全文获取类型
收费全文 | 707篇 |
免费 | 9篇 |
国内免费 | 16篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 43篇 |
地球物理 | 144篇 |
地质学 | 263篇 |
海洋学 | 52篇 |
天文学 | 141篇 |
自然地理 | 80篇 |
出版年
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 26篇 |
2015年 | 17篇 |
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 19篇 |
2011年 | 30篇 |
2010年 | 23篇 |
2009年 | 38篇 |
2008年 | 27篇 |
2007年 | 33篇 |
2006年 | 33篇 |
2005年 | 24篇 |
2004年 | 37篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1972年 | 3篇 |
1964年 | 2篇 |
排序方式: 共有732条查询结果,搜索用时 0 毫秒
731.
Carbon storage in the grasslands of China based on field measurements of above- and below-ground biomass 总被引:7,自引:0,他引:7
Jiangwen Fan Huaping Zhong Warwick Harris Guirui Yu Shaoqiang Wang Zhongmin Hu Yanzhen Yue 《Climatic change》2008,86(3-4):375-396
Above- and below-ground biomass values for 17 types of grassland communities in China as classified by the Chinese Grasslands
Resources Survey were obtained from systematic replicated sampling at 78 sites and from published records from 146 sites.
Most of the systematic samples were along a 5,000-km-long transect from Hailar, Inner Mongolia (49°15′N, 119°15′E), to Pulan,
Tibet (30°15′N, 81°10′E). Above-ground biomass was separated into stem, leaf, flower and fruit, standing dead matter, and
litter. Below-ground biomass was measured in 10-cm soil layers to a depth of 30 cm for herbs and to 50 cm for woody plants.
Grassland type mean total biomass carbon densities ranged from 2.400 kg m−2 for swamp to 0.149 kg m−2 for alpine desert grasslands. Ratios of below- to above-ground carbon density varied widely from 0.99 for tropical tussock
grassland to 52.28 for alpine meadow. Most below-ground biomass was in the 0–10 cm soil depth layer and there were large differences
between grassland types in the proportions of living and dead matter and stem and leaf. Differences between grassland types
in the amount and allocation of biomass showed patterns related to environments, especially aridity gradients. Comparisons
of our estimates with other studies indicated that above-ground biomass, particularly forage-yield biomass, is a poor predictor
of total vegetation carbon density. Our estimate for total carbon storage in the biomass of the grasslands of China was 3.32 Pg
C, with 56.4% contained in the grasslands of the Tibet-Qinghai plateau and 17.9% in the northern temperate grasslands. The
need for further standardized and systematic measurements of vegetation biomass to validate global carbon cycles is emphasised. 相似文献
732.
M. T. D. Wingate I. H. Campbell L. B. Harris 《Australian Journal of Earth Sciences》2013,60(2):309-313
Recent high‐resolution aeromagnetic data have delineated an extensive swarm of undeformed northeast‐trending dolerite dykes in the southeastern Yilgarn Craton, known previously only from isolated exposures in surface mining operations. Owing to parallelism of the dykes to the Fraser Mobile Belt, the eastern segment of the Albany‐Fraser Orogen, the swarm is referred to here as the Fraser Dyke Swarm. Ion‐microprobe dating of baddeleyite from a granophyric segregation in the centre of one dyke yields a mean 207Pb/206Pb age of 1212 ± 10 Ma (95% confidence limits). The location of the Fraser Dyke Swarm, adjacent and parallel to the Fraser Mobile Belt, suggests that the dykes may have been emplaced into lines of weakness that originated during tectonic loading and downwards flexure of the craton margin. This is the first evidence of ca 1210 Ma mafic dykes and associated crustal‐scale extension in the southeast Yilgarn Craton, although the age is similar to those reported recently for dolerite and quartz diorite dykes in the central and southern part of the craton, suggesting that a genetic relationship may exist between intrusions in the two areas. 相似文献