全文获取类型
收费全文 | 307篇 |
免费 | 26篇 |
国内免费 | 10篇 |
专业分类
安全科学 | 6篇 |
废物处理 | 2篇 |
环保管理 | 111篇 |
综合类 | 97篇 |
基础理论 | 64篇 |
污染及防治 | 9篇 |
评价与监测 | 7篇 |
社会与环境 | 41篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 10篇 |
2013年 | 12篇 |
2012年 | 21篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 32篇 |
2008年 | 21篇 |
2007年 | 24篇 |
2006年 | 18篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有343条查询结果,搜索用时 31 毫秒
321.
Models of carbon storage in softwood and hardwood trees and forest soils and its emission from timber products and waste are developed and integrated with data on storage benefits to yield estimates of the value of the net carbon flux generated by afforestation. The long-term nature of the processes under consideration and the impact of varying the discount rate are explicitly incorporated within the model. A geographical information system (GIS) is used to apply carbon sequestration models to data on tree growth and soil type distribution for a large study area (the entire country of Wales). The major findings are: (1) all three elements under analysis (carbon sequestration in livewood, release from different products and waste, and storage or emission from soils) play a vital role in determining overall carbon flux; (2) woodland management has a substantial impact upon carbon storage in livewood however the choice of discount rate exerts the largest overall influence upon estimated carbon flux values; (3) timber growth rates (yield class) also have a major impact upon values; (4) tree species does affect storage values, however this is less important than the other factors listed above; (5) non-peat soils generally sequester relatively low levels of carbon. Planting upon peat soils can result in very substantial emissions of carbon which exceed the level of storage in livewood.The GIS is used to produce valuation maps which can be readily incorporated within cost-benefit analyses regarding optimal locations for conversion of land into forestry. 相似文献
322.
ESTIMATING THE LOCAL COST OF PROTECTING KOSHI TAPPU WILDLIFE RESERVE, NEPAL: A CONTINGENT VALUATION APPROACH 总被引:1,自引:0,他引:1
RAM K. SHRESTHA JANAKI R.R. ALAVALAPATI ANDREW F. SEIDL KARL E. WEBER TRI B. SUSELO 《Environment, Development and Sustainability》2007,9(4):413-426
We estimate the compensation required by the local communities to forego access to the natural resources within the Koshi
Tappu Wildlife Reserve (KTWR), Nepal using the contingent valuation method (CVM). In addition to contributing a CVM application
from a seldom studied location to the literature, this case illustrates the sensitivity of WTA estimates to the analytical
technique adopted. We analyze households’ willingness to accept (WTA) compensation using Tobit and double-hurdle regression
models that account for the censored distribution of WTA and nested yes/no decision implicit in the WTA responses. The average
WTA of a household residing in the vicinity of KTWR is estimated to be US $238, which amounts to nearly $ 1.64 million for
the neighboring region. The results provide a basis to address local people’s concerns in the process of sustainable management
of natural resources and wetland ecosystems in KTWR, Nepal. 相似文献
323.
薛达元 《生态与农村环境学报》1999,(2)
在分析生物多样性经济价值类型的基础上探讨了自然保护区生物多样性经济价值的类型和内涵,并将其分为直接实物价值、直接非实物服务价值、生态功能间接价值和非使用类价值(包括存在价值、遗产价值和选择价值),进而提出评估这些价值的方法。 相似文献
324.
Mountains are important global reservoirs of water resources. However they are highly vulnerable to climate change as limited alterations in temperature and precipitation may cause harmful effects to water systems. Southern Europe and especially Greece are expected to undergo a drought trend over the next decades, resulting in less recharge for the aquifers and water services reduction. Thus, climate change may distort both natural and socioeconomic characteristics of freshwater ecosystem services deteriorating the general social welfare related to them. This paper examines the economic impacts of climate change on river uses of the Aoos basin in Greece. In this regard, a choice experiment is conducted to estimate the value changes in different ecological and economic services in a mountain community. The econometric simulations using conditional logit, random parameters logit and latent class models reveal that despite existing preference heterogeneity, respondents on average derive positive and significant welfare effects from climate change adaptation measures. The findings of the survey may assist in adaptation planning for the Aoos River basin, with possible extensions to other river systems enduring similar climate change indications. 相似文献
325.
