全文获取类型
收费全文 | 2133篇 |
免费 | 129篇 |
国内免费 | 74篇 |
专业分类
测绘学 | 65篇 |
大气科学 | 93篇 |
地球物理 | 109篇 |
地质学 | 326篇 |
海洋学 | 125篇 |
天文学 | 2篇 |
综合类 | 160篇 |
自然地理 | 1456篇 |
出版年
2023年 | 15篇 |
2022年 | 74篇 |
2021年 | 78篇 |
2020年 | 89篇 |
2019年 | 91篇 |
2018年 | 77篇 |
2017年 | 94篇 |
2016年 | 98篇 |
2015年 | 86篇 |
2014年 | 86篇 |
2013年 | 137篇 |
2012年 | 111篇 |
2011年 | 100篇 |
2010年 | 82篇 |
2009年 | 85篇 |
2008年 | 90篇 |
2007年 | 96篇 |
2006年 | 84篇 |
2005年 | 80篇 |
2004年 | 87篇 |
2003年 | 80篇 |
2002年 | 77篇 |
2001年 | 68篇 |
2000年 | 69篇 |
1999年 | 46篇 |
1998年 | 57篇 |
1997年 | 46篇 |
1996年 | 27篇 |
1995年 | 23篇 |
1994年 | 25篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有2336条查询结果,搜索用时 62 毫秒
991.
Karl Harvey Schultz 《Climate Policy》2013,13(2):187-197
Climate mitigation credits have mobilized considerable resources for projects in developing countries, but similar funding to adapt to climate change has yet to emerge. The Copenhagen Accord targets up to US$50 billion per year in adaptation funding, but commitments to date have been trivial compared to what is needed. Although there are some studies and suggestions, it remains unclear where the money will come from and how it will be disbursed. Beyond this, many development experts believe that the main hurdle in climate adaptation is effective implementation. A framework, based on the polluter pays principle, is presented here regarding the mobilization of resources for adaptation in developing countries using market mechanisms. It is assumed that mitigation and adaptation are at least partly fungible in terms of long-term global societal costs and benefits, and that quantifying climate vulnerability reductions is possible at least sometimes. The scheme's benefits include significant, equitable and flexible capital flows, and improved and more efficient resource allocation and verification procedures that incentivize sustained project management. Challenges include overcoming political resistance to historical responsibility-based obligations and scepticism of market instruments, and, critically, quantifying climate impact costs and verifying investments for vulnerability reduction credits. 相似文献
992.
A carbon tax will form the central carbon pricing instrument in South Africa. The country, however, is also in the process of setting specific short-term emissions limits at a subnational level. Additional mitigation policy instruments will thus be required to meet these targets. Although it is possible to combine sector-level quantity targets with a broad-based carbon tax, this article finds that this greatly complicates mitigation policy design, increasing both the information requirements and the likelihood of unintended consequences. The trade-offs between economic efficiency (optimized by the use of a broad-based price set by a carbon tax) and environmental effectiveness (optimized by using instruments that ensure emissions reduction targets are met) are ever present. A clear understanding of subnational quantity targets and an appreciation of the characteristics of the instruments to achieve such targets (quantity-based instruments, QBIs), the framework through which the instruments are combined, and their possible interactions, are required for effective policy making. Three possible frameworks for combining instruments are identified in the article, and some specific implications of interaction between particular QBIs and a carbon tax are suggested.Policy relevanceThis article explores the interaction of a carbon tax with mitigation policy instruments to meet subnational emissions targets in the South African context (where both a carbon tax and subnational emissions targets are currently being developed). As international negotiations progress towards countries accepting binding GHG emissions restrictions, quantity-based mitigation policy approaches become more important. In countries where a broad-based emissions trading scheme (ETS) is not feasible in the short to medium term, combining a broad-based carbon tax with subnational emission targets provides an alternative mechanism for achieving the economic efficiency and emissions certainty benefits derived from an ETS. This paper considers the mechanisms through which such a combination of instruments can be achieved. Three possible frameworks for combining instruments are identified, some specific implications of interaction between particular QBIs and a carbon tax are suggested, and guidelines and concept tools are presented to assist policy-makers in designing efficient and coherent mitigation policy. 相似文献
993.
