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381.
R. Misra K.P. Harikrishnan G. Ambika A.K. Kembhavi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2897-2900
The Black hole system GRS 1915+105 exhibits various types of long term variability. Here we show that this behavior can be explained in terms of a deterministic non-linear system. In particular, evidence is provided for a non-linear deterministic limit cycle origin of the low frequency QPO exhibited by this source. 相似文献
382.
383.
J.-S. He C.-Y. Tu H. Tian E. Marsch 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Coronal hole (CH) and the quiet Sun (QS) are considered to account for sources of fast and slow solar wind streams, respectively. The differences between the solar wind streams flowing out from the CH and the QS are thought to be related with different plasma generation and acceleration mechanisms in the respective source regions. Here we review recent studies on the solar wind origin in the CH and the QS, compare the possible flow geometries and magnetic structures in these two kinds of solar regions, and summarize the physics associated with two different origin scenarios. 相似文献
384.
Tim Johannsen Dimitrios Psaltis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothesis with observations in the electromagnetic spectrum. The approach is formulated in terms of a Kerr-like spacetime containing a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric quadrupole has to be zero. We show how upcoming VLBI imaging observations of Sgr A∗ as well as spectroscopic observations of iron lines from accreting black holes with IXO may lead to the first astrophysical test of the no-hair theorem. 相似文献
385.
H. Gutiérrez L. Taliashvili Z. Mouradian 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We study the short-term topological changes of equatorial and polar coronal hole (CH) boundaries, such as a variation of their area and disintegration, associated to reconnection with nearby (within 15° distance) quiescent prominence magnetic fields leading to eruptions and subsequent Coronal Mass Ejections (CMEs). The examples presented here correspond to the recent solar minimum years 2008 and 2009. We consider a temporal window of one day between the CH topological changes and the start and end times of prominence eruptions and onset of CMEs. To establish this association we took into account observational conditions related to the instability of prominence/filaments, the occurrence of a CME, as well as the subsequent evolution after the CME. We found an association between short-term local topological changes in CH boundaries and the formation/disappearance of bright points near them, as well as, between short-term topological changes within the whole CH and eruptions of nearby quiescent prominences followed by the appearance of one or more CMEs. 相似文献
386.
复合材料层板的直边和圆孔自由边缘效应的三维应力分析,国内外已有不少的数值解和近似解析解。Rybicki等提出了各向异性板椭圆孔2维问题变换为圆孔问题的方法,本文论证了这种变换方法的3维情形,从而可根据圆孔自由边缘效应结果来估计椭圆孔自由边缘效应。 相似文献
387.
在飞机和船体结构设计中,由于管路穿行、电缆布置等总体布局要求,在机翼梁的腹板上的指定位置开有多个孔,引发多个孔应力互相干扰。利用ANSYS有限元软件分别对圆孔间距、圆孔数和方形孔圆角半径对含孔带板应力集中系数的影响进行了分析,并与特定情况的试验值进行了对比,两者基本一致。研究结果表明:在孔数一定时,对于不同的孔间距,存在不同的最佳值,使应力集中系数得到最有利的缓和,且板宽对该最佳值的影响不大;对于方形孔, 当圆角半径为1/14方形孔边长时,对缓和应力集中系数最有利。文中并给出了特定情况下最有利于降低应力集中系数的孔的个数。 相似文献
388.
谭春晓 《沈阳航空工业学院学报》2005,22(1):29-31
根据公差项目的特征要求,对某产品零件孔系加工的生产实际进行了工艺分析,对造成零件孔系加工误差的各项因素进行了定性和定量分析,找出了造成误差的根本原因是工艺装备结构设计带来的系统误差过大和加工工艺方法的缺陷的影响。在此分析的基础上对工艺装备的设计进行了改进,并对加工工艺进行了相应的调整,达到了预期的加工目的。这种技术工作方法,对生产现场的工程技术人员来说是基本要求,也是解决机械制造工艺问题的有效途径。 相似文献
389.
Ken Ebisawa Toshihiro Kawaguchi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2862-2866
Our current theoretical and observational understandings of the accretion disks around Galactic black-holes are reviewed. Historically, a simple phenomenological accretion disk model has been used to interpret X-ray observations. Although such a phenomenological interpretation is still useful, high quality X-ray data from contemporary instruments allow us to test more realistic accretion disk models. In a simple and ideal case, the standard optically thick accretion disk model is successful to explain observations, such that the inner disk radius is constant at three times the Schwarzschild radius over large luminosity variations. However, when disk luminosity is close to or exceeds the Eddington luminosity, the standard disk model breaks, and we have to consider the “slim disk” solution in which radial energy advection is dominant. Recent observations of Ultra-luminous X-ray sources (ULXs), which may not be explained by the standard disk model, strongly suggest the slim disk solution. We compare theoretical X-ray spectra from the slim disk with observed X-ray spectra of ULXs. We have found that the slim disk model is successful to explain ULX spectra, in terms of the massive stellar black-holes with several tens of solar mass and the super-Eddington mass accretion rates. In order to explain the large luminosities (>1040 ergs s−1) of ULXs, “intermediate black-holes” (>100M) are not required. Slim disks around massive stellar black-holes of up to several tens of solar mass would naturally explain the observed properties of ULXs. 相似文献
390.