全文获取类型
收费全文 | 3963篇 |
免费 | 167篇 |
国内免费 | 189篇 |
专业分类
航空 | 2194篇 |
航天技术 | 1231篇 |
综合类 | 165篇 |
航天 | 729篇 |
出版年
2021年 | 25篇 |
2020年 | 32篇 |
2019年 | 35篇 |
2018年 | 51篇 |
2017年 | 27篇 |
2016年 | 49篇 |
2015年 | 40篇 |
2014年 | 106篇 |
2013年 | 121篇 |
2012年 | 108篇 |
2011年 | 166篇 |
2010年 | 146篇 |
2009年 | 167篇 |
2008年 | 218篇 |
2007年 | 137篇 |
2006年 | 103篇 |
2005年 | 119篇 |
2004年 | 108篇 |
2003年 | 136篇 |
2002年 | 112篇 |
2001年 | 129篇 |
2000年 | 82篇 |
1999年 | 110篇 |
1998年 | 133篇 |
1997年 | 104篇 |
1996年 | 130篇 |
1995年 | 159篇 |
1994年 | 123篇 |
1993年 | 84篇 |
1992年 | 121篇 |
1991年 | 62篇 |
1990年 | 45篇 |
1989年 | 97篇 |
1988年 | 37篇 |
1987年 | 34篇 |
1986年 | 39篇 |
1985年 | 88篇 |
1984年 | 92篇 |
1983年 | 60篇 |
1982年 | 85篇 |
1981年 | 92篇 |
1980年 | 36篇 |
1979年 | 42篇 |
1978年 | 32篇 |
1977年 | 22篇 |
1976年 | 21篇 |
1975年 | 37篇 |
1974年 | 24篇 |
1972年 | 29篇 |
1967年 | 20篇 |
排序方式: 共有4319条查询结果,搜索用时 15 毫秒
181.
B. Rizk C. Drouet dAubigny C.W. Hergenrother B.J. Bos D.R. Golish R. Malhotra D.S. Lauretta J. Butt J. Patel M. Fitzgibbon C. May E.B. Bierhaus S. Freund M. Fisher S. Cambioni C.A. Bennett S.S. Balram-Knutson K. Harshman M. Moreau 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):672-691
We analyzed high-angular rate streaks first recorded by OSIRIS-REx’s MapCam during a 2017 search for Earth Trojan asteroids. We interpret them as water-ice particles that translated across the imager’s field of view, originating from the spacecraft itself. Their translation velocities approximated 0.1–1?m/s based on reasonable conclusions about their range. Pursuing several lines of investigation to seek a coherent hypothesis, we conclude that the episodic releases of the water ice particles are associated with spacecraft attitudes that resulted in solar illumination of previously shadowed regions. This correlation suggests that the OSIRIS-REx spacecraft itself possesses micro-climatic zones consisting of hot regions and cold traps that may temporarily potentially pass volatiles back and forth before losing most of them. 相似文献
182.
Guojun Wang Jiankui Shi Weihua Bai Ivan Galkin Zeng Wang Yueqian Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3119-3130
Global observations of S4 amplitude scintillation index by the GPS Occultation Sounder (GNOS) on FengYun-3 C (FY3C) satellite reveal global dynamic patterns of a strong pre-midnight scintillations in F-region of the ionosphere during the St. Patrick’s Day geomagnetic super storm of 17–19 March 2015. The observed strong scintillations mainly occurred in the low latitudes, caused by equatorial plasma bubbles. During the main storm phase (March 17), the scintillations were first triggered in the New Zealand sector near 160°E longitudes, extending beyond 40°S dip latitude. They were also enhanced in the Indian sector, but significantly suppressed in East Asia near 120°E longitude and in Africa around 30°E longitude. During the initial recovery phase (March 18–19), the global scintillations were seldom observed in GNOS data. During the later recovery phase (after March 19), the scintillations recovered to the pre-storm level in Indian, African, and American sectors, but not in East Asian and any of Pacific sectors. These results closely correlate with observations of the density depletion structures by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite, and ground-based instruments. Such consistency indicates reliability of our scintillation sensing approach even in a case-by-case comparison study. The prompt penetration electric field and disturbance dynamo electric field are suggested as the main factors that control the enhancement and inhibition of the scintillations during the storm, respectively. 相似文献
183.
184.
现代高效刀具和工具工业的发展特点
1 现代高效刀具的内涵
现代高效刀具是相对传统标准刀具而言的.传统的工具工业以生产供应标准化、通用化的刀具为基本特点.长期以来,制造业有一种共识:除了少量特殊需要,尽量选用标准刀具.标准刀具虽然性能不是最优,但因经济实用而被广泛接受.但到20多年前,这种观念在发达国家开始发生变化. 相似文献
185.
186.
187.
188.
189.
190.
阐述了液相法中制备超薄功能膜的新方法——连续离子层吸附反应法(Successive Ionic Layer Adsorption and Reaction,SILAR)。探究了它的薄膜生长机理、工艺参数影响以及应用现状,指出了尚需深入研究的问题。 相似文献