Sergey Paltsev Valerie Karplus Henry Chen Ioanna Karkatsouli John Reilly Henry Jacoby 《Climate Policy》2013,13(4):438-457
Passenger vehicles and power plants are major sources of GHG emissions. While economic analyses generally indicate that a broader market-based approach to GHG reduction would be less costly and more effective, regulatory approaches have found greater political success. We evaluate a global regulatory regime that replaces coal with natural gas in the electricity sector and imposes technically achievable improvements in the efficiency of personal transport vehicles. Its performance and cost are compared with other scenarios of future policy development including a no-policy world, achievements under the Copenhagen Accord, and a price-based policy to reduce global emissions by 50% by 2050. The assumed regulations applied globally achieve a global emissions reduction larger than projected for the Copenhagen agreements, but they do not prevent global GHG emissions from continuing to grow. The reduction in emissions is achieved at a high cost compared to a price-based policy. Diagnosis of the reasons for the limited yet high-cost performance reveals influences including the partial coverage of emitting sectors, small or no influence on the demand for emissions-intensive products, leakage when a reduction in fossil use in the covered sectors lowers the price to others, and the partial coverage of GHGs. If these regulatory measures are in part correcting other barriers or behavioural limitations consumers face, the benefits of overcoming these could offset at least some of the costs we estimate. The extent of any efficiency gap – the difference between engineering estimates of best practice and what actually happens – is highly contested, and offers an important avenue for future research.Policy relevanceWhile analysts concerned with national cost of GHG control have long advocated a GHG pricing policy, by a cap-and-trade system or a tax, covering all emissions sources and gases, governments more often pursue sectoral policies and technology standards. Given these political realities, the regulations represent a more politically practical approach to GHG reductions, focusing on solutions that are within reach and that do not depend on technological breakthroughs. If regulations are imposed as a way to get started on larger emissions reductions, and then combined with a broader GHG pricing policy pursuing a deep global cut in emissions, its requirements will eventually be overtaken by the pricing policy. The remaining higher costs of the regulatory targets become diluted so that in later years the difference in average cost per ton between a least-cost approach and one preceded by a period of regulatory action becomes very small. 相似文献
994.
《Climate Policy》2013,13(4):395-396
In 2007 the US Congress began considering a set of bills to implement a cap-and-trade system to limit the nation's greenhouse gas (GHG) emissions. The MIT Integrated Global System Model (IGSM)—and its economic component, the Emissions Prediction and Policy Analysis (EPPA) model—were used to assess these proposals. In the absence of policy, the EPPA model projects a doubling of US greenhouse gas emissions by 2050. Global emissions, driven by growth in developing countries, are projected to increase even more. Unrestrained, these emissions would lead to an increase in global CO2 concentration from a current level of 380 ppmv to about 550 ppmv by 2050 and to near 900 ppmv by 2100, resulting in a year 2100 global temperature 3.5–4.5°C above the current level. The more ambitious of the Congressional proposals could limit this increase to around 2°C, but only if other nations, including developing countries, also strongly controlled greenhouse gas emissions. With these more aggressive reductions, the economic cost measured in terms of changes in total welfare in the United States could range from 1.5% to almost 2% by the 2040–2050 period, with 2015 CO2-equivalent prices between $30 and $55, rising to between $120 and $210 by 2050. This level of cost would not seriously affect US GDP growth but would imply large-scale changes in its energy system. 相似文献
995.
地热水既是一种宝贵的自然资源,又具有典型的稀有性和难以再生性.在大力提倡低碳经济,节能减排,积极应对全球气候变暖的今天,既要利用地热水资源,又要重视地热水资源的可持续性.西安市的地热资源得天独厚,具有分布广,储量大,温度高,水量丰,水压大,水质优等显著特点.是大自然馈赠西安人民的十分珍贵的清洁能源.用得好,可为西安人们... 相似文献
996.
生态经济研究中的整体性视角 总被引:16,自引:15,他引:1
在简要介绍整体性视角含义的基础上,总结了生态经济学基本思想、主要问题、学科演替、新兴领域及未来研究主题中体现的整体性视角.分析了传统的水资源社会经济循环规律研究的劣势,在简单介绍了上升性(效率)、发展能力、恢复力和可持续性等指标及其含义后,开发了整体性视角下的水资源社会经济循环规律研究框架.最后系统地总结了整体性视角在... 相似文献
997.
甘肃省各地区相对资源承载力及可持续发展研究 总被引:1,自引:1,他引:0
根据相对资源承载力研究方法,以全国及甘肃省为参照区域,计算了2001—2008年甘肃省各地区相对自然资源承载力、相对经济资源承载力和综合资源承载力.结果表明:甘肃省的承载状态在2001—2002年呈超载状态,但自2003年以后处于富余状态;甘肃省超载最严重的是临夏,其次是陇南,然后依次是天水、甘南、定西、武威.省会兰州... 相似文献
998.
999.
1000.