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   1047篇
  免费   138篇
  国内免费   129篇
测绘学   38篇
大气科学   52篇
地球物理   158篇
地质学   740篇
海洋学   43篇
天文学   2篇
综合类   92篇
自然地理   189篇
  2024年   8篇
  2023年   16篇
  2022年   28篇
  2021年   33篇
  2020年   24篇
  2019年   31篇
  2018年   20篇
  2017年   27篇
  2016年   31篇
  2015年   25篇
  2014年   63篇
  2013年   56篇
  2012年   48篇
  2011年   45篇
  2010年   50篇
  2009年   96篇
  2008年   79篇
  2007年   85篇
  2006年   82篇
  2005年   72篇
  2004年   61篇
  2003年   53篇
  2002年   41篇
  2001年   48篇
  2000年   41篇
  1999年   42篇
  1998年   17篇
  1997年   12篇
  1996年   12篇
  1995年   16篇
  1994年   7篇
  1993年   11篇
  1992年   5篇
  1991年   7篇
  1990年   3篇
  1989年   3篇
  1988年   5篇
  1987年   4篇
  1986年   1篇
  1985年   1篇
  1984年   4篇
  1982年   1篇
排序方式: 共有1314条查询结果,搜索用时 15 毫秒
41.
蔡敏  黄艳  朱宵峰  沈锦栋  金培  吴惠娟 《气象》2009,35(7):95-100
地质灾害成因复杂,其中以气象因素、地质地貌因素引发的地质灾害最为常见.以金华地区为例,通过对金华市地质地貌条件及其对地质灾害点的调查,将全区划分为4个地质灾害隐患风险等级的网格区域.在此基础上利用金华中尺度气象资料,采用BP神经网络模型,建立地质灾害细网格预报模型,对该模型进行模拟和预报试验.结果表明,合理的隐患风险等级分区能使预报模型更符合科学规律,而采用分布较细的中尺度资料作为预报因子能进一步提高预报精度.模型的预报结果达到一定的可信度,为防灾减灾工作提供了科学依据.  相似文献   
42.
Globalization would appear to be a subject that easily could be addressed in geography classrooms, yet this is not always the case. In terms of pedagogy, many geographers are concerned whether the field has been adequately engaging various components of this topic (e.g., connectivity, core-periphery), especially in terms of making the subject matter relevant to students. This article presents the results of a recent course project situated at the intersection of city-level resilience to hazards and connectivity with the global economy, utilizing SWOT analysis. The student projects demonstrated that this comparatively simple analytical tool was a useful means for exploring and integrating key topics in globalization and urban-economic geography, while also facilitating a problem-based learning environment.  相似文献   
43.
A number of different lahars have been recognized from a systematic survey of a mapping project. The high setting temporamre feature of the deposits indicates a relationship between the lahar and the Millennium eruption event of Tianchi Volcano. The lahars caused a dramatic disaster. Recognize of the huge avalanche scars and deposits around Tianchi Volcano imply another highly destructive hazard. Three types of different texture of the avalanche deposits have been recognized. There was often magma mixing processes during the Millennium eruption of Tianchi Volcano, indicating a mixing and co-eruption regime of the eruption.  相似文献   
44.
临沂市地处郯庐大断裂带中段,地质构造运动强烈,灾害易发区占全市国土面积的52.5%,地质灾害问题已成为制约全市经济社会可持续发展和影响社会稳定的重要因素之一。近年来临沂市坚持以人为本、预防为主、防治结合、综合治理,连续6年保持地质灾害“零伤亡”,被国土资源部表彰为“全国地质灾害防治工作先进单位”。  相似文献   
45.
Deliberately or indirectly, most of the terrestrial surface has been affected by the actions of human beings. For that reason, geomorphologists have needed to broaden their scope of inquiry to encompass the human-landscape system. Four themes related to human actions emerge in recent research in geomorphology: (1) human impacts on geomorphic systems, (2) human-landscape feedbacks, (3) geomorphic hazards and (4) stratigraphic markers of anthropogenic origin. The importance of humans as geomorphic agents challenges geomorphologists and their collaborators to move beyond unidirectional cause-and-effect (human impacts), and develop new research frameworks that better integrate the ongoing interactions between people and landscapes.  相似文献   
46.
