全文获取类型
收费全文 | 5852篇 |
免费 | 1369篇 |
国内免费 | 35篇 |
专业分类
测绘学 | 169篇 |
大气科学 | 374篇 |
地球物理 | 2563篇 |
地质学 | 2096篇 |
海洋学 | 508篇 |
天文学 | 1039篇 |
综合类 | 4篇 |
自然地理 | 503篇 |
出版年
2023年 | 9篇 |
2022年 | 10篇 |
2021年 | 63篇 |
2020年 | 101篇 |
2019年 | 238篇 |
2018年 | 278篇 |
2017年 | 350篇 |
2016年 | 434篇 |
2015年 | 406篇 |
2014年 | 449篇 |
2013年 | 555篇 |
2012年 | 411篇 |
2011年 | 428篇 |
2010年 | 383篇 |
2009年 | 350篇 |
2008年 | 389篇 |
2007年 | 305篇 |
2006年 | 240篇 |
2005年 | 223篇 |
2004年 | 210篇 |
2003年 | 211篇 |
2002年 | 189篇 |
2001年 | 158篇 |
2000年 | 170篇 |
1999年 | 85篇 |
1998年 | 88篇 |
1997年 | 46篇 |
1996年 | 45篇 |
1995年 | 34篇 |
1994年 | 30篇 |
1993年 | 36篇 |
1992年 | 25篇 |
1991年 | 32篇 |
1990年 | 15篇 |
1989年 | 18篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1973年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有7256条查询结果,搜索用时 15 毫秒
111.
Jean‐Jacques Macaire Saïda Bellemlih Christian Di‐Giovanni Patrick De Luca Lionel Visset Jacques Bernard 《地球表面变化过程与地形》2002,27(9):991-1009
In the Négron River catchment area (162 km2), surface‐sediment stores are composed of periglacial calcareous ‘grèze’ (5 × 106 t) and loess (21 × 106 t), and Holocene alluvium (12·6 × 106 t), peat (0·6 × 106 t) and colluvium (18·5 × 106 t). Seventy‐five per cent of the Holocene sediments is stored along the thalwegs. Present net sediment yield, calculated from solid discharge at the Négron outlet, is low (0·6 t km?2 a?1) due to the dominance of carbonate rocks in the catchment. Mean sediment yield during the Holocene period is 7·0 t km?2 a?1 from alluvium stores and 7·6 t km?2 a?1 from colluvium stores. Thus, the gross sediment yield during the Holocene period is about 18·7 t km?2 a?1 and the sediment delivery ratio 3 per cent. The yield considerably varies from one sub‐basin to another (3·9 to 24·5 t km?2 a?1) according to lithology: about 25 per cent and 50 per cent of initial stores of periglacial grèze and loess respectively were reworked during the Holocene period. Sediment yield has increased by a factor of 6 in the last 1000 years, due to the development of agriculture. The very high rate of sediment storage on the slope during that period (88 per cent of the yield) can be accounted for by the formation of cultivation steps (‘rideaux’). It is predicted that the current destruction of these steps will result in a sediment wave reaching the valley floors in the coming decades. Subboreal and Subatlantic sediments and pollen assemblages in the Taligny marsh, where one‐third of the alluvium is stored, show the predominant influence of human activity during these periods in the Négron catchment. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
112.
This is the second part of a contribution to the debate on the possibilities of leveraging economic globalisation — through incorporation in international production networks and global commodity chains (GCCs) — as a strategy for developing countries to industrialise and advance their position in the world economy. In the first part, we analysed the experience of the East Asian apparel industry and addressed the issues of sustaining positions, upgrading to more rewarding roles, and advancing to less dependent positions within production networks and GCCs. We developed an analytical framework at both the firm and industry levels, and subsequently identified alternative firm- and industry-level strategies and trajectories. The present paper deals with these issues in the context of the Singapore apparel industry. Based on extensive empirical research, we demonstrate that although the East Asian experience of upgrading and repositioning within the GCC is to some extent emulated in the case of the Singapore apparel industry, the outcomes have been less favourable in terms of the depth, extent and strength of these trajectories. The differing outcomes can be explained in terms of different (systemic) conditions in the Singapore business environment, including the agency of local players, the geography of sourcing networks, and the role of the state and prevailing business attitudes. Our conclusions merit continued attention in both research and policy circles on the development of capabilities at the firm level, and the role of local business and institutional environments in local industry development processes under globalisation. 相似文献
113.
114.
Data and model uncertainty estimation for linear inversion 总被引:1,自引:0,他引:1
Kasper van Wijk John A. Scales William Navidi Luis Tenorio 《Geophysical Journal International》2002,149(3):625-632
115.
116.
117.
Pore‐ice sublimation is a prerequisite for aeolian activity in cold environments where surface sediments hold significant amounts of frozen water. Few quantitative studies have defined the rate of grain release from cemented surfaces by pore‐ice sublimation. In 1996–1997, controlled field experiments at Presqu'ile Beach, Ontario, were implemented to measure sediment release from frozen surfaces. The release rates were compared to the local wind regime, ambient temperature and humidity. In additional field experiments, the effect of sediment water content on grain release by sublimation was examined. From the experimental results, an equation which predicts grain release based on local wind speed, ground temperature, humidity, and surface water content is proposed. Predicted release rates show reasonable agreement with natural deflation measured on the beach at Presqu'ile Provincial Park. 相似文献
118.
Shear wave statics using receiver functions 总被引:1,自引:0,他引:1
119.
120.