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   451篇
  免费   43篇
  国内免费   61篇
测绘学   28篇
大气科学   52篇
地球物理   58篇
地质学   208篇
海洋学   49篇
天文学   2篇
综合类   31篇
自然地理   127篇
  2023年   3篇
  2022年   7篇
  2021年   2篇
  2020年   5篇
  2019年   4篇
  2018年   6篇
  2017年   9篇
  2016年   9篇
  2015年   14篇
  2014年   15篇
  2013年   15篇
  2012年   20篇
  2011年   19篇
  2010年   20篇
  2009年   23篇
  2008年   28篇
  2007年   23篇
  2006年   33篇
  2005年   22篇
  2004年   27篇
  2003年   24篇
  2002年   24篇
  2001年   28篇
  2000年   19篇
  1999年   24篇
  1998年   18篇
  1997年   16篇
  1996年   8篇
  1995年   20篇
  1994年   18篇
  1993年   15篇
  1992年   11篇
  1991年   6篇
  1990年   8篇
  1989年   4篇
  1987年   6篇
  1984年   1篇
  1983年   1篇
排序方式: 共有555条查询结果,搜索用时 21 毫秒
91.
淀山湖水环境质量评价及污染防治研究   总被引:20,自引:6,他引:14  
阮仁良  王云 《湖泊科学》1993,5(2):153-158
从淀山湖环境研究入手。全面考察湖区点源和非点源污染物的分布及其对湖泊的输入,分析湖内污染物的动态变化,采用模糊矩阵复合运算方法对水质进行综合评价,并建立水质污染预测模型,进行水质污染趋势分析。最后,提出了淀山湖水污染防治的对策和措施。  相似文献   
92.
Brazil is the first major developing country to pledge for absolute reductions in greenhouse gas emissions. This article explores the extent to which fiscal policies could contribute to this reduction and to greening the Brazilian economy. It was found that the use of green fiscal policies is at an early stage in Brazil, but a growing number of measures have been adopted in recent years led by subnational-level policies. An econometric analysis of 24 Brazilian manufacturing sectors for the years 2001–2008 shows that some fiscal instruments, such as low-cost (subsidized) finance for innovation and fiscal incentives for sustainable practices, have been effective in inducing green innovation. However, less than 14% of more than 100 thousand companies included in the study have adopted greener technologies. Even though Brazilian green fiscal policies have been rather uncoordinated and ad hoc, their significant impact on the uptake of green technologies indicates these can play an important role in a transition to a green economy.

POLICY RELEVANCE

Faced with the challenge of reducing its greenhouse gas emissions in absolute terms, Brazil now needs to put in place policies to help deliver the country’s pledge. This article analyses which fiscal policies should be adopted and how these policies could form part of a low carbon policy framework in the country. Among our policy-relevant findings is that subnational green fiscal policies are relatively less complex to introduce and encourage uptake of green technologies. Thus, they could be an entry point to a wider green fiscal policy strategy. We also found that fiscal incentives for green innovation projects can present more than proportional impact on the uptake of green technologies owing to positive feedbacks, increasing returns to scale and spill-overs. These are attractive features of green innovations to developing countries in addition to environmental benefits, as they favour the accumulation of indigenous technological capabilities that are critical for long-term technological and economic development. These lessons learned from green fiscal policies in Brazil are applicable to other developing countries.  相似文献   

