全文获取类型
收费全文 | 57篇 |
免费 | 21篇 |
国内免费 | 44篇 |
专业分类
航空 | 41篇 |
航天技术 | 19篇 |
综合类 | 4篇 |
航天 | 58篇 |
出版年
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
排序方式: 共有122条查询结果,搜索用时 562 毫秒
91.
Ioannis Haranas Ioannis Gkigkitzis George D. Zouganelis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
It is possible that the nucleolous inside the cell plays the role of a “gravity receptor”. Furthermore, cells up to 10 μm in diameter can demonstrate some effect due to the redistribution of mitochondria or nucleolous. Effects of gravity should be present in various cell systems where larger objects such as the ribosomes move from cell to cell. In this paper we study the effects of gravity on cells. In particular, we examine the resulting intracellular molecular distribution due to Brownian motion and the ordered distribution of molecules under the action of gravity, where n0 is the number per unit volume at certain level, and n is the number per unit volume above that level. This is an experiment that takes place at a certain orbital altitude in a spacecraft in orbit around Earth, where the acceleration due to the central field is corrected for the oblateness and also the rotation of the Earth. We found that equatorial circular and elliptical orbits have the highest n/n0 ratios. This experiment takes place in circular and elliptical orbits, with eccentricities e = 0, 0.1 and involves a bacterial cell at an orbital altitude of 300 km. We found that n/n0 = 1.00299 and 1.0037 respectively, which is still a 0.6–0.7 % higher than n/n0 = 0.0996685 calculated on the surface of the Earth. Examining mitochondria in similar orbital experiments we found that equatorial orbits result to higher n/n0 ratios. In particular, we found that n/n0 = 8.38119, where an elliptical orbit of eccentricity e = 0.1 results to n/n0 = 13.8525. Both are high above 100%, signifying the importance of Brownian motion over gravity. Our results are of interest to biomedical applications. Molecular concentrations are important for various processes such as the embryogenesis, positional homeostasis and its relation to cell energy expenditure, cell torque, cell deformation, and more. These results indicate that statistical molecular distributions play an important role for the recognition of a particular environment by the cell, in biological space experiment to come. 相似文献
92.
Bernhard Schläppi Kathrin Altwegg Timm Riesen Martin Rubin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The Pioneer anomaly, an unexpected acceleration of the Pioneer 10 and 11 spacecraft of ∼8.5 × 10−10 ms−2 directed towards the inner Solar System, has been of great interest for the physics community during the past decade: considered explanations range from new physical concepts to conventional mechanism. It is shown that non-isotropic outgassing of the complete spacecraft structure is comparable in magnitude and direction to the effect and should be considered as a significant contribution to the anomalous acceleration. Although gas leaks from e.g. the propulsion system and propulsive mass loss mechanism have been discarded as possible explanations for the anomaly, the arguments used against such mechanisms do not apply to global outgassing from the spacecraft. 相似文献
93.
实用化图像式油液污染实时检测系统研究 总被引:6,自引:0,他引:6
针对油液实时分析的应用需求,分析了基于显微图像的全采样式油液分析系统的各种特征参数,提出了系统改进的若干关键措施,建立了基于分流采样原理的实用化油液污染分析系统。同时根据实用化系统的特点,提出了结合图像运动特征和自动阈值选取的颗粒识别方法,分析了流场速度分布,解决了污染度计算的问题,并进行了与传统仪器的对比实验,获得较好的效果。 相似文献
94.
祁联仲 《海军航空工程学院学报》2006,21(6):618-622
分析了伺服机构油液污染产生的原因以及油液污染对舵机的危害性,提出了污染控制的措施及办法,总结了在舵机工作液问题上所做的工作并提出了几点建议。 相似文献
95.
建立了测定GAP分子量及分子量分布的GPC法。该法应用LC-6A高效液相色谱仪及示差折光检测器,以THF为溶剂和淋洗剂。色谱柱组由HSG-20、HR-4E和μ10^5A三根GPC柱组成,采用多点宽分布标样法标定柱系。 相似文献
96.
以分子拓朴指数(分子价连通指数)作为分子的结构的数值化方法,定量地研究了某些硝胺和脂肪族硝基化合物的冲击波感度(SS)与分子结构的关系。结果表明,零级和一级分子价连通性指数与冲击波感度之间线性相关系数均大于0.95。由此可以看出,将分子拓扑指引入含能化合物结构与生质的相关性研究是可行的。 相似文献
97.
王先荣%颜则东%王鹢%肖强 《宇航材料工艺》2003,33(6):60-62
基于相关理论研究,并借助新近研究的“分子污染低温凝结效应设备”,就我国飞行器型号设计密切相关的分子凝结与凝结表面温度的关系机制进行了四个多月的试验研究,取得了相关的二千余个数据。在此基础上,结合相关的理论对数据进行了拟合和分析,得到了分子凝结与凝结表面温度广泛遵循的一般关系——指数关系。对型号设计具有重要的参考价值。 相似文献
98.
99.
高度污染敏感有效载荷的真空烘烤技术 总被引:4,自引:2,他引:4
对分子污染高度敏感的航天产品,如光学相机、CCD成像系统等,真空烘烤是有效的污染控制手段。文章介绍了真空烘烤设备的结构和技术指标,并详细地描述了具体的烘烤程序,以满足航天器洁净度等级的要求。 相似文献
100.