全文获取类型
收费全文 | 1901篇 |
免费 | 210篇 |
国内免费 | 172篇 |
专业分类
航空 | 1202篇 |
航天技术 | 421篇 |
综合类 | 260篇 |
航天 | 400篇 |
出版年
2024年 | 7篇 |
2023年 | 24篇 |
2022年 | 29篇 |
2021年 | 51篇 |
2020年 | 54篇 |
2019年 | 50篇 |
2018年 | 52篇 |
2017年 | 58篇 |
2016年 | 59篇 |
2015年 | 50篇 |
2014年 | 131篇 |
2013年 | 110篇 |
2012年 | 106篇 |
2011年 | 143篇 |
2010年 | 78篇 |
2009年 | 102篇 |
2008年 | 141篇 |
2007年 | 156篇 |
2006年 | 145篇 |
2005年 | 121篇 |
2004年 | 79篇 |
2003年 | 96篇 |
2002年 | 73篇 |
2001年 | 57篇 |
2000年 | 41篇 |
1999年 | 37篇 |
1998年 | 39篇 |
1997年 | 19篇 |
1996年 | 23篇 |
1995年 | 22篇 |
1994年 | 18篇 |
1993年 | 28篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 4篇 |
排序方式: 共有2283条查询结果,搜索用时 15 毫秒
961.
乳腺癌是癌症中引起妇女死亡的首要因素。本文采用绿色量子点作为荧光显色材料,建立了一种用于早期乳腺癌诊断的原位成像技术。利用生物素标记的抗HER2/neu抗体与乳腺癌细胞表面表达的HER2结合的特点,然后用偶联绿色量子点的链霉亲和素作为荧光检测标记物,与HER2抗原抗体复合物中的生物素发生特异结合,检测出乳腺癌细胞的存在。结果表明,在荧光显微镜下用绿色量子点原位显色的乳腺癌细胞,相对有机染料组显色亮度增强,故检测灵敏度有所提高。 相似文献
962.
袁玉亮 《华北航天工业学院学报》2008,(6):22-25
空气悬架以其优良的减振性能,在汽车振动控制中得到越来越广泛的应用。本文以空气悬架为研究对象,构建了带附加空气室空气悬架系统的1/4车辆振动模型;分析了空气悬架刚度调节原理和控制特性,本文采用了不依赖于被控对象精确数学模型的模糊控制策略进行空气悬架控制器的设计。 相似文献
963.
964.
S.I. Bartsev A.A. Pochekutov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
A continual model of humification and mineralization of soil organic matter (SOM) formed under the conditions of a Lunar base from biological waste materials is proposed. The model parameters corresponding to the conditions of several Earths climatic regions are estimated. The time necessary for the formation of organic matter in the soil based on regolith and higher plant residues has been evaluated. Soil formation under tropical conditions are shown to be the most appropriate for Lunar base CELSS due to high matter turnover rate, relatively short formation time, minimum deposited mass, and satisfactory predictability of expected soil parameters. 相似文献
965.
经济贫困女大学生是高校的一个特殊的弱势群体。她们疲惫的身心承受着巨大的经济和心理压力。以沈阳航空航天大学511名贫困女大学生为调查对象,对她们的心理问题进行了深入的分析,探讨了通过加强心理健康教育和思想政治教育提高其身心健康水平的策略。 相似文献
966.
V. Ivanova V. Kurkin V. Ivanov G. Vertogradov V. Uryadov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
An estimation of the F2 ionospheric region critical frequency (foF2) variations using analysis of round-the-world radio sounding data has been made. Experimental data obtained by the Russian chirp-sounders network have been used. For the first time, using experimental data and numerical simulation, the quantitative dependency between the minimum foF2 magnitudes over round-the-world propagation paths and round-the-world maximum usable frequencies has been obtained. 相似文献
967.
陕西省高职高专教育学会学报工作委员会,依托陕西省高校学报研究会、全国高职高专学报研究会等行业学会组织,团结本省高职高专院校学报20多个会员单位,根据会员学报办刊现状和实际需求开展学报编辑规范化建设、学报编辑学研究和学术讲座等一系列学术活动,注重学会服务功能,推动以特色栏目为主要特征的高职高专学报创新实践,有效地提高了陕西省高职高专院校学报的整体办刊水平。 相似文献
968.
A study of long-term climatology of ionospheric irregularities by using GPS phase fluctuations at the Brazilian longitudes 总被引:1,自引:0,他引:1
F.D. Chu C.C. Lee W.S. Chen J.Y. Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(4):645-649
We have examined the ionospheric plasma irregularities that were recorded by using three ground-based receivers of the global positioning system (GPS) located at Brazilian longitudes during the period of a complete solar cycle, 1995–2005. The statistic results show that ionospheric irregularities are very easy to occur in December solstice months but rare to occur in June solstice months. Besides, the occurrence rates of irregularities in both December and June solstice months are little dependent on solar activity. However, in equinoctial months, the development of irregularities is obviously dependent on solar activity. There is a new finding in this study that if strong irregularities are distinguished from moderate ones, their occurrence rates would increase with solar activity during the December solstice months. 相似文献
969.
杨琳 《西安航空技术高等专科学校学报》2008,26(2):11-13
为了弥补在文学语言中的不足,形成了以象寓意的话语蕴藉现象。本文运用了列举、分析等方式诠释话语蕴藉与文学词语、文学修辞、标点符号及文章结构之间的联系,揭示出文学话语蕴藉带给读者的丰富想象和再创造的审美空间。 相似文献
970.
In this paper we review the current predictions of numerical simulations for the origin and observability of the warm hot
intergalactic medium (WHIM), the diffuse gas that contains up to 50 per cent of the baryons at z∼0. During structure formation, gravitational accretion shocks emerging from collapsing regions gradually heat the intergalactic
medium (IGM) to temperatures in the range T∼105–107 K. The WHIM is predicted to radiate most of its energy in the ultraviolet (UV) and X-ray bands and to contribute a significant
fraction of the soft X-ray background emission. While O vi and C iv absorption systems arising in the cooler fraction of the WHIM with T∼105–105.5 K are seen in FUSE and Hubble Space Telescope observations, models agree that current X-ray telescopes such as Chandra and XMM-Newton do not have enough sensitivity to detect the hotter WHIM. However, future missions such as Constellation-X and XEUS might be able to detect both emission lines and absorption systems from highly ionised atoms such as O vii, O viii and Fe xvii. 相似文献