全文获取类型
收费全文 | 379篇 |
免费 | 24篇 |
国内免费 | 13篇 |
专业分类
安全科学 | 7篇 |
废物处理 | 1篇 |
环保管理 | 140篇 |
综合类 | 84篇 |
基础理论 | 85篇 |
环境理论 | 1篇 |
污染及防治 | 22篇 |
评价与监测 | 15篇 |
社会与环境 | 33篇 |
灾害及防治 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 23篇 |
2016年 | 21篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 47篇 |
2012年 | 12篇 |
2011年 | 29篇 |
2010年 | 7篇 |
2009年 | 25篇 |
2008年 | 13篇 |
2007年 | 21篇 |
2006年 | 27篇 |
2005年 | 12篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有416条查询结果,搜索用时 15 毫秒
171.
172.
JONATHAN D. SALERNO MONIQUE BORGERHOFF MULDER SHAWN C. KEFAUVER 《Conservation biology》2014,28(3):841-850
A recent discussion debates the extent of human in‐migration around protected areas (PAs) in the tropics. One proposed argument is that rural migrants move to bordering areas to access conservation outreach benefits. A counter proposal maintains that PAs have largely negative effects on local populations and that outreach initiatives even if successful present insufficient benefits to drive in‐migration. Using data from Tanzania, we examined merits of statistical tests and spatial methods used previously to evaluate migration near PAs and applied hierarchical modeling with appropriate controls for demographic and geographic factors to advance the debate. Areas bordering national parks in Tanzania did not have elevated rates of in‐migration. Low baseline population density and high vegetation productivity with low interannual variation rather than conservation outreach explained observed migration patterns. More generally we argue that to produce results of conservation policy significance, analyses must be conducted at appropriate scales, and we caution against use of demographic data without appropriate controls when drawing conclusions about migration dynamics. La Migración Humana, Áreas Protegidas y el Alcance de la Conservación en Tanzania 相似文献
173.
The rains are disappointing us: dynamic vulnerability and adaptation to multiple stressors in the Afram Plains, Ghana 总被引:3,自引:0,他引:3
Lisa Westerhoff Barry Smit 《Mitigation and Adaptation Strategies for Global Change》2009,14(4):317-337
This paper builds on work on the dynamics of vulnerability and multiple stressors through a case study in the Afram Plains
of the Eastern region in Ghana. A vulnerability framework is applied in the community of Mimkyemfre to identify and explain
the multiple underlying political, socioeconomic and environmental forces that influence the ways in which people are exposed
and sensitive to climate, and their capacities to adapt to changing conditions. The results of the study indicate that the
community experiences a range of biophysical and socioeconomic conditions that contribute to its vulnerability. Vulnerability
was found to change over time and in some cases was cyclical, in that certain actions taken for the purposes of adaptation
were found to exacerbate existing vulnerabilities. Processes of vulnerability were also found to occur at several scales and
were experienced unevenly at the community level. The findings of this assessment have important implications for the design
and implementation of successful adaptation initiatives, both in Africa and elsewhere. In particular, they demonstrate the
need to understand the social, economic and institutional challenges to development as a basis for any contemplation of adaptation
to climate change. 相似文献
174.
Abstract: Small-scale, local disturbance of tropical forests, for example from selective logging, is widespread, but its effects on biodiversity and ecosystem function have rarely been studied. In 3 East African tropical rainforests, we investigated the effect of different levels of local forest disturbance on the frugivore community and on tree visitation and fruit removal rates of the small-seeded tree Celtis durandii. We quantified birds and primates in little and heavily disturbed sites, distinguishing between forest specialists, forest generalists, and forest visitors. We quantified frugivorous tree visitors and seed removal rates of C. durandii trees in the same sites. Forest disturbance reduced the species richness and density of the frugivore community and of forest specialists. Frugivorous species and individuals visiting the study trees were reduced significantly, which led to a marginally significant decline in fruit removal by all frugivores and a significant reduction in removal by forest specialists. Reduction in fruit removal by forest specialists was not compensated for by increases in removal by forest generalists or visitors. Results did not differ among the 3 rainforests, which suggests they were consistent at a regional scale. So local forest disturbance led to a loss of frugivores and their seed removal services. This suggests that large-seeded tree species and trees with small fruits are losing seed dispersers. Thus, local forest disturbance appears to have a more general negative impact on frugivores and their seed dispersal services than anticipated previously. 相似文献
175.
