全文获取类型
收费全文 | 409篇 |
免费 | 61篇 |
国内免费 | 95篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 136篇 |
地球物理 | 85篇 |
地质学 | 220篇 |
海洋学 | 33篇 |
天文学 | 14篇 |
综合类 | 18篇 |
自然地理 | 44篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 16篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 21篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 21篇 |
2012年 | 22篇 |
2011年 | 24篇 |
2010年 | 23篇 |
2009年 | 21篇 |
2008年 | 24篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 22篇 |
1999年 | 24篇 |
1998年 | 23篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1978年 | 1篇 |
1971年 | 1篇 |
1938年 | 1篇 |
1936年 | 4篇 |
排序方式: 共有565条查询结果,搜索用时 875 毫秒
421.
拉萨河流域高寒湿地分布(英文) 总被引:6,自引:1,他引:6
The Lhasa River Basin is one of the typical distribution regions of alpine wetlands on the Tibetan Plateau.It is very important to get a better understanding of the background and characteristics of alpine wetland for monitoring,protection and utilization.Wetland construction and distribution in the basin were analyzed based on multi-source data including field investigation data,CBERS remote sensing data and other thematic data provided by 3S technology.The results are(1) the total area of wetlands is 209,... 相似文献
422.
Bo Peng Xiaoyan Tang Changxun Yu Shurong Xie Meilian Xiao Zhi Song Xianglin Tu 《Environmental Geology》2009,57(2):421-434
The acid mine drainage (AMD) discharged from the Hejiacun uranium mine in central Hunan (China) was sampled and analyzed using
ICP-MS techniques. The analyzing results show that the AMD is characterized by the major ions FeTotal, Mn, Al and Si, and is concentrated with heavy metals and metalloids including Cd, Co, Ni, Zn, U, Cu, Pb, Tl, V, Cr, Se,
As and Sb. During the AMD flowing downstream, the dissolved heavy metals were removed from the AMD waters through adsorption
onto and co-precipitation with metal-oxhydroxides coated on the streambed. Among these metals, Cd, Co, Ni, Zn, U, Cu, Pb and
Tl are negatively correlated to pH values, and positively correlated to major ions Fe, Al, Si, Mn, Mg, Ca and K. The metals/metalloids
V, Cr, Se, As and Sb are conservative in the AMD solution, and negatively-correlated to major ions Na, Ca and Mg. Due to the
above different behaviors of these chemical elements, the pH-negatively related metals (PM) and the conservative metals (CM)
are identified; the PM metals include Cd, Co, Ni, Zn, U, Cu, Pb and Tl, and the CM metals V, Cr, Se, As and Sb. Based on understanding
the geochemistry of PM and CM metals in the AMD waters, a new equation: EXT = (Acidity + PM)/pH + CM × pH, is proposed to
estimate and evaluate extent of heavy-metal pollution (EXT) of AMD. The evaluation results show that the AMD and surface waters
of the mine area have high EXT values, and they could be the potential source of heavy-metal contamination of the surrounding
environment. Therefore, it is suggested that both the AMD and surface waters should be treated before they are drained out
of the mine district, for which the traditional dilution and neutralization methods can be applied to remove the PM metals
from the AMD waters, and new techniques through reducing the pH value of the downstream AMD waters should be developed for
removal of the CM metals. 相似文献
423.
424.
425.
Xiangyang Chang Shanming Fu Hui Liu Nan Chen Xiaofeng Zhao Bingquan Zhu Xianglin Tu 《中国地球化学学报》2011,30(1):138-144
The protection system of products of geographical origin has become one hot subject with which various countries throughout the world are concerned. Results of element-Pb isotope geochemical mapping indicate that there emerge a number of famous-brand high-quality product groups of geographical origin in China. The environment of production of China’s famous-brand white spirits of geographical origin at the Sichuan-Guizhou border is still a mystery to be solved. China has two main communities of white spirits of geographical origin, i.e., the most famous are Moutai and Wuliangye spirits. By element-Pb isotope geochemical tracing, we can establish the natural background geological, geographical and geochemical scientific data mark ers in close relation with source areas. Research on the product of geographical origin, named Kaempferia galangal L. in the Shuangjiao district, Yangchun, Guangdong Province, showed that the trace elements have an excellent heritance between Kaempferia galangal L. and soil in this area, and the trace elements are highly effective for tracing the origin. 相似文献
426.
广西地处华南地块、印支地块与西太平洋板块的汇合部位,因特殊的构造部位,广西区内大地构造单元归属、构造单元边界等许多基础地质问题一直存在争议.自新生代以来的板块构造运动对岩石圈的改造,广西地壳与上地幔在地震波速度及温度结构方面具有显著差异.应用卫星重、磁异常数据以及区域重力和航磁资料对广西地区岩石圈密度和磁化率结构及其与上地壳构造的关系开展了研究,结果显示广西地区地壳密度和上地壳磁性结构与现今地表构造较为契合,但下地壳密度结构与上地幔存在不连续现象;此外,岩石圈磁化率结构指示中下地壳存在不同范围和程度的解耦.对广西岩石圈密度与磁性结构的解读认为,在中生代以来岩石圈被大规模改造的背景下,幔源物质上侵至上地壳的规模和范围都有限,这可能是整个广西地区上地幔结构与地壳构造不对应的主要原因. 相似文献
427.
428.
论述了湛江海洋大学校园树木景观的现状和规划。指出要以园林生态学原则为指导思想建设热带生态园林式校园 相似文献
429.
Wang Kexin Xu Xinghua Sun Xuefeng Tu Hua Zeng Qiongxuan Lu Yiming Lu Huayu Wang Shejiang 《地理学报(英文版)》2019,29(3):406-416
Journal of Geographical Sciences - The Luonan Basin is a key region of early human settlement in Central China with more than 300 discovered Paleolithic sites. Artifact layer 1 of the Liuwan site... 相似文献
430.
Rural restructuring is a process of reshaping socio-economic morphology and spatial pattern in rural territory in response to the changes of elements both in kernel system and external system of rural development, by optimally allocating and efficiently managing the material and non-material elements in the two systems. It aims at ultimately optimizing the structure and promoting the function within rural territorial system as well as realizing the coordination of structure and complementation of function between urban and rural territorial system. This paper establishes a theoretical framework of rural restructuring through elaborating the concept and connotations as well as analyzing the mechanism pushing forward rural restructuring based on the evolution of “elements-structure-function”, and probes the approaches from the three aspects of spatial restructuring, economic restructuring and social restructuring. Besides, the authors argue that the study of rural restructuring in China in the future needs to focus on the aspects of long-term and multi-scale process and pattern, mechanism, regional models, rural planning technology system and standard, policy and institutional innovations concerning rural restructuring as well as the impacts of globalization on rural restructuring, in order to serve the current national strategic demands and cope with the changes of rural development elements in the process of urban-rural development transformation. 相似文献