全文获取类型
| 收费全文 | 591篇 |
| 免费 | 323篇 |
| 国内免费 | 34篇 |
专业分类
| 航空 | 506篇 |
| 航天技术 | 198篇 |
| 综合类 | 12篇 |
| 航天 | 232篇 |
出版年
| 2025年 | 8篇 |
| 2024年 | 31篇 |
| 2023年 | 26篇 |
| 2022年 | 31篇 |
| 2021年 | 46篇 |
| 2020年 | 32篇 |
| 2019年 | 25篇 |
| 2018年 | 28篇 |
| 2017年 | 22篇 |
| 2016年 | 36篇 |
| 2015年 | 18篇 |
| 2014年 | 49篇 |
| 2013年 | 43篇 |
| 2012年 | 40篇 |
| 2011年 | 42篇 |
| 2010年 | 42篇 |
| 2009年 | 31篇 |
| 2008年 | 14篇 |
| 2007年 | 51篇 |
| 2006年 | 40篇 |
| 2005年 | 35篇 |
| 2004年 | 25篇 |
| 2003年 | 20篇 |
| 2002年 | 27篇 |
| 2001年 | 24篇 |
| 2000年 | 16篇 |
| 1999年 | 22篇 |
| 1998年 | 24篇 |
| 1997年 | 20篇 |
| 1996年 | 13篇 |
| 1995年 | 16篇 |
| 1994年 | 8篇 |
| 1993年 | 10篇 |
| 1992年 | 6篇 |
| 1991年 | 6篇 |
| 1990年 | 6篇 |
| 1989年 | 3篇 |
| 1988年 | 3篇 |
| 1987年 | 9篇 |
排序方式： 共有948条查询结果，搜索用时 15 毫秒
491.
Hao ZHOU Xiaoyu ZHANG Huizhong ZENG Huning YANGa Hongshuai LEI Xiao LI Yaobing WANG 《中国航空学报》2019,32(7):1727-1732
Thermal controllers equipped with phase-change materials are widely used for maintaining the moderate temperatures of various electric devices used in spacecraft. Yet, the structures of amounts of thermal controllers add up to such a large value that restricts the employment of scientific devices due to the limit of rocket capacity. A lightweight structure of phase-change thermal controllers has been one of the main focuses of spacecraft design engineering. In this work, we design a lightweight phase-change thermal controller structure based on lattice cells. The structure is manufactured entirely with AlSi10 Mg by direct metal laser melting. The dimensions of the structure are 230 mm × 170 mm × 15 mm, and the mass is 190 g, which is 60% lighter than most traditional structures(500–600 g) with the same dimensions. The 3 D-printed structure can reduce the risk of leakage at soldering manufacture by a welding process. Whether the strength of the designed structure is sufficient is determined through mechanical analysis and experiments. Thermal test results show that the thermal capacity of the lattice-based thermal controller is increased by50% compared to that of traditional controllers with the same volume. 相似文献
492.
分别使用62Sn36Pb2Ag焊料和63Sn37Pb共晶焊料焊接模拟式太阳敏感器硅光电池电极,通过力学试验和加速热循环试验,对比分析了两种焊料形成的焊点性能和显微组织结构。研究表明,由于Ag元素的加入,与63Sn37Pb焊料相比,62Sn36Pb2Ag焊料焊点显微组织内部颗粒状的Ag3Sn有效起到了位错钉扎的作用,在强化焊点的同时,也提高了焊点抗热失配能力和抗蠕变性能。在经历力学试验和-105~+105℃循环试验后,62Sn36Pb2Ag焊点裂纹扩展率远低于63Sn37Pb焊点。在给定的试验条件和温度循环范围内,62Sn36Pb2Ag焊料的抗热失配能力和高温抗蠕变性能较63Sn37Pb焊料表现更加优异。 相似文献
493.
