全文获取类型
收费全文 | 782篇 |
免费 | 56篇 |
国内免费 | 84篇 |
专业分类
测绘学 | 292篇 |
大气科学 | 34篇 |
地球物理 | 32篇 |
地质学 | 209篇 |
海洋学 | 32篇 |
综合类 | 72篇 |
自然地理 | 251篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 23篇 |
2021年 | 58篇 |
2020年 | 45篇 |
2019年 | 41篇 |
2018年 | 25篇 |
2017年 | 63篇 |
2016年 | 54篇 |
2015年 | 54篇 |
2014年 | 88篇 |
2013年 | 47篇 |
2012年 | 43篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 40篇 |
2008年 | 24篇 |
2007年 | 28篇 |
2006年 | 20篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 14篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1996年 | 8篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有922条查询结果,搜索用时 296 毫秒
31.
32.
丹霞山世界地质公园蜂窝状洞穴特征及成因分析 总被引:1,自引:0,他引:1
蜂窝状洞穴以其精致的形貌和众说纷纭的成因吸引着科研人员和普通大众的兴趣。丹霞山世界地质公园蜂窝状洞穴主要产于晚白垩世丹霞组二段(锦石岩段)风成砂岩的崖壁上。本文以园区长老峰锦石岩寺和睡美人禄意堂两处蜂窝状洞穴为研究对象,通过野外实地调查,了解洞穴生长环境,定量统计分析其形态特征,并采集砂岩样品进行显微镜下观察,探讨洞穴形成与盐风化作用的关系。研究表明:蜂窝状洞穴所在的岩性主要为中—细粒长石岩屑砂岩,发育大型高角度交错层理,渗透性较好;洞穴开口均向下朝向锦江,有利于来自锦江河流的湿润水汽较长时间地保持在小洞内部;洞穴开口基本服从泰森多边形分布。因此,碎屑颗粒相对比较均匀的风成砂岩为丹霞山蜂窝状洞穴的发育提供了重要的岩石基础,锦江河流为盐风化提供了必要的湿润水汽和盐分。在初始发育阶段,从岩壁上最适合盐风化作用的若干个点开始形成细小的坑洼,逐步向同层位扩张。单个小洞穴由于盐风化作用,洞穴内部风化速率大于洞穴开口边缘,导致蜂窝状洞穴内部空间扩大较快。然后,蜂窝状洞穴的发育突破纹层的限制,逐步加大、变深而呈泰森多边形规则分布。最终,随着洞穴加深,在重力、风力的影响下,蜂窝状洞穴隔壁减薄失稳,洞穴消亡。 相似文献
33.
34.
本文在系统收集、整理阜新—义县盆地和医巫闾山地区的地质学、古生物学、地貌学和年代地质学资料的基础上,对辽宁锦州古生物化石和花岗岩国家地质公园的地质遗迹景观资源进行了系统总结.进一步的研究揭示了阜新—义县盆地和医巫闾山同属于医巫闾山变质核杂岩系统,阜新—义县盆地的发育、热河生物群兴起与医巫闾山的形成密切相关.这一结论为整合地质遗迹资源,整体规划建设锦州国家地质公园,打造地质旅游品牌提供了科学支撑,同时也为将来申报世界地质公园提供了基础地质学理论依据. 相似文献
35.
试论西部大开发与国防建设 总被引:3,自引:0,他引:3
根据我国国土形状呈三叶螺旋浆形的特征,指出了我国经济建设,国防建设和行政管理均应实行中心辐射型结构模式,述了我国经济建设与国防建设相结合的措施,将经济区以国防功能区分为核心经济区,纽带经济区,支撑经济区,有序建成这三类经济区,以适应形势发展的需要,扩大我国的战略防御向纵深发展。 相似文献
36.
David Newman 《GeoJournal》2001,53(3):235-246
Territory remains a central component of national identity in the contemporary political discourse between Israelis and Palestinians, both populations opposing power sharing within the same space, for fear of the other's domination. The contemporary political discourse relates to conflict management and the desire for separate spaces within which national identities are strengthened through territorial/national homogeneity. The Zionist national ideology of most Jewish citizens of Israel has strong territorial roots; hence they reject the post-Zionist post-nationalist ideology, regardless of whether they accept the possibility of change in Israel's territorial configuration or of a diminishment in the importance of the territorial dimension of national struggle. The rights of residency and citizenship even of second and third generation Jewish citizens remain linked with the territorial configurations of a State that will continue to be called Israel and have a national anthem expressing the aspirations of a single, exclusive, national group. But within territorial readjustment, issues of configuration may become less relevant and in it is this sense that post-Zionism focuses on a discourse of territorial pragmatism, rather than the disappearance of territory from the nationality-citizenship debate altogether. It is part of a process of re-territorialization and spatial reconfiguration of political and national identities, not a reversal of territorialization, if only because there is no such thing as a post-territorial notion of the organization of political power. The boundaries of national identity become more permeable, more inclusive, but they do not disappear altogether. 相似文献
37.
