全文获取类型
收费全文 | 5942篇 |
免费 | 7篇 |
国内免费 | 16篇 |
专业分类
航空 | 3098篇 |
航天技术 | 1813篇 |
综合类 | 14篇 |
航天 | 1040篇 |
出版年
2021年 | 25篇 |
2019年 | 27篇 |
2018年 | 181篇 |
2017年 | 147篇 |
2016年 | 70篇 |
2015年 | 44篇 |
2014年 | 89篇 |
2013年 | 123篇 |
2012年 | 138篇 |
2011年 | 283篇 |
2010年 | 243篇 |
2009年 | 325篇 |
2008年 | 348篇 |
2007年 | 250篇 |
2006年 | 92篇 |
2005年 | 178篇 |
2004年 | 144篇 |
2003年 | 169篇 |
2002年 | 92篇 |
2001年 | 177篇 |
2000年 | 84篇 |
1999年 | 149篇 |
1998年 | 157篇 |
1997年 | 119篇 |
1996年 | 139篇 |
1995年 | 185篇 |
1994年 | 167篇 |
1993年 | 102篇 |
1992年 | 134篇 |
1991年 | 60篇 |
1990年 | 59篇 |
1989年 | 124篇 |
1988年 | 46篇 |
1987年 | 55篇 |
1986年 | 47篇 |
1985年 | 138篇 |
1984年 | 122篇 |
1983年 | 100篇 |
1982年 | 128篇 |
1981年 | 156篇 |
1980年 | 56篇 |
1979年 | 63篇 |
1978年 | 48篇 |
1977年 | 32篇 |
1976年 | 34篇 |
1975年 | 50篇 |
1974年 | 33篇 |
1972年 | 39篇 |
1969年 | 29篇 |
1967年 | 24篇 |
排序方式: 共有5965条查询结果,搜索用时 296 毫秒
981.
Space radiation dosimetry with active detections for the scientific program of the second Bulgarian cosmonaut on board the Mir space station. 总被引:1,自引:0,他引:1
J V Dachev TsPMatviichuk YuN Semkova R T Koleva B Boichev P Baynov N A Kanchev P Lakov P T Ivanov YaJTomo V M Petrov V I Redko V I Kojarinov R Tykva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1989,9(10):247-251
A dosimetry-radiometry system has been developed at the Space Research Institute of the Bulgarian Academy of Science to measure the fluxes and dose rates on the flight of the second Bulgarian cosmonaut. The dosimetry system is designed for monitoring the different space radiations, such as solar cosmic rays, galactic cosmic rays and trapped particles in the earth radiation belts. The system consists of a battery operated small size detector unit and a "read-write" and telemetry microcomputer unit. The sensitivity of the instrument (3.67 x 10(-8) rad/pulse) permits high resolution measurements of the flux and dose rate along the track of the Mir space station. We report our initial results for the period of the flight between the 7th and 17th June 1988. 相似文献
982.
983.
Margolis M.D. Messenger G.C. Fitch S.H. 《IEEE transactions on aerospace and electronic systems》1972,(6):771-779
A hardness assurance program suitable for a retaliatory or deterrent missile system is discussed. The program consists of three phases: the establishment of suitable controls and screens to ensure piece part hardness, a supplier data monitoring program to measure hardness related parameters in a timely fashion to obtain advanced warning of potential problems, and a hardness assurance verification testing (HAVT) program to periodically measure the radiation response of parts, circuits, subsystems, and systems on a sample basis to ensure proper functioning in simulated radiation environments. All of the data relevant to hardness assurance is stored in computer memory and routinely interrogated with programs which compare current results with the engineering baseline data and other data from preceding lots. Other computer programs enable statistical estimation of system response to the radiation environment with confidence based on the expanding data base provided by the HAVT program. 相似文献
984.
985.
986.
C.R. Philbrick D.P. Sipler B.B. Balsley J.C. Ulwick 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(6):129-132
The ructure and tmospheric urbulence nvironment (STATE) experiment was conducted during the second week of June 1983 at Poker Flat Research Range, Alaska. The measurements focus on a study of the middle atmosphere dynamics by comparison between in-situ probe measurements and MST radar measurements. Rocket launchings were conducted at three periods which were selected by monitoring the doppler velocity spectra of the MST radar.The STATE program has included the efforts of several scientists in planning and carrying out the ground-based and rocket measurements. An overview of the program is given together with some preliminary results. The regions in intense backscatter signals detected by the MST radar are shown to correlate with large irregularities in the electron profiles measured. 相似文献
987.
A.R. Engel K. Beurle A. Bewick P.K.S. Harper J.J. Quenby N.J.C. Spooner A.G. Fenton K.B. Fenton A.B. Giles J.G. Greenhill D.M. Warren I.M. Martin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
Hard X-ray balloon altitude measurements with a 1600 cm2 phoswich array are described. Data from observations on Sco X-1, GX1+4, GX5−1, Nova Oph. 1977, SMC X-1, SS433, IC 4329A and MR 2251-178 are presented. The role of Comptonisation in X-ray production for Sco X-1 and GX1+4 is discussed. 相似文献
988.
G.S. Orton A.P. Ingersoll L. Froidevaux G. Neugebauer G. Münch S.C. Chase 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):179-182
The Pioneer 11 Infrared Radiometer instrument made observations of Saturn and its rings in broadband channels centered at 20 and 45 μm and obtained whole-disk information on Titan. A planetary average effective temperature of 96.5±2.5 K implies a total emission 2.8 times the absorbed sunlight. Correlation with radio science results implies that the molar fraction of H2 is 90±3% (assuming the rest is He). Temperatures at the 1 bar level are 137 to 140 K; regions appearing cooler may be overlain by a cloud acting as a 124 K blackbody surface. A minimum temperature averaging 87 K is reached near 0.06 bars. Ring boundaries and optical depths are consistent with those at optical wavelengths. Ring temperatures are 64–86 K on the south (illuminated) side, ~54 K on the north (unilluminated) side, and at least 67 K in Saturn's shadow. There is evidence for a south to north drop in ring temperatures. Titan's 45 μm brightness temperature is 75±5 K. 相似文献
989.
Temesmber C.L. Thompson W.E. 《IEEE transactions on aerospace and electronic systems》1975,(2):183-189
Useful new properties are obtained with a coherent pulse-burst waveform if the FM slopes are allowed to change from pulse to pulse. A design feature using such a "slope-coded" waveform is the ability to transfer, in a controllable manner, ambiguity volume from the range ambiguity peaks to regions located between the peaks (in the frequency direction). Slope coding thus provides a useful mechanism for matching the waveform to the environment; i. e., it permits the signal designer to make some compromise between range ambiguity-peak heights and low-velocity clutter rejection. 相似文献
990.
The development of pulse compression radar at Sperry is related on the basis of the author's personal recollections. He discusses the first experiments, concept improvements, demonstration of the concept, system implementations, dealings with the US Patent Office, and finishing touches 相似文献