全文获取类型
| 收费全文 | 264993篇 |
| 免费 | 5264篇 |
| 国内免费 | 3512篇 |
专业分类
| 测绘学 | 7148篇 |
| 大气科学 | 19693篇 |
| 地球物理 | 55762篇 |
| 地质学 | 92716篇 |
| 海洋学 | 22380篇 |
| 天文学 | 56737篇 |
| 综合类 | 1082篇 |
| 自然地理 | 18251篇 |
出版年
| 2021年 | 2240篇 |
| 2020年 | 2673篇 |
| 2019年 | 2914篇 |
| 2018年 | 4340篇 |
| 2017年 | 3904篇 |
| 2016年 | 6259篇 |
| 2015年 | 4335篇 |
| 2014年 | 7089篇 |
| 2013年 | 14420篇 |
| 2012年 | 6879篇 |
| 2011年 | 8557篇 |
| 2010年 | 7446篇 |
| 2009年 | 10073篇 |
| 2008年 | 8937篇 |
| 2007年 | 8438篇 |
| 2006年 | 9831篇 |
| 2005年 | 7955篇 |
| 2004年 | 7879篇 |
| 2003年 | 7355篇 |
| 2002年 | 6910篇 |
| 2001年 | 6133篇 |
| 2000年 | 6036篇 |
| 1999年 | 5238篇 |
| 1998年 | 5263篇 |
| 1997年 | 5073篇 |
| 1996年 | 4702篇 |
| 1995年 | 4453篇 |
| 1994年 | 4121篇 |
| 1993年 | 3870篇 |
| 1992年 | 3640篇 |
| 1991年 | 3599篇 |
| 1990年 | 3768篇 |
| 1989年 | 3525篇 |
| 1988年 | 3314篇 |
| 1987年 | 3863篇 |
| 1986年 | 3431篇 |
| 1985年 | 4243篇 |
| 1984年 | 4757篇 |
| 1983年 | 4426篇 |
| 1982年 | 4331篇 |
| 1981年 | 3940篇 |
| 1980年 | 3655篇 |
| 1979年 | 3517篇 |
| 1978年 | 3499篇 |
| 1977年 | 3280篇 |
| 1976年 | 2985篇 |
| 1975年 | 2909篇 |
| 1974年 | 2869篇 |
| 1973年 | 3067篇 |
| 1972年 | 1993篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
141.
142.
143.
144.
145.
146.
Michail I. PETAEV 《Meteoritics & planetary science》1996,31(6):807-815
Abstract— Olivine grains from selected meteorites (the Springwater pallasite, the Lowicz mesosiderite, the ALH 84025 brachinite, the Krymka LL3 chondrite, and the Calcalong Creek lunar meteorite) and terrestrial rocks (San Carlos forsterite and Rockport fayalite) were studied by optical microscopy and high-precision electron microprobe analysis. Detailed microprobe traverses revealed regular igneous zoning in the Krymka and Calcalong Creek olivines. Traverses across the San Carlos forsterite grain are flat and display no chemical variations larger than the 2σ range of counting error (±0.2 mol% Fa). Traverses across olivine grains in the ALH 84025, Lowicz, and Springwater meteorites show regular patterns of periodic or wavy chemical variations well exceeding the 2σ uncertainty range. However, no lamellar structure was seen in backscattered electron images. It is suggested that the periodic chemical variations may be due to spinodal decomposition of primary, more or less homogeneous grains. I conclude that the absence of earlier reports of such variations simply means that olivine grains in equilibrated meteorites have not been examined closely enough to detect them. 相似文献
147.
Long-term changes in growth of Norwegian spring-spawning herring 总被引：3，自引：1，他引：2
148.
The growth of Glasgow from a small town into a heavily industrialised conurbation depended greatly on its local geological riches. Extensive mining and quarrying of a range of minerals took place from the 18th century onwards. The early underground stoop and room (pillar and stall) workings, and the backfilled quarries, together with variably consolidated natural superficial deposits, have bequeathed to the city a heritage of unwanted engineering problems which cannot easily be quantified. Recent work by the British Geological Survey (BGS) illustrates the scale of both geological and man-made problems. 相似文献
149.
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
150.