data with artificially implanted signals. 相似文献
223.
A conceptual system is proposed and described for the control of a multiplicity of drone aircraft. Each target (drone) aircraft is controlled, during a given mission, over a separate preprogrammed path comprised of straight line and circular arc segments. Full control of each target's altitude, plan position, and velocity is available. Position measurement can be obtained by use of either a radar or a bilateration method where altitude is measured in either case by each aircraft and telemetered to a central control point. Velocity is obtained by smoothing position data in a central computer, which also controls the entire mission complex. 相似文献
224.
J. D. Anderson J. W. Armstrong J. K. Campbell F. B. Estabrook T. P. Krisher E. L. Lau 《Space Science Reviews》1992,60(1-4):591-610
The gravitation and celestial mechanics investigations during the cruise phase and Orbiter phase of the Galileo mission depend on Doppler and ranging measurements generated by the Deep Space Network (DSN) at its three spacecraft tracking sites in California, Australia, and Spain. Other investigations which also rely on DSN data, and which like ours fall under the general discipline of spacecraft radio science, are described in a companion paper by Howard et al. (1992). We group our investigations into four broad categories as follows: (1) the determination of the gravity fields of Jupiter and its four major satellites during the orbital tour, (2) a search for gravitational radiation as evidenced by perturbations to the coherent Doppler link between the spacecraft and Earth, (3) the mathematical modeling, and by implication tests, of general relativistic effects on the Doppler and ranging data during both cruise and orbiter phases, and (4) an improvement in the ephemeris of Jupiter by means of spacecraft ranging during the Orbiter phase. The gravity fields are accessible because of their effects on the spacecraft motion, determined primarily from the Doppler data. For the Galilean satellites we will determine second degree and order gravity harmonics that will yield new information on the central condensation and likely composition of material within these giant satellites (Hubbard and Anderson, 1978). The search for gravitational radiation is being conducted in cruise for periods of 40 days centered around solar opposition. During these times the radio link is least affected by scintillations introduced by solar plasma. Our sensitivity to the amplitude of sinusoidal signals approaches 10-15 in a band of gravitational frequencies between 10-4 and 10-3 Hz, by far the best sensitivity obtained in this band to date. In addition to the primary objectives of our investigations, we discuss two secondary objectives: the determination of a range fix on Venus during the flyby on 10 February, 1990, and the determination of the Earth's mass (GM) from the two Earth gravity assists, EGA1 in December 1990 and EGA2 in December 1992. 相似文献
225.
Efron A.J. Swaszek P.E. Tufts D.W. 《IEEE transactions on aerospace and electronic systems》1992,28(4):932-943
A detector which is designed to operate in a correlated Gaussian-plus-impulsive-noise environment is presented. The detector whitens the data robustly and then uses a two-sided threshold test to determine the presence of impulsive samples. The impulsive samples are discarded, and the remaining samples are used to detect the presence or absence of a signal using a matched filter. An approximate analysis is presented, and simulations are used to demonstrate the effectiveness of this approach 相似文献
226.
Halpin S.M. Grigsby L.L. 《IEEE transactions on aerospace and electronic systems》1992,28(4):1033-1041
Alternative methods for power flow and fault analysis of single-phase distribution systems are presented. The algorithms for both power flow and fault analysis utilize a generalized approach to network modeling. The generalized admittance matrix, formed using elements of linear graph theory, is an accurate network model for all possible single-phase network configurations. Unlike the standard nodal admittance matrix formulation algorithms, the generalized approach uses generalized component models for the transmission line and transformer. The standard assumption of a common node voltage reference point is not required to construct the generalized admittance matrix. Therefore, truly accurate simulation results can be obtained for networks that cannot be modeled using traditional techniques 相似文献
227.
Susan M. P. McKenna-Lawlor 《Space Science Reviews》1982,32(1-2):235-250
McMath Plage 15266, which transited the solar disk during Carrington Rotation 1667, gave rise during its passage to a spectacular sequence of five proton producing flares. Solar circumstances leading up to the formation of the active plage are described. An account is given of the magnetic affiliations and optical characteristics of the flares themselves, and it is suggested that four of these events might be interpreted as two twin phase flares displaying secondary maxima and minima such that the second phase in each case could in some sense be deemed a consequence of phenomena initiated during the first phase. Those particle phenomena associated with the observed activity are reviewed, and it is suggested that the azimuthal propagation of solar cosmic rays in the corona may occur more efficiently for flares at eastern longitudes in which the magnetic axis is aligned in a roughly north to south rather than an east-to-west direction.An invited paper presented at STIP Workshop on Shock Waves in the Solar Corona and Interplanetary Space, 15–19 June, 1980, Smolenice, Czechoslovakia. 相似文献
228.
An algorithm is described for initial synchronization in a communication system with a digital adaptive array. This algorithm can also be used for message extraction. A set of consecutive complex video samples of the array output is processed to obtain optimum adaptive array weights, based on a least mean square (LMS) error criterion. This computation is performed for each of the possible alternative signals which may be present during an observation interval. The correct synchronization time or message symbol is selected as the one which yields the minimum LMS error. Assuming orthogonality of the alternative codes, a probability distribution for the output of this processor has been derived. 相似文献
229.
Methods are discussed for establishing the optical identification of X ray sources in the medium and deep X-ray surveys of the Einstein Observatory. Of the 63 X-ray sources with a statistical significance of 5 in the medium survey (Maccacaro et al. 1981), optical identification work is summarized for 51, of which identifications have been made with 30 active galactic nuclei. The optical properties of some of these X-ray selected objects are briefly discussed.The Einstein deep survey of Pavo (Griffiths et al. 1981) is used to illustrate the problems and methods used for securing optical identifications for X-ray sources in the deep survey fields. Identifications have been made with 4 QSOs at the bright end of the optical candidate distribution (together with 3 G stars) and it is shown that a further 7 fainter objects are also likely to be QSOs. 相似文献
230.