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   195篇
  免费   0篇
  国内免费   1篇
安全科学   4篇
环保管理   24篇
综合类   2篇
基础理论   162篇
污染及防治   3篇
灾害及防治   1篇
  2014年   20篇
  2013年   19篇
  2012年   3篇
  2011年   10篇
  2010年   20篇
  2009年   14篇
  2008年   12篇
  2007年   14篇
  2006年   12篇
  2005年   13篇
  2004年   7篇
  2003年   5篇
  2002年   3篇
  2001年   6篇
  1999年   4篇
  1997年   2篇
  1996年   2篇
  1995年   6篇
  1993年   1篇
  1992年   5篇
  1991年   5篇
  1990年   2篇
  1989年   5篇
  1988年   2篇
  1985年   1篇
  1978年   2篇
  1977年   1篇
排序方式: 共有196条查询结果,搜索用时 15 毫秒
61.
Abstract:  Demographic data of rare and endangered species are often too sparse to estimate vital rates and population size with sufficient precision for understanding population growth and decline. Yet, the combination of different sources of demographic data into one statistical model holds promise. We applied Bayesian integrated population modeling to demographic data from a colony of the endangered greater horseshoe bats (Rhinolophus ferrumequinum) . Available data were the number of subadults and adults emerging from the colony roost at dusk, the number of newborns from 1991 to 2005, and recapture data of subadults and adults from 2004 and 2005. Survival rates did not differ between sexes, and demographic rates remained constant across time. The greater horseshoe bat is a long-lived species with high survival rates (first year: 0.49 [SD 0.06]; adults: 0.91 [SD 0.02]) and low fecundity (0.74 [SD 0.12]). The yearly average population growth was 4.4% (SD 0.1%) and there were 92 (SD 10) adults in the colony in year 2005. Had we analyzed each data set separately, we would not have been able to estimate fecundity, the estimates of survival would have been less precise, and the estimate of population growth biased. Our results demonstrate that integrated models are suitable for obtaining crucial demographic information from limited data.  相似文献   
62.
Abstract: Informally gathered species lists are a potential source of data for conservation biology, but most remain unused because of questions of reliability and statistical issues. We applied two alternative analytical methods (contingency tests and occupancy modeling) to a 35‐year data set (1973–2007) to test hypotheses about local bird extinction. We compiled data from bird lists collected by expert amateurs and professional scientists in a 2‐km2 fragment of lowland tropical forest in coastal Ecuador. We tested the effects of the following on local extinction: trophic level, sociality, foraging specialization, light tolerance, geographical range area, and biogeographic source. First we assessed extinction on the basis of the number of years in which a species was not detected on the site and used contingency tests with each factor to compare the frequency of expected and observed extinction events among different species categories. Then we defined four multiyear periods that reflected different stages of deforestation and isolation of the study site and used occupancy modeling to test extinction hypotheses singly and in combination. Both types of analyses supported the biogeographic source hypothesis and the species‐range hypothesis as causes of extinction; however, occupancy modeling indicated the model incorporating all factors except foraging specialization best fit the data.  相似文献   
63.
Abstract: Marine protected areas (MPAs) are a popular conservation strategy, but their impacts on human welfare are poorly understood. To inform future research and policy decisions, we reviewed the scientific literature to assess MPA impacts on five indicators of human welfare: food security, resource rights, employment, community organization, and income. Following MPA establishment, food security generally remained stable or increased in older and smaller MPAs. The ability of most fishing groups to govern MPA resources changed. Increased resource rights were positively correlated with MPA zoning and compliance with MPA regulations. Small sample sizes precluded statistical tests of the impacts of MPAs on employment, community organization, and income. Our results demonstrate that MPAs shape the social well‐being and political power of fishing communities; impacts (positive and negative) vary within and among social groups; and social impacts are correlated with some—but not all—commonly hypothesized explanatory factors. Accordingly, MPAs may represent a viable strategy for enhancing food security and empowering local communities, but current practices negatively affect at least a minority of fishers. To inform policy making, further research must better document and explain variation in the positive and negative social impacts of MPAs.  相似文献   
64.
Strategies to mitigate climate change can protect different types of cool environments. Two are receiving much attention: protection of ephemeral refuges (i.e., places with low maximum temperatures) and of stable refugia (i.e., places that are cool, have a stable environment, and are isolated). Problematically, they are often treated as equivalents. Careful delineation of their qualities is needed to prevent misdirected conservation initiatives; yet, no one has determined whether protecting one protects the other. We mapped both types of cool environments across a large (~3.4M ha) mixed‐use landscape with a geographic information system and conducted a patch analysis to compare their spatial distributions; examine relations between land use and their size and shape; and assess their current protection status. With a modest, but arbitrary, threshold for demarcating both types of cool environments (i.e., values below the 0.025 quantile) there were 146,523 ha of ephemeral refuge (62,208 ha) and stable refugia (62,319 ha). Ephemeral refuges were generally aggregated at high elevation, and more refuge area occurred in protected areas (55,184 ha) than in unprotected areas (7,024 ha). In contrast, stable refugia were scattered across the landscape, and more stable‐refugium area occurred on unprotected (40,135 ha) than on protected land (22,184 ha). Although sensitivity analysis showed that varying the thresholds that define cool environments affected outcomes, it also exposed the challenge of choosing a threshold for strategies to address climate change; there is no single value that is appropriate for all of biodiversity. The degree of overlap between ephemeral refuges and stable refugia revealed that targeting only the former for protection on currently unprotected land would capture ~17% of stable refugia. Targeting only stable refugia would capture ~54% of ephemeral refuges. Thus, targeting one type of cool environment did not fully protect the other. Evaluación de la Distribución y Estado de Protección de Dos Tipos de Ambientes Fríos para Facilitar su Conservación bajo el Cambio Climático  相似文献   
65.