Ecological conflicts in Poland 总被引:1,自引:0,他引:1
Transformation of the political system, observed in Poland for 10 years in connection with economic restructuring and basic
socio-economic reforms to harmonise with European Union structures, is also evident in terms of environmental management.
Pollution has been reduced in many ways but the rise in living standards, linked with the rapid growth of cars and other forms
of consumption, has had a negative effect and environmental conditions have deteriorated in the central areas of large cities.
The growth of waste water and refuse is a considerable problem. More areas are now officially protected and the three levels
of local government established at the beginning of January 1999 (voivodeship, district and community) all have certain defined
environmental protection responsibilities which are cumulatively greater than before. Meanwhile there is a greater awareness
in society of environmental issues, although it does not yet lead to a high level of participation in protection work. However,
there are strongly-expressed opinions on the ecological acceptability of certain economic developments and conflicts are frequently
arising within communities and local governments and also between investors on the one side and ecological organisations and
environmental protection institutions on the other. Most controversial are new roads, power stations (like the Zarnowiec nuclear
project) and reservoirs like the one on the Dunajec river at Czorsztyn. Local communities frequently resist plans for waste
dumps, incinerating plants and other developments which are seen as injurious to health or the quality of life. The planned
reprivatisation of the state-owned forests is also criticised by foresters and ecological movements. Conflicts are likely
to grow as economic development accelerates but better information and greater public understanding of the need for sustainability
should make for consensus.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
38.
Yong-Woong Kim 《GeoJournal》2001,53(1):5-15
In the early stages of economic development in Korea, national territorial planning was used as a policy tool to guide spatial structure and to provide physical infrastructure for urban and industrial development. Such a top-down approach was inevitable because Korea maintained the centralized political and government system until the early 1990s. Circumstances, however, have changed recently since the 1990s with progress in democratization and localization. In addition, forces of globalization are making significant impacts on the parameters of national territorial planning. Reflecting these changes in both internal and external conditions, the Fourth National Territorial Plan (2000–2020) has adopted a different approach from the past three territorial plans. This paper reviews the socio-economic background that necessitated such changes in approaches to national territorial planning. A major thrust of the Fourth Plan, a focus on emergent or anticipated planning issues in Korea, is discussed. Finally, the paper examines the rationale for long-term strategic planning in the highly fluctuating situation facing Korean society in the new century. 相似文献
39.
着重讨论一种基于灰色GM(1,1)模型及国民收入决定函数模型而建立的新组合模型。该模型建模方法简单,组合性强,并且在各模型的拟合精度提高。该模型汲取了灰色GM(1,1)模型模拟国民收入变化趋势的优点和国民收入决定函数模型模拟国民收入波动的优点,使组合模型不但在趋势上符合国民收入的发展,而且也给出了在波动方面的比较一致的模拟。 相似文献
40.
Jungho Kim Laura Read Lynn E. Johnson David Gochis Rob Cifelli Heechan Han 《水文科学杂志》2020,65(10):1652-1666
ABSTRACT This study experiments with reservoir representation schemes to improve the ability to model active water management in the National Water Model (NWM). For this purpose, we developed an integrated water management model, NWM-ResSim, by coupling the NWM with HEC-ResSim, and two reservoir representation schemes are tested: simulation of reservoir operations and retrieval of scheduled operations. The experiments focus on a pilot reservoir domain in the Russian River basin – Lake Mendocino, California – and its contributing watershed. The evaluation results suggest that the NWM-ResSim improves the simulation performance of reservoir outflow from this managed reservoir over the NWM default level pool routing scheme. The degree of this improvement depends on the suitability of the operation guidance; the reservoir operations simulation scheme could have acceptable errors for the purposes of water resources management, but not for flood operations. Results of the retrieval scheme of scheduled operations demonstrated better performance for sub-daily flood operations. 相似文献