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891.
Honeywell has conducted a series of flight tests of a 35 GHz digital microprocessor controlled forward looking radar altimeter. A Bell 206L Jet Ranger helicopter was used to evaluate the capability of the sensor as a detector of various types of terrain collision hazards. The sensor was composed of a covert, spread spectrum radar altimeter processor driving a 35 GHz converter and antenna assembly mounted on a steerable platform. Excellent correlation between predicted performance and observed performance was obtained 相似文献
892.
893.
M. M. Shvarts S. M. Grach E. N. Sergeev V. L. Frolov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(12):59-62
Results of computer simulations of the broad continuum (BC) feature of stimulated electromagnetic emissions (SEE) of the ionosphere are presented. The simulations were performed using the model of BC generation based on the double transformation of electromagnetic waves to upper hybrid (UH) waves and back with artificial small scale irregularities (ASI) of plasma density. An induced scattering of the UH waves by thermal ions provided a wide spectrum of SEE. For the simulations an empirical model of the ASI spectrum, development and decay was used. 相似文献
894.
Microorganisms and enzyme activity in permafrost after removal of long-term cold stress 总被引:1,自引:0,他引:1
E.A Vorobyova V.S Soina A.L Mulukin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(12):103-108
Associations of immobilized microbial cells and organic-mineral complexes containing active enzymes are resistant to long-term (from tens of thousands to millions of years) effects of extremely low temperatures. This association enables the cells to restore their metabolic activity during permafrost thawing, because interactions with the heterogenous medium is made possible by the availability of active immobilized enzymes. The long-term effect of the cold probably favors an adaptational change of microbial metabolism that activates enzymes and cells during thawing. 相似文献
895.
L O'C Drury 《Space Science Reviews》1996,75(1-2):269-277
The possibility of observing gamma ray emission from supernova remnants is discussed. It is shown that this could be possible in the 100 MeV band accessible to satellite instruments, but that confusion with the Galactic background is a major problem. At TeV energies and with modern imaging atmospheric cherenkov telescopes the situation should be much better and at least some of the nearby remnants may be detectable. Positive detections in both bands would provide a decisive test of current theoretical ideas on particle acceleration in supernova remnants and the origin of the Galactic cosmic rays. 相似文献
896.
Mikhail Ya. Marov 《Space Policy》1992,8(3)
The space programme of the former USSR has been in disarray since the disintegration of the Soviet empire and it faces formidable economic and political problems. Attempts are being made, however, to formalize a programme for the Commonwealth of Independent States (CIS) and a Russian space agency has been established. A senior Russian scientist here gives his personal view of the past, present and future of his country's space activities. He emphasizes the need to take advantage of new opportunities for cooperation, argues for the lifting of US restrictions on technology transfer and stresses the importance of space technology in monitoring environmental problems. This should remain a top priority. 相似文献
897.
Rosenthal P.L. Brownlow J.D. 《IEEE transactions on aerospace and electronic systems》1985,(6):821-822
A method is developed for estimating circular error probable values and circular error probable rate values of an inertial navigation system using the concepts of Kalman filtering and time averaging. 相似文献
898.
L. L. Regel 《Space Science Reviews》1988,48(1-2):169-186
This paper is a review dealing with recent publications on theoretical and experimental investigations on space materials science under lower gravity. The importance of the results obtained by the present time and the wide perspectives for future investigations in this field are outlined. 相似文献
899.
J T Lett E L Peters 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(2-3):51-58
For decades, theories of cellular radiosensitivity relied upon the initial patterns of energy deposition to explain radiation lethality. Such theories are unsound: cellular (DNA) repair also underlies cellular radiosensitivity. For the charged particles encountered in deep space, both the types of DNA damage caused in cellular deoxyribonucleoproteins and the efficacies of their repair are dependent on linear energy transfer (LET infinity), and repair efficiency is also influenced by cell and tissue type, i.e., the actual recovery processes involved. Therefore, quality factors derived from radiation quality alone are inadequate parameters for assessing the radiation risks of space flight. Until recently, OH radicals formed in bulk nuclear water were believed to be the major causes of DNA damage that results in cell death, especially for sparsely ionizing radiations. That hypothesis has now been challenged, if not refuted. Lethal genomic DNA damage is determined mainly by energy deposition in deoxyribonucleoproteins, and their hydration shells, and charge (energy) transfer processes within those structures. 相似文献
900.
A E Nicogossian J D Rummel L Leveton R Teeter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(1):329-337
By the turn of this century, long-duration space missions, either in low Earth orbit or for got early planetary missions, will become commonplace. From the physiological standpoint, exposure to the weightless environment results in changes in body function, some of which are adaptive in nature and some of which can be life threatening. Important issues such as environmental health, radiation protection, physical deconditioning, and bone and muscle loss are of concern to life scientists and mission designers. Physical conditioning techniques such as exercise are not sufficient to protect future space travellers. A review of past experience with piloted missions has shown that gradual breakdown in bone and muscle tissue, together with fluid losses, despite a vigorous exercise regimen can ultimately lead to increased evidence of renal stones, musculoskeletal injuries, and bone fractures. Biological effects of radiation can, over long periods of time increase the risk of cancer development. Today, a vigorous program of study on the means to provide a complex exercise regimen to the antigravity muscles and skeleton is under study. Additional evaluation of artificial gravity as a mechanism to counteract bone and muscle deconditioning and cardiovascular asthenia is under study. New radiation methods are being developed. This paper will deal with the results of these studies. 相似文献