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   518篇
  免费   5篇
  国内免费   10篇
安全科学   28篇
废物处理   13篇
环保管理   103篇
综合类   86篇
基础理论   119篇
污染及防治   108篇
评价与监测   55篇
社会与环境   19篇
灾害及防治   2篇
  2023年   2篇
  2022年   10篇
  2021年   7篇
  2020年   7篇
  2019年   5篇
  2018年   10篇
  2017年   12篇
  2016年   21篇
  2015年   11篇
  2014年   23篇
  2013年   45篇
  2012年   40篇
  2011年   37篇
  2010年   13篇
  2009年   25篇
  2008年   35篇
  2007年   22篇
  2006年   33篇
  2005年   21篇
  2004年   21篇
  2003年   22篇
  2002年   16篇
  2001年   1篇
  2000年   8篇
  1999年   3篇
  1998年   5篇
  1997年   4篇
  1996年   5篇
  1995年   3篇
  1994年   6篇
  1993年   4篇
  1992年   3篇
  1991年   1篇
  1990年   6篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1986年   6篇
  1985年   5篇
  1984年   4篇
  1983年   7篇
  1982年   8篇
  1981年   8篇
  1978年   2篇
  1977年   2篇
排序方式: 共有533条查询结果,搜索用时 15 毫秒
461.
Cases of strong local opposition to the planned introduction of new high-voltage power lines (HVPLs) have been documented in the past. During and after the planning process for a new HVPL, local residents will be informed about the siting process and its outcomes. Although it has been suggested in the literature that this communication plays an important role in residents' responses to a new HVPL, it has been rarely empirically studied. In this qualitative study, we conducted in-depth interviews with 15 residents about their experiences with the planned introduction of a new HVPL near their homes. Thematic analysis revealed that residents' experiences were centred around negative expectations of living near the new HVPL and perceived injustice of the planning process and its outcomes. Residents' perception that communication was not tailored to their information needs played a significant role in these negative experiences. Suggestions for improving communication will be discussed.  相似文献   
462.
During August, 1982 and January and February, 1983, General Motors Research Laboratories operated air monitoring sites on the Atlantic Coast near Lewes, Delaware and 1250 km to the east on the southwest coast of Bermuda. The overall purpose of this project was to study the transformations of the principal acid precipitation precursors, NO x and SO x species, as they transport under conditions not complicated by emissions from local sources. In this paper, the measurements of gas and particulate species from Lewes are described and the composition and sources of sulfate aerosol, which is the most important haze-producing species, are investigated.

On the average, the total suspended particulate (TSP) concentration was 27.9 μg/m3 while the PM10 (mass of particles with a diameter less than or equal to 10 μm) concentration was 22.0 μg/m3 or 79 percent of the TSP. The PM10 consisted of 6.1 μg/m3 of coarse particles (CPM, diameter = 2.5 ? 10μm) and 15.9 μg/m3 of fine particles (FPM, diameter < 2.5 μm).

On a mass basis the most important constituents of the fine particulate fraction were sulfate compounds, 50 percent, and organic compounds, 30 percent. The mean light extinction coefficient corresponds to a visual range of 18-20 km. Most of the extinction can be attributed to the sulfate (60 percent) and organic carbon (13 percent). Particle size measurements show that the mass median aerodynamic diameter for both species is 0.43 μm. This is a typical size for a hydrated sulfate aerosol. For carbon, however, this is a larger size than previously reported and results in a more efficient light scattering aerosol. Principal component analyses indicate that coal combustion emissions from the midwestern U.S. are the most significant source of sulfate in Lewes during the summer and winter.  相似文献   
463.
