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61.
A process has been developed to select watersheds that are representative of terrestrial ecoregions and that are relatively undisturbed by human activity. Using an existing land classification system at two hierarchical levels of resolution, representative subsets (ecodistricts) of large-scale ecoregions were selected, on the basis of their physiographic, biological, and climatological attributes, to represent the ecoregions. This was achieved using a frequency distribution analysis of existing attribute data and choosing the ecodistrict most closely resembling the most common set of conditions for that ecoregion. Within each ecodistrict, river basins were selected through a best-judgement evaluation of land use, coupled with an assessment of the size and location of each river basin, in order to meet the condition of minimal human impact. Preliminary assessment of water quality data collected from six watersheds selected in this way suggests that the process is effective in targeting regional scale river basins exhibiting the desired characteristics.  相似文献   
62.
The present work presents the results of 137Cs concentration in seawater, fish and sediments samples collect in 11 sampling points, crossing the Brazilian Southeastern coastal region, from Vitória (ES) to Santos (SP), on a routine basis from 1997 to 2002. This monitoring program was carried out by the Instituto de Radioproteção e Dosimetria (IRD/CNEN/MCT), in cooperation with the Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM/Brazilian Navy), aiming at determining artificial radionuclides in marine samples. Additionally to the 137Cs results, 90Sr concentrations in fish samples from 1998 to 2002 are also reported.The 137Cs in seawater follows a lognormal distribution, with a geometric mean of 1.8 Bq m-3 and a geometric standard deviation of 1.4 (n=54), decay corrected to June/2002. For 137Cs levels in fish samples a geometric mean of 0.19 Bq kg−1 and a geometric standard deviation of 2.9 (n=39), decay corrected to June/2002, with a range of 0.03 to 1.7 Bq kg−1, were obtained. Based on the 137Cs mean concentration in fish as well as in seawater, a transfer factor of 1 × 102 was calculated, which is quite in agreement with the recommended value found in the Safety Report Serie 19.  相似文献   
63.
ABSTRACT: A multivariate approach was used to analyze hydrologic, geologic, geographic, and water-chemistry data from small order watersheds in the Quabbin Reservoir Basin in central Massachusetts. Eighty three small order watersheds were delineated and landscape attributes defining hydrologic, geologic, and geographic features of the watersheds were compiled from geographic information system data layers. Principal components analysis was used to evaluate 11 chemical constituents collected bi-weekly for 1 year at 15 surface-water stations in order to subdivide the basin into subbasins comprised of watersheds with similar water quality characteristics. Three principal components accounted for about 90 percent of the variance in water chemistry data. The principal components were defined as a biogeochemical variable related to wet. land density, an acid-neutralization variable, and a road-salt variable related to density of primary roads. Three subbasins were identified. Analysis of variance and multiple comparisons of means were used to identify significant differences in stream water chemistry and landscape attributes among subbasins. All stream water constituents were significantly different among subbasins. Multiple regression techniques were used to relate stream water chemistry to landscape attributes. Important differences in landscape attributes were related to wetlands, slope, and soil type.  相似文献   
64.
海草是海洋被子植物,广泛分布在温带和热带的海岸带水域,是地球上水生生态系统中最具生产力的生物之一.  相似文献   
65.
66.
In much of the Third World, access to secure water for irrigation, particularly groundwater, reduces vulnerability, stabilizes livelihoods,alleviates poverty and 'entitles' populations to education and other forms of capital accumulation. Water resource development can, as a result, be used as a key tool for addressing the social roots of instability. The reverse is also true — problems such as groundwater overdraft contribute to poverty and are often at the root of forced migration and the creation of underemployed and unstable displaced populations. Water is fundamental to regional as well as local security.
The benefits of water resource development and the risks associated with unsustainable use patterns are particularly critical in arid regions. Patterns of water use that are unsustainable can play a positive role in the transition of populations from nomadic or migratory to stable communities, where people have access to education and asset accumulation. The exit is, however, as important as the entry. In many regions, the majority of the population now need to make the transition from agriculture to non–agricultural livelihoods. Many people, particularly the wealthy, may already be doing this. Understanding and enabling transition represents one of the most important policy challenges for coming decades.
