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41.
M.D. Ngobeni M.S. Potgieter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Observations of galactic cosmic rays (GCRs) from the two Voyager spacecraft inside the heliosheath indicate significant differences between them, suggesting that in addition to a possible global asymmetry in the north–south dimensions (meridional plane) of the heliosphere, it is also possible that different modulation (turbulence) conditions could exist between the two hemispheres of the heliosphere. We focus on illustrating the effects on GCR Carbon of asymmetrical modulation conditions combined with a heliosheath thickness that has a significant dependence on heliolatitude. To reflect different modulation conditions between the two heliospheric hemispheres in our numerical model, the enhancement of both polar and radial perpendicular diffusion off the ecliptic plane is assumed to differ from heliographic pole to pole. The computed radial GCR intensities at polar angles of 55° (approximating the Voyager 1 direction) and 125° (approximating the Voyager 2 direction) are compared at different energies and for both particle drift cycles. This is done in the context of illustrating how different values of the enhancement of both polar and radial perpendicular diffusion between the two hemispheres contribute to causing differences in radial intensities during solar minimum and moderate maximum conditions. We find that in the A > 0 cycle these differences between 55° and 125° change both quantitatively and qualitatively for the assumed asymmetrical modulation condition as reflected by polar diffusion, while in the A < 0 cycle, minute quantitative differences are obtained. However, when both polar and radial perpendicular diffusion have significant latitude dependences, major differences in radial intensities between the two polar angles are obtained in both polarity cycles. Furthermore, significant differences in radial intensity gradients obtained in the heliosheath at lower energies may suggest that the solar wind turbulence at and beyond the solar wind termination shock must have a larger latitudinal dependence. 相似文献
42.
N. Wichaipanich P. Supnithi T. Tsugawa T. Maruyama T. Nagatsuma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
In this work, the foF2 and hmF2 parameters at the conjugate points near the magnetic equator of Southeast Asia are studied and compared with the International Reference Ionosphere (IRI) model. Three ionosondes are installed nearly along the magnetic meridian of 100°E; one at the magnetic equator, namely Chumphon (10.72°N, 99.37°E, dip angle 3.0°N), and the other two at the magnetic conjugate points, namely Chiang Mai (18.76°N, 98.93°E, dip angle 12.7°N) and Kototabang (0.2°S, 100.30°E, dip angle 10.1°S). The monthly hourly medians of the foF2 and hmF2 parameters are calculated and compared with the predictions obtained from the IRI-2007 model from January 2004 to February 2007. Our results show that: the variations of foF2 and hmF2 predicted by the IRI-2007 model generally show the similar feature to the observed data. Both parameters generally show better agreement with the IRI predictions during daytime than during nighttime. For foF2, most of the results show that the IRI model overestimates the observed foF2 at the magnetic equator (Chumphon), underestimates at the northern crest (Chiang Mai) and is close to the measured ones at the southern crest of the EIA (Kototabang). For hmF2, the predicted hmF2 values are close to the hmF2(M3000F2OBS) during daytime. During nighttime, the IRI model gives the underestimation at the magnetic equator and the overestimation at both EIA crests. The results are important for the future improvements of the IRI model for foF2 and hmF2 over Southeast Asia region. 相似文献
43.
44.
本文利用位错理论和夹杂理论研究了Ⅰ型裂纹前方的位错塞积群和氢气团以及它们之间的交互作用,求得了塞积群的位借密度、应力集中系数和裂纹扩展速率。所得结果表明,氢气团促进裂纹尖端位猪源开动,即促进滞后塑性变形,提高塞积群的应力集中系数,引起材料脆化,促进微裂纹核形成。 相似文献
45.
邹贵生 《南昌航空工业学院学报》1994,(1):71-76
本文通过10CrMo910钢大口径厚壁管道高温模拟试验证实,焊后热处理是一个短时超高温运行过程,它使10CrMo910钢管接头组织提前老化,显著降低了接头的持久寿命。试验结果表明,传统的焊后热处理工序应当取消。 相似文献
46.
