全文获取类型
收费全文 | 165篇 |
免费 | 13篇 |
国内免费 | 7篇 |
专业分类
航空 | 70篇 |
航天技术 | 75篇 |
综合类 | 6篇 |
航天 | 34篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2021年 | 1篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 17篇 |
2013年 | 10篇 |
2012年 | 13篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1995年 | 4篇 |
1994年 | 13篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1988年 | 1篇 |
排序方式: 共有185条查询结果,搜索用时 15 毫秒
101.
102.
通过研究光引发剂、光敏剂和链转移剂等对双酚A型环氧树脂阳离子光固化的影响,确定了双酚A型环氧树脂光固化体系的配方组成。利用湿法手工铺叠工艺和紫外光辐照固化技术,制备了玻璃布/双酚A型环氧树脂复合材料,研究了光敏剂和链转移剂等对光固化复合材料力学性能的影响。结果表明:可利用紫外光辐射固化成型技术制备玻璃布/双酚A型环氧树脂复合材料,加入链转移剂的光敏树脂基复合材料具有良好的力学性能。 相似文献
103.
光学系统在空间环境条件下的衰变对卫星遥感仪器探测精度有重要影响.漫反射板是星载光学遥感仪器辐射定标的重要工具.本文通过对ADEOS/TOMS和Earth Probe/TOMS仪器馒反射板漫反射率衰变特性的比较,分析研究了原子氧和太阳紫外辐射对漫反射板的影晌.结果表明,太阳紫外辐照和原子氧剥蚀引起的漫反射板反射率衰变系数分别为0.00049/h和1.2 × 10-17cm2,但在卫星入轨初期,太阳紫外辐照的影响可增加约4倍. 相似文献
104.
105.
F. Stalport P. Coll C. Szopa F. Raulin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The life on Mars remains an open question because of the lack of proof of its past emergence and its current presence. The only indices of a potential Martian life were provided by the Viking Landers, and the study of the Martian meteorite ALH84001 discovered in the Antarctic. In the two case, the results of experiments could be explained either by the presence of life forms or by abiotic processes. The recent data of Mars Express orbiter and Mars Exploration Rovers show different proofs of a past environment favourable for life. Among the targets we seek, the organic molecules are primordial because they are necessary to the origin of life. A key question is to know if they are present, in which concentration and under which form. Within the framework of a search for organic, we are developing an experimental setup simulating as close as possible the environmental conditions of Mars surface in order to determine how organic species evolve. We present here the first step of the development of this experiment which focuses on the study of the impact of the solar UV radiations reaching the Mars surface on glycine. First results show that glycine does not resist if directly exposed to UV radiations. 相似文献
106.
107.
108.
充气型紫外光敏管噪声过大是紫外火警探测系统最难克服的问题。本文从器件制造和使用的角度分析了影响紫外光敏管噪声的重要因素,探讨了降噪措施:制造工艺方面,采用高纯度金属镍基阴极材料和保持阴极表面质量良好,充分老化器件,选择高纯度氢气为主充气体并控制充入氦气比例不高于15%;使用方面,降低器件工作电流和工作电压可进一步减小器件噪声。最后采用锁相放大进行噪声测试,在120ms内,测得紫外光敏管噪声电压均值为0.0065V,测试不确定度为7.4%;在无外界紫外照射下,经脉冲计数,测得单位时间内紫外光敏管累积输出噪声脉冲为10cpm,显著降低器件噪声。 相似文献
109.
通过应用回归分析方法,对西安市某水厂的出水、管网中间水和管网末梢水的TOC、UV254和浊度的监测数据进行了相关性分析。结果表明:随着供水管网的延长,浊度和UV254的线性相关系数明显增加;随着供水管网的延长,浊度和TOC的线性相关系数明显降低。 相似文献
110.
A.K. Sharma N. Sridhara 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
A spacecraft with a passive thermal control system utilizes various thermal control materials to maintain temperatures within safe operating limits. Materials used for spacecraft applications are exposed to harsh space environments such as ultraviolet (UV) and particle (electron, proton) irradiation and atomic oxygen (AO), undergo physical damage and thermal degradation, which must be considered for spacecraft thermal design optimization and cost effectiveness. This paper describes the effect of synergistic radiation on some of the important thermal control materials to verify the assumptions of beginning-of-life (BOL) and end-of-life (EOL) properties. Studies on the degradation in the optical properties (solar absorptance and infrared emittance) of some important thermal control materials exposed to simulated radiative geostationary space environment are discussed. The current studies are purely related to the influence of radiation on the degradation of the materials; other environmental aspects (e.g., thermal cycling) are not discussed. The thermal control materials investigated herein include different kind of second-surface mirrors, white anodizing, white paints, black paints, multilayer insulation materials, varnish coated aluminized polyimide, germanium coated polyimide, polyether ether ketone (PEEK) and poly tetra fluoro ethylene (PTFE). For this purpose, a test in the constant vacuum was performed reproducing a three year radiative space environment exposure, including ultraviolet and charged particle effects on North/South panels of a geostationary three-axis stabilized spacecraft. Reflectance spectra were measured in situ in the solar range (250–2500 nm) and the corresponding solar absorptance values were calculated. The test methodology and the degradations of the materials are discussed. The most important degradations among the low solar absorptance materials were found in the white paints whereas the rigid optical solar reflectors remained quite stable. Among the high solar absorptance elements, as such the change in the solar absorptance was very low, in particular the germanium coated polyimide was found highly stable. 相似文献