Zbigniew W. Kundzewicz 《Journal of the American Water Resources Association》2011,47(3):550-562
Kundzewicz, Zbigniew W., 2011. Nonstationarity in Water Resources – Central European Perspective. Journal of the American Water Resources Association (JAWRA) 47(3): 550‐562. DOI: 10.1111/j.1752‐1688.2011.00549.x Abstract: Nonstationarity in variables describing water quantity and water quality characteristics is reviewed, and an attempt to interpret nonstationary behavior is made with particular reference to the Central European region. Nonstationarity in water‐related variables results from several nonclimatic and climatic factors. Albeit evidence of climate change in Central Europe is clear, anthropogenic nonclimatic change, such as land‐use or land‐cover changes, water engineering measures, and in‐catchment water management play important roles. Systemic socioeconomic and political changes are the main factors responsible for the observed change in water quality in the region. The observed climate change in the Central European region has not been dramatic enough to persuade the water management community that changes of standards, criteria, and evaluation procedures should be made. Projections for the future largely differ between models and scenarios, hence information obtained from climate models is found too vague to be used. However, the water management community shows interest in climate change observations, projections, and impact assessments. Numerous hydrological research projects to tackle nonstationarity have been undertaken in the region. Also important acts of legislation, such as the European Union’s Water Framework Directive and Floods Directive can be regarded in the context of nonstationarity of water‐related variables. 相似文献
176.
GEORGE WITTEMYER 《Conservation biology》2011,25(5):1002-1009
Abstract: Declines in economic activity and associated changes in human livelihood strategies can increase threats of species overexploitation. This is exemplified by the effects of economic crises, which often drive intensification of subsistence poaching and greater reliance on natural resources. Whereas development theory links natural resource use to social‐economic conditions, few empirical studies of the effect of economic downturns on wild animal species have been conducted. I assessed the relations between African elephant (Loxodonta africana) mortality and human‐caused wounds in Samburu, Kenya and (1) livestock and maize prices (measures of local economic conditions), (2) change in national and regional gross domestic product (GDP) (measures of macroeconomic conditions), and (3) the normalized difference vegetation index (NDVI) (a correlate of primary productivity). In addition, I analyzed household survey data to determine the attitudes of local people toward protected areas and wild animals in the area. When cattle prices in the pastoralist study region were low, human‐caused wounds to and adult mortality of elephants increased. The NDVI was negatively correlated with juvenile mortality, but not correlated with adult mortality. Changes in Kenyan and East Asian (primary market for ivory) GDP did not explain significant variation in mortality. Increased human wounding of elephants and elephant mortality during periods of low livestock prices (local economic downturns) likely reflect an economically driven increase in ivory poaching. Local but not macroeconomic indices explained significant variation in mortality, likely due to the dominance of the subsistence economy in the study area and its political and economic isolation. My results suggest economic metrics can serve as effective indicators of changes in human use of and resulting effects on natural resources. Such information can help focus management approaches (e.g., antipoaching effort or proffering of alternative occupational opportunities) that address variation in local activities that threaten plant and animal populations. 相似文献
177.