探讨了离散作业型(Job shop)车间中的作业调度的分阶段模型,并根据离散作业调度的阶段性提出了基于作业状态空间的逐段式车间作业调度算法,通过对一个实际车间作业调度仿真比较,此算法运算速度比最短加工时间(SPT)和最少工作量剩余(LWR)算法快,其调度结果在实际作业车间具有可执行性。 相似文献
47.
Yongliao Zou Yan Zhu Yunfei Bai Lianguo Wang Yingzhuo Jia Weihua Shen Yu Fan Yang Liu Chi Wang Aibing Zhang Guobin Yu Jihong Dong Rong Shu Zhiping He Tielong Zhang Aimin Du Mingyi Fan Jianfeng Yang Yongqing Peng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(2):812-823
This paper describes the scientific objectives and payloads of Tianwen-1, China’s first exploration mission to Mars. An orbiter, carrying a lander and a rover, lifted-off in July 2020 for a journey to Mars where it should arrive in February 2021. A suite of 13 scientific payloads, for in-situ and remote sensing, autonomously commanded by integrated payload controllers and mounted on the orbiter and the rover will study the magnetosphere and ionosphere of Mars and the relation with the solar wind, the atmosphere, surface and subsurface of the planet, looking at the topography, composition and structure and in particular for subsurface ice. The mission will also investigate Mars climate history. It is expected that Tianwen-1 will contribute significantly to advance our scientific knowledge of Mars. 相似文献
48.
空间舱外机动装置发展综述 总被引:6,自引:0,他引:6
介绍了国外几种主要空间舱外机动装置的特点和性能,比较分析了系绳、机械、喷气机动等舱外机动装置的特点。认为小型的喷气机动装置(SAFER)最适合作为我国今后航天员空间活动的机动与救生工具。 相似文献
49.
H.S. Ahluwalia 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The descent of sunspot cycle 23 to an unprecedented minimum of long duration in 2006–2009 led to a prolonged galactic cosmic ray (GCR) recovery to the highest level observed in the instrumental era for a variety of energetic charged particle species on Earth, over a wide range of rigidities. The remarkable GCR increase measured by several ground-based, balloon-borne, and detectors on a satellite is described and discussed. It is accompanied by a decrease in solar wind velocity and interplanetary magnetic field at 1 a.u., reaching the lowest values since measurements of the solar wind began in October 1963; the solar polar field strength (μT) measured at the Wilcox Solar Observatory (WSO) is also significantly reduced compared to prior cycles since the start of the program in 1976, the polar field in the northern hemisphere reversed in June 2012 and again in February 2014, that in the southern hemisphere reversed in July 2013. If updates of WSO data confirm the second reversal in northern solar hemisphere, it would pose a serious challenge to the Dynamo Theory. The long-term change in solar behavior may have begun in 1992, perhaps earlier. The physical underpinnings of these solar changes need to be understood and their effect on GCR modulation processes clarified. The study discusses the recent phenomena in the context of GCR modulation since 1900. These happenings affected our empirical predictions for the key parameters for the next two sunspot cycles (they may be progressively less active than sunspot cycle 24) but it enhanced support for our prediction that solar activity is descending into a Dalton-like grand minimum in the middle of the twentyfirst century, reducing the frequency of the coronal mass ejections; they determine the space weather affecting the quality of life on Earth, radiation dose for hardware and human activities in space as well as the frequency of large Forbush decreases at 1 a.u. 相似文献
50.
针对智能环境中活动模式的学习和挖掘花销大、难以实际操作等问题,提出了能够有效地将已有活动模式迁移到新环境的整体框架。迁移学习框架将活动模式的迁移过程分解为轨迹的迁移和触发持续时间的迁移,首先对已有活动模式中的活动轨迹以及触发持续时间模糊化;然后采用备选轨迹生成(ATSG)算法在新环境中生成备选轨迹集;最后采用相似度计算(SC)算法进行活动模式中的轨迹与备选轨迹间的匹配,利用活动轨迹映射(TM)算法和触发持续时间迁移(TDT)算法对活动信息进行迁移,从而在新环境中得到活动模式。理论分析和实验结果表明,相比于基于频繁模式挖掘得到活动模式的方法,本文方法大幅度地降低了得到活动模式所需的时间开销,同时,利用本文方法获取的活动模式取得了较好的活动识别效果。 相似文献