首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   47篇
  免费   6篇
  国内免费   19篇
测绘学   14篇
大气科学   9篇
地球物理   5篇
地质学   16篇
海洋学   10篇
综合类   10篇
自然地理   8篇
  2022年   3篇
  2021年   7篇
  2020年   5篇
  2019年   3篇
  2018年   1篇
  2017年   1篇
  2016年   4篇
  2015年   1篇
  2014年   2篇
  2013年   5篇
  2012年   8篇
  2011年   4篇
  2010年   7篇
  2009年   3篇
  2008年   4篇
  2004年   1篇
  2000年   3篇
  1999年   2篇
  1996年   2篇
  1992年   1篇
  1991年   1篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
排序方式: 共有72条查询结果,搜索用时 31 毫秒
11.
中国西南地区面临着因缅甸内战和毒品经济产生的跨国影响而形成的恶劣的地缘政治环境。通过文本分析法,本文聚焦缅甸内战和毒品经济,在分析缅甸内战历史和现实致因、缅甸毒品经济起源与发展的基础上,从地缘政治学视角,揭示了缅甸内战与毒品经济之间的相互关联。本文试图回答的问题是:缅甸内战状态下的毒品经济为何在缅甸蔓延?毒品经济又如何加深缅甸内战并阻碍内战的终结?缅甸内战与毒品经济相互纠缠,即缅甸内战不是由毒品经济利益所触发,但缅甸内战刺激了鸦片种植和催生了畸形的毒品经济,而毒品经济重塑了缅甸联邦政府与少数民族地方武装等各方利益,从而为缅甸内战解决蒙上了阴影。  相似文献   
12.
由于地壳运动、地下水使用及矿床开采等因素的影响,会造成地表的形变,特别是垂直(高程)方向影响更大。为了维持高程基准的现势性,本文提出了一种以InSAR地表形变监测和水准测量相结合的方法,实现地表形变区高程基准动态维持。并以黄河三角洲区域为例,对2种成果精度进行了对比验证,水准测量和InSAR监测结果基本相符,可实现2种技术手段融合以获取点、面综合的高程变化信息。  相似文献   
13.
Graphical methods have been widely used for visualization, classification, and interpretation of aqueous geochemical data to obtain a better understanding of surface and subsurface hydrologic systems. This method note presents WQChartPy, an open-source Python package developed to plot a total of 12 diagrams for analysis of aqueous geochemical data. WQChartPy can handle various data formats including Microsoft Excel, comma-separated values (CSV), and general delimited text. The 12 diagrams include eight traditional diagrams (trilinear Piper, Durov, Stiff, Chernoff face, Schoeller, Gibbs, Chadha, and Gaillardet) and four recently proposed diagrams (rectangle Piper, color-coded Piper, contour-filled Piper, and HFE-D) that have not been implemented in existing graphing software. The diagrams generated by WQChartPy can be saved as portable network graphics (PNG), scalable vector graphics (SVG), or portable document format (PDF) files for scientific publications. Jupyter and Google Colab notebooks are available online to illustrate how to use WQChartPy with example datasets. The geochemical diagrams can be generated with several lines of Python codes. Source codes of WQChartPy are publicly available at GitHub ( https://github.com/jyangfsu/WQChartPy ) and PyPI ( https://pypi.org/project/wqchartpy/ ).  相似文献   
14.
在自然地理要素基础上对陕西省进行"陕北―关中―陕南"的自然区域划分,是陕西省地理国(省)情监测试点首要解决的问题之一。根据地域分异规律将陕西省划分为3个自然区,详细论述陕西省的自然区域划分以水文地貌关系为依据的可行性,明确划分出"陕北―关中―陕南"的自然区划界限,并从划分结果的区域形状、位置、特征统计参数和区域要素特点等方面,论述区域划分方法和结果的合理性。这不仅对陕西省地理国(省)情具有认识意义,而且是陕西省地理国(省)情监测成果的区划统计支撑,可以作为宏观把握社会、人口、经济等要素区域差异的基础数据,因而也具有重要的现实意义。  相似文献   
15.
Tectonic Geomorphology is an important branch of Geomorphology. Now the scope of tectonic geomorphology study has covered the interactions between tectonics, climate, surface processes and the influence on geomorphic evolution. The study of tectonic geomorphology in China started at the beginning of the 20th century, developed gradually in the 1950s, and entered a rapid development stage in the new century. Based on the long-term development, the study of tectonic geomorphology in China has formed a relatively complete theoretical and methodological system, and now presents a trend of the continuous intersection and integration with other adjacent disciplines. Now, several books on tectonic geomorphology have been published. The representative book abroad is Tectonic Geomorphology which was edited by Burbank D. W. and Anderson R. S., and was first published in 2001 and reprinted in 2012. In China, the first book on tectonic geomorphology is Active Tectonic Geomorphology which was edited by Yang Jingchun and Li Youli and was first published in 2011.In recent years, the tectonic geomorphology study has been absorbing and integrating the new ideas and new methods of other disciplines, significantly promoting the development of tectonic geomorphology. At the 2019 China Geographic Congress & the 110th anniversary of the establishment of the Chinese Geographical Society, the authors organized the session "Theory, Method and Application of Tectonic Geomorphology", aiming to present the recent progresses of tectonic geomorphology study in China. Later, invited by the editorial office, the authors organized the special column with the same name in the journal Advances in Earth Science. The contents of this column mainly dealt with the classical theoretical problems of geomorphology (the evolution and the controlling mechanism of river terrace, planation surface, and alluvial fan), new methods (such as K-feldspar thermoluminescence thermochronology, detrital zircon U-Pb chronology), and models and numerical simulation of tectonic geomorphology evolution. Because of the limited number of the articles, it was impossible for this column to comprehensively present the recent progresses in the study of tectonic geomorphology in China. Therefore, this paper first briefly reviewed the history of the development of tectonic geomorphology in China and the basic trend of tectonic geomorphology. The authors started the study of neotectonics and tectonic geomorphology in the Tian Shan range and its foreland basins about 15 years ago (exactly in 2002). The main aim of this paper was to explore the contributions of the interdisciplinary and new methods to the development of tectonic geomorphology study, by reviewing the main achievements in the tectonic geomorphology study conducted in the Tian Shan and its foreland basins during the past 20 years. These achievements include the history of uplift and exhumation during the Cenozoic times, the chronology and genesis of the late Cenozoic terrigenous sedimentary sequences in the foreland basins, the characteristics of the late Quaternary active tectonic deformation in the foreland and intermontane basins, the late Quaternary river geomorphology (geomorphic framework, chronology, and cause of formation), and erosion rates of the catchment basins. At the end of this paper, it was pointed out that, two aspects may need more attention in the future tectonic geomorphology study, i.e. the comparative study at different time scales and the better constraint of the formation age of river terrace.  相似文献   
16.
