全文获取类型
收费全文 | 8726篇 |
免费 | 1378篇 |
国内免费 | 1610篇 |
专业分类
测绘学 | 641篇 |
大气科学 | 935篇 |
地球物理 | 2233篇 |
地质学 | 4387篇 |
海洋学 | 1168篇 |
天文学 | 23篇 |
综合类 | 603篇 |
自然地理 | 1724篇 |
出版年
2024年 | 36篇 |
2023年 | 133篇 |
2022年 | 287篇 |
2021年 | 361篇 |
2020年 | 363篇 |
2019年 | 413篇 |
2018年 | 342篇 |
2017年 | 388篇 |
2016年 | 414篇 |
2015年 | 386篇 |
2014年 | 607篇 |
2013年 | 594篇 |
2012年 | 522篇 |
2011年 | 583篇 |
2010年 | 541篇 |
2009年 | 568篇 |
2008年 | 578篇 |
2007年 | 619篇 |
2006年 | 607篇 |
2005年 | 498篇 |
2004年 | 413篇 |
2003年 | 374篇 |
2002年 | 371篇 |
2001年 | 286篇 |
2000年 | 246篇 |
1999年 | 187篇 |
1998年 | 196篇 |
1997年 | 142篇 |
1996年 | 134篇 |
1995年 | 105篇 |
1994年 | 92篇 |
1993年 | 78篇 |
1992年 | 87篇 |
1991年 | 34篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 8篇 |
1977年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
961.
962.
随着经济、科技的不断发展,测绘产品不断丰富,我省的部分测绘产品检查验收规定已无法满足现阶段测绘产品的质检需要,为了保证我省测绘产品的质量,提高检验工作的科学性、全面性,我站对现行的省测绘成果检查验收规定进行了修订和扩充,制定了适合我省现阶段测绘产品质量评定的规定——《黑龙江省基础地理信息成果质量检查与验收》。 相似文献
963.
以1∶10 000图库一体化数据成果为研究对象,结合1∶10 000图库一体化数据生产流程,分析了图库一体化数据特征,对图库一体化数据生产过程中各个环节的质量控制方法和质量评价内容进行探讨试验,提出了一体化数据的质量评价内容和图库一体化生产环节中的质量控制方法. 相似文献
964.
潍北凹陷是昌潍坳陷的次一级凹陷盆地,也是胜利油田外围常规油气开采区。潍北凹陷孔店组二段发育了较厚的暗色泥页岩,是页岩气形成最有利层段,也是常规油气的生烃母岩。利用昌页参1井数据,结合以往资料,对潍北凹陷孔店组二段岩性特征,有机地球化学特征、矿物组成、泥页岩含气性特征等进行分析研究,认为孔店组二段上亚段下部和中亚段下部具备页岩气资源勘查开发潜力。 相似文献
965.
966.
967.
968.
Abstract The Samborombón Bay area (Argentina) is a coastal plain environment that contains groundwater resources with high salinity. In addition, there are local freshwater lenses associated with shell ridges and sand sheets in the region. In this work, the groundwater travel time in these freshwater lenses is estimated based on their geological conditions, which include hydraulic conductivity, recharge, morphology and discharge to surface freshwater or to saline groundwater. Groundwater travel times in the freshwater lenses were calculated from the equations developed by Chesnaux and Allen. The travel times estimated for the different scenarios were relatively short. The results indicate that the groundwater flow tends to be strongly dependent on the recharge conditions, with an excess of water in the water balance. The results can be applied to help design sustainable management methods to exploit this water resource system and also to assess the impact of contaminant plumes on this groundwater resource. Citation Carol, E., Kruse, E. & Roig, A. (2010) Groundwater travel time in the freshwater lenses of Samborombón Bay, Argentina. Hydrol. Sci. J. 55(5), 754–762. 相似文献
969.
DRASTIC has drawbacks in groundwater risk assessment that are important in guiding activities to prevention agricultural diffuse groundwater pollution. This paper presents an improved and GIS‐based D‐DRASTIC approach for groundwater nitrate risk assessment from diffuse agricultural sources based on DRASTIC. D‐DRASTIC considers the risk concept, nitrate loading, pollutant transport with runoff, depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone media, and the hydraulic conductivity of the aquifer. D‐DRASTIC was developed within an ArcGIS environment and applied to the Upper Bann Catchment, Northern Ireland as a case study. D‐DRASTIC shows that ‘very high’ and ‘high’ zones of groundwater nitrate risk occupy 5% and 11% of the case study area, respectively. When considering groundwater pollution sources and pathways, the results using D‐DRASTIC are helpful in guiding the activities of groundwater pollution prevention at the catchment scale in the context of better implementation of the EU Water Framework Directive. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
970.
ZHANG Libing CHENG Jilin JIN Juliang JIANG Xiaohong 《中国海洋大学学报(英文版)》2006,5(4):300-304
The attribute recognition model (ARM) has been widely used to make comprehensive assessment in many engineering fields, such as environment, ecology, and economy. However, large numbers of experiments indicate that the value of weight vector has no relativity to its initial value but depends on the data of Quality Standard and actual samples. In the present study, the ARM is enhanced with the technique of data driving, which means some more groups of data from the Quality Standard are selected with the uniform random method to make the calculation of weight values more rational and more scientific. This improved attribute recognition model (IARM) is applied to a real case of assessment on seawater quality. The given example shows that the IARM has the merits of being simple in principle, easy to operate, and capable of producing objective results, and is therefore of use in evaluation problems in marine environment science. 相似文献