全文获取类型
收费全文 | 5484篇 |
免费 | 800篇 |
国内免费 | 964篇 |
专业分类
测绘学 | 465篇 |
大气科学 | 726篇 |
地球物理 | 1435篇 |
地质学 | 2084篇 |
海洋学 | 873篇 |
天文学 | 598篇 |
综合类 | 362篇 |
自然地理 | 705篇 |
出版年
2024年 | 20篇 |
2023年 | 51篇 |
2022年 | 176篇 |
2021年 | 209篇 |
2020年 | 216篇 |
2019年 | 251篇 |
2018年 | 192篇 |
2017年 | 215篇 |
2016年 | 208篇 |
2015年 | 266篇 |
2014年 | 271篇 |
2013年 | 329篇 |
2012年 | 318篇 |
2011年 | 321篇 |
2010年 | 253篇 |
2009年 | 349篇 |
2008年 | 329篇 |
2007年 | 397篇 |
2006年 | 379篇 |
2005年 | 320篇 |
2004年 | 282篇 |
2003年 | 234篇 |
2002年 | 229篇 |
2001年 | 196篇 |
2000年 | 178篇 |
1999年 | 188篇 |
1998年 | 166篇 |
1997年 | 123篇 |
1996年 | 107篇 |
1995年 | 100篇 |
1994年 | 97篇 |
1993年 | 86篇 |
1992年 | 54篇 |
1991年 | 30篇 |
1990年 | 32篇 |
1989年 | 16篇 |
1988年 | 24篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有7248条查询结果,搜索用时 46 毫秒
11.
M. J. Carson J. C. Davies E. Daw R. J. Hollingworth V. A. Kudryavtsev T. B. Lawson P. K. Lightfoot J. E. McMillan B. Morgan S. M. Paling M. Robinson N. J. C. Spooner D. R. Tovey 《Astroparticle Physics》2004,21(6):667-687
Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10−9–10−10 pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector. 相似文献
12.
13.
IMPACTS OF FUTURE SEA LEVEL RISE ON SALT WATER INTRUSION IN THE CHANGJIANG RIVER ESTUARY 总被引:1,自引:0,他引:1
杨桂山 《中国地理科学(英文版)》1992,2(1):30-41
Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water. The implications of sea level rise for increasing salinity have been examined in the Changjiang (Yangtze) River estuary. By correlative analysis of chlorinity, discharge and tidal level and calculation of two-dimensional chlorinity, distribution of the Changjiang River estuary, the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50-100 cm. The intensity of salt water intrusion in the future will be far more serious than current trend. 相似文献
14.
15.
Ignacio Ferreras Alessandro Melchiorri Domenico Tocchini-Valentini 《Monthly notices of the Royal Astronomical Society》2003,344(1):257-261
The age of the Universe has been increasingly constrained by different techniques, such as the observations of type Ia supernovae (SNIa) at high redshift or dating the stellar populations of globular clusters. In this paper, we present a complementary approach using the colours of the brightest elliptical galaxies in clusters over a wide redshift range ( z ≲ 1) . We put new and independent bounds on the dark energy equation of state parametrized by a constant pressure-to-density ratio w Q and by a parameter (ξ) which determines the scaling between the matter and dark energy densities. We find that accurate estimates of the metallicities of the stellar populations in moderate and high-redshift cluster galaxies can pose stringent constraints on the parameters that describe dark energy. Our results are in good agreement with the analysis of dark energy models using SNIa data as a constraint. Accurate estimates of the metallicities of stellar populations in cluster galaxies at z ≲ 2 will make this approach a powerful complement to studies of cosmological parameters using high-redshift SNIa. 相似文献
16.
17.
松辽盆地中生代沉积基准面变化研究 总被引:6,自引:0,他引:6
利用地质资料研究来恢复沉积基准面变化。首先根据沉积物的分布规律、沉积构造、古生物组合及古生态、自生矿物和波基面等特征来获得古水深,然后利用对地层做脱水压实校正获得沉积物原始厚度。对湖盆地区古水深和沉积物原始厚度累加起来就可得到沉积基准面变化曲线。沉积基准面变化曲线为在松辽盆地中进行地层对比提供了依据。 相似文献
18.
19.
20.
Using a set of compilations of measurements for extragalactic radio sources, we construct all-sky maps of the Faraday rotation produced by the Galactic magnetic field. In order to generate the maps, we treat the radio source positions as a kind of 'mask' and construct combinations of spherical harmonic modes that are orthogonal on the masked sky. As long as relatively small multipoles are used, the resulting maps are quite stable to changes in the selection criteria for the sources, and show clearly the structure of the local Galactic magnetic field. We also suggest the use of these maps as templates for cosmic microwave background (CMB) foreground analysis, illustrating the idea with a cross-correlation analysis between the Wilkinson Microwave Anisotropy Probe ( WMAP ) data and our maps. We find a significant cross-correlation, indicating the presence of a significant residual contamination. 相似文献