全文获取类型
收费全文 | 6753篇 |
免费 | 396篇 |
国内免费 | 361篇 |
专业分类
测绘学 | 1292篇 |
大气科学 | 434篇 |
地球物理 | 376篇 |
地质学 | 964篇 |
海洋学 | 236篇 |
天文学 | 5篇 |
综合类 | 589篇 |
自然地理 | 3614篇 |
出版年
2024年 | 32篇 |
2023年 | 63篇 |
2022年 | 328篇 |
2021年 | 347篇 |
2020年 | 329篇 |
2019年 | 391篇 |
2018年 | 245篇 |
2017年 | 361篇 |
2016年 | 339篇 |
2015年 | 329篇 |
2014年 | 329篇 |
2013年 | 589篇 |
2012年 | 366篇 |
2011年 | 391篇 |
2010年 | 265篇 |
2009年 | 296篇 |
2008年 | 345篇 |
2007年 | 356篇 |
2006年 | 280篇 |
2005年 | 260篇 |
2004年 | 217篇 |
2003年 | 185篇 |
2002年 | 160篇 |
2001年 | 118篇 |
2000年 | 117篇 |
1999年 | 93篇 |
1998年 | 71篇 |
1997年 | 58篇 |
1996年 | 39篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 34篇 |
1992年 | 12篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1980年 | 1篇 |
排序方式: 共有7510条查询结果,搜索用时 31 毫秒
111.
E. O. Oladipo 《Natural Hazards》1993,8(3):235-261
Drought has been a recurring feature of the arid and semi-arid areas of Nigeria. This paper reviews the extent, severity, and consequences of drought and desertification in Nigeria with particular emphasis on the northern part of the country. The haphazard manner in which these environmental hazards have been tackled is examined and a systematic approach for the formulation of a national policy is proposed. It is recommended that a detailed formulation and implementation of the proposed policy plan is imperative to mitigate the often devastating impacts of drought and desertification in the very prone areas of Nigeria. Until such is done, some areas of Nigeria will always be vulnerable to the whims of an inevitable climatic hazard of drought and associated land degradation in the form of desertification. 相似文献
112.
私有车辆的迅猛增加是造成城市交通堵塞、环境污染加重、能源形势严峻的"祸首"。文章对我国城市道路公共交通不配套的优先发展政策、粗制滥造的公交规划设计和简陋的公交服务设施的现状进行了分析,提出应制定限定私权、扩大公权、鼓励人们使用高效率的交通工具等利于道路公交优先发展的政策以及编制科学的道路公交规划和道路公交设施配套建设时序的建议。 相似文献
113.
114.
Sustainable strategies such as green roofs have been implemented as stormwater management tools to mitigate disturbance of the hydrologic cycle resulting from urbanization. Green roofs, also referred to as vegetated roofs, can improve the urban landscape by reducing heat island effects, providing ecosystem services, and facilitating the retention and treatment of stormwater. Green roofs have received particular attention because they do not require acquisition and development of land and represent an application of biomimicry in design and construction. In this paper, we evaluate the effects of precipitation, evapotranspiration (ET), antecedent dry period (ADP), and seasonal variation on the run‐off quantity and distribution of an extensive, sedum covered, green roof on a commercial building in Syracuse, NY, USA. The green roof greatly facilitated retention of precipitation events without significant changes over the 4‐year study. The green roof retained on average 95.9 ± 3.6% (6.5 ± 5.6 mm) per rainfall event, with a range from 75% to 99.6% (33.2 to 3.3 mm). However, as precipitation quantity increased, the retention of water decreased. This high water retention capacity was the result of the combined effects of ET, stormwater storage (plants, growth media, and stormwater retention layer), and limited surface run‐off from the roof deck due to variation in the sloping of the green roof and the tapered insulation to the deck drains. The water retention capacity of the green roof did not change significantly between growing and nongrowing seasons. Slightly greater precipitation during the growing season coincided with increased ET. Average potential ET during the growing season was approximately 3 times greater than during the nongrowing season. The hydrologic performance of the green roof was not significantly impacted by an ADP greater than 2 days. 相似文献
115.
116.
Brian Hoyle 《GeoJournal》2001,53(2):183-197
The urban waterfront redevelopment diaspora, formerly confined to advanced countries, is starting to impact upon coastal settlements in former colonial territories. In diverse contexts ranging from postcolonialism and globalization to cultural revival and tourism development, developing countries are seeking to revive their historic port cities. This paper reports on the experience of Mombasa, Kenya, where waterfront redevelopment is a problematic element in the conservation of the historic urban core, and relates local issues to wider policies, relevant literature and experience elsewhere. 相似文献
117.
Fulong Wu 《Geoforum》2007,38(2):379-392
Rather than being abandoned along with the demise of the centrally planned economy, city planning as a profession is flourishing in China. New hybrid plans such as strategic development plans (concept plans) have been invented, and the planning procedure has become more flexible. Design competition and planning consultancy are widespread. This paper examines the development of new strategic development plans and design competition. It is argued that city planning has been re-orientated from a technical rationale, i.e. allocating state development projects to the city, to the imperative derived from market-oriented development, i.e. consolidating competitiveness during inter-city competition. The contradiction between market and planning is that while the status of city planning has been raised and its approach is becoming more strategic, the actual functionality of city planning has become more instrumental. 相似文献
118.
总结了吉林省“十一五”期间地质勘查、矿产资源领域取得的成就和存在的问题,研究了“十二五”地质矿产供需形势,提出了全省“十二五”矿产资源规划指导思想、规划目标、主要任务和保证措施. 相似文献
119.
本文回顾了50年代以来贵阳城市地质工作的概况,建议贵阳市新的城市地质工作的开展宜早不宜迟,提出了下一步开展贵阳市地质工作的新思路、新理论、新方法及主要预期成果。 相似文献
120.
这次会议是进入新世纪我局第一次工作会议,是一次总结过去,谋划未来的重要会议,开好这次会议对我局在新世纪实现新发展有着十分重要的意义.会议的主要内容是认真学习温家宝副总理的重要讲话精神,总结回顾"九五"地矿工作改革发展的基本情况,讨论修改我局"十五"改革发展纲要、"十五"前三年经济责任制考核办法和精神文明建设考核办法,安排部署2001年工作.下面我代表局党组作工作报告. 相似文献