全文获取类型
收费全文 | 37905篇 |
免费 | 6737篇 |
国内免费 | 10942篇 |
专业分类
测绘学 | 3311篇 |
大气科学 | 4339篇 |
地球物理 | 6538篇 |
地质学 | 26268篇 |
海洋学 | 3828篇 |
天文学 | 3372篇 |
综合类 | 2339篇 |
自然地理 | 5589篇 |
出版年
2024年 | 180篇 |
2023年 | 572篇 |
2022年 | 1446篇 |
2021年 | 1627篇 |
2020年 | 1550篇 |
2019年 | 2023篇 |
2018年 | 1535篇 |
2017年 | 1773篇 |
2016年 | 1813篇 |
2015年 | 1971篇 |
2014年 | 2421篇 |
2013年 | 2482篇 |
2012年 | 2628篇 |
2011年 | 2543篇 |
2010年 | 2219篇 |
2009年 | 2736篇 |
2008年 | 2630篇 |
2007年 | 2719篇 |
2006年 | 2647篇 |
2005年 | 2451篇 |
2004年 | 2164篇 |
2003年 | 1980篇 |
2002年 | 1650篇 |
2001年 | 1480篇 |
2000年 | 1490篇 |
1999年 | 1304篇 |
1998年 | 1108篇 |
1997年 | 828篇 |
1996年 | 673篇 |
1995年 | 568篇 |
1994年 | 548篇 |
1993年 | 456篇 |
1992年 | 329篇 |
1991年 | 289篇 |
1990年 | 189篇 |
1989年 | 157篇 |
1988年 | 126篇 |
1987年 | 76篇 |
1986年 | 43篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 14篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Relict rock glaciers have considerable potential for contributing to palaeoclimatic reconstruction, but this potential is often undermined by lack of dating control and problems of interpretation. Here we reinvestigate and date four proposed ‘rock glaciers’ in the Cairngorm Mountains and show that the morphology of only one of these appears consistent with that of a true rock glacier produced by creep of underlying ice or ice‐rich sediment. All four features comprise rockslide or rock avalanche runout debris, and the possibility that all four represent unmodified runout accumulations cannot be discounted. Surface exposure dating of the four debris accumulations using cosmogenic 10Be produced uncertainty‐weighted mean ages of 15.4 ± 0.8 ka, 16.2 ± 1.0 ka, 12.1 ± 0.6 ka and 12.7 ± 0.8 ka. All four ages imply emplacement under cold stadial conditions, two prior to the Windermere Interstade of ca. 14.5–12.9 cal. ka BP and two during the Loch Lomond Stade of ca. 12.9–11.5 cal. ka BP. The above ages indicate that paraglacial rock‐slope failure on granite rockwalls occurred within a few millennia after deglaciation. The mean exposure ages obtained for runout debris at two sites – Strath Nethy (16.2 ± 1.0 ka) and Lairig Ghru (15.4 ± 0.8 ka) – are consistent with basal radiocarbon ages from Loch Etteridge, 22 km to the southwest (mean = 15.6 ± 0.3 cal. ka BP) and imply widespread deglaciation of the Cairngorms and adjacent valleys before 15 ka and possibly 16 ka. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
103.
The sand–loess transition zone in north China is sensitive to climate change, and is an ideal place to investigate past environmental changes. However, past climate change at millennial–centennial timescales in this region has not been well reconstructed because of limited numerical dating. Alternations of sandy loam soils with aeolian sand layers in the Mu Us and Otindag sand fields, which lie along the sand–loess transition zone, indicate multiple intervals of dune activity and stability. This change is probably a response to variations of the East Asian monsoon climate during the late Quaternary. The single aliquot regeneration (SAR) optically stimulated luminescence (OSL) dating protocol, which has been successfully applied to aeolian deposits worldwide, is applied to these two sand fields in this study. The OSL ages provide reliable constraints for reconstruction of past climate changes at suborbital timescale. Sections in both sand fields contain aeolian sand beds recording millennial‐scale episodes of dry climate and widespread dune activation, including episodes at about the same time as Heinrich Event 5 and the Younger Dryas in the North Atlantic region. These results demonstrate the potential of aeolian sediments in semi‐arid north China to record millennial‐scale climatic events, and also suggest that dry–wet climate variation at the desert margin in China may be linked to climatic change elsewhere in the Northern Hemisphere, through atmospheric circulation. This article was published online on 27 November 2008. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected (16 December 2008). Copyright © 2008 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.