全文获取类型
收费全文 | 1171篇 |
免费 | 219篇 |
国内免费 | 180篇 |
专业分类
航空 | 480篇 |
航天技术 | 409篇 |
综合类 | 75篇 |
航天 | 606篇 |
出版年
2024年 | 12篇 |
2023年 | 44篇 |
2022年 | 43篇 |
2021年 | 62篇 |
2020年 | 52篇 |
2019年 | 45篇 |
2018年 | 79篇 |
2017年 | 45篇 |
2016年 | 52篇 |
2015年 | 57篇 |
2014年 | 111篇 |
2013年 | 67篇 |
2012年 | 102篇 |
2011年 | 102篇 |
2010年 | 81篇 |
2009年 | 82篇 |
2008年 | 76篇 |
2007年 | 74篇 |
2006年 | 57篇 |
2005年 | 40篇 |
2004年 | 25篇 |
2003年 | 35篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
排序方式: 共有1570条查询结果,搜索用时 46 毫秒
181.
182.
183.
航天光学采样成像系统MTF的优化设计与MTFC 总被引:2,自引:1,他引:1
简要介绍了成像链、成像系统和遥感系统的概念;对像质和像质差异的表征和度量、成像系统性能的表征等予以说明;重点探讨航天光学采样成像系统MTF的优化设计与MTFC问题,并给出讨论结果。 相似文献
184.
航天光学遥感器工作于太空中,长期恶劣的空间环境及短暂发射入轨时的状态对光学系统的设计与装调提出了苛刻的要求,确保光学系统在轨像质优异是航天光学遥感器研制的关键技术.文章结合国际上航天光学遥感器的发展需求对光学系统装调技术及发展现状进行了分析、总结,提出了中国后续航天光学遥感器装调与测试技术的突破方向. 相似文献
185.
G.L. Smith K.J. Priestley N.G. Loeb B.A. Wielicki T.P. Charlock P. Minnis D.R. Doelling D.A. Rutan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The Clouds and Earth Radiant Energy System (CERES) project’s objectives are to measure the reflected solar radiance (shortwave) and Earth-emitted (longwave) radiances and from these measurements to compute the shortwave and longwave radiation fluxes at the top of the atmosphere (TOA) and the surface and radiation divergence within the atmosphere. The fluxes at TOA are to be retrieved to an accuracy of 2%. Improved bidirectional reflectance distribution functions (BRDFs) have been developed to compute the fluxes at TOA from the measured radiances with errors reduced from ERBE by a factor of two or more. Instruments aboard the Terra and Aqua spacecraft provide sampling at four local times. In order to further reduce temporal sampling errors, data are used from the geostationary meteorological satellites to account for changes of scenes between observations by the CERES radiometers. 相似文献
186.
Shuanggen Jin Attila Komjathy 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The Global Navigation Satellite System (GNSS) has been a very powerful and important contributor to all scientific questions related to precise positioning on Earth’s surface, particularly as a mature technique in geodesy and geosciences. With the development of GNSS as a satellite microwave (L-band) technique, more and wider applications and new potentials are explored and utilized. The versatile and available GNSS signals can image the Earth’s surface environments as a new, highly precise, continuous, all-weather and near-real-time remote sensing tool. The refracted signals from GNSS radio occultation satellites together with ground GNSS observations can provide the high-resolution tropospheric water vapor, temperature and pressure, tropopause parameters and ionospheric total electron content (TEC) and electron density profile as well. The GNSS reflected signals from the ocean and land surface could determine the ocean height, wind speed and wind direction of ocean surface, soil moisture, ice and snow thickness. In this paper, GNSS remote sensing applications in the atmosphere, oceans, land and hydrology are presented as well as new objectives and results discussed. 相似文献
187.
N. Fouladi Moghaddam M.R. Sahebi A.A. Matkan M. Roostaei 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Land subsidence, due to natural or anthropogenic processes, causes significant costs in both economic and structural aspects. That part of subsidence observed most is the result of human activities, which relates to underground exploitation. Since the gradual surface deformation is a consequence of hydrocarbon reservoirs extraction, the process of displacement monitoring is amongst the petroleum industry priorities. Nowadays, Differential SAR Interferometry, in which satellite images are utilized for elevation change detection and analysis – in a millimetre scale, has proved to be a more real-time and cost-effective technology in contrast to the traditional surveying method. In this study, surface displacements in Aghajari oil field, i.e. one of the most industrious Iranian hydrocarbon sites, are being examined using radar observations. As in a number of interferograms, the production wells inspection reveals that surface deformation signals develop likely due to extraction in a period of several months. In other words, different subsidence or uplift rates and deformation styles occur locally depending on the geological conditions and excavation rates in place. 相似文献
189.
C.M. Wrasse J. Fechine H. Takahashi C.M. Denardini J. Wickert M.G. Mlynczak J.M. Russell C.L. Barbosa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(9):1423-1428
Global Positioning System (GPS) receiver on the CHAllenging Mini-satellite Payload (CHAMP) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, one of four on board the TIMED satellite, provide middle atmosphere temperature profiles by Radio Occultation (RO) and limb viewing infrared emission measurements, respectively. These temperature profiles retrieved by two different techniques in the stratosphere are compared with each other using more than 1300 correlative profiles in March, September and December 2005. The over-all mean differences averaged over 15 and 35 km are approximately −2 K and standard deviation is less than 3 K. Below 20 km of altitude, relatively small mean temperature differences ∼1 K are observed in wide latitudinal range except for June (during the SABER nighttime observation). In the middle to low latitudes, between 30°S and 30°N, the temperature difference increases with height from ∼0–1 K at 15 km, to ∼−4 K at 35 km of altitude. Large temperature differences about −4 to −6 K are observed between 60°S and 30°N and 31–35 km of altitude for all months and between 0° and 30°N below 16 km during June (nighttime). 相似文献
190.