Alluvial fans can preserve historical records of sediment transport to middle and lower river systems or piedmont basins, which are considered to be sensitive recorders of climate change and tectonic activity. In this paper, the morphological characteristics, control factors and future development trend of alluvial fan are summarized and described. The main understanding is as follows: According to the gravity flow and traction flow process, fan can be divided into debris flow alluvial fan and fluvial fan. The former is formed under the action of debris gravity flow deposits, which is related to the occasional flood and burst flow in a short time. The latter is braided tributaries depositions which are gradually shallower and spread radially in the direction of fan toe under the traction water transport. The erodibility of underlying bedrock can affect the scale of downstream alluvial fan, which depends on the sediment production and store factors in the catchment. The easily eroded bedrock may produce more sediment, making the alluvial fan area larger. In the contrast, the erodibility of rocks in the source area can also affect the slope and hydrological characteristics of the valley so that more sediment is deposited in the upstream basin and the alluvial fan formed in the downstream is smaller. Tectonic activity is the pre-condition for the development of alluvial fans, which provides a space for alluvial fans depositions. Faulting in the piedmont can change the position and morphology of the ancient alluvial fan, and also cause deformation or distortion of the thick sedimentary sequence to record the regional tectonic activity. The quaternary alluvial fan sequence corresponds well to the climate change during the glacial-interglacial period. However, the influence of the flood events caused by extreme meteorological events on alluvial fan deposition should be focused on. The application of a series of new techniques and methods will help to carry out deep research on alluvial fan in the future, such as high-resolution observation technique, physical simulation experiment, and precise dating.  相似文献   
17.
Marine ecosystem services are the benefits which people obtain from the marine ecosystem, including provisioning ser-vices, regulating services, cultural services and supporting services. The human species, while buffered against environmental changes by culture and technology, is fundamentally dependent on the flow of ecosystem services. Marine ecosystem services be-come increasingly valuable as the terrestrial resources become scarce. The value of marine ecosystem services is the monetary flow of ecosystem services on specific temporal and spatial scales, which often changes due to the variation of the goods prices, yields and the status of marine exploitation. Sensitivity analysis is to study the relationship between the value of marine ecosystem services and the main factors which affect it. Uncertainty analysis based on varying prices, yields and status of marine exploitation was carried out. Through uncertainty analysis, a more credible value range instead of a fixed value of marine ecosystem services was obtained in this study. Moreover, sensitivity analysis of the marine ecosystem services value revealed the relative importance of different factors.  相似文献   
18.
I~IOXWith regard tO the 5,tudy on the planktonic copeal distributions in the Kuroshio waters ofthe East China Sea and its adjacent areas, a great ~nt of reSearch work has been made by somescholars at home (He and Yang, 1990; Meng et al., 1990; He, 1990; Liu et al., 1991; He etal., 1992; He et al., 1994). HOwever, the most of them were made in a single season, and it isabet about in the research of the various aspects of species comPOSition, abundance distributionand ecological characte…  相似文献   
19.
插件式GIS应用框架的设计与实现   总被引:3,自引:3,他引:0  
应用框架已经成为软件开发中一种非常实用的编程规范和设计架构.采用了C#插件式应用开发,并利用ArcGISEngine提供的一套完备的嵌入式GIS组件库和工具库,完成了插件式GIS应用框架的核心即框架宿主程序及各功能插件的设计与实现,以及插件式GIS应用框架平台的设计与实现;采用了动态插件加载配置的开发技术优势,通过可视...  相似文献   
20.
在优选、创新计量方法并建立省际面板矩阵的基础上,发挥面板模型兼具截面和时序分析的优长,利用EViews和ArcGIS软件,探讨影响经济增长的投入要素及其时空演变过程与耦合规律,给出驱动结构的中国经验模式.结果显示:(1)总体上,研究结论符合发展经济学关于经济动力系统由资本、劳动力及人力资本等组分构成的基本假说,投资占绝对主导地位(贡献率为82.5%),而人力资本弹性最大(0.772),预示了发展的前景方向;(2)时序上,经济驱动结构因受真实时间影响而呈现出阶段性特征,3个解释变量表现出4种组合形式及有序过程,印证了经济驱动力必将向资本、人力资本演进的一般规律;(3)在空间维度上,经济驱动类型涵盖了3大类7亚类,集聚为由9个板块构成的经济地图,突破了关于中国传统经济地带(类型)假说的认知,勾绘出地域主体功能深入演进及分异的新格局;(4)经济驱动结构不是简单的时空耦合,而是在契合一般时序规律的同时,在空间上表现出复杂性及自适应性.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号