全文获取类型
收费全文 | 794篇 |
免费 | 14篇 |
国内免费 | 9篇 |
专业分类
大气科学 | 7篇 |
地球物理 | 31篇 |
地质学 | 20篇 |
海洋学 | 10篇 |
天文学 | 737篇 |
综合类 | 1篇 |
自然地理 | 11篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2015年 | 48篇 |
2014年 | 34篇 |
2013年 | 23篇 |
2012年 | 42篇 |
2011年 | 36篇 |
2010年 | 28篇 |
2009年 | 62篇 |
2008年 | 80篇 |
2007年 | 69篇 |
2006年 | 86篇 |
2005年 | 49篇 |
2004年 | 27篇 |
2003年 | 24篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 24篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 26篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有817条查询结果,搜索用时 15 毫秒
81.
The Atacama Cosmology Telescope is a project to map the microwave background radiation at arcminute angular resolution and high sensitivity in three frequency bands over substantial sky areas. Cosmological signals driving such an experiment are reviewed, and current progress in hardware construction is summarized. Complementary astronomical observations in other wavebands are also discussed. 相似文献
82.
We present results of simulations performed with the Geant4 software code of the effects of Galactic Cosmic Ray impacts on
the photoconductor arrays of the PACS instrument. This instrument is part of the ESA-Herschel payload, which will be launched
in 2008 and will operate at the Lagrangian L2 point of the Sun-Earth system. Both the Satellite plus the cryostat (the shield)
and the detector act as source of secondary events, affecting the detector performance. Secondary event rates originated within
the detector and from the shield are of comparable intensity. The impacts deposit energy on each photoconductor pixel but
do not affect the behaviour of nearby pixels. These latter are hit with a probability always lower than 7%.
The energy deposited produces a spike which can be hundreds times larger than the noise. We then compare our simulations with
proton irradiation tests carried out for one of the detector modules and follow the detector behaviour under ‘real’ conditions. 相似文献
83.
Observations of the afterglows of gamma ray bursts (GRBs) in different spectral ranges yield valuable information both about the nature of GRBs and about the properties of the surrounding medium. A powerful infrared (IR) afterglow has been observed at the site of the strong GRB041219. Here we interpret the observed IR afterglow as the result of a reprocessing of gamma radiation on dust in a cloud surrounding the GRB source. In this model we do not expect the appearance of a prompt optical afterglow which should be absorbed by the surrounding dust cloud. We estimate the collimation angle of the gamma radiation and obtain limits on the red shift (distance to the GRB source) by matching the model parameters to the experimental data.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 439–444 (August 2005). 相似文献
84.
85.
86.
A. R. Bell 《Monthly notices of the Royal Astronomical Society》2005,358(1):181-187
A large flux of cosmic rays streaming through a magnetized plasma creates cavities of low plasma density and low magnetic field. The magnetic field focuses the cosmic ray trajectories into the cavities with the possible formation of filaments or beams of high-energy cosmic rays. 相似文献
87.
Large-scale, decelerating, relativistic X-ray jets from microquasar XTE J1550−564 has been recently discovered with Chandra by Corbel et al. (2002). We find that the dynamical evolution of the approaching jet at the late time is consistent with
the well-known Sedov evolutionary phase R∝ t
2/5. A trans-relativistic external shock dynamic model by analogy with the evolution of gamma-ray burst remnants, is shown to
be able to fit the proper-motion data of the approaching jet reasonably well. The inferred interstellar medium density around
the source is well below the canonical value n
ISM∼1 cm−3. The rapidly fading X-ray emission can be interpreted as synchrotron radiation from the non-thermal electrons in the adiabatically
expanding ejecta. These electrons were accelerated by the reverse shock (moving back into the ejecta) which becomes important
when the inertia of the swept external matter leads to an appreciable slowing down of the original ejecta. 相似文献
88.
89.
90.
Fast heuristically weighted, or pseudo-Cℓ, estimators are a frequently used method for estimating power spectra in CMB surveys with large numbers of pixels. Recently, Challinor and Chon showed that the E–B mixing in these estimators can become a dominant contaminant at low noise levels, ultimately limiting the gravity wave signal which can be detected on a finite patch of sky. We define a modified version of the estimators which eliminates E–B mixing and is near-optimal at all noise levels. 相似文献