全文获取类型
收费全文 | 65篇 |
免费 | 7篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 13篇 |
废物处理 | 1篇 |
环保管理 | 6篇 |
综合类 | 24篇 |
基础理论 | 8篇 |
污染及防治 | 11篇 |
评价与监测 | 5篇 |
社会与环境 | 9篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 4篇 |
排序方式: 共有77条查询结果,搜索用时 46 毫秒
11.
A universal approach to estimate biomass and carbon stock in tropical forests using generic allometric models 总被引:1,自引:0,他引:1
Vieilledent G Vaudry R Andriamanohisoa SF Rakotonarivo OS Randrianasolo HZ Razafindrabe HN Rakotoarivony CB Ebeling J Rasamoelina M 《Ecological applications》2012,22(2):572-583
Allometric equations allow aboveground tree biomass and carbon stock to be estimated from tree size. The allometric scaling theory suggests the existence of a universal power-law relationship between tree biomass and tree diameter with a fixed scaling exponent close to 8/3. In addition, generic empirical models, like Chave's or Brown's models, have been proposed for tropical forests in America and Asia. These generic models have been used to estimate forest biomass and carbon worldwide. However, tree allometry depends on environmental and genetic factors that vary from region to region. Consequently, theoretical models that include too few ecological explicative variables or empirical generic models that have been calibrated at particular sites are unlikely to yield accurate tree biomass estimates at other sites. In this study, we based our analysis on a destructive sample of 481 trees in Madagascar spiny dry and moist forests characterized by a high rate of endemism (> 95%). We show that, among the available generic allometric models, Chave's model including diameter, height, and wood specific gravity as explicative variables for a particular forest type (dry, moist, or wet tropical forest) was the only one that gave accurate tree biomass estimates for Madagascar (R2 > 83%, bias < 6%), with estimates comparable to those obtained with regional allometric models. When biomass allometric models are not available for a given forest site, this result shows that a simple height-diameter allometry is needed to accurately estimate biomass and carbon stock from plot inventories. 相似文献
12.
化肥零增长行动对农业污染的减量贡献分析——基于GM(1,1)模型及脱钩理论 总被引:3,自引:0,他引:3
2015年2月,农业部制定《到2020年化肥使用量零增长行动方案》。为深入分析该政策在农业面源污染减量、农业产地环境改善及农业绿色发展中发挥的作用,借助灰色GM(1,1)模型及脱钩理论,模拟若无该行动实施时我国的化肥施用情况,探讨该行动对我国农业面源污染的减量贡献。研究发现:(1)我国化肥实际施用较模拟值减量明显;氮肥、磷肥及复合肥的实际施用量较模拟值均有不同程度的减少,其中复合肥的增长幅度虽有所放缓,但仍呈增长态势。(2)化肥零增长行动对我国农业面源污染防治工作意义重大;行动实施3年(2015~2017年)内的化肥污染排放减量占2014年总排放量的五分之一以上。(3)化肥零增长行动实施后,农业生产对化肥投入的依赖大大减弱;近几年农业生产与施用化肥导致的面源污染间逐渐表现为强脱钩状态,两者呈反向变化。(4)从施肥结构看,氮肥、磷肥均由弱脱钩转变为强脱钩状态,并保持基本稳定;复合肥脱钩指数虽有所下降,但仍未改变弱脱钩状态。(5)在空间层面上,各省区的农业生产与化肥面源污染之间的脱钩状态总体向好,东北、西南以及东南部区域农业生产对化肥投入的依赖性逐渐减弱,山东、江苏等5个农业大省已实现完全脱钩。最后从提高化肥利用效率,调整施肥结构,优化农业产业统计体系等角度提出建议,为政府制定相关政策提供参考。 相似文献
13.
天气专家们正在寻求导致全球变暖的“温室效应”起因及其影响。现在,已是认真讨论这种全球变暖将如何影响我们未来生活的时候了。 1987年,南极冰域一座两倍于罗德岛的巨大冰山崩裂溅入大海。 1988年8月,在非洲西海岸外海刚刚孕育形成的“吉尔伯特”号飓风,时速已超过200英里。它的高峰,是迄今西半球所遭遇最具破坏力的一次飓风。 1988年夏季,袭击美国许多城市的热浪打破了有史以来的高温纪录。该年8月1日,以“火炉”著称的弗尼斯克里克和加利福尼亚名符其实地创下了新的纪录,最高气温达46.7℃(或116°F)。 相似文献
14.
Persistent organochlorine pesticides (OCPs) such as DDT and its metabolites (DDDs and DDEs). chlordane, hexachlorobenzene (HCB), heptachlor and endosulfan were determined in drinking-, ground-, surface- and marine waters from the Eastern Cape Province of South Africa. Percentage recoveries of the OCPs from spiked river water ranged from 71.03 +/- 8.15% (dieldrin) to 101.25 +/- 2.17% (alpha-BHC). The levels of OCPs ranged from 5.5 ng/L (2,4-DDD) to 160 ng/L (HCB) in the water samples. Some endocrine disrupting OCPs such as DDT, DDE, heptachlor, endosulfan and chlordane were detected. 相似文献
15.
The role of algae (Isochrysis galbana) enrichment on the bioaccumulation of benzo[a]pyrene and its effects on the blue mussel Mytilus edulis 总被引:2,自引:0,他引:2
Okay OS Donkin P Peters LD Livingstone DR 《Environmental pollution (Barking, Essex : 1987)》2000,110(1):103-113
The role of algal concentration in the transfer of organic contaminants in a food chain has been studied using the ubiquitous model polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) as the contaminant, Isochrysis galbana as the phytoplankton food source, and the common mussel (Mytilus edulis) as the primary consumer. The effect of algal concentration on BaP uptake by M. edulis was determined by feeding M. edulis daily with I. galbana which had previously been kept in the presence of BaP for 24 h. Four combinations of concentrations of algae and BaP were used to give final exposure concentrations of 30,000 or 150,000 algal cells ml(-1) in combination with either 2 or 50 microg BaP l(-1). BaP concentrations were determined fluorometrically in rest tissues (excluding digestive glands) and digestive gland microsomal fractions of M. edulis after 1, 7 and 15 days exposure, and also in isolated algae. Potentially toxic effects of BaP on M. edulis were examined in terms of blood cell lysosomal membrane damage (neutral red dye retention assay) and induction of digestive gland microsomal mixed-function oxygenase (MFO) parameters [BaP hydroxylase (BPH) and NADPH-cytochrome c (P450) reductase activities]. BaP bioaccumulation in rest tissues (and to a lesser extent in digestive gland microsomes) of M. edulis increased with both increasing BaP and algal exposure concentrations, and over time, producing maximal bioconcentration factors in rest tissues after 15 days exposure to 150,000 algal cells ml(-1) and 50 microg BaP l(-1) of 250,000. The five-fold higher concentration of algae increased BaP bioaccumulation by a factor of approximately 2 for 50 microg BaP l(-1) at day 15. Blood cell neutral red dye retention time decreased linearly with increasing log(10) tissue BaP body burden, indicating an increased biological impact on M. edulis with increasing BaP exposure possibly due to a direct effect of BaP on blood cell lysosomal membrane integrity. An increase was seen in NADPH-cytochrome c reductase activity, and indicated in BPH activity, with 1 but not 7 or 15 days exposure to BaP, indicating a transient response of the digestive gland microsomal MFO system to BaP exposure. 相似文献
16.
18.
19.