全文获取类型
收费全文 | 115篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 3篇 |
地球物理 | 4篇 |
地质学 | 23篇 |
海洋学 | 4篇 |
天文学 | 71篇 |
自然地理 | 2篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有117条查询结果,搜索用时 15 毫秒
41.
42.
We present the results of a detailed analysis of RXTE observations of classω (Klein-Woltet al. 2002) which show an unusual state transition between high-soft and low-soft states in the Galactic microquasar GRS 1915 +
105. Out of about 600 pointed RXTE observations, the source was found to exhibit such state transition only on 16 occasions.
An examination of the RXTE/ASM data in conjunction with the pointed observations reveals that these events appeared as a series
of quasi-regular dips in two stretches of long duration (about 20 days during each occasion) when hard X-ray and radio flux
were very low. The X-ray light curve and colour-colour diagram of the source during these observations are found to be different
from any reported so far. The duration of these dips is found to be of the order of a few tens of seconds with a repetition
time of a few hundred seconds. The transition between these dips and non-dips which differ in intensity by a factor of ∼ 3.5,
is observed to be very fast (∼ a few seconds). It is observed that the low-frequency narrow QPOs are absent in the power density
spectrum (PDS) of the dip and non-dip regions of classω and the PDS is a power law in the 0.1–10 Hz frequency range. There is a remarkable similarity in the spectral and timing
properties of the source during the dip and non-dip regions in this set of observations. These properties of the source are
distinctly different from those seen in the observations of other classes. This indicates that the basic accretion disk structure
during both dip and non-dip regions of classω is similar, but differ only in intensity. To explain these observations, we invoke a model in which the viscosity is very
close to critical viscosity and the shock wave is weak or absent. 相似文献
43.
Kinsuk Acharya Sandip K. Chakrabarti D. Molteni 《Journal of Astrophysics and Astronomy》2002,23(1-2):155-164
Accretion shocks are known to oscillate in presence of cooling processes in the disk. This oscillation may also cause quasi-periodic
oscillations of black holes. In the presence of strong winds, these shocks have oscillations in vertical direction as well.
We show examples of shock oscillations under the influence of both the effects. When the shocks are absent and the flow is
cooler, the wind becomes weaker and the vertical oscillation becomes negligible. 相似文献
44.
Long distance detection of electron anti-neutrinos from reactors at distances of order 200 km has been achieved with the 1000
ton liquid scintillator-based KamLAND instrument in Japan. In summer 2005 the KamLAND group reported the first detection of
anti-neutrinos from the natural radioactivity of the earth. These measurements are due to uranium and thorium decays dominantly
from the nearby crust in Japan, and are expected to have only a small contribution from the earth’s mantle (and core). Several
new detectors are under consideration around the world for measurements which when taken together can reveal the location
of these heavy elements, which are expected to contribute a major share of the internal earth’s heating via their radioactivity.
This heating is of course associated with providing the power to drive the geomagnetic field and plate tectonics. Geologists
have only indirect evidence about the deep earth, mostly from seismic wave velocity and inferences from a few meteorites.
Anti-neutrino detection, on the other hand, yields direct information about earth’s interior. The location and magnitude of
the earth’s uranium and thorium are crucial to understanding the origin and evolution of the earth and present day activity.
Lead Article in Proceedings of Neutrino Sciences 2005 相似文献
45.
46.
Sandip More Rajarshi Rit Mahasin Ali Khan Dipak Kumar Paruya Suchana Taral Tapan Chakraborty Subir Bera 《Journal of the Geological Society of India》2018,91(3):301-306
Fossil leaf impressions and pollen grains comparable to modern Sloanea sp. of Elaeocarpaceae collected from the middle part of the Siwalik sediments (Geabdat Sandstone Formation; Pliocene) in Darjeeling foothills of eastern Himalaya are reported in the present communication. On the basis of macro morphological features, leaf remains are described as a new species Sloanea siwalika sp. nov. This is the first authentic record of the occurrence of leaf and pollen grains comparable to the genus Sloanea L. from the Cenozoic sediments of India and Asia as well. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period. The present study further suggests that after Pliocene the taxon might have shifted from Darjeeling Himalayan region to the adjoining southeast Asian land masses, due to possible climate change caused by post-Pliocene orogenic movement of the Himalaya. 相似文献
47.
Profiles of the 4430 band are calculated for resonant absorbers distributed within graphite particles, silicate particles and solid H2 grains. The sizes of grains adopted are those which give agreement with the interstellar extinction. Only in the latter two cases can satisfactory agreement be obtained with recent observational data. 相似文献
48.
49.
The λ2200 Å interstellar absorption band, generally attributed to graphite grains, could equally well arise from π → π*electronic transitions in conjugated double bonds of organic molecules. These molecules, which should comprise ~ 10% of the total interstellar dust mass, may be lodged within clumps of100 Å-sized refractory grains. 相似文献
50.
Magnetized accretion flows around black holes which include standing or oscillating shock waves can produce very realistic
spectrum till a few MeV. These shocks accelerate hot electrons which produce power-law spectrum. The post-shock region intercepts
soft-photons from an external source, namely, a Keplerian disk and also from distributed sources such as the synchrotron photons
emitted from thermal and non-thermal electrons originated in the pre-shock and post-shock flow. These photons are inverse
Comptonized by the thermal and the non-thermal electrons present in the CENBOL region. Computations show that the emitted
radiation is extended till a few MeV. We include the bulk motion Comptonization as well and discuss its importance vis-a-vis
the power-law spectrum produced by non-thermal electrons.
相似文献