全文获取类型
收费全文 | 39274篇 |
免费 | 6937篇 |
国内免费 | 8212篇 |
专业分类
测绘学 | 3451篇 |
大气科学 | 4426篇 |
地球物理 | 7141篇 |
地质学 | 23239篇 |
海洋学 | 4053篇 |
天文学 | 3372篇 |
综合类 | 2580篇 |
自然地理 | 6161篇 |
出版年
2024年 | 196篇 |
2023年 | 528篇 |
2022年 | 1311篇 |
2021年 | 1542篇 |
2020年 | 1397篇 |
2019年 | 1831篇 |
2018年 | 1305篇 |
2017年 | 1531篇 |
2016年 | 1597篇 |
2015年 | 1744篇 |
2014年 | 2193篇 |
2013年 | 2211篇 |
2012年 | 2390篇 |
2011年 | 2567篇 |
2010年 | 2195篇 |
2009年 | 2740篇 |
2008年 | 2701篇 |
2007年 | 2771篇 |
2006年 | 2624篇 |
2005年 | 2494篇 |
2004年 | 2189篇 |
2003年 | 2101篇 |
2002年 | 1808篇 |
2001年 | 1589篇 |
2000年 | 1601篇 |
1999年 | 1392篇 |
1998年 | 1195篇 |
1997年 | 860篇 |
1996年 | 705篇 |
1995年 | 607篇 |
1994年 | 569篇 |
1993年 | 490篇 |
1992年 | 373篇 |
1991年 | 307篇 |
1990年 | 210篇 |
1989年 | 163篇 |
1988年 | 127篇 |
1987年 | 68篇 |
1986年 | 41篇 |
1985年 | 32篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 15篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1954年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Miniature gravity corer for recovering short sediment cores 总被引:12,自引:0,他引:12
John R. Glew 《Journal of Paleolimnology》1991,5(3):285-287
103.
Richard C. Preece Simon A. Parfitt G. Russell Coope Kirsty E. H. Penkman Philippe Ponel John E. Whittaker 《第四纪科学杂志》2009,24(6):557-580
Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north‐western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the ‘Sidestrand Unio‐bed’, here defined as the Sidestrand Hall Member of the Cromer Forest‐bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio‐bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomys savini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the ‘Cromerian Complex’ and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial – probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the ‘new glacial stratigraphy’ during MIS 16, 12, 10 and 6. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
104.
105.
106.
107.
108.
109.
从胶东所处的板块构造位置和区域控热构造入手,根据地热传导理论,对胶东温泉的地热属性进行分析研究,认为胶东半岛温泉地热属性为毗邻板块边缘高温地热带的板内中低温地热系统,它以偏高的大地热流值为地热背景,以局部控热构造聚敛的大地热流为热源,以地形高差影响和相应的水力压差作用为动力,入渗的大气降水被岩石中的热量加热,并沿断裂出露形成温泉地热水。根据山东半岛温泉地热属性的特点和地热水开发中所面临的问题,提出保持胶东温泉可持续开发的相关对策。 相似文献
110.