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   2008篇
  免费   44篇
  国内免费   36篇
安全科学   67篇
废物处理   128篇
环保管理   185篇
综合类   361篇
基础理论   373篇
环境理论   2篇
污染及防治   580篇
评价与监测   235篇
社会与环境   133篇
灾害及防治   24篇
  2023年   25篇
  2022年   75篇
  2021年   92篇
  2020年   47篇
  2019年   40篇
  2018年   85篇
  2017年   83篇
  2016年   88篇
  2015年   60篇
  2014年   109篇
  2013年   155篇
  2012年   86篇
  2011年   120篇
  2010年   85篇
  2009年   95篇
  2008年   100篇
  2007年   91篇
  2006年   63篇
  2005年   73篇
  2004年   72篇
  2003年   75篇
  2002年   63篇
  2001年   63篇
  2000年   33篇
  1999年   27篇
  1998年   18篇
  1997年   12篇
  1996年   7篇
  1995年   13篇
  1994年   12篇
  1993年   14篇
  1992年   16篇
  1991年   3篇
  1990年   4篇
  1989年   6篇
  1988年   6篇
  1987年   2篇
  1986年   5篇
  1985年   9篇
  1984年   4篇
  1983年   8篇
  1