Abstract: Recognition of the need to include economic criteria in the conservation policy decision-making process has encouraged the use of economic-valuation techniques. Nevertheless, whether it is possible to accurately assign economic values to biodiversity and if so what these values really represent is being debated. We reviewed 60 recent papers on economic valuation of biodiversity and carried out a meta-analysis of these studies to determine what factors affect willingness to pay for biodiversity conservation. We analyzed the internal variables of the contingent-valuation method (measure of benefits, vehicle of payment, elicitation format, or timing of payment) and anthropomorphic, anthropocentric and scientific factors. Funding allocation mostly favored the conservation of species with anthropomorphic and anthropocentric characteristics instead of considering scientific factors. We recommend researchers and policy makers contemplate economic valuations of biodiversity carefully, considering the inherent biases of the contingent-valuation method and the anthropomorphic and anthropocentric factors resulting from the public's attitude toward species. Because of the increasing trend of including economic considerations in conservation practices, we suggest that in the future interdisciplinary teams of ecologists, economists, and social scientists collaborate and conduct comparative analyses, such as we have done here. Use of the contingent-valuation method in biodiversity conservation policies can provide useful information about alternative conservation strategies if questionnaires are carefully constructed, respondents are sufficiently informed, and the underlying factors that influence willingness to pay are identified. 相似文献
326.
选择试验模型法在耕地资源保护中的应用——以浙江省温岭市为例 总被引:4,自引:0,他引:4
选择试验模型法是目前国际上用于评估具有公共物品特性的自然资源和环境物品经济价值的一种相对较新的方法。论文以浙江省温岭市耕地资源保护为例,探讨选择试验模型法在耕地资源保护经济价值评估实践的可行性。在专家咨询和小组讨论的基础上,确定耕地景观、田间设施、土壤肥力和耕地保护费为温岭市耕地资源保护的4个属性。在对温岭市246名居民进行随机抽样调查的基础上,分析了温岭市耕地资源保护不同属性的价值以及耕地资源保护不同替代方案的相对价值。结果表明,对于温岭市全体居民来说,今后耕地资源保护的实施应该重点改善田间设施和提高土壤肥力,而耕地景观的改善也同样可以增加温岭市居民的福利水平。 相似文献
327.
Energy analysis of nonmarket values of the Mississippi Delta 总被引:1,自引:0,他引:1
An energy analysis was used to estimate nonmarket values under various land cover scenarios in the Mississippi Delta. Land
loss since 1900 has led to a decline in nonmarket values from $3.1 billion/year in 1900 to $2.5 billion in 1990, resulting
in a total loss of $29.4 billion. This loss is concentrated in the Barataria-Terrebonne basins, where nonmarket value has
dropped from $1.6 billion/year in 1956 to $1.3 billion/year in 1988. Although values are projected to increase in the Atchafalaya
basin (from $723 million/year in 1988 to $756 million/year in 2058), total nonmarket value for the Louisiana coast is projected
to decrease to $2.1 billion/year under currently approved levels of restoration. 相似文献
328.
Thomas A. More James R. Averill Thomas H. Stevens 《Journal of environmental management》1996,48(4):397-409
Several categories of non-market value have been identified for forests and other natural environments: use value, option value, altruism, bequest value, existence value and intrinsic value. In this paper, we view these values from a psychological perspective. Non-market values arise because natural resources play important roles in furthering human goals. This goal perspective contrasts with intrinsic value—the idea that natural objects have value as ends in themselves regardless of their relationship to man. Because of the lack of precise definitions, elements of intrinsic value are often mixed with existence value, creating confusion in the literature. These resource values need to be examined on a logical as well as an empirical basis. We argue that careful scrutiny reveals problems with both existence value and intrinsic value so that it is important to question their role in policy formation and analysis. 相似文献
329.
Abstract: Two CVM surveys were administered to 211 urban households and 188 rural farmer‐irrigators in the Comarapa watershed in Bolivia, South America, to estimate stakeholder willingness to pay (WTP) for a proposed upper watershed restoration program. Mean monthly household WTP to improve drinking water was $1.95 (65% of current charges), while mean annual WTP among farmer‐irrigators to improve irrigation water was $17 per hectare (34% of current costs). Aggregated to the entire population of households and farmer‐irrigators total WTP is $77,400 per year, which is 77% of the minimum cost to implement a watershed restoration program. 相似文献
330.