全文获取类型
收费全文 | 93748篇 |
免费 | 18610篇 |
国内免费 | 42470篇 |
专业分类
测绘学 | 3869篇 |
大气科学 | 25224篇 |
地球物理 | 24638篇 |
地质学 | 54355篇 |
海洋学 | 21064篇 |
天文学 | 16130篇 |
综合类 | 4085篇 |
自然地理 | 5463篇 |
出版年
2022年 | 588篇 |
2021年 | 1077篇 |
2020年 | 2401篇 |
2019年 | 5851篇 |
2018年 | 6896篇 |
2017年 | 6490篇 |
2016年 | 6831篇 |
2015年 | 5600篇 |
2014年 | 5646篇 |
2013年 | 7796篇 |
2012年 | 6162篇 |
2011年 | 6502篇 |
2010年 | 6259篇 |
2009年 | 6495篇 |
2008年 | 5327篇 |
2007年 | 5253篇 |
2006年 | 4706篇 |
2005年 | 4174篇 |
2004年 | 4572篇 |
2003年 | 4183篇 |
2002年 | 3836篇 |
2001年 | 3406篇 |
2000年 | 2955篇 |
1999年 | 2798篇 |
1998年 | 2921篇 |
1997年 | 2956篇 |
1996年 | 2362篇 |
1995年 | 2283篇 |
1994年 | 2066篇 |
1993年 | 1894篇 |
1992年 | 1694篇 |
1991年 | 1427篇 |
1990年 | 1488篇 |
1989年 | 1274篇 |
1988年 | 1120篇 |
1987年 | 1223篇 |
1986年 | 1001篇 |
1985年 | 1160篇 |
1984年 | 1276篇 |
1983年 | 1126篇 |
1982年 | 1065篇 |
1981年 | 1006篇 |
1980年 | 868篇 |
1979年 | 827篇 |
1978年 | 792篇 |
1977年 | 710篇 |
1976年 | 684篇 |
1975年 | 661篇 |
1974年 | 616篇 |
1973年 | 651篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
We discuss long-time changes of polar activity of the Sun using the new observational data sets in the optical range during
1872–2001. A study of the secular and cycle variations of the magnetic activity at the high-latitude regions is the main goal
that includes polar magnetic field reversals during 1872–2001 and secular changes of the duration of polar activity cycles.
The secular increase of the area of polar zones during the minimum activity in the last 120 years and as consequence a decrease
of coronal temperature of the Sun in the high-latitude zones during the last 50 years. Correlation between the polar cycles
of Caii-K bright points with the Wolf sunspot numbers cycles, W(t), and the 22-year polar magnetic cycles of Caii-K bright points at the high latitudes during 1905–1995 is discussed. 相似文献
44.
W. H. Jefferys G. F. Benedict P. D. Hemenway P. J. Shelus R. L. Duncombe 《Celestial Mechanics and Dynamical Astronomy》1985,37(3):299-305
The Hubble Space Telescope (HST), a large optical telescope having an aperture of 2.4 meters and a length of 8.8 meters, is being developed by the National Aeronautics and Space Administration. This telescope will be placed into earth orbit by the space shuttle. Astrometric observations with the HST are made using a Fine Guidance Sensor which is capable of measuring the position of one object relative to another with an accuracy of ±0.002 arcseconds. The astrometric user of HST will be provided with an Astrometric Data Reduction Software package (ADRS). The variety of astrometric problems to be investigated with HST is discussed. 相似文献
45.
Maarten A. Prins Hongbo Zheng Kay Beets Simon Troelstra Patrick Bacon Ilse Kamerling Wouter Wester Martin Konert Xiangtong Huang Wang Ke Jef Vandenberghe 《第四纪科学杂志》2009,24(1):75-84
The Mangshan Plateau is located on the south bank of the Huang He (Yellow River) just west of the city of Zhengzhou, well outside the Loess Plateau in central China. Mixing models of the grain‐size data indicate that the loess deposits are mixtures of three loess components. Comparison of the mixing model with existing models established for a series of loess–palaeosol sequences from the Loess Plateau indicates that the Mangshan loess has been supplied from a proximal dust source, the Huang He floodplain, during major dust outbreaks. The high accumulation rates, the composition of the loess components, and especially the high proportions of a sandy loess component support this. Owing to the exceptionally high accumulation rates, the Mangshan grain size, magnetic susceptibility and carbonate records provide a high‐resolution archive of environmental and climate change. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
46.
47.
48.
Rostov State Pedagogical Institute; All-Union Scientific Research Institute Gradient. Translated from Astrofizika, Vol. 33, No. 3, pp. 379–393, November–December, 1990. 相似文献
49.
It is shown that the kinematical parameters associated with the congruence formed by tachyonic motion can be defined in the manner of Greenberg, but not that of Ehlers. The space-like counterpart of Raychaudhuri's equation has also been obtained. 相似文献
50.
地壳对海洋潮汐的响应 总被引:2,自引:2,他引:0
应用三维动态有限元方法研究了中国北部地区的地壳对邻近的渤海与黄海海平面变化的响应。虽然此应力场过于微弱不足以引发地震,但发现应力集中的位置及应力场变化较大的位置恰好与某些现代地震的震中一致。这一结果表明研究地壳对广泛分布的载荷的响应对研究区域地震构造是有帮助的。 相似文献