全文获取类型
收费全文 | 3551篇 |
免费 | 404篇 |
国内免费 | 422篇 |
专业分类
测绘学 | 1422篇 |
大气科学 | 216篇 |
地球物理 | 675篇 |
地质学 | 1146篇 |
海洋学 | 227篇 |
天文学 | 24篇 |
综合类 | 382篇 |
自然地理 | 285篇 |
出版年
2024年 | 18篇 |
2023年 | 45篇 |
2022年 | 64篇 |
2021年 | 91篇 |
2020年 | 117篇 |
2019年 | 110篇 |
2018年 | 84篇 |
2017年 | 149篇 |
2016年 | 139篇 |
2015年 | 156篇 |
2014年 | 219篇 |
2013年 | 271篇 |
2012年 | 273篇 |
2011年 | 288篇 |
2010年 | 178篇 |
2009年 | 209篇 |
2008年 | 220篇 |
2007年 | 286篇 |
2006年 | 263篇 |
2005年 | 221篇 |
2004年 | 188篇 |
2003年 | 183篇 |
2002年 | 133篇 |
2001年 | 102篇 |
2000年 | 75篇 |
1999年 | 72篇 |
1998年 | 53篇 |
1997年 | 29篇 |
1996年 | 30篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有4377条查询结果,搜索用时 406 毫秒
231.
笔者从地下地质工程和上水库工程地质调查这两个特殊问题论述了工程物探应用的对策和实效,具有一定的实用性和理论依据,对今后在抽水蓄能电站工程地质勘察中应用工程物探有一定的参考意义。 相似文献
232.
233.
研制的多功能为数字化地籍测绘系统,其集数据传输,平差计算,碎部点处理,图形处理和报表输出为一体,既适合于全站仪,并站仪,也可采用电子平板作业方式。该系统已用于生产中,效果好。 相似文献
234.
Donna C. Marron 《地球表面变化过程与地形》1992,17(7):675-685
Arsenic-contaminated mine tailings that were discharged into Whitewood Creek at Lead, South Dakota, from 1876 to 1978, were deposited along the floodplains of Whitewood Creek and the Belle Fourche River. The resulting arsenic-contaminated floodplain deposit consists mostly of overbank sediments and filled abandoned meanders along White-wood Creek, and overbank and point-bar sediments along the Belle Fourche River. Arsenic concentrations of the contaminated sediments indicate the degree of dilution of mine tailings by uncontaminated alluvium. About 13 per cent of the 110 × 106 Mg of mine tailings that were discharged at Lead were deposited along the Whitewood Creek floodplain. Deposition of mine tailings near the mouth of Whitewood Creek was augmented by an engineered structure. About 29 per cent of the mine tailings delivered by Whitewood Creek were deposited along the Belle Fourche River floodplain. About 60 per cent of that sediment is contained in overbank deposits. Deposition along a segment of the Belle Fourche River was augmented by rapid channel migration. The proportions of contaminated sediment stored along Whitewood Creek and the Belle Fourche River are consistent with sediment storage along the floodplains of perennial streams in other, similar sized watersheds. 相似文献
235.
Jonathan D. Phillips 《地球表面变化过程与地形》1992,17(7):699-709
Extensive storage of upper-basin Piedmont sediment and apparent low sediment supply to streams in lower-basin Coastal Plain areas generates questions as to the source of alluvium in lower reaches of rivers of the U.S. Atlantic drainage. This was investigated on the Neuse River, North Carolina, using a mineralogical indicator of sediment source areas. The utility of mica flakes for discriminating between Piedmont and non-Piedmont sources of sediment in the lower Coastal Plain reaches of the Neuse was established on the basis of an examination of the U.S. National Soils Database and of 26 soil surveys of the North Carolina Coastal Plain. From the Neuse River estuary to 48 km upstream there are no mica flakes in floodplain soils or in river bank and channel shelf sediments. Mica flakes become more common upstream. This suggests that a very small proportion of the sediment eroded in the Piedmont portion of the watershed is delivered to the river mouth. The small amounts which presumably do reach the lower Coastal Plain are so diluted by Coastal Plain-derived alluvium that no Piedmont origin can be discerned. This demonstrates a dominantly Coastal Plain source and underscores the importance of storage and discontinuous transport in fluvial sediment systems. More importantly, results suggest that upper- and lower-basin sediment dynamics are not only non-linearly related, but may be virtually decoupled. 相似文献
236.
呼图壁储气库是中国目前存储量最大的天然气储气库,位于新疆准噶尔盆地南缘,北天山山前坳陷带内的呼图壁背斜上.储气库靠近百万人口大城市乌鲁木齐,气库的注放气活动对其周缘地震活动的长期影响是事关生产和生活的重要安全问题.本文以呼图壁储气库为中心,在86.5°E—87.5°E,43.5°N—44.5°N的范围内,基于新疆维吾尔自治区地震局在该区域建立的密集流动台阵数据,应用模板匹配滤波技术对2016年全年的波形数据进行搜索识别,检测到遗漏地震事件151个,完善扩充了原有地震目录,使得该区域完备震级由1.1降到约0.7.通过分析新目录中404个地震的时空分布规律,我们发现2016年,即气库建成第三年以后,储气库的气压变化依然会影响周缘地区的地震活动.当储气库的气压增大到超过约22 MPa的阈值后,较小的气压波动也会导致该区域地震活动性明显增强;气压变化对距储气库中心最远约40 km范围内区域的地震活动存在较为明显的影响. 相似文献
237.
Michael Silberbauer 《水文科学杂志》2020,65(5):726-734
ABSTRACTNational and regional water quality monitoring networks have been operated in South Africa since the early 1970s. These originally had text-based inventories that were convenient for specialists who were familiar with the national networks and knew the locations of their sites of interest. However, within two decades the networks had expanded in geographical extent and variables monitored to such an extent that users needed spatial context in order to locate sites that fitted their information requirements. Mapping applications running on the Internet, such as Google Earth and Leaflet, form the foundation of a system for providing online inventories and summaries of the data available on the water quality database. The interfaces were constructed using available software, mainly ArcInfo and R. A recent concern is a decrease in the collection of water quality data, which is reducing the value of data summaries for water resource management. 相似文献
238.
ABSTRACTIndia has been the subject of many recent groundwater studies due to the rapid depletion of groundwater in large parts of the country. However, few if any of these studies have examined groundwater storage conditions in all of India’s river basins individually. Herein we assess groundwater storage changes in all 22 of India’s major river basins using in situ data from 3420 observation locations for the period 2003–2014. One-month and 12-month standardized precipitation index measures (SPI-1 and SPI-12) indicate fluctuations in the long-term pattern. The Ganges and Brahmaputra basins experienced long-term decreasing trends in precipitation in both 1961–2014 and the study period, 2003–2014. Indeterminate or increasing precipitation trends occurred in other basins. Satellite-based and in situ groundwater storage time series exhibited similar patterns, with increases in most of the basins. However, diminishing groundwater storage (at rates of >0.4 km3/year) was revealed in the Ganges-Brahmaputra River Basin based on in situ observations, which is particularly important due to its agricultural productivity. 相似文献
239.
240.
GIS是国土资源信息系统及办公自动化系统的基石 ,亦将是国土资源工作的各个领域中最具影响力、应用最广泛的一种技术。本文在分析已有矿产资源含量数据库特点和GIS应用现状的基础上 ,提出了在GIS平台上建立浙江省矿产资源储量管理信息系统的初步设想 ,概要论述了系统的功能、软件流程和系统结构 相似文献