全文获取类型
收费全文 | 2612篇 |
免费 | 864篇 |
国内免费 | 754篇 |
专业分类
测绘学 | 115篇 |
大气科学 | 478篇 |
地球物理 | 482篇 |
地质学 | 1570篇 |
海洋学 | 680篇 |
天文学 | 72篇 |
综合类 | 184篇 |
自然地理 | 649篇 |
出版年
2024年 | 18篇 |
2023年 | 37篇 |
2022年 | 105篇 |
2021年 | 167篇 |
2020年 | 137篇 |
2019年 | 150篇 |
2018年 | 146篇 |
2017年 | 136篇 |
2016年 | 154篇 |
2015年 | 178篇 |
2014年 | 184篇 |
2013年 | 217篇 |
2012年 | 165篇 |
2011年 | 145篇 |
2010年 | 126篇 |
2009年 | 172篇 |
2008年 | 186篇 |
2007年 | 179篇 |
2006年 | 159篇 |
2005年 | 170篇 |
2004年 | 148篇 |
2003年 | 142篇 |
2002年 | 145篇 |
2001年 | 113篇 |
2000年 | 106篇 |
1999年 | 92篇 |
1998年 | 89篇 |
1997年 | 66篇 |
1996年 | 70篇 |
1995年 | 51篇 |
1994年 | 53篇 |
1993年 | 40篇 |
1992年 | 50篇 |
1991年 | 26篇 |
1990年 | 35篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有4230条查询结果,搜索用时 46 毫秒
101.
Claude Boutron Kevin Rosman Carlo Barbante Michael Bolshov Freddy Adams Sungmin Hong Christophe Ferrari 《Comptes Rendus Geoscience》2004,336(10):847-867
The investigation of the occurrence of lead in dated snow and ice from Greenland and Antarctica has played a major role in our understanding of the history of the pollution of the atmosphere of our planet by this metal. Such studies have however proved to be very demanding, mainly because of the extreme purity of polar snow and ice. Reliable measurements can be obtained only if ultra-clean and highly sensitive procedures are used, as pioneered by Clair Patterson. The Greenland data show evidence of large-scale pollution of the atmosphere of the Northern Hemisphere for lead as early as two millennia ago during Greco–Roman times, especially because of mining and smelting activities in southern Spain. It peaked at the end of the 1960s, with lead concentrations in snow about 200 times higher than natural values, before declining during recent times because of the fall in the use of leaded gasoline. Lead pollution in Antarctica was already significant at the end of the 19th century as a consequence of whaling activities, the traffic of coal-powered ships crossing the Cape Horn, and mining activities in South America, South Africa and Australia. After declining because of the opening of the Panama Canal, the great economic depression and World War II, it reached a maximum during the 1980s, with lead concentrations 20 times higher than natural values. Other studies focus on past natural variations of lead in ancient ice dated from the last climatic cycles. To cite this article: C. Boutron et al., C. R. Geoscience 336 (2004). 相似文献
102.
103.
LIU Shiyin WANG Ninglian DUAN Keqin XIAO Cunde DING Yongjian HAN Haidong 《地理学报(英文版)》2004,14(4):401-410
1IntroductionIn the early 1960s, glaciers in western China were classified into maritime- and continental-types by different glacial environment and physical characteristics (Shi and Xie, 1964). With extensive glaciological investigations in the western regions (Lanzhou Institute of Glaciology and Geocryology of CAS, 1988), Lai and Huang (1990) suggested a new classification of temperate, subpolar and quasipolar glaciers, corresponding to the maritime-, subcontinental- and extremely contin… 相似文献
104.
105.
MODIS数据在黄河凌汛监测中的应用 总被引:11,自引:0,他引:11
对MODIS数据的特性及其在黄河凌汛监测中的应用情况进行了探讨和总结。试验结果表明 ,MODIS数据在冰雪检测方面具有很大的潜力 相似文献
106.
Glacier inventory compilation during the past 20 years and modifications of that for the Eastern Pamir and Banggong Lake indicate that there are 46,342 modern glaciers with a total area and volume of 59415 km2 and 5601 km3 respectively in China. These glaciers can be classified into maritime and continental (including sub-continental and extremely continental) types. Researches show that glaciers in China have been retreating since the Little Ice Age and the mass wastage was accelerated during the past 30 to 40 years. Being an important part of glaciological studies in China, ice core climatic and environmental studies on Tibetan Plateau and in the Antarctica have provided abundant, high resolution information about past climatic and environmental evolution over the Tibetan Plateau and Antarctica. Except for different parameters recorded in ice cores relating to climate and environment changes on Tibetan Plateau, records from ice cores extracted from different glaciers show that the discrepancies in climatic and environmental changes on the north and south parts of the plateau may be the consequence of different influencing effects from terrestrial and solar sources. Glaciological and meteorological phenomena imply that Lambert Glacier valley is an important boundary of climate in the east Antarctica, which is thought to be connected with cyclonic activities and Circum-polar Waves over the Antarctica. 相似文献
107.
108.
109.
110.
Pollen collected from snow samples on the Quelccaya Ice Cap in 2000 and 2001 reveals significant interannual variability in pollen assemblage, concentration, and provenance. Samples from 2000, a La Niña year, contain high pollen concentrations and resemble samples from the Andean forests (Yungas) to the east. Samples from 2001, an El Niño year, contain fewer pollen and resemble those from the Altiplano. We suggest that varying wind patterns under different El Niño/Southern Oscillation (ENSO) conditions may affect the processes of pollen transport over the Altiplano and on the ice cap, although confounding variables such as flowering phenology and sublimation should also be considered 相似文献