93.
The effects of circular economy on biodiversity are poorly understood. This study provides observations on approaches for assessing circular economy and illustrates, with a Finnish case study, the potential of circular economy to mitigate pressures on biodiversity. The case study focuses on the construction and real estate sectors, as well as the forest industry. The findings imply that circular economy actions that reduce the extraction of virgin raw materials and relieve land use pressures are effective. Improving material efficiency, increasing the cascading use of wood, and optimizing the use and reuse of materials and products, as well as extending the lifetime of buildings and optimizing space use, have good potential for mitigating pressures on biodiversity in Finland. However, as forest utilization has a major impact on Finnish biodiversity, certain actions that possibly increase the use of forest resources (e.g., replacing fossil-based, concrete, or steel materials with wood-based solutions) may impair biodiversity if biodiversity-enhancing forest management practices are not utilized. Assessing the biodiversity impacts of circular economy is challenging, and the need for further research and the development of indicators and assessment methods is clear.  相似文献   
94.
Groundwater of Egypt: “an environmental overview”   总被引:1,自引:0,他引:1  
Although Egypt has the great Nile River, which is the main supply of water, Egypt’s water is limited to 55.5 billion m3 per annum. Owing to the rapid growth of the population and the increasing consumption of water in agriculture, industry, domestic use, etc., it is expected that Egypt will rely to some extent on groundwater to develop the new projects such as Tushka in Upper Egypt and East Oweinat. Issues related to groundwater in Egypt are identified with the common geological features associated with formation of the aquifers and demonstrating the location of the main resources of groundwater, followed by the main objective of this paper, which is addressing the environmental issues related to groundwater in Egypt. Several studies have been reviewed and personal communication made with the authorities to introduce this work and provide an overview of the groundwater quality problems in Egypt with examples from different parts of the country.  相似文献   
95.
基础设施与人类生存环境之关系研究   总被引:18,自引:4,他引:18  
人类在其发展中倾注了大量的人力、物车、财力建设基础设施,希图构筑理想生存环境。但基础设施为人类带来了什么?对人类的发展产生了何种影响?如何认识基础设施在人类生存环境演化中的作用?本文从积极角度阐述了基础设施与人类生存环境之关系,透视了基础设施在活动空间扩展、资源共享和生存环境优化方面的作用与意义。  相似文献   
96.
西辽河平原东部沼泽发育与中全新世早期以来古环境演变   总被引:11,自引:9,他引:11  
根据典型沼泽剖面14 C测年及其树木年轮校正、孢粉分析、粘土矿物X 衍射分析、泥炭植物残体鉴定和沉积物的化学元素聚集与迁移资料 ,研究了中全新世以来西辽河平原东部沼泽发育过程与古环境演变及其二者的关系。结果表明 ,位于生态环境过渡带、脆弱带的沼泽发生、发育对环境变化尤为敏感。中全新世早期以来 ,环境变化频繁 ,由此导致沼泽发育出现多次形成、发育、退化、消亡、再生循环变化。沼泽发育与古环境演变可划分为 6个时期 :中全新世早期沼泽孕育与萌芽发育期 ;中全新世中期沼泽旺盛发育期 ;中全新世中晚期沼泽间断发育期 ;中全新世晚期沼泽退化发育期 ;晚全新世早期沼泽复苏期 ;晚全新世晚期沼泽消亡期。距今 5 80 0年左右为本区全新世沼泽最早发育期。沼泽发育也遵循富营养沼泽长期发展的模式  相似文献   
97.
南京市矿山尾矿利用现状及加快尾矿利用的对策   总被引:1,自引:1,他引:1  
随着矿业开发规模的加大,大量尾矿的露天堆存,不仅造成了资源的浪费,对环境和人类的危害也日益严重。尾矿利用是充分利用资源和消除尾矿对环境的危害的重要途径,对此 有充分认识,南京尾矿库存总量约2500万t,每年新增尾矿量50万t,尾矿的利用程度和范围还远远不够,就加快南京市尾矿利用步伐提出了对策。  相似文献   
98.
河流谷坡工程地质环境评价是水电工程的前期工作,直接关系到工程的选址、建设规模和水利资源的充分利用。 本文利用现有航空遥感资料,对四川雅砻江中游的鲜水河口至官地河段,约510 km河流谷坡的物理地质现象进行了判读,运用数理统计和工程地质综合分析的方法,对该河流区段的工程地质环境进行了评价,并对其发展趋势进行了预测,为该地区丰富的水利资源的开发利用提供了决策依据;对于区域工程地质环境评价,尤其是基础工作薄弱、自然条件恶劣、地面工作难以开展的高山峡谷地区的河流谷坡工程地质环境评价和发展趋势预测提出了新的方法。  相似文献   
99.
人口、资源、灾害与环境是困扰当代人类的几个重大问题.人口的增长,要求有更多的资源,而资源开发、利用的合理与否,又势必对环境产生有利或有害的影响;环境的改善或恶化,反过来又必然影响到资源的增减.因此,如何处理好它们之间的关系,使资源得到合理的开发和利用,同时又保护或改善环境,形成资源开发利用与环境保护改善之间的良性循环,应当是人类共同奋斗的一个目标. 本文依据一些实际资料论述了上述问题以及地球物理学在解决这些问题中所应起的作用.  相似文献   
100.
在野外实地考察和大量文献资料分析研究的基础上,运用人地相关的思想,对河洛地区这个独特的地理单元的自然条件和人文要素如政治、经济、文化和军事之间的相互关系进行了探讨。  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