Using examples from India, Yemen, Saudi Arabia and other countries, this article documents some of the connections between water and security and clarifies the importance of effective solutions to water problems and to social transition in arid regions.  相似文献   
67.
This paper presents an in-depth analysis of a multi-stakeholder process, the Banff Bow Valley Round Table (BBVRT) convened by a federally appointed task force in 1995 to provide public input and participation in the Banff Bow Valley Study (BBVS). The purpose of this initiative was to address environmental concerns and conflict over governance, development and growth in Banff National Park, Canada. A key finding from the analysis discussed in this paper is how various participants struggled for legitimation at the negotiation table, and how the discourses of science and instrumental reason served to empower certain interests and agendas in the process. While the discursive appropriation of ecological science enabled some interests to dominate and to legitimize their concerns, this strategy may have intangible and costly consequences for consensus-based processes and for society overall. Analysis of these discursive struggles demonstrates the challenge of bringing ecology and the general public to the same negotiating table in a meaningful way. It shows the conflicting roles and identities of environmental groups who aspire to re-present nature (as a stakeholder) at the negotiating table. Recommendations for multi-stakeholder processes in planning and governance of national parks are presented, along with social implications in the context of historic human-environment dualism and conflict.  相似文献   
68.
渔业资源是重要的食物来源,对沿850km长的坦桑尼亚海岸线和无数岛屿进行渔业活动的当地居民作出了有价值的经济贡献.小规模的个体渔业占该国家43 000多渔民渔获量的大部分,个体渔民主要是在大陆架内的浅水海域中作业,使用传统的捕鱼船,包括小船、阿拉伯三角帆船、轻舟、舷外撑杆船以及舢板等.采用了使用不复杂的捕捞方法,例如诱捕篓、围栏捕鱼器、网以及不同的钓具技术等.鱼的物种组成和大小随渔具的类型和位置而变.  相似文献   
69.
PROBLEM: Although there has been considerable interest in safety climate, relatively little attention has been given to the factors that determine safety climate or to testing the hypothesized mediating role of safety climate with respect to safety-related outcomes. METHOD: Questionnaire responses were obtained from 2,208 employees of a large national retail chain in 21 different locations. RESULTS: After controlling for demographic variables, three factors: environmental conditions, safety-related policies and programs, and general organizational climate, accounted for 55% of the variance in perceived safety climate. Interestingly, organizational climate made a significant contribution to safety climate, even after controlling for the other more safety-relevant variables. Partial correlations showed that safety policies and programs had the largest observed correlation with safety climate, followed by two of the dimensions of organizational climate (communication and organizational support). Using Baron and Kenny's (J. Pers. Soc. Psychol. 51 (1986) 1173) procedures, the principal effects of the various work situation factors on perceived safety at work were found to be direct rather than mediated by safety climate. Safety climate influenced perceived safety at work, but its role as a mediator was limited. IMPACT ON INDUSTRY: These results are discussed in terms of other recent findings on safety climate and the growing interest in understanding management and organizational factors in the context of workplace safety.  相似文献   
70.
The relationship between out-migration of labor in the Qinling mountain area and households’ firewood consumption is explored. Migration and remittances reduce households’ firewood consumption due to increases in both income and opportunity cost of firewood collection. Previous studies have been equivocal because they ignored uncertainty in household economy, which is widespread in forest areas of less developed countries. This study provides additional insight by considering vulnerability and subjective assessment of poverty generated by unstable income and an uncertain future. We provide evidence that the amount of firewood consumed depends on income and opportunity cost of firewood collection, but also on a prudent consumption strategy, due to farmers’ subjective assessment of their future possible poverty. We also find out-migration of labor can reduce per capita firewood consumption but subjective poverty also acts against reduction of firewood consumption.  相似文献   
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