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   1715篇
  免费   225篇
  国内免费   267篇
测绘学   52篇
大气科学   16篇
地球物理   459篇
地质学   1003篇
海洋学   193篇
天文学   108篇
综合类   55篇
自然地理   321篇
  2024年   6篇
  2023年   16篇
  2022年   42篇
  2021年   43篇
  2020年   58篇
  2019年   59篇
  2018年   49篇
  2017年   50篇
  2016年   56篇
  2015年   72篇
  2014年   82篇
  2013年   159篇
  2012年   74篇
  2011年   81篇
  2010年   60篇
  2009年   131篇
  2008年   105篇
  2007年   106篇
  2006年   117篇
  2005年   122篇
  2004年   86篇
  2003年   64篇
  2002年   76篇
  2001年   54篇
  2000年   68篇
  1999年   45篇
  1998年   60篇
  1997年   41篇
  1996年   34篇
  1995年   29篇
  1994年   33篇
  1993年   20篇
  1992年   16篇
  1991年   18篇
  1990年   13篇
  1989年   19篇
  1988年   5篇
  1987年   6篇
  1986年   9篇
  1985年   8篇
  1984年   6篇
  1983年   3篇
  1982年   2篇
  1978年   1篇
  1973年   1篇
  1963年   2篇
排序方式: 共有2207条查询结果,搜索用时 15 毫秒
991.
大巴山前陆构造的抬升剥蚀与保存条件对其矿床和油气藏勘探潜力评价极为重要。应用磷灰石裂变径迹热年代学方法,通过研究大巴山前陆构造热演化史,恢复构造隆升过程,确定其中—新生代构造抬升剥蚀量,探讨大巴山前陆晚期构造隆升对矿床和油气资源的影响。结果表明:大巴山前陆构造在152Ma以前快速沉降,沉降速率平均高达150m·Ma-1,此后便长期处于隆升过程;136~152Ma时期为快速隆升阶段,隆升速率平均为56.3m·Ma-1,隆升量约为900m,是燕山运动导致秦岭造山期后的一次陆内挤压;70~136Ma时期为较缓慢隆升阶段,隆升速率平均为39.4m·Ma-1,隆升量约为2 600m,是秦岭造山晚期挤压的结果;0~70Ma时期的隆升速率为42.8m·Ma-1,持续时间较长,隆升幅度约3 000m,是喜马拉雅构造运动的结果。中生代构造隆升对本区低温热液矿体和油气保存极为不利;上新统以来(8Ma或5Ma),青藏高原快速隆升向东扩展的远程效应对大巴山前陆构造的影响不明显。  相似文献   
992.
应用环境同位素水文地球化学方法,结合区域沉积演化史,对关中盆地固市凹陷、咸阳-礼泉断阶和西安凹陷深部地下热水成因类型进行了探讨,并就残存沉积水存在的可能性,寻找氢氧同位素关系、硫氧同位素关系、碳氧同位素关系、N(87Sr)/N(86Sr)与古盐度的关系等环境同位素证据,rNa/rCl值、ρ(Cl-)/ρ(Br-)、rBr/rI值与ρ(Cl-)的关系等水文地球化学证据以及沉积演化史证据。结果表明:固市凹陷华阴地下热水的同位素、水文地球化学特征已基本符合沉积水的特征,推测其为混有古入渗水的残存沉积水;固市凹陷华阴之外的其他构造单元、咸阳—礼泉断阶和西安凹陷地下热水的同位素和水文地球化学特征部分接近沉积水的特征,部分介于古入渗水和沉积水之间;咸阳—礼泉断阶东部地下热水可能为古入渗水或残存沉积水与后期入渗水的混合;西安凹陷及咸阳—礼泉断阶西部地下热水属于现代入渗水与古入渗水的混合水。  相似文献   
993.
黑龙江省第一次地理国情普查已全面展开,其目的是全面掌握黑龙江地理国情现状,系统掌握全省自然、人文地理要素的现状和空间分布情况。黑龙江省是资源大省,除煤、木、粮、油、机外,旅游资源也十分丰富。作为连接中原与黑龙江地区的水陆大通道,黑龙江冰雪丝绸之路比西北丝绸之路早了1000多年,且一直繁荣了几千年,存有大量的历史遗迹,但近百年来却鲜为人知。充分利用基于现代测绘地理信息技术获得的地理国情数据和信息,恢复和开辟黑龙江冰雪丝绸之路旅游带,对弘扬黑龙江历史文化,宣传黑龙江意义重大,功在当代,利在后世。  相似文献   
994.
中国黄牛的起源及驯化一直是遗传学家和考古学家共同关注的热点问题.中国拥有丰富的牛种资源,仅中国地方黄牛品种就多达55个,境内及周边还分布着能与黄牛杂交的近缘野牛,这导致中国黄牛的遗传背景和形成历史非常复杂.利用DNA可以解析中国黄牛的起源和利用历史,通过Y染色体、线粒体和核基因组遗传标记已经从父系遗传、母系遗传和基因组...  相似文献   
995.
Geografisk Tidsskrift—Danish Journal of Geography 110(2):337–355, 2010

In northern Greenland, the Cape Grinnell beach ridge plain offers a 9,000year multi-proxy record for isostatic recovery, storm history, and the hydrological changes related to precipitation and slope evolution. The chronology of uplifted beach ridges is constrained by ten geological 14C ages on shell and sea mammal bones and eleven upper limiting ages from archaeological sites that span the last 3,000 years. Beach ridges formed under the influence of open water storms with renewed frequency and intensity ca. 3 ka and 1 ka ago. A lack of shell may reflect cooler sea surface temperatures. The presence and absence of ice can be inferred by push-features. Three intervals of heightened precipitation produced extensive fan deltas: (a) after 9 ka BP (b) prior to 4.5 ka BP and (c) during the Little Ice Age (AD 1350–1900). Active solifluction lobes and colluvia cover beach ridge deposits that are between 9 and 7 ka old.  相似文献   
996.
Leinbach, Thomas R. and Brunn, Stanley D. (eds.) Worlds of E-Commerce: Economic, Geographical, and Social Dimensions

