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   43篇
  免费   1篇
环保管理   3篇
综合类   1篇
基础理论   32篇
污染及防治   4篇
评价与监测   3篇
社会与环境   1篇
  2023年   1篇
  2020年   1篇
  2018年   1篇
  2016年   1篇
  2015年   1篇
  2014年   5篇
  2013年   4篇
  2012年   4篇
  2011年   4篇
  2010年   6篇
  2007年   1篇
  2005年   3篇
  2003年   1篇
  2002年   2篇
  2001年   1篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1989年   2篇
  1988年   1篇
  1986年   2篇
排序方式: 共有44条查询结果,搜索用时 384 毫秒
21.
Abstract: Hundreds of epiphytic bromeliads species are harvested from the wild for trade and for cultural uses, but little is known about the effects of this harvest. We assessed the potential demographic effects of harvesting from the wild on 2 epiphytic bromeliads: Tillandsia macdougallii, an atmospheric bromeliad (adsorbs water and nutrients directly from the atmosphere), and T. violaceae, a tank bromeliad (accumulates water and organic material between its leaves). We also examined an alternative to harvesting bromeliads from trees—the collection of fallen bromeliads from the forest floor. We censused populations of T. macdougallii each year from 2005 to 2010 and of T. violaceae from 2005 to 2008, in Oaxaca, Mexico. We also measured monthly fall rates of bromeliads over 1 year and monitored the survival of fallen bromeliads on the forest floor. The tank bromeliad had significantly higher rates of survival, reproduction, and stochastic population growth rates (λs) than the atmospheric bromeliad, but λs for both species were <1, which suggests that the populations will decline even without harvest. Elasticity patterns differed between species, but in both, survival of large individuals had high elasticity values. No fallen bromeliads survived more than 1.5 years on the forest floor and the rate of bromeliad fall was comparable to current harvest rates. Low rates of population growth recorded for the species we studied and other epiphytic bromeliads and high elasticity values for the vital rates that were most affected by harvest suggest that commercial harvesting in the wild of these species is not sustainable. We propose the collection of fallen bromeliads as an ecologically and, potentially, economically viable alternative.  相似文献   
22.
The deployment of biofuels is significantly affected by policy in energy and agriculture. In the energy arena, concerns regarding the sustainability of biofuel systems and their impact on food prices led to a set of sustainability criteria in EU Directive 2009/28/EC on Renewable Energy. In addition, the 10% biofuels target by 2020 was replaced with a 10% renewable energy in transport target. This allows the share of renewable electricity used by electric vehicles to contribute to the mix in achieving the 2020 target. Furthermore, only biofuel systems that effect a 60% reduction in greenhouse gas emissions by 2020 compared with the fuel they replace are allowed to contribute to meeting the target. In the agricultural arena, cross-compliance (which is part of EU Common Agricultural Policy) dictates the allowable ratio of grassland to total agricultural land, and has a significant impact on which biofuels may be supported. This paper outlines the impact of these policy areas and their implications for the production and use of biofuels in terms of the 2020 target for 10% renewable transport energy, focusing on Ireland. The policies effectively impose constraints on many conventional energy crop biofuels and reinforce the merits of using biomethane, a gaseous biofuel. The analysis shows that Ireland can potentially satisfy 15% of renewable energy in transport by 2020 (allowing for double credit for biofuels from residues and ligno-cellulosic materials, as per Directive 2009/28/EC) through the use of indigenous biofuels: grass biomethane, waste and residue derived biofuels, electric vehicles and rapeseed biodiesel.  相似文献   
23.
The green alga Cladophora glomerata (L.) is a common macrophyte in the northern Baltic Sea, where it forms drifting mats during summer. We studied the effect of its stage of decomposition on the density, diversity, and resource usage of associated meio- and macrofauna. We hypothesised that mobile species would show small variation in food preferences among decomposition stages, while high variation was expected in stationary species, as reflected in their stable isotope signatures. The assemblage structure of the fauna differed between the 3 studied algal degradation stages, Green (attached, healthy), Degraded (attached, but starting to decay), and Drift (detached, decaying). C/N ratios were highest in green algae and decreased in decaying algal stages. Variation in stable isotope ratios of stationary and mobile species supported our resource use hypothesis. The decomposition stage of C. glomerata significantly affected the carbon and nitrogen stable isotope ratios of both the alga and its main grazer species. Higher invertebrate diversity in the more decaying stages was probably facilitated by decomposer microbes adding resource types and by the proximity of the detached algal mats to the sediment.  相似文献   
24.
Pelagic species have been traditionally thought to occupy vast, genetically interconnected, geographic ranges in an essentially homogeneous environment. Although this view has been challenged recently for some mesopelagic planktonic taxa, the population structure of hyponeustonic (surface-drifting) species remains unknown. Here, we test the hypothesis of panmixis in Glaucus atlanticus, a cosmopolitan neustonic nudibranch, by assessing the genetic differentiation of multiple representatives from a global neustonic sampling effort. Specimens were collected from all subtropical oceanic gyre systems (North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean). We sequenced a fragment of the mitochondrial cytochrome oxidase I gene for 98 individuals and performed population structure, differentiation (analysis of molecular variance, spatial analysis of molecular variance, F ST, Jost’s D), and molecular clock analyses. Our results indicate that G. atlanticus is not globally panmictic, but that populations appear to be panmictic within ocean basins. We detected several topologically ectopic haplotypes in the Atlantic Ocean, but the molecular clock analysis indicates that these have diverged from closely related Indo-Pacific haplotypes over 1.2 MYA, coinciding with cooling in waters around in the southern tip of Africa and resulting oceanographic changes. These data and the fact that G. atlanticus is not known from polar latitudes suggest that gene flow between ocean basins is hindered by physical barriers (supercontinents) and water temperatures in the Arctic and Southern Oceans.  相似文献   
25.