Status Assessment of Biodiversity Protection   总被引:1,自引:0,他引:1  
  相似文献   
66.
67.
This paper focuses on the roles of governments of developing countries in the oil exploration area; roles ranging from passive tax collectors to production sharers to full State ownership and control. The historical failure of governments to take full control of this key area is seen as partially due to myths: that only the big international oil companies have the necessary technology and capital and can afford the risk of oil exploration and development. Three case studies showing the large benefits to a developing country from full State control are examined: Mexico, India and Vietnam. It is concluded that only full State control can ensure that the riches of oil can be harnessed for a developing country, and governments are urged to develop greater knowledge both about the international oil industry and their country's potential resources.  相似文献   
68.
It is often unclear what the role of a local jurisdiction is with regard to land use management on nearby federal properties. Yet federal lands clearly impact nearby local communities. The US Department of Energy (DOE), with over 100 sites across the United States with varying degrees of environmental contamination, may be in a very difficult position with regard to relationships with local government about land use. Yet few, if any, studies have examined DOE land use issues. This study asks: (1) In general, how do local planners feel about federal government relationships with them? (2) Do local planners feel differently about the DOE than they do about other federal agencies? (3) What reasons explain any differences observed in answer to the second question? To answer these questions, local planners were interviewed from communities adjacent to non-DOE federal properties, and their responses compared to those of planners located near DOE facilities in the same regions. Findings showed that compared to other federal agencies that own land in the same regions, the DOE is relatively poorer at actively involving local officials in land use decisions at its sites. Primary reasons are the historic legacy of a culture of secrecy, focus on mission, and especially the lack of experience, training, or mandates in local planning cooperation. Findings also suggest that this attitude is markedly stronger in areas west of the Rocky Mountains. Recommendations for improved federal–local communications include the development of a vision for local government involvement that is supported by top levels of management and filtered effectively to the site level.  相似文献   
69.
A Quantitative Method for Estimating Probable Public Costs of Hurricanes   总被引:2,自引:0,他引:2  
/ A method is presented for estimating probable public costs resulting from damage caused by hurricanes, measured as local government expenditures approved for reimbursement under the Stafford Act Section 406 Public Assistance Program. The method employs a multivariate model developed through multiple regression analysis of an array of independent variables that measure meteorological, socioeconomic, and physical conditions related to the landfall of hurricanes within a local government jurisdiction. From the regression analysis we chose a log-log (base 10) model that explains 74% of the variance in the expenditure data using population and wind speed as predictors. We illustrate application of the method for a local jurisdiction-Lee County, Florida, USA. The results show that potential public costs range from $4.7 million for a category 1 hurricane with winds of 137 kilometers per hour (85 miles per hour) to $130 million for a category 5 hurricane with winds of 265 kilometers per hour (165 miles per hour). Based on these figures, we estimate expected annual public costs of $2.3 million. These cost estimates: (1) provide useful guidance for anticipating the magnitude of the federal, state, and local expenditures that would be required for the array of possible hurricanes that could affect that jurisdiction; (2) allow policy makers to assess the implications of alternative federal and state policies for providing public assistance to jurisdictions that experience hurricane damage; and (3) provide information needed to develop a contingency fund or other financial mechanism for assuring that the community has sufficient funds available to meet its obligations. KEY WORDS: Hurricane; Public costs; Local government; Disaster recovery; Disaster response; Florida; Stafford Act  相似文献   
70.
Sustainability indicator sets are increasingly being discussed on the policy level as fruitful contributions to the improvement of political decision- making and to the implementation of programs oriented towards the achievement of strategic goals of sustainable development. The vast number of different indicator type tools, their varying contexts of use and their differing objectives indicate that there is no simple answer to what sustainable indicator type tools should look like or could be used for. Instead, more than the final products (e.g. a specific indicators set), the analyses of the discourse on this topic reveal a lot of information. Thus, an innovative research approach is recommended focusing on understanding the production of social meaning and processes of social interaction within political-administrative systems. Firstly, there is a need to identify the development, purpose and use of sustainability indicator sets, which depend on the different interests of policy actors, their relationships and existing governance structures. Secondly, one should identify any reasons for the ineffective use of indicator sets where the goals of sustainability are concerned. The approach of ‘interactive research’ understood as a research process, in which ‘researchers’ and ‘practitioners’ develop knowledge for solving problems in a communicative, reflexive and collaborative way, facilitates this challenging research task. This paper critically examines the approach of interactive research and sheds some light on benefits as well as challenges of it via extracting the lessons learnt in an EU-funded project called ‘Promoting Action for Sustainability through Indicators at the Local Level in Europe’ (PASTILLE), which applied an interactive research approach.  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