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101.
All four giant planets in the solar system possess irregular satellites, characterized by large, highly eccentric and/or highly
inclined orbits. These bodies were likely captured from heliocentric orbit, probably in association with planet formation
itself. Enabled by the use of large-format digital imagers on ground-based telescopes, new observational work has dramatically
increased the known populations of irregular satellites, with 74 discoveries in the last few years. A new perspective on the
irregular satellite systems is beginning to emerge.We find that the number of irregular satellites measured to a given diameter
is approximately constant from planet to planet. This is surprising, given the radically different formation scenarios envisioned
for the gas giants Jupiter and Saturn compared to the (much less massive and compositionally distinct) ice giants Uranus and
Neptune. We discuss the new results on the irregular satellites and show how these objects might be used to discriminate amongst
models of giant planet formation. 相似文献
102.
冰晶在涡扇发动机内相变换热特性 总被引:2,自引:2,他引:2
通过对低压压气机通道内气流参数的分析,结合冰晶的运动轨迹方程及相变传热传质方程的离散处理,计算分析了冰晶在涡扇发动机内涵通道内运动过程的粒子半径、冰晶温度、冰晶速度、冰水混合粒子中液态水质量分数、以及冰晶表面与低压压气机通道内气流的传热系数和传质系数沿压气机轴向距离的分布,得到了冰晶在低压压气机内涵通道内运动的轨迹及与叶片碰撞的特性。结果显示:20μm冰晶黏附位置处液态水质量分数为10.22%,而100μm冰晶在压气机出口处液态水质量分数仅为2.1%且不会在压气机内结冰。 相似文献
103.
The volatile species released in the coma are an important clue to the composition of the cometary nucleus ices. Their identification
and the measurement of their abundances is possible by remote sensing. Considerable progress has been made recently using
radio and infrared spectroscopy, especially with the observations of the two exceptional comets C/1996 B2 (Hyakutake) and
C/1995 O1 (Hale-Bopp).) 24 molecules likely to be parent molecules outgassed from the nucleus have now been identified. Significant
upper limits exist for many other species, and the presence of unidentified lines suggests that further species are to be
identified. In addition, isotopic varieties have been observed for hydrogen, carbon, nitrogen and sulphur. We will review
these results with a special emphasis on the reliability of the identifications and of the molecular production rate determinations.
A critical point is to assess whether a given species is a genuine parent molecule outgassed from nuclear ices, or is a secondary
product coming from grains or from gas-phase photochemistry. Ground-based spectral imaging, such as radio interferometry,
may help resolving this problem.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
104.
105.
106.
Researches have indicated that impinging droplets can be entrapped as liquid in the ice matrix and the temperature of accreting ice surface is below the freezing point. When liquid entrapment by ice matrix happens, this kind of ice is called spongy ice. A new spongy icing model for the ice accretion problem on airfoil or aircraft has been developed to account for entrapped liquid within accreted ice and to improve the determination of the surface temperature when enter- ing clouds with supercooled droplets. Different with conventional icing model, this model identifies icing conditions in four regimes: rime, spongy without water film, spongy with water film and glaze. By using the Eulerian method based on two-phase flow theory, the impinging droplet flow was investigated numerically. The accuracy of the Eulerian method for computing the water collection efficiency was assessed, and icing shapes and surface temperature distributions predicted with this spongy icing model agree with experimental results well. 相似文献
107.
108.
某型飞机发动机短舱防冰系统设计计算 总被引:7,自引:3,他引:4
介绍了某型飞机发动机短舱防冰系统的结构形式和防冰原理,按照可利用热量应大于所需热量的原则,通过计算完全蒸发和湿状态下的热载荷,确定了发动机短舱防冰严酷状态及所需热流量.基于机翼水收集系数和数据相似原则,利用欧拉法两相流计算方法,确定了短舱防冰系统水收集系数.按照在湿状态下允许有一定结冰量存在的设计原则,根据发动机的吞冰能力,利用VSAERO/ICE工具对发动机短舱防冰系统进行了计算,计算结果表明,在严酷状态下,防冰系统能够满足允许结冰厚度要求. 相似文献
109.
110.
浅析过冷大水滴规章对防冰系统设计的影响 总被引:2,自引:1,他引:1
阐述了FAA颁布过冷大水滴规章的背景,浅析了即将新增的FAR25.1420过冷大水滴结冰条件条款,以及其对机翼防冰系统和结冰探测系统设计的影响;相比14CFR附录C结冰条件,过冷大水滴结冰条件的水滴撞击区较大,更容易在结冰防护区后部形成严重的后溜冰,应增加上表面弦向防护区的范围;基于已有的结冰探测系统,在机翼上表面容易形成后溜冰的部位,装备能够齐平安装的结冰探测器作为补充,是一种有效探测过冷大水滴结冰条件的方式;浅析了FAR25附录O过冷大水滴结冰条件的分类;给出了修订后的25.1093(b)的防冰译文。 相似文献