全文获取类型
收费全文 | 5566篇 |
免费 | 715篇 |
国内免费 | 850篇 |
专业分类
测绘学 | 750篇 |
大气科学 | 341篇 |
地球物理 | 1467篇 |
地质学 | 1743篇 |
海洋学 | 341篇 |
天文学 | 1782篇 |
综合类 | 294篇 |
自然地理 | 413篇 |
出版年
2024年 | 25篇 |
2023年 | 48篇 |
2022年 | 130篇 |
2021年 | 130篇 |
2020年 | 180篇 |
2019年 | 225篇 |
2018年 | 129篇 |
2017年 | 166篇 |
2016年 | 206篇 |
2015年 | 224篇 |
2014年 | 253篇 |
2013年 | 305篇 |
2012年 | 237篇 |
2011年 | 255篇 |
2010年 | 257篇 |
2009年 | 388篇 |
2008年 | 367篇 |
2007年 | 438篇 |
2006年 | 399篇 |
2005年 | 315篇 |
2004年 | 316篇 |
2003年 | 296篇 |
2002年 | 258篇 |
2001年 | 236篇 |
2000年 | 227篇 |
1999年 | 201篇 |
1998年 | 173篇 |
1997年 | 121篇 |
1996年 | 111篇 |
1995年 | 82篇 |
1994年 | 84篇 |
1993年 | 83篇 |
1992年 | 48篇 |
1991年 | 51篇 |
1990年 | 43篇 |
1989年 | 28篇 |
1988年 | 33篇 |
1987年 | 26篇 |
1986年 | 14篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有7131条查询结果,搜索用时 46 毫秒
31.
In this paper the tidal phenomena on the Earth are concisely specified, including solid tides, ocean tides and atmospheric tides due to the luni-solar tide-generating force, and the Earth pole tide due to the motion of the Earth's rotation axis (polar motion); as well as their effects on the Earth rotation. The outcomes of scientific researches of Chinese astronomers on these topics are described in some detail. These researches deal with the mechanisms responsible for tidal effects on the earth rotation, and on the measurements of the Earth rotation parameters. Finally, the effects discovered by Chinese researchers on the measurements of the period and change in period of pulsars are discussed. These effects are very small in magnitude but not negligible. 相似文献
32.
33.
34.
Dark energy has a dramatic effect on the dynamics of the Universe, causing the recently discovered acceleration of the expansion. The dynamics are also central to the behaviour of the growth of large-scale structure, offering the possibility that observations of structure formation provide a sensitive probe of the cosmology and dark energy characteristics. In particular, dark energy with a time-varying equation of state can have an influence on structure formation stretching back well into the matter-dominated epoch. We analyse this impact, first calculating the linear perturbation results, including those for weak gravitational lensing. These dynamical models possess definite observable differences from constant equation of state models. Then we present a large-scale numerical simulation of structure formation, including the largest volume to date involving a time-varying equation of state. We find the halo mass function is well described by the Jenkins et al. mass function formula. We also show how to interpret modifications of the Friedmann equation in terms of a time-variable equation of state. The results presented here provide steps toward realistic computation of the effect of dark energy in cosmological probes involving large-scale structure, such as cluster counts, the Sunyaev–Zel'dovich effect or weak gravitational lensing. 相似文献
35.
36.
37.
38.
Nikolay Sidorenkov 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):27-38
Spectral analysis of the components of the relative atmospheric angular momentum vector is performed based on the series of these components for the 6 h intervals within the period of 1958–2000. These series have been computed in the Subbureau of the Atmospheric Angular Momentum of the International Earth Rotation Service using the NCEP/NCAR reanalysis of atmospheric observations. The basic harmonics of diurnal tides are determined. New results on the fortnight's and week's duration oscillations of the equatorial components of the atmospheric angular momentum are obtained. The zonal tides transformation mechanisms in the atmosphere are discussed. It is shown that the main mechanism of the zonal tides effect on the atmospheric variability is the amplitude modulation of daily oscillations of the relative atmospheric angular momentum. The effects of the atmospheric tides on the Earth rotation are discussed. 相似文献
39.
40.
S.W. Allen 《Astrophysics and Space Science》2003,285(1):247-256
Chandra X-ray observations of rich, dynamically relaxed galaxy clusters allow the properties of the X-ray gas and the total
gravitating mass to be determined precisely. Here, we discuss how Chandra observations may be used as a powerful tool for
cosmological studies. By combining Chandra X-ray results on the X-ray gas mass fractions in clusters with independent measurements
of the Hubble constant and the mean baryonic matter density of the universe, we obtain a tight constraint on the mean total
matter density of the universe, Οm, and an interesting constraint on the cosmological constant, ΟΛ. Using these results, together with the observed local X-ray luminosity function of the most X-ray luminous galaxy clusters,
a mass-luminosity relation determined from Chandra and ROSAT X-ray data and weak gravitational lensing observations, and the
mass function predicted by numerical simulations, we obtain a precise constraint on the normalization of the power spectrum
of density fluctuations in the nearby universe,σ8. We compare our results with those obtained from other, independent methods.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献