全文获取类型
收费全文 | 7810篇 |
免费 | 1169篇 |
国内免费 | 1713篇 |
专业分类
测绘学 | 114篇 |
大气科学 | 230篇 |
地球物理 | 890篇 |
地质学 | 4713篇 |
海洋学 | 833篇 |
天文学 | 2170篇 |
综合类 | 365篇 |
自然地理 | 1377篇 |
出版年
2024年 | 40篇 |
2023年 | 114篇 |
2022年 | 343篇 |
2021年 | 349篇 |
2020年 | 335篇 |
2019年 | 358篇 |
2018年 | 302篇 |
2017年 | 299篇 |
2016年 | 281篇 |
2015年 | 351篇 |
2014年 | 351篇 |
2013年 | 418篇 |
2012年 | 372篇 |
2011年 | 373篇 |
2010年 | 324篇 |
2009年 | 579篇 |
2008年 | 475篇 |
2007年 | 515篇 |
2006年 | 570篇 |
2005年 | 439篇 |
2004年 | 424篇 |
2003年 | 475篇 |
2002年 | 389篇 |
2001年 | 322篇 |
2000年 | 321篇 |
1999年 | 269篇 |
1998年 | 287篇 |
1997年 | 199篇 |
1996年 | 147篇 |
1995年 | 133篇 |
1994年 | 136篇 |
1993年 | 97篇 |
1992年 | 91篇 |
1991年 | 48篇 |
1990年 | 48篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1963年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
911.
D. J. Wilman † M. L. Balogh ‡ R. G. Bower J. S. Mulchaey A. Oemler Jr R. G. Carlberg S. L. Morris R. J. Whitaker 《Monthly notices of the Royal Astronomical Society》2005,358(1):71-87
The evolution of galaxies in groups may have important implications for the evolution of the star formation history of the Universe, since many processes which operate in groups may suppress star formation and the fraction of galaxies in bound groups grows rapidly between z = 1 and the present day. In this paper, we present an investigation of the properties of galaxies in galaxy groups at intermediate redshift ( z ∼ 0.4) . The groups were selected from the Canadian Network for Observational Cosmology Redshift Survey (CNOC2) redshift survey as described by Carlberg et al., with further spectroscopic follow-up undertaken at the Magellan telescope in order to improve the completeness and depth of the sample. We present the data for the individual groups, and find no clear trend in the fraction of passive galaxies with group velocity dispersion and group concentration. We stack the galaxy groups in order to compare the properties of group galaxies with those of field galaxies at the same redshift. The groups contain a larger fraction of passive galaxies than the field, this trend being particularly clear for galaxies brighter than M B J < −20 in the higher velocity dispersion groups. In addition, we see evidence for an excess of bright passive galaxies in the groups relative to the field. In contrast, the luminosity functions of the star-forming galaxies in the groups and the field are consistent. These trends are qualitatively consistent with the differences between group and field galaxies seen in the local Universe. 相似文献
912.
We present our numerical simulations of the dynamical evolution of the Hyades open cluster. The simulations were performed usinga modified NBODY6 algorithm that included tidal forces and a realistic orbit of the cluster in a gravitational field described by the Miyamoto-Nagai potential. Our goal was to study the nature of movingclu sters. We show that the stars that were earlier cluster members could be later identified within a sphere of 50 pc in diameter around the Sun. The number of such stars for the chosen initial mass and virial radius of the cluster does not exceed ten. The maximum space velocity of these stars relative to the core of the current cluster does not exceed 3 km s?1. Our numerical simulations confirm the assumption that some of the moving clusters near the Sun could consist of stars that have escaped from open clusters in the course of their dynamical evolution. 相似文献
913.
914.
915.
916.
917.
918.
919.
Alexander Knebe Chris Power Stuart P. D. Gill Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2006,368(2):741-750
We investigate the importance of interactions between dark matter substructures for the mass loss they suffer whilst orbiting within a sample of high-resolution galaxy cluster mass cold dark matter (CDM) haloes formed in cosmological N -body simulations. We have defined a quantitative measure that gauges the degree to which interactions are responsible for mass loss from substructures. This measure indicates that interactions are more prominent in younger systems when compared to older more relaxed systems. We show that this is due to the increased number of encounters a satellite experiences and a higher mass fraction in satellites. This is in spite of the uniformity in the distributions of relative distances and velocities of encounters between substructures within the different host systems in our sample.
Using a simple model to relate the net force felt by a single satellite to the mass loss it suffers, we show that interactions with other satellites account for ∼30 per cent of the total mass loss experienced over its lifetime. The relation between the age of the host and the importance of interactions increases the scatter about this mean value from ∼25 per cent for the oldest to ∼45 per cent for the youngest system we have studied. We conclude that satellite interactions play a vital role in the evolution of substructure in dark matter haloes and that a significant fraction of the tidally stripped material can be attributed to these interactions. 相似文献
Using a simple model to relate the net force felt by a single satellite to the mass loss it suffers, we show that interactions with other satellites account for ∼30 per cent of the total mass loss experienced over its lifetime. The relation between the age of the host and the importance of interactions increases the scatter about this mean value from ∼25 per cent for the oldest to ∼45 per cent for the youngest system we have studied. We conclude that satellite interactions play a vital role in the evolution of substructure in dark matter haloes and that a significant fraction of the tidally stripped material can be attributed to these interactions. 相似文献
920.