The Mohave Power Project (MPP) is an isolated 1580-MW coal-fired electric generating plant located in Laughlin, NV. Laughlin is a small desert gambling town situated in the lower Colorado River Valley near the junction of three states: Nevada, California, and Arizona. The location of the MPP is approximately 115 km southwest of the western end of the Grand Canyon National Park and about 240 km southwest from the Grand Canyon Village. This paper describes the summer transport patterns of the MPP emittants using illustrated examples from the Project MOHAVE (Measurements of Haze and Visual Effects) 1992 summer intensive study. The intensive study lasted 50 days from mid-July through August and encompassed the major meteorological patterns associated with southwestern U.S. summer meteorology. The MPP emittants were transported toward the Grand Canyon (north to the northeast) during more than 80% of the total hours. Airflow was from the south most of the time due to a combination of the semi-permanent thermal low, differential heating between the Gulf of California and lower Colorado River Valley, and upslope heating of the southern and western slopes of the nearby Colorado Plateau.  相似文献   
464.
Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113-1430 mg Cl L−1 (reconstituted water, 100 mg CaCO3 L−1). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278-322 mg CaCO3 L−1) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265-1559 mg Cl L−1) than in reconstituted water (EC50 285 mg L−1). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L−1). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk.  相似文献   
465.

Introduction  

Complex organic compounds found in oil and sediments linked with a particular source (such as algae, bacteria or vascular plants) are defined as biomarkers and are useful dating indicators in organic geochemistry.  相似文献   
466.
Illegal activities and use of park resources are the main challenges facing mountain gorilla (Gorilla beringei beringei) conservation and the protection of their habitats in the East Africa’s Greater Virunga Transboundary Landscape (GVTL). Indigenous residents around GVTL are considered the primary illegal users of park resources. Despite this, there is limited understanding of the current and past perceptions of indigenous residents living in communities adjacent to two GVTL parks; Volcanoes National Park in Rwanda and Mgahinga Gorilla National Park in Uganda. Equally, there is also limited understanding regarding the actual incidences of illegal activities inside both parks. This paper addresses these gaps. Perception data were collected from indigenous residents living adjacent to both parks. Further, Ranger-based Monitoring (RbM) data from both parks were analyzed to determine actual numbers and types of illegal activities over the 9-year period. Interestingly, findings indicated that residents perceived the prevalence of illegal activities to be decreasing across GVTL. To the contrary, RbM findings indicated that the number of actual illegal activities was increasing significantly, particularly in Volcanoes National Park. The discrepancy found between the two perspectives provides for a discussion of the social biases potentially present in these data, and their implications for management. Results also illuminated the subsistence-related nature of most illegal behaviors and suggest that to reduce illegal activities and local dependency on park resources, park management must work with communities and support them in tapping into alternative livelihoods and finding ways to address community household subsistence needs.  相似文献   
467.
In the early 2000s, the development of local food systems in advanced industrial countries has expanded beyond creation and support of farmers’ markets and community supported agriculture farms and projects to include targeted Buy Local Food campaigns. Non-governmental groups in many U.S. places and regions have launched such campaigns with the intent of motivating and directing consumers toward more local food purchasing in general. This article examines the current manifestations and possibilities for social justice concerns in Buy Local Food campaigns, by considering them within the more general category of “selective patronage“ campaigns. Historical campaign examples, such as Buy Union, Buy American, and Buy Black campaigns, offer instructive comparisons to contemporary consumer campaigns promoting local food. Through examining the construction of threats, intended beneficiaries, products to be avoided, and those to be preferentially selected, the paper demonstrates how selective patronage campaigns have emphasized social justice needs and concerns for designated groups in ways that have been potentially exclusionary of other disadvantaged groups and thus undermining of social justice more broadly. As a contemporary instance of “selective patronage,“ Buy Local Food campaigns exhibit similar contradictory impulses, which are intensified by the conceptual and practical pitfalls in designating “local.“ The article concludes by considering how the challenges and prospects for commitments to social justice in local food consumer campaigns reinforce the importance of emerging initiatives centered on domestic fair trade.  相似文献   
468.