Abstract: The demographic impacts of harvesting nontimber forest products (NTFP) have been increasingly studied because of reports of potentially unsustainable harvest. Nevertheless, our understanding of how plant demographic response to harvest is altered by variation in ecological conditions, which is critical for developing realistic sustainable‐use plans, is limited. We built matrix population models to test whether and how variation in ecological conditions affects population responses to harvest. In particular, we examined the effect of bark and foliage harvest on the demography of populations of African mahogany (Khaya senegalensis) in two contrasting ecological regions of Benin, West Africa. K. senegalensis bark and foliage harvest significantly reduced its stochastic population growth rates, but ecological differences between regions had a greater effect on population growth rates than did harvest. The effect of harvest on population growth rates (Δλ) was slightly stronger in the moist than in the drier region. Life‐table response experiments revealed that the mechanism by which harvesting reduced λ differed between ecological regions. Lowered stasis (persistence) of larger life stages lead to a reduction in λ in the drier region, whereas lowered growth of all life stages lowered λ in moist region. Potential strategies to increase population growth rates should include decreasing the proportion of individuals harvested, promoting harvester‐owned plantations of African mahogany, and increasing survival and growth by promoting no‐fire zones in gallery forests. Our results show how population responses to harvest of NTFP may be altered by ecological differences across sites and emphasize the importance of monitoring populations over the climatic range in which they occur to develop more realistic recommendations for conservation. 相似文献
178.
Roger L. Tanner William J. Parkhurst Myra L. Valente K. Lynn Humes Kathy Jones Jeff Gilbert 《Atmospheric environment (Oxford, England : 1994)》2001,35(36)
The impact of the Central American fires on PM2.5 mass concentration and composition in the Tennessee Valley region during portions of May, 1998, has been quantified. Elevated concentrations of smoke aerosol tracers—fine potassium, (and to a lesser extent, calcium and silicon) and, where available, organic and elemental carbon—were observed in the region during times in which satellite imagery (TOMS and GOES-8) showed regional transport of hazy, smoky airmasses from southern Mexico and adjacent areas of Central America. Back-trajectories from network sites in the Tennessee Valley network were consistent with this regional transport. The extent of transport of extra-regional fine particle mass during May, 1998, is discussed relative to the new US fine particle mass-based standards for fine particulate matter. 相似文献
179.
Danielle Tessaro 《国际发展与全球生态学杂志》2013,20(5):471-479
In South Africa, extreme rural poverty often geographically overlaps with areas of high and important biodiversity. Attempts to bring about land-based poverty reduction projects in such areas tends to trigger tensions among stakeholders purporting to be concerned about local people’s welfare, as well as the environment. Using discursive document analysis and semi-structured interviews, the paper discusses a case study of the Wild Coast, an area celebrated for its high biodiversity and ‘beauty’, which reveals that a tension among environmental non-government organisations, government agencies and the private sector, on the best development option, exacerbates the threats to local livelihood options and biodiversity conservation. 相似文献
180.
《Environmental Communication: A Journal of Nature and Culture》2013,7(2):206-224
Tourism is the way we understand the world: tourists travel in an increasingly mediated environment in which ubiquitous promotional material and other popular artifacts employ stunning images and romantic travel narratives to describe local environments. Tourist texts “sell” local landscapes to entice visitors, employing an environmental aesthetic that urges travel. With its mission to “explore the planet,” the National Geographic Society contributes to this tourist aesthetic. This essay examines three special issues on Africa simultaneously published by the National Geographic Society: its official journal, National Geographic, and its sister magazines, National Geographic Traveler, and National Geographic Adventure. The photographic images and travel narratives in these tourist texts produce an environmental aesthetic that positions the traveler at the center of these environments. This essay first analyzes how National Geographic constructs Africa's environmental landscapes. These magazines depict Africa as a vast desert plain, a wilderness theme park, and a part of the global scenery. The second part of the analysis examines how National Geographic locates the tourist in these environments. I discuss how National Geographic positions the tourist as protagonist, expert, and hero of Africa's environment. In the conclusions, I argue this environmental aesthetic renders Africa invisible through anthropocentric distance, and I discuss the need for more critical readings of tourist discourse. 相似文献