We used aerial photographs, satellite images, and field surveys to monitor forest cover in the core zones of the Monarch Butterfly Biosphere Reserve in Mexico from 2001 to 2012. We used our data to assess the effectiveness of conservation actions that involved local, state, and federal authorities and community members (e.g., local landowners and private and civil organizations) in one of the world's most iconic protected areas. From 2001 through 2012, 1254 ha were deforested (i.e., cleared areas had <10% canopy cover), 925 ha were degraded (i.e., areas for which canopy forest decreased), and 122 ha were affected by climatic conditions. Of the total 2179 ha of affected area, 2057 ha were affected by illegal logging: 1503 ha by large‐scale logging and 554 ha by small‐scale logging. Mexican authorities effectively enforced efforts to protect the monarch reserve, particularly from 2007 to 2012. Those efforts, together with the decade‐long financial support from Mexican and international philanthropists and businesses to create local alternative‐income generation and employment, resulted in the decrease of large‐scale illegal logging from 731 ha affected in 2005–2007 to none affected in 2012, although small‐scale logging is of growing concern. However, dire regional social and economic problems remain, and they must be addressed to ensure the reserve's long‐term conservation. The monarch butterfly (Danaus plexippus) overwintering colonies in Mexico—which engage in one of the longest known insect migrations—are threatened by deforestation, and a multistakeholder, regional, sustainable‐development strategy is needed to protect the reserve. Tendencias en la Deforestación y la Degradación de Forestal después de una Década de Monitoreo en la Reserva de la Biósfera de la Mariposa Monarca en México  相似文献   
26.
Environmental Chemistry Letters - Biogas is a renewable fuel produced from modern biomass, yet biogas contains traces of hydrogen sulfide, a toxic compound, that must be removed before biogas...  相似文献   
27.
Polychlorinated biphenyls (PCBs) pose a threat to the environment due to their high adsorption capacity to soil organic matter, stability and low reactivity, low water solubility, toxicity and ability to bioaccumulate. With Icelandic soils, research on contamination issues has been very limited and no data has been reported either on PCB degradation potential or rate. The goals of this research were to assess the bioavailability of aged PCBs in the soils of the old North Atlantic Treaty Organization facility in Keflavík, Iceland and to find the best biostimulation method to decrease the pollution. The effectiveness of different biostimulation additives (N fertiliser, white clover and pine needles) at different temperatures (10 and 30 °C) and oxygen levels (aerobic and anaerobic) were tested. PCB bioavailability to soil fauna was assessed with earthworms (Eisenia foetida). PCBs were bioavailable to earthworms (bioaccumulation factor 0.89 and 0.82 for earthworms in 12.5 ppm PCB soil and in 25 ppm PCB soil, respectively), with less chlorinated congeners showing higher bioaccumulation factors than highly chlorinated congeners. Biostimulation with pine needles at 10 °C under aerobic conditions resulted in nearly 38 % degradation of total PCBs after 2 months of incubation. Detection of the aerobic PCB degrading bphA gene supports the indigenous capability of the soils to aerobically degrade PCBs. Further research on field scale biostimulation trials with pine needles in cold environments is recommended in order to optimise the method for onsite remediation.  相似文献   
28.
Abstract

Sources and concentrations of indoor nitrogen dioxide (NO2) were examined in Barcelona, Spain, during 1996– 1999. A total of 340 dwellings of infants participating in a hospital-based cohort study were selected from different areas of the city. Passive filter badges were used for indoor NO2 measurement over 7–30 days. Dwelling inhabitants completed a questionnaire on housing characteristics and smoking habits. Data on outdoor NO2 concentrations were available for the entire period of the study in the areas of the city where indoor concentrations were determined. Bivariate analysis was performed to investigate relationships between indoor NO2 concentrations on one hand and outdoor NO2 concentrations, housing, and occupant characteristics on the other. Stepwise multiple linear regression was performed with variables that were 1996 and 27.02 ppb in 1999, with the highest yearly value of 27.82 ppb in 1997. In the same time period, mean outdoor NO2 concentration ranged between 25.26 and 25.78 ppb with a peak of 30.5 ppb in 1998. Multiple regression analysis showed that principal sources of indoor NO2 concentrations were the use of a gas cooker, the absence of an extractor fan when cooking, and cigarette smoking. The absence of central heating was also associated with higher NO2 concentrations. Finally, each ppb increase in outdoor NO2 was associated with a 1% increase in indoor concentrations.  相似文献   
29.
30.
Abstract: The Iberian lynx (Lynx pardinus) may be the first charismatic felid to become extinct in a high‐income country, despite decades of study and much data that show extinction is highly probable. The International Union for Conservation of Nature categorizes it as critically endangered; about 200 free‐ranging individuals remain in two populations in southern Spain. Conservation measures aimed at averting extirpation have been extensively undertaken with 4 of the former 10 Iberian lynx populations recorded 25 years ago. Two of the four populations have been extirpated. The number of individuals in the third population have declined by 83%, and in the fourth the probability of extirpation has increased from 34% to 95%. Major drivers of the pending extinction are the small areas to which conservation measures have been applied; lack of incorporation of evidence‐based conservation, scientific monitoring, and adaptive management into conservation efforts; a lack of continuity in recovery efforts, and distrust by conservation agencies of scientific information. In contrast to situations in which conservation and economic objectives conflict, in the case of the Iberian lynx all stakeholders desire the species to be conserved.  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