马宗科 《西北地质》2006,39(4):105-109
宝鸡市地质环境复杂,加之近年来人类不合理工程、经济活动的加剧,地质灾害时有发生,已成为陕西省地质灾害多发、高发区之一。目前全市有各类地质灾害点784处,已引起当地政府和社会各界的普遍关注。笔者详细分析了宝鸡市地质灾害现状、地质灾害分布规律、地质灾害形成条件与影响因素以及目前地质灾害防治中存在的各类问题,并在此基础上,对宝鸡市今后地质灾害的防治工作提出了几点建议,为宝鸡市地质灾害的正确防治具有一定的指导意义。  相似文献   
47.
针对单一角度采集的图像检测样本存在的高误检率、错误率等问题,文章提出一种特殊的打光方案及相机安装方案,实现对胶囊360°全方位的缺陷检测,利用彩色相机填补了胶囊异色点、黑点,印字、小切口以及混批等缺陷不能检测的空白。在胶囊有序传送的前提下,提出“隔组间排”原理,以更多时间和空间使电磁铁伸缩杆完成踢废动作,平衡“传送效率”“检测效率”“踢废效率”三者之间的矛盾,提高设备的处理能力,实现胶囊的缺陷检测。  相似文献   
48.
Snow avalanche hazards in mountainous areas of developing countries have received scant attention in the scientific literature. The purpose of this paper is to describe this hazard and mitigative measures in Kaghan Valley, Pakistan Himalaya, and to review alternatives for future reduction of this hazard. Snow avalanches have long posed a hazard and risk to indigenous populations of the Himalaya and Trans-Himalaya mountains. Land use intensification due to population growth, new transportation routes, military activity and tourism is raising levels of risk. The history of land use in the study area is such that investigations of avalanche hazard must rely on different theoretical bases and data than in most industrialised countries. Despite the intensive use of valley-bottom land which is affected by avalanches, a number of simple measures are currently employed by the indigenous population to mitigate the hazard. Out-migration during the winter months is the most important one. During the intensive use period of summer avalanche-transported snow provides numerous resources for the population. In Kaghan the avalanche hazard is increasing primarily as a result of poorly located new buildings and other construction projects. The large scale of avalanche activity there rules out any significant improvement or protection of the currently difficult winter access. Instead, future mitigation of the hazard should focus on protecting the small number of winter inhabitants and minimising property damage.  相似文献   
49.
基于OFDM核心技术的WiMAX(全球微波接入互操作性)具有4G技术的特点。与3G和WiFi无线通讯技术相比具有明显的高速率、大容量数据传输优势。本文就基于WiMAX的地质灾害应急通讯系统的几种技术方案加以详细论述,说明WiMAX在地质灾害应急指挥中具有广阔前景。  相似文献   
50.
Abstract

To investigate geological mining hazards using digital techniques such as high-resolution remote sensing, a semi-automatically geological mining hazards extraction method is proposed based on the case of the Shijiaying coal mine, located in Fangshan District, Beijing, China. In the method, the vegetation is first removed using the normalized difference vegetation index (NDVI) on the GeoEye-1 data. Then, geological mining hazards interpretation features are determined after color enhancement using principal component analysis (PCA) transformation. Bitmaps mainly covered by geological mining hazards are isolated by masking operation in the environment for visualizing images software. Next, each bitmap is classified into a two-valued imagery using support vector machine algorithm. In the two-valued imagery, 1 denotes the geological mining hazards, while 0 denotes none. Afterwards, the two-valued imagery is converted into a vector graph by corresponding functions in the ArcGIS software and no geological mining hazards regions in the vector graph are deleted manually. Finally, the correlation between factors (such as mining activity, lithology, geological structure, and slope) and geological mining hazards is analyzed using a logistic regression and a hazardous-area forecasting model is built. The results of field verification show that the accuracy of the geological mining hazards extraction method is 98.1% and the results of the hazardous-area forecasting indicate that the logistic regression is an effective model in assessing geological hazard risks and that mining activity is the main contributing factor to the hazards, while geological structure, slope, lithology, roughness of the surface, and aspect are the secondary.  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