Calthorpe, Peter and Fulton, William The Regional City: Planning for the End of Sprawl

Furuseth, Owen J. and Lapping, Mark B. (eds.) Contested Countryside: The Rural-Urban Fringe in North America

Sharp, Joanne P. Condensing the Cold War: Reader's Digest and American Identity

Gleeson, Brendan and Low, Nicholas (eds.) Governing for the Environment: Global Problems, Ethics, and Democracy

Isenberg, Andrew The Destruction of the Bison: An Environmental History, 1750 – 1920

Albert, Donald P., Gesler, Wilbert M. and Levergood, Barbara (eds.) Spatial Analysis, GIS, and Remote Sensing Applications in the Health Sciences

Wright, Dawn J. and Bartlett, Darius J. (eds.) Marine and Coastal Geographical Information Systems

Jankowski, Piotr and Nyerges, Timothy Geographic Information Systems for Group Decision Making: Towards a Participatory Geographic Information Science

Gerber, Rod and Chuan, Goh Kim (eds.) Fieldwork in Geography: Reflections, Perspectives, and Actions

Craige, Betty Jean Eugene Odom: Ecosystem Ecologist and Environmentalist

Lowenthal, David George Perkins Marsh: Prophet of Conservation

Schroeder, Richard Shady Practices: Agroforestry and Gender Practices in The Gambia

Lovell, W. George A Beauty that Hurts: Life and Death in Guatemala

Lichtenberger, Elisabeth Austria: Society and Regions  相似文献   
997.
At the end of the 19th century geography became a mandatory subject in primary and secondary schools in Norway. Geography was seen as a useful subject that contributed to the modernization of society, but also as a subject that strengthened the national ideology. A need for better education in geography arose and consequently some authors of geography textbooks wrote about teaching geography. In order to strengthen teachers’ education, geography was taught at university level, and to develop the subject it became necessary to relate it to other subjects, especially geology. The author shows that there are several similarities between the content of geography taught in Norwegian schools in the late 19th century and geography taught in schools today.  相似文献   
998.
This article explores the “unpopular” archived life of Charles P. Daly, thirty-five-year president (1864–1899) of the New York–based American Geographical Society. This one-time highly prominent judge and civic leader popularized geography among professionals and the public alike. Daly's popular geography, along with his subsequent containment within the archives, suggests explanations for his dismissal among geographical audiences of today. It is a useful and necessary exercise to trace the neglect of Daly within histories of geography and recapture him for today's audiences, not only because of his influence on post–Civil War American geography but also because his story can shed light on how “disciplinary remembering” functions in geography.  相似文献   
999.
Book Reviews     

Committee on Protection and Management of Pacific Northwest Anadromous Salmonids Upstream: Salmon and Society in the Pacific Northwest

Cook, Ian G; Doel, Marcus A. and Li, Rex (eds.) Fragmented Asia: Regional Integration and National Disintegration in Pacific Asia

Crush, Jonathan Power of Development

de Blij, H. J., and Muller, Peter O. Physical Geography of the Global Environment

Hayward, David J. International Trade and Regional Economies: The Impacts of European Integration on the United States

Kennedy, Michael The Global Positioning System and GIS: An Introduction

Lowe, Philip; Marsden, Terry and Whatmore, Sarah (eds) Regulating Agriculture

Marsden, Terry; Lowe, Philip and Whatmore, Sarah (eds) Labour and Locality: Uneven Development and the Rural Labour Process

Marsden, Terry; Lowe, Philip and Whatmore, Sarah (eds) Rural Restructuring: Global Processes and Their Responses

Whatmore, Sarah; Marsden, Terry and Lowe, Philip (eds) Gender and Rurality

Whatmore, Sarah; Marsden, Terry and Lowe, Philip (eds) Rural Enterprise: Shifting Perspectives on Small-Scale Production

Martopo, Sugeng and Mitchell, Bruce (eds) Bali: Balancing Environment, Economy and Culture

Ould-Mey, Mohameden Global Restructuring and Peripheral States: The Carrot and the Stick in Mauritania

Redclift, Michael and Benton, Ted (eds) Social Theory and the Global Environment

Thomas–Slayter, Barbara and Rocheleau, Dianne Gender, Environment, and Development in Kenya: A Grassroots Perspective

Wallach, Bret Losing Asia: Modernization and the Culture of Development

Wennberg, John E. Dartmouth Atlas of Health Care

Wilson, David and Huff, James O. (eds) Marginalized Places and Populations: A Structurationist Agenda  相似文献   
1000.
We examined the life history and secondary production of four Ephemeroptera species (Baetis alpinus Pictet, 1843–1845, Baetis rhodani Pictet, 1843–1845, Rhithrogena carpatoalpina Klonowska, Olechowska, Sartoriet & Weichselbaumer, 1987 and Habroleptoides confusa Sartori & Jacob, 1986) in a temperature stable cold spring stream at Prosiek valley (Cho?ské vrchy Mts., West Carpathians, Slovakia). We have found asynchronous bivoltine life cycle for the most abundant species B. alpinus with growth rate positively correlated to photoperiod length. R. carpatoalpina have shown unusual asynchronous univoltine life cycle and B. rhodani have shown uncommonly low abundance in mayfly community. Total secondary production of mayfly community was very low, reaching 1654.8 mg DW m?2 y?1. We suggest that the observed asynchrony in growth could be related to the lack of temperature control.  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