Keywords: Astrophysics; X-ray binaries; Neutron stars; Black holes 相似文献
全文获取类型
收费全文 | 260篇 |
免费 | 49篇 |
国内免费 | 12篇 |
专业分类
航空 | 82篇 |
航天技术 | 204篇 |
综合类 | 8篇 |
航天 | 27篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 18篇 |
2013年 | 9篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 26篇 |
2007年 | 10篇 |
2006年 | 37篇 |
2005年 | 6篇 |
2004年 | 35篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 19篇 |
排序方式: 共有321条查询结果,搜索用时 15 毫秒
281.
针对传统的X射线脉冲星信号检测算法计算量大及在低信噪比下检测性能差的问题,提出了一种结合S变换的恒虚警率检测算法。首先,根据高斯白噪声的S变换域功率谱分布特性对累积信号的时频功率谱进行阀值滤波;然后累加阀值滤波后的信号功率谱作为检测统计量,从理论上对检测统计量的分布特性进行分析,得出检测统计量服从高斯分布,并用蒙特卡罗方法进行了验证。在此基础上,利用检测统计量的概率密度函数计算判决门限,从而实现了恒虚警率检测。理论分析和实验结果表明,本文算法的检测性能优于同类基于高斯分布的恒虚警率检测算法,并且具有较低的复杂度。 相似文献
282.
针对能量色散X荧光(Energy dispersive X-ray fluorescence,EDXRF)分析技术应用于煤炭中硫分快速测量过程中存在的基体效应和边缘效应干扰问题,采用蒙特卡罗计算程序Electron-Gamma Shower(EGS)模拟了在不同管电压、不同样品直径、厚度以及不同硫元素浓度条件下的X荧光强度。结果表明,合适的X光管的管电压为15 kV,样
品的临界直径和厚度分别大于1.04 cm和0.05 cm。根据模拟结果,通过实验得到X荧光强度与硫元素浓度的关系曲线,实验结果经过探测效率修正后与EGS模拟结果符合良好,为后续的煤炭中硫分在线快速分析系统的设计和实施提供了有力的技术支撑。 相似文献
283.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):731-743
In this paper, the Cramér-Rao Lower Bound (CRLB) for estimating the rotation parameters of pulsars using X-ray pulsar observation data is deduced, and the calculation equation is presented. In order to verify the correctness of the deduced equation, we use the X-ray pulsar observation data to estimate pulsar rotation parameters, and obtain the root mean square error (RMSE) of the estimated pulsar rotation parameters through conducting repeated experiments. The experimental results suggest that when the observation time increases, the RMSE gradually approaches the estimated CRLB, and that when the observation time is 2.4 × 106 s, the error between the RMSE of pulsar frequency estimation and the CRLB stays at 10?11 order of magnitude. This verifies that the CRLB expression deduced in this paper is the theoretical lower bound for estimating pulsar rotation parameters. The deduced CRLB in this paper helps determine the minimum variance estimator for pulsar rotation parameter estimation using X-ray pulsar data, providing a benchmark for the comparison between the minimum variance estimator and other estimators. 相似文献
284.
285.
为了降低地面测控系统的负担、提高深空探测器的导航效率,提出了基于星联网的航天器自主导航概念,对星联网的应用体系进行了设计。借助脉冲星、星间链路等手段实现星联网系统中基准航天器完全自主的高精度导航,用户航天器通过与基准航天器或其他用户航天器的交互通信与测量就可以实现自身状态估计。以地月转移任务为例,设计了星联网系统在地月空间的具体应用方案,分析了地月空间基准航天器的配置与自主导航方法,阐述了用户航天器的单层与多层导航策略。对基于脉冲星与星间链路观测的基准航天器自主导航进行了仿真,验证了观测基准航天器或者其他用户航天器时,地月转移段航天器自主导航的可行性。结果表明:基准航天器可以达到20 m的定位精度,用户航天器可以达到优于30 m的定位精度。基于星联网的航天器自主导航是可行的,发展星联网可以为我国构建天基自主基准导航系统提供有力支持。 相似文献
286.
Alan M. Levine Hale Bradt Edward H. Morgan Ron Remillard The MIT/GSFC ASM Team 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2970-2975
Selected results from the Rossi X-ray Timing Explorer All-Sky Monitor are presented to illustrate the phenomenology of the light curves. The sensitivity to periodic intensity variations is indicated by the folded light curve of AM Her. The gray line between transient and persistent sources is emphasized. Light curves of a range of systems comprising black holes or neutron stars and low and high mass companion stars show that the behavior of these systems is often, but not always, characteristic. 相似文献
287.
Marina M. Romanova Akshay Kulkarni Min Long Richard V.E. Lovelace Justin V. Wick Galina V. Ustyugova Alexander V. Koldoba 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2887-2892
We performed 2D and full 3D magnetohydrodynamic simulations of disk accretion to a rotating star with an aligned or misaligned dipole magnetic field. We investigated the rotational equilibrium state and derived from simulations the ratio between two main frequencies: the spin frequency of the star and the orbital frequency at the inner radius of the disk. In 3D simulations we observed different features related to the non-axisymmetry of the magnetospheric flow. These features may be responsible for high-frequency quasi-periodic oscillations (QPOs). Variability at much lower frequencies may be connected with restructuring of the magnetic flux threading the inner regions of the disk. Such variability is specifically strong at the propeller stage of evolution. 相似文献
288.
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
289.
E.P.J. van den Heuvel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2667-2672
Three recent developments in the field of formation and evolution of neutron stars and black holes in binaries are addressed:
- • The finding that there is a class of neutron stars, formed in interacting binaries, that do not receive kick velocities in their birth events. This finding is particularly important for our understanding of the formation – and formation rates – of double neutron stars. It is argued that these low-kick neutron stars, which tend to have low masses, are formed by a different physical mechanism than the neutron stars that receive large kick velocities at birth.
• The occurrence of velocity kicks in the formation events of stellar black holes.
• The nature of the companions of millisecond X-ray pulsars.
290.
Charles E. Schlemm II Richard D. Starr George C. Ho Kathryn E. Bechtold Sarah A. Hamilton John D. Boldt William V. Boynton Walter Bradley Martin E. Fraeman Robert E. Gold John O. Goldsten John R. Hayes Stephen E. Jaskulek Egidio Rossano Robert A. Rumpf Edward D. Schaefer Kim Strohbehn Richard G. Shelton Raymond E. Thompson Jacob I. Trombka Bruce D. Williams 《Space Science Reviews》2007,131(1-4):393-415
NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of
the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital
phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft
will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface
of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12°
field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis
due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority
of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes
XRS’s science objectives, technical design, calibration, and mission observation strategy. 相似文献