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771.
Stright J.R. Rogers S.K. Quinn D.W. Fielding K.H. 《IEEE transactions on aerospace and electronic systems》1996,32(2):768-774
The theory of embedded time series is shown applicable for determining a reasonable lower bound on the length of test sequence required for accurate classification of moving objects. Sequentially recorded feature vectors of a moving object form a training trajectory in feature space. Each of the sequences of feature vector components is a time series, and under certain conditions, each of these time series has approximately the same fractal dimension. The embedding theorem may be applied to this fractal dimension to establish a sufficient number of observations to determine the feature space trajectory of the object. It is argued that this number is a reasonable lower bound on test sequence length for use in object classification. Experiments with data corresponding to five military vehicles (observed following a projected Lorenz trajectory on a viewing sphere) show that this bound is indeed adequate 相似文献
772.
S Black K Larkin N Jacqmotte R Wassersug S Pronych K Souza 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(6-7):209-217
To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate for the first time that a vertebrate can ovulate in the virtual absence of gravity, and that the eggs can develop to a free-living stage. 相似文献
773.
T Fujii Y Midorikawa M Shiba M Terai K Omasa K Nitta 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(5):29-32
For the Closed Ecological Life Support System (CELSS) of a manned lunar base which is planned to be built on the moon early in the 21st century, several proposed programs exist to grow vegetables inside a farming module. At the 40th IAF (Malaga, 1989) the author et al presented a proposal for supplying food and nutrients to a crew of eight members, a basic concept which is based on growing four kinds of vegetables. This paper describes measures for biohazard protection in farming modules. In this study, biohazard protection means prevention of the dispersion of plant diseases to other plant species or other portions of farming beds. 相似文献
774.
Tarn T.J. Bejczy A.K. Yun X. 《IEEE transactions on aerospace and electronic systems》1988,24(5):571-583
Multiple coordinated robot arms are modeled by considering the arms as closed kinematic chains and as a force-constrained mechanical system working on the same object simultaneously. In both formulations, a novel dynamic control method is discussed. It is based on feedback linearization and simultaneous output decoupling technique. By applying a nonlinear feedback and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, it was found that by choosing a general output equation it became possible simultaneously to superimpose the position and velocity error feedback with the force-torque error feedback in the task space 相似文献
775.
To fully utilize the theoretical processing gain achievable when an adaptive array and frequency hopping are combined, frequency compensation is required. Improved versions of an anticipative adaptive array are examined that provide efficient compensation by adapting the complex weights at each antenna element to the appropriate values for a carrier frequency before that frequency is received. The underlying adaptive algorithm used is the maximum algorithm. Computer simulation results are used to compare the different versions of anticipative processing. These results show that an appropriate version ensures the rapid convergence of weights to values that provide wideband nulling of the interference and noise 相似文献
776.
C. E. Fichtel D. L. Bertsch B. Dingus R. C. Hartman S. D. Hunter G. Kanbach D. A. Kniffen P. W. Kwok Y. C. Lin J. R. Mattox H. A. Mayer-Hasselwander P. F. Michelson C. von Montigny P. L. Nolan K. Pinkau H. Rothermel E. J. Schneid M. Sommer P. Sreekumar D. J. Thompson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):637-646
The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's. 相似文献
777.
Liu R. Lee C.Q. Upadhyay A.K. 《IEEE transactions on aerospace and electronic systems》1992,28(3):697-707
When an LLC-type parallel resonant converter (LLC-PRC) operates above resonant frequency, the switching transistors can be turned off at zero voltage. Further study reveals that the LLC-PRC possesses the advantage of lower converter voltage gain as compared with the conventional PRC. Based on the analytic results derived, a complete set of design curves from which a systematic design procedure is developed is obtained. Experimental results from a 150-W, 150-kHz, multioutput LLC-type PRC power supply are presented 相似文献
778.
It is well known that passive target tracking by a single observer, commonly referred to as target motion analysis (TMA), can be done using angle and/or frequency measurements. Depending on the measurement set, different passive tracking procedures result: angle-only tracking (AOT), frequency-only tracking (FOT), and angle/frequency tracking (AFT). Whereas the two-dimensional passive tracking problem has been solved for a multitude of scenarios, thus giving a good insight into the parametric dependences, the three-dimensional problem has been discussed only in a few specific cases. To get a deeper insight into the parametric dependences of three-dimensional TMA, this work analyzes AOT and AFT in typical three-dimensional Airborne Warning and Control System (AWACS) scenarios. A Cramer Rao (CR) analysis of the problem reveals the parametric dependences of both methods and gives a clear idea of the increase in estimation accuracy by using AFT instead of AOT. The results obtained in this way are well confirmed by Monte Carlo simulations taking maximum likelihood (ML) as estimation procedure. 相似文献
779.
K.Ya. Kondratyev V.V. Kozoderov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(6):105-109
Based on the 1974–78 NOAA data, characteristic features of the variability of the Earth's radiation budget and its components over the area of the Northern Atlantic have been analyzed. Calculations of the mean square deviation for the ERB and its components have let to the conclusions that anomalous regions of maximum variability may be considered as energy-active zones. 相似文献
780.
M. K. Hudson W. Lotko C. A. Cattell R. L. Lysak I. Roth M. Temerin 《Space Science Reviews》1995,71(1-4):623-646
Intermediate or mesoscale processes mediate the transfer of mass, momentum, and energy across the dynamic solar wind-magnetosphere interface, and the propagation of this input through the system to the ionosphere and atmosphere. The Dartmouth-Berkeley-Minnesota theory team has identified a number of mesoscale phenomena to be investigated as part of the GGS program, including: (1) effects of upstream density fluctuations on magnetopause dynamics, (2) three-dimensional reconnection, (3) magnetopause depletion layer studies, (4) ring current interaction with Pc 1 and Pc 5 waves, (5) generation of ion Larmor-scale current layers in the near Earth plasmasheet, (6) test particle studies in the magnetotail, (7) simulation of magnetosphere- ionosphere coupling including effects of kinetic Alfvén waves and (8) auroral acceleration region studies of the effects of kinetic Alfvén waves on particle distribution functions. A broad range of techniques will be implemented including ideal and reduced MHD, two fluid, hybrid, particle-in-cell and test particle simulations. Detailed comparison of simulation results with GGS satellite and ground based data will be undertaken. 相似文献