Y. Liu X.X. Pan G.H. Li X. Liu L.X. Jiang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Based on the Monte Carlo ray-tracing method, the network coefficients of thermal network model describing the radiation heat transfer among satellite surfaces is solved by considering the surface material optical characters. It is superiority to the conventional Gebhart’s method in view of the grey body and the diffuse reflection assumptions. The zone leveling method is used to discrete the governing equations and the solar absorpivity is separated and considered to be an important correction parameter. Effects of the solar incidence round angle, the zenith angle and the ratio of absorpivity to emissivity (RAE) on temperature distribution are numerically simulated and discussed in detail. The higher or the lower the RAE may be lead to the alternative heating and cooling tend with a larger heating or cooling velocity of main body surfaces than the solar array surfaces. Furthermore, maximum temperature of main body is almost larger than solar arrays. Under the same RAE, solar incidence angle make a great effect on the uniform character of temperature distribution. 相似文献
494.
The critical conditions for aeroelastic stability and the stability boundaries of a flexible two-dimensional heated panel subjected to an impinging oblique shock are considered using theoretical analysis and numerical computations, respectively. The von-Karman large deflection theory of isotropic flat plates is used to account for the geometrical nonlinearity of the heated panel, and local first-order piston theory is employed in the region before and after shock waves to estimate the aerodynamic pressure. The coupled partial differential governing equations, according to the Hamilton principle, are established with thermal effect based on quasi-steady thermal stress theory. The Galerkin discrete method is employed to truncate the partial differential equations into a set of ordinary differential equations, which are then solved by the fourth-order Runge-Kutta numerical integration method. Lyapunov indirect method is applied to evaluate the stability of the heated panel. The results show that a new aeroelastic instability (distinct from regular panel flutter) arises from the complex interaction of the incident and reflected wave system with the panel flexural modes and thermal loads. What’s more, stability of the panel is reduced in the presence of the oblique shock. In other words, the heated panel becomes aeroelastically unstable at relatively small flight aerodynamic pressure. 相似文献
495.
新型星用导电型Kapton基热控材料 总被引：3，自引：0，他引：3
介绍了一种新型导电型Ｋａｐｔｏｎ基热控材料,其导电层采用了ＴＯ（氧化锡）膜。这种ＴＯ膜具有很高的光学透明度,方阻在１０＾４Ω￣１０＾６Ω范围内,可有效地抑制卫星表面的充放电现象。经过８２００ｈ太阳当量紫外辐照后,ＴＯ／Ｋａｐｔｏｎ／Ａｌ热控材料的αｓ相对变化率Δα３／α５仅为６．７％。在ＴＯ／Ｋａｐｔｏｎ与Ｋａｐｔｏｎ试样的８０００ｈ的紫外辐照对照实验中,表明ＴＯ膜具有明显的紫外辐射防护功能。在－ 相似文献
496.
为了解微重力条件下空穴对相变传热过程的影响,在焓法的基础上增加了基于温度排序算法的空穴模型,在求解过程分析了温度场和空穴之间的相互作用;建立了相变装置的二维模型;研究了空穴在周期外热流条件下的移动规律。结果表明,从初始时刻到第8个轨道周期,低温区空穴逐渐消失并在高温区出现,空穴沿等温线方向扩散并最终积聚在高温边界附近,空穴的移动使传热路径上的热阻增大,导致相变装置冷热边界的传热温差增加了3℃。 相似文献
497.
电子封装用金属基复合材料的研究现状 总被引：17，自引：0，他引：17
本文介绍了电子封装用金属基复合材料的研究现状 ,分别从基体、增强体、制备工艺几方面讨论了其对复合材料性能的影响 ,着重介绍了作为电子封装材料应用前景较好的高比例SiC颗粒增强铝基复合材料及其已部分实现规模工业化生产的铸造法。并进一步提出了尚待解决的问题 相似文献
498.
499.
500.
为了更好地进行载波相位跟踪,Galileo L1F信号相比于GPS信号增加了没有导航数据的导频信道,使数据信道能够使用不受导航数据限制的鉴别器。但是Galileo L1F信号载波相位跟踪环中传统的鉴别器组合方式仍有不足。基于适用于单一导频信道的鉴别器性能优于适用于单一数据信道的鉴别器的原理,提出了新的鉴别器组合方式,并通过仿真实验对比在不同热噪声环境下传统组合方式的两种鉴别器组合和新组合方式的两种鉴别器组合的性能。研究结果表明新的鉴别器组合在Galileo L1F接收信号的抑制噪声和防止失锁控制方面比传统鉴别器组合有明显优势。 相似文献