全文获取类型
收费全文 | 821篇 |
免费 | 98篇 |
国内免费 | 99篇 |
专业分类
航空 | 498篇 |
航天技术 | 174篇 |
综合类 | 129篇 |
航天 | 217篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 20篇 |
2019年 | 18篇 |
2018年 | 93篇 |
2017年 | 56篇 |
2016年 | 8篇 |
2015年 | 26篇 |
2014年 | 41篇 |
2013年 | 45篇 |
2012年 | 57篇 |
2011年 | 56篇 |
2010年 | 59篇 |
2009年 | 78篇 |
2008年 | 61篇 |
2007年 | 47篇 |
2006年 | 44篇 |
2005年 | 44篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 27篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 21篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1981年 | 1篇 |
排序方式: 共有1018条查询结果,搜索用时 359 毫秒
141.
142.
143.
Nicholas Achilleos Nicolas André Xochitl Blanco-Cano Pontus C. Brandt Peter A. Delamere Robert Winglee 《Space Science Reviews》2015,187(1-4):229-299
The rapid rotation of the gas giant planets, Jupiter and Saturn, leads to the formation of magnetodisc regions in their magnetospheric environments. In these regions, relatively cold plasma is confined towards the equatorial regions, and the magnetic field generated by the azimuthal (ring) current adds to the planetary dipole, forming radially distended field lines near the equatorial plane. The ensuing force balance in the equatorial magnetodisc is strongly influenced by centrifugal stress and by the thermal pressure of hot ion populations, whose thermal energy is large compared to the magnitude of their centrifugal potential energy. The sources of plasma for the Jovian and Kronian magnetospheres are the respective satellites Io (a volcanic moon) and Enceladus (an icy moon). The plasma produced by these sources is globally transported outwards through the respective magnetosphere, and ultimately lost from the system. One of the most studied mechanisms for this transport is flux tube interchange, a plasma instability which displaces mass but does not displace magnetic flux—an important observational constraint for any transport process. Pressure anisotropy is likely to play a role in the loss of plasma from these magnetospheres. This is especially the case for the Jovian system, which can harbour strong parallel pressures at the equatorial segments of rotating, expanding flux tubes, leading to these regions becoming unstable, blowing open and releasing their plasma. Plasma mass loss is also associated with magnetic reconnection events in the magnetotail regions. In this overview, we summarise some important observational and theoretical concepts associated with the production and transport of plasma in giant planet magnetodiscs. We begin by considering aspects of force balance in these systems, and their coupling with the ionospheres of their parent planets. We then describe the role of the interaction between neutral and ionized species, and how it determines the rate at which plasma mass and momentum are added to the magnetodisc. Following this, we describe the observational properties of plasma injections, and the consequent implications for the nature of global plasma transport and magnetodisc stability. The theory of the flux tube interchange instability is reviewed, and the influences of gravity and magnetic curvature on the instability are described. The interaction between simulated interchange plasma structures and Saturn’s moon Titan is discussed, and its relationship to observed periodic phenomena at Saturn is described. Finally, the observation, generation and evolution of plasma waves associated with mass loading in the magnetodisc regions is reviewed. 相似文献
144.
论文通过对桂林航天工业高等专科学校部分学生的英语学习策略调查问卷及相关数据进行SPSS数据分析,分析通过大学英语四级的学生英语学习策略使用情况,及通过分析调查对象的英语学习策略使用情况,是否知道学习策略对于学习策略的选择的影响,各学习策略之间的关系等提出,指导学生,提高大学英语四级通过率。 相似文献
145.
为了定量描述空域扇区的复杂性,引入交通内禀性概念,通过计算扇区内航空器间的逼近时间、侵略函数、关系矩阵、相关度函数,建立扇区的复杂性测度模型;并通过仿真算例,对扇区复杂度影响因素进行了分析.研究结果表明:复杂性值大小反映了扇区内飞机数量及汇聚、分散程度,复杂性值曲线拐点数量反映了扇区交通有序/无序程度,复杂性值曲线突变反映了扇区交通数量变化情况,可为管制员的监视和冲突解脱方案选择提供一定支持. 相似文献
146.
Huiling Qin Hiroshi Kawamura 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Using Atmospheric Infrared Sounder (AIRS) products of atmospheric temperature and geopotential height, we investigate the atmospheric response to HE0611, which was found and investigated by [Qin, H., Kawamura, H., Sakaida, F., Ando, K. A case study of the tropical Hot Event in November 2006 (HE0611) using a geostationary meteorological satellite and the TAO/TRITON mooring array. J. Geophys. Res. 113, C08045, doi: 10.1029/2007JC004640, 2008]. HE0611 was formed by connecting two very high SST areas, HE0611-East and HE0611-West. The period-mean atmosphere temperatures at levels of 925 and 850 hPa in HE0611-West are higher, by about 0.5 K, than those in WE0611-East while the atmospheric temperatures at middle to high levels (700–300 hPa) are higher in HE0611-East. The period-mean geopotential heights HE0611-East are much lower than those in HE0611-West for the levels from the surface to 400 hPa. The mean geopotential heights from 400 hPa to 200 hPa are higher in HE0611-East. In the middle and high layers over HE0611-West, the atmosphere temperatures gradually decrease from 7th to 17th, and then increase significantly. The increase in HE0611-East starts from 15th November, which is earlier than that of HE0611-West. The geopotential heights in the high layer of both the areas also show corresponding behaviors. The lagged atmospheric response in the western part is confirmed by the correlation analysis. It emerges that the atmospheric response to HE0611 is well organized and associated with deep convention in HE0611-East and subsidence in HE0611-West. These are also consistent with the HE0611 features and evolution revealed by earlier HE studies. 相似文献
147.
In this paper, a brief review and generalization of studies on the heat transfer and heat conduction problem in a variable
domain are presented. The equations of the process, where the boundary displacement velocity is the control, are obtained
taking into account heat inflow.
This article was submitted by the authors in English. 相似文献
148.
SPOT-5卫星系统性能概述 总被引:4,自引:0,他引:4
概要介绍SPOT - 5卫星的主要成像传感器 ,精确定位技术及数据格式。介绍分析卫星数据的应用前景 相似文献
149.
150.