全文获取类型
收费全文 | 369篇 |
免费 | 106篇 |
国内免费 | 76篇 |
专业分类
航空 | 356篇 |
航天技术 | 70篇 |
综合类 | 55篇 |
航天 | 70篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 42篇 |
2013年 | 32篇 |
2012年 | 29篇 |
2011年 | 33篇 |
2010年 | 26篇 |
2009年 | 14篇 |
2008年 | 27篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1987年 | 1篇 |
排序方式: 共有551条查询结果,搜索用时 31 毫秒
121.
Jean-Paul Zahn 《Space Science Reviews》1998,85(1-2):79-90
While the solar convection zone is very well mixed by its turbulent motions, chemical composition gradients build up in the
radiative interior due to microscopic diffusion and settling, and to nuclear burning. Standard models, which ignore any type
of macroscopic transport, cannot explain the depletion of lithium in solar-type stars, as they evolve; neither do they account
for the observed profile of molecular weight at the base of the solar convection zone.
Such macroscopic transport can be achieved through thermally driven meridian currents, through turbulent diffusion generated
by differential rotation and possibly through gravity waves. These processes transport also angular momentum, and therefore
the internal rotation profile of the Sun provides a crucial test for their relative importance. So does also the behavior
of tidally locked binaries, which appear to destroy less lithium than single stars of the same mass.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
122.
Sergey Pulinets Dmitry Davidenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The electromagnetic coupling between the seismically activated area and the ionosphere is considered within the framework of the Global Electric Circuit (GEC) conception. First we consider the anomalous variations in the ionosphere associated with the earthquake preparation process, their temporal and spatial characteristics using the results from recent publications. Then the GEC conception is presented shortly with main accent put on ionization processes which play key role in the complex chain of physical and chemical interactions changing the electric properties of the planetary boundary layer of atmosphere. We treat this part of troposphere as an open complex system with dissipation where so called “blow up” processes are developed leading to sharp and fast changes of atmospheric parameters including the electric properties of the boundary layer. The new concept named Spatial Scintillation Index is introduced in the last part of the paper. In general, this paper may be considered as a short review of the recent achievements in understanding of the seismo-ionospheric coupling. 相似文献
123.
124.
姚姣 《中国民航飞行学院学报》2014,25(5):30-32
针对ATC3000空管自动化系统的运行要求以及飞行管制区现场实际工作的需要,介绍了ATC3000航空地图制作软件的关键技术。文中分析了该软件的结构以及在Windows系统中使用Delphi开发的具体实现技术。 相似文献
125.
为了进行微小型单旋翼飞行器的动力学建模,通过建立多个坐标系来反映各部分间的相对运动.首先,利用坐标变换得到位置、速度及加速度等向量,并代入拉格朗日方程得到运动学模型;然后,对模型进行数值求解,得到飞行器的姿态响应.仿真结果表明,飞行器定点盘旋时合外力为零,能量保持不变;爬升或前飞时有非保守力做正功,能量增大. 相似文献
126.
Fuel tank inerting technologies are able to reduce the fire risk by injection of inert gas into the ullage or fuel, the former called ullage washing and the latter fuel scrubbing. The Green On-Board Inert Gas Generation System (GOBIGGS) is a novel technology based on flameless catalytic combustion, and owning to its simple structure and high inerting efficiency, it has received a lot of attentions. The inert gas in the GOBIGGS is mainly comprised of CO2, N2, and O2 (hereinafter, Mixed Inert Gas (MIG)), while that in the On-Board Inert Gas Generation System (OBIGGS), which is one of the most widely used fuel tank inerting technologies, is Nitrogen-Enriched Air (NEA). The solubility of CO2 is nearly 20 times higher than that of N2 in jet fuels, so the inerting capability and performance are definitely disparate if the inert gas is selected as NEA or MIG. An inerting test bench was constructed to compare the inerting capabilities between NEA and MIG. Experimental results reveal that, if ullage washing is adopted, the variations of oxygen concentrations on the ullage and in the fuel are nearly identical no matter the inert gas is NEA or MIG. However, the ullage and dissolved oxygen concentrations of MIG scrubbing are always higher than those of NEA scrubbing. 相似文献
127.
A data-driven health indicator extraction method for aircraft air conditioning system health monitoring 总被引:2,自引:0,他引:2
Prognostics and Health Management (PHM) has become a very important tool in modern commercial aircraft. Considering limited built-in sensing devices on the legacy aircraft model, one of the challenges for airborne system health monitoring is to find an appropriate health indicator that is highly related to the actual degradation state of the system. This paper proposed a novel health indicator extraction method based on the available sensor parameters for the health monitoring of Air Conditioning System (ACS) of a legacy commercial aircraft model. Firstly, a specific Airplane Condition Monitoring System (ACMS) report for ACS health monitoring is defined. Then a non-parametric modeling technique is adopted to calculate the health indicator based on the raw ACMS report data. The proposed method is validated on a single-aisle commercial aircraft widely used for short and medium-haul routes, using more than 6000 ACMS reports collected from a fleet of aircraft during one year. The case study result shows that the proposed health indicator can effectively characterize the degradation state of the ACS, which can provide valuable information for proactive maintenance plan in advance. 相似文献
128.
张发荣 《中国民航学院学报》1999,17(1):64-68
阐述了在国内外航空市场的竞争压力下航空公司应采取的措施。针对过去和未来一段时期内国际航空市场的变化,结合云南航空公司的实际情况,分析了国内航线和国际航线运营状况,提出了具有其自身特色的发展战略和经营策略。 相似文献
129.
供应链变迁与航空货运经营模式的转变 总被引:2,自引:0,他引:2
赵桂红 《中国民航学院学报》2002,20(6):57-61
通过对供应链理论的演变过程、渠道理论及目前中国航空货运经营模式的分析,认为中国航空货运已经具备了采用多种经营模式的能力,并且应当进行经营模式的转变;在采用多种模式时,首先要处理好渠道冲突和合作问题。 相似文献
130.
本文简要评述了国外当前弹用小发动机的设计特点,描述了2000年弹用小涡轮发动机的发展概貌,还介绍了未来弹用小发动机发展的材料、空气动力学和结构技术三方面的关键技术. 相似文献