全文获取类型
收费全文 | 186篇 |
免费 | 24篇 |
国内免费 | 101篇 |
专业分类
航空 | 143篇 |
航天技术 | 65篇 |
综合类 | 23篇 |
航天 | 80篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 24篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 18篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
排序方式: 共有311条查询结果,搜索用时 453 毫秒
21.
将nc-Si:H薄膜进行等离子和高温氧化处理,测量了样品的氢,氧含量,Raman谱,红外吸收谱,光致发光(PL),结果表明两种氧化方式都将氧掺入薄膜中,但不同处理方式氧在薄膜中的键合形式不同Raman谱表明氧化处理对薄膜中晶粒大小及晶态比没有影响,用晶粒-表面模型对氧化引起的光致发光(PL)蓝移进行了解释。 相似文献
22.
We study kinetic excitation mechanisms for high-frequency dispersive Alfvén waves in the solar corona, solar wind, and Earth's
magnetosphere. The ion-cyclotron and Cherenkov kinetic effects are important for these waves which we call the ion-cyclotron
kinetic Alfvén waves (ICKAWs). Ion beams, anisotropic particles distributions and currents provide free energy for the excitation
of ICKAWs in space plasmas. As particular examples we consider ICKAW instabilities in the coronal magnetic reconnection events,
in the fast solar wind, and in the Earth's magnetopause. Energy conversion and transport initiated by ICKAW instabilities
is significant for the whole dynamics of Sun-Earth connection chain, and observations of ICKAW activity could provide a diagnostic/predictive
tool in the space environment research.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
23.
为解决基于SRAM(Static Random Access Memory,静态随机存储器)型FPGA(Field Programmable Gate Array,现场可编程门阵列)的扩频应答机在空间环境中时常发生功能故障的难题,提出了一种低轨卫星基于SRAM型FPGA的应答机的单粒子综合防护方案。该方案在代码级、器件级、单机级、整星级综合采用器件优选、结构屏蔽设计、巡检自愈、自主复位等多种方法,有效杜绝了单粒子事件带来的种种危害,已成功应用于某在轨卫星。在轨测试结果表明:遥测、遥控、跟踪测量等功能、性能指标满足任务要求,且未发生需要地面干预的问题或现象。该技术还可推广应用于其他采用低等级器件及其他类型FPGA、DSP(Digital Signal Processing,数字信号处理)等大规模集成电路的星载单机防护。 相似文献
24.
考虑真实气体效应的一维非定常平衡流的随机选取法计算 总被引:1,自引:1,他引:0
本文提出一种近似随机选取法,计算一维非定常的高温平衡流动。采用稀疏激波替代等熵稀疏波,选用拟合经验方程计算高温热力学性质,并利用切割迭代方法加快收敛,从而计算大为简化,并有很好精度。 相似文献
25.
26.
S.A. Demin Y.A. Nefedyev A.O. Andreev N.Y. Demina S.F. Timashev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(2):639-644
The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously. 相似文献
27.
随着越来越多先进复合材料应用在民用飞机上以及民用飞机上使用的电子电气设备重要度和集成度越来越高,飞机的闪电防护设计越来越重要。CCAR-23第23.867条对民用飞机机体结构闪电直接效应防护进行了规定。研究了该条款的制定和修订的背景和历程,明确了条款的实质要求。23部飞机的使用用途和设计特点使得23部飞机的闪电防护设计和符合性验证也有自己的特点,为此,重点研究了23.867条款的基本设计、审定步骤和审查关注要素等,梳理出了飞机机体结构的闪电直接效应防护设计和适航审定的基本流程,给出了可接受的符合性方法,提出了23部飞机闪电直接效应防护设计、审定各流程的主要工作、可指导或可参考的文件、重点关注要素和技术审查要点,为民用飞机的闪电直接效应防护的设计和适航审定提供了参考。 相似文献
28.
Design and optimization of a novel electrically controlled high pressure fuel injection system for heavy fuel aircraft piston engine 总被引:1,自引:1,他引:0
The heavy fuel compression ignition engines are widely equipped as aircraft piston engines. The fuel injection system is one of the key technologies that determines the performance of engine. One of the main challenges is to precisely control the injected fuel quantity and flow rate in the presence of pressure fluctuation. This challenge is even more serious for heavy fuel. An original design for electrically controlled high pressure fuel injection system called Multi-Pumppressure-reservoirs fuel injection System(MPS) was demonstrated to reduce the pressure fluctuation and help keep injection stable. MPS was compared with an ordinary high pressure Common Rail fuel injection System(CRS). This work established one-dimensional AMESim and mathematical models for both CRS and MPS to study the effect of different structures and geometric parameters on the pressure fluctuations. The calculations show that the average fuel pressure fluctuation of MPS can be reduced by 57% for the crankshaft speed of 1900 r/min, and the pressure fluctuation before injection reduced by 100%. It is concluded that the pressure performance of MPS is less sensitive to pressure reservoir volume than that of CRS, and there is an opportunity for further volume reduction. 相似文献
29.
30.