Regionalization frameworks cluster geographic data to create contiguous regions of similar climate, geology and hydrology by delineating land into discrete regions, such as ecoregions or watersheds, often at several spatial scales. Although most regionalization schemes were not originally designed for aquatic ecosystem classification or management, they are often used for such purposes, with surprisingly few explicit tests of the relative ability of different regionalization frameworks to group lakes for water quality monitoring and assessment. We examined which of 11 different lake grouping schemes at two spatial scales best captures the maximum amount of variation in water quality among regions for total nutrients, water clarity, chlorophyll, overall trophic state, and alkalinity in 479 lakes in Michigan (USA). We conducted analyses on two data sets: one that included all lakes and one that included only minimally disturbed lakes. Using hierarchical linear models that partitioned total variance into within-region and among-region components, we found that ecological drainage units and 8-digit hydrologic units most consistently captured among-region heterogeneity at their respective spatial scales using all lakes (variation among lake groups = 3% to 50% and 12% to 52%, respectively). However, regionalization schemes capture less among-region variance for minimally disturbed lakes. Diagnostics of spatial autocorrelation provided insight into the relative performance of regionalization frameworks but also demonstrated that region size is only partly responsible for capturing variation among lakes. These results suggest that regionalization schemes can provide useful frameworks for lake water quality assessment and monitoring but that we must identify the appropriate spatial scale for the questions being asked, the type of management applied, and the metrics being assessed.  相似文献   
469.
We consider the extent to which the Mackenzie Valley Resource Management Act (MVRMA) provides an opportunity for deliberative democracy to emerge within the context of resource management in Canada's North. The focus is on the extent to which the tenets of deliberative democracy are exercised in the environmental assessment (EA) of the Snap Lake diamonds project. Data collection included semi-structured interviews with assessment participants, and a review of documentation surrounding the EA process, and the case study. Results combined four principles of deliberative democracy: generality, autonomy, power neutrality, and ideal role taking. The EA conducted under the MVRMA can serve as a deliberative process, as illustrated by opportunities for dialogue, access to different perspectives, and learning outcomes. However, many of these positive results occurred through nonmandated technical sessions. The absence of participant funding also limits the deliberative potential of the MVRMA.  相似文献   
470.
PROBLEM: To assess effects of the 1999 Maryland graduated driver licensing (GDL) law on both 16-year-old drivers and other road users. METHOD: Calculation and comparison of crash involvement rates and non-fatal injury rates pre-GDL (1996-1998) and post-GDL (2001-2003) by type of road user, per population, and per licensed driver, with adjustment for trends among 30-59-year-old drivers. RESULTS: Post-GDL, prevalence of licensure decreased 24% among 16-year-olds, and rates of 16-year-old drivers involved in crashes significantly decreased per 16-year-old population (corrected rate ratio (RRc) 0.82; 95% CI (0.71, 0.96)). A significant decrease also was observed for non-fatal injuries per 16-year-old population among 16-year-old drivers involved in crashes (RRc 0.63; 95% CI (0.41, 0.98)). Similarly, decreases, albeit not statistically significant, were observed among their passengers and other vehicle occupants. Per 16-year-old licensed driver, a slight non-significant increase was observed in crash involvement rates; non-fatal injury rates per 16-year-old licensed driver suggest decreased risk (non-significant) among 16-year-old drivers, their passengers, and other vehicle occupants. SUMMARY: Maryland's GDL delayed licensure and reduced crashes and non-fatal injuries among 16-year-old drivers per population. Trends in injuries among other road users involved in crashes with 16-year-old drivers were suggestive of a benefit from GDL, although observed decreases were not significant. Per licensed driver, findings were not significant, but suggested little change in crash involvement and decreased non-fatal injuries. Because one-third fewer 16-year-olds were licensed post-GDL, these results may suggest a selection effect in licensure. IMPACT ON INDUSTRY: Because Maryland had nighttime restrictions for new drivers before 1999, this study suggests other components of GDL are beneficial for drivers and possibly for other road users. States with weak GDL laws should strongly consider revising them.  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