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   175篇
  免费   5篇
  国内免费   3篇
安全科学   14篇
废物处理   3篇
环保管理   30篇
综合类   29篇
基础理论   62篇
环境理论   1篇
污染及防治   29篇
评价与监测   4篇
社会与环境   8篇
灾害及防治   3篇
  2023年   5篇
  2022年   2篇
  2021年   5篇
  2020年   2篇
  2019年   2篇
  2018年   1篇
  2017年   5篇
  2016年   11篇
  2015年   10篇
  2014年   8篇
  2013年   18篇
  2012年   16篇
  2011年   8篇
  2010年   4篇
  2009年   15篇
  2008年   11篇
  2007年   10篇
  2006年   9篇
  2005年   4篇
  2004年   5篇
  2003年   2篇
  2002年   4篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   2篇
  1995年   2篇
  1994年   3篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1986年   1篇
  1984年   2篇
  1979年   2篇
排序方式: 共有183条查询结果,搜索用时 409 毫秒
71.
We examined the cost of conserving species as climate changes. We used a Maxent species distribution model to predict the ranges from 2000 to 2080 of 74 plant species endemic to the forests of Madagascar under 3 climate scenarios. We set a conservation target of achieving 10,000 ha of forest cover for each species and calculated the cost of achieving this target under each scenario. We interviewed managers of projects to restore native forests and conducted a literature review to obtain the net present cost per hectare of management actions to maintain or establish forest cover. For each species, we added hectares of land from lowest to highest cost per additional year of forest cover until the conservation target was achieved throughout the time period. Climate change was predicted to reduce the size of species' ranges, the overlap between species' ranges and existing or planned protected areas, and the overlap between species' ranges and existing forest. As a result, climate change increased the cost of achieving the conservation target by necessitating successively more costly management actions: additional management within existing protected areas (US$0-60/ha); avoidance of forest degradation (i.e., loss of biomass) in community-managed areas ($160-576/ha); avoidance of deforestation in unprotected areas ($252-1069/ha); and establishment of forest on nonforested land within protected areas ($802-2710/ha), in community-managed areas ($962-3226/ha), and in unprotected areas ($1054-3719/ha). Our results suggest that although forest restoration may be required for the conservation of some species as climate changes, it is more cost-effective to maintain existing forest wherever possible.  相似文献   
72.
Using a large national sample based on Workplace and Employee Survey data collected by Statistics Canada in 2001 and 2002, we examined the effects of employee usage of seven organizational work–life interface benefits on promotions. Analysis predicted promotions in 2002 when number of promotions received by 2001 were controlled. The main effect of using work–life interface benefits on promotions was positive, indicating that using these benefits is not a career‐limiting move. Gender, presence of young children, and marital status interacted with the use of work–life interface benefits. Single parents benefitted less than other employees from using work–life interface options. Altogether, these findings suggest that the ongoing positive effects of conservation of time and energy resources for employees outweigh the initial short‐term negative effects of signaling and stigmatization. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
73.
Conservation of biodiversity relies heavily on protected areas but their role and effectiveness under a warming climate is still debated. We estimated the climate-driven changes in the temperature niche compositions of bird communities inside and outside protected areas in southern Canada. We hypothesized that communities inside protected areas include a higher proportion of cold-dwelling species than communities outside protected areas. We also hypothesized that communities shift to warm-dwelling species more slowly inside protected areas than outside. To study community changes, we used large-scale and long-term (1997–2019) data from the Breeding Bird Survey of Canada. To describe the temperature niche compositions of bird communities, we calculated the community temperature index (CTI) annually for each community inside and outside protected areas. Generally, warm-dwelling species dominated communities with high CTI values. We modeled temporal changes in CTI as a function of protection status with linear mixed-effect models. We also determined which species contributed most to the temporal changes in CTI with a jackknife approach. As anticipated, CTI was lower inside protected areas than outside. However, contrary to our expectation, CTI increased faster over time inside than outside protected areas and warm-dwelling species contributed most to CTI change inside protected areas. These results highlight the ubiquitous impacts of climate warming. Currently, protected areas can aid cold-dwelling species by providing habitat, but as the climate warms, the communities’ temperature compositions inside protected areas quickly begin to resemble those outside protected areas, suggesting that protected areas delay the impacts of climate warming on cold-dwelling species.  相似文献   
74.
The effect of bottom-water dissolved oxygen on the structure of demersal fish communities off south Namibia was analized. Collections were made during two cruises of the zone in winter 1987 and summer 1988, i.e., before and after the intensive upwelling season. Multivariate analysis revealed four distinct associations, separated by latitude (ca 27°S) and depth (ca 300 m isobath), indicating that dissolved oxygen is an important factor affecting the distribution of demersal fish communities in the zone. Faunal diversity decreased in areas of low oxygen levels. The seasonal variation in upwelling reflected the extent of fish association, their composition, and the seasonal geographical displacement of their boundaries.  相似文献   
75.
Water tables are strictly controlled throughout much of the Netherlands. Higher water tables could permit the restoration of wetland ecosystems. Deriving benefits from this requires the spatial matching of physical planning, eco-hydrological processes, and economic activities. This paper reports on a study combining spatial analysis and disciplinary integration to assess management strategies for the Vecht river basin in the Netherlands. The paper addresses two research questions. How can the information generated by spatial models be condensed into performance indicators for the evaluation of strategies? How can spatial information be retained in the evaluation, and does this lead to different rankings and/or insights? Procedures for the construction of performance indicators for three criteria – net present value, environmental quality and spatial equity – are presented. The evaluation concludes that recreation and higher water tables provide a means for restoration, recouping of costs, and stimulating regional incomes. Maintenance of spatial detail led to different insights, and in particular indicated uncertainty about this conclusion.  相似文献   
76.
Reproduction in opportunistically breeding bird species has traditionally been considered non-seasonal with individuals taking advantage of favourable environmental conditions as they arise. However, some studies imply that this opportunistic breeding may be superimposed on an underlying seasonality, which has effects on the readiness to breed when conditions are favourable. The zebra finch (Taeniopygia guttata) is the classic opportunistic breeder and widely used as such in studies. In a series of laboratory-based breeding experiments, we found evidence to suggest that there are seasonal differences in maternal reproductive investment in the zebra finch even when photoperiod, temperature, relative humidity and diet were held constant. Females showed highly significant seasonal differences in clutch size and egg mass with laying order. Clutch size showed a spring/summer peak typical of multi-brooded species in the wild. There was also a significant increase in egg mass with laying order in all seasons except winter. This variation in breeding parameters with season may allow females to adjust investment depending on the potential fitness returns from a given reproductive attempt. These findings also raise a warning about interpreting results of multiple zebra finch breeding experiments that have been carried out in different seasons.  相似文献   
77.
The conservation of forests in expanding frontier landscapes is critically important to maintain intact forest ecosystems and support forest dependent communities. To conserve frontier forests, policy approaches are needed that conserve forests and advance the well-being of local resource dependent communities. To identify such approaches, the forest conservation and development framework (FCDF) was designed to find place-based conservation-development policies that target system leverage-points influencing land-use practices. To demonstrate the utility of the FCDF, a portfolio of conservation-development policies were identified for Peru’s Manu-Tambopata Corridor (MAT) and evaluated by local land-users. Results of the MAT case study show high levels of interest in the proposed policies, but a wide variation in interest levels relative to personal circumstances and policies proposed. Barriers to implementing conservation-development policies in frontier environments were also identified, including high value land-use alternatives generating high opportunity costs for accepting PES payments (e.g., REDD+), insecure land tenure and conflicting authorizations limiting land-users policy choices, and broad demographic diversity among local land-users. Collectively, this research suggests the FCDF is a useful approach for identifying policies matched to local conditions that advance conservation and human development. This research also indicates policy design in frontier environments is most effective when adapted to local conditions, seeks to identify a mix of complementary policies, and is targeted at key system variables influencing land-use practices (i.e., system leverage-points). Importantly, the MAT case study also highlights how even in rapidly changing frontier landscapes, land-users are interested in policies that advance conservation and development goals.  相似文献   
78.
Despite broad recognition of the value of social sciences and increasingly vocal calls for better engagement with the human element of conservation, the conservation social sciences remain misunderstood and underutilized in practice. The conservation social sciences can provide unique and important contributions to society's understanding of the relationships between humans and nature and to improving conservation practice and outcomes. There are 4 barriers—ideological, institutional, knowledge, and capacity—to meaningful integration of the social sciences into conservation. We provide practical guidance on overcoming these barriers to mainstream the social sciences in conservation science, practice, and policy. Broadly, we recommend fostering knowledge on the scope and contributions of the social sciences to conservation, including social scientists from the inception of interdisciplinary research projects, incorporating social science research and insights during all stages of conservation planning and implementation, building social science capacity at all scales in conservation organizations and agencies, and promoting engagement with the social sciences in and through global conservation policy‐influencing organizations. Conservation social scientists, too, need to be willing to engage with natural science knowledge and to communicate insights and recommendations clearly. We urge the conservation community to move beyond superficial engagement with the conservation social sciences. A more inclusive and integrative conservation science—one that includes the natural and social sciences—will enable more ecologically effective and socially just conservation. Better collaboration among social scientists, natural scientists, practitioners, and policy makers will facilitate a renewed and more robust conservation. Mainstreaming the conservation social sciences will facilitate the uptake of the full range of insights and contributions from these fields into conservation policy and practice.  相似文献   
79.
Arsenic is a known human carcinogen and relevant environmental contaminant in drinking water systems. We set out to comprehensively examine statewide arsenic trends and identify areas of public health concern. Specifically, arsenic trends in North Carolina private wells were evaluated over an eleven-year period using the North Carolina Department of Health and Human Services database for private domestic well waters. We geocoded over 63,000 domestic well measurements by applying a novel geocoding algorithm and error validation scheme. Arsenic measurements and geographical coordinates for database entries were mapped using Geographic Information System techniques. Furthermore, we employed a Bayesian Maximum Entropy (BME) geostatistical framework, which accounts for geocoding error to better estimate arsenic values across the state and identify trends for unmonitored locations. Of the approximately 63,000 monitored wells, 7712 showed detectable arsenic concentrations that ranged between 1 and 806 μg/L. Additionally, 1436 well samples exceeded the EPA drinking water standard. We reveal counties of concern and demonstrate a historical pattern of elevated arsenic in some counties, particularly those located along the Carolina terrane (Carolina slate belt). We analyzed these data in the context of populations using private well water and identify counties for targeted monitoring, such as Stanly and Union Counties. By spatiotemporally mapping these data, our BME estimate revealed arsenic trends at unmonitored locations within counties and better predicted well concentrations when compared to the classical kriging method. This study reveals relevant information on the location of arsenic-contaminated private domestic wells in North Carolina and indicates potential areas at increased risk for adverse health outcomes.  相似文献   
80.
The Wisconsin Department of Natural Resources (WDNR), with support from the U.S. EPA, conducted an assessment of wadeable streams in the Driftless Area ecoregion in western Wisconsin using a probabilistic sampling design. This ecoregion encompasses 20% of Wisconsin’s land area and contains 8,800 miles of perennial streams. Randomly-selected stream sites (n = 60) equally distributed among stream orders 1–4 were sampled. Watershed land use, riparian and in-stream habitat, water chemistry, macroinvertebrate, and fish assemblage data were collected at each true random site and an associated “modified-random” site on each stream that was accessed via a road crossing nearest to the true random site. Targeted least-disturbed reference sites (n = 22) were also sampled to develop reference conditions for various physical, chemical, and biological measures. Cumulative distribution function plots of various measures collected at the true random sites evaluated with reference condition thresholds, indicate that high proportions of the random sites (and by inference the entire Driftless Area wadeable stream population) show some level of degradation. Study results show no statistically significant differences between the true random and modified-random sample sites for any of the nine physical habitat, 11 water chemistry, seven macroinvertebrate, or eight fish metrics analyzed. In Wisconsin’s Driftless Area, 79% of wadeable stream lengths were accessible via road crossings. While further evaluation of the statistical rigor of using a modified-random sampling design is warranted, sampling randomly-selected stream sites accessed via the nearest road crossing may provide a more economical way to apply probabilistic sampling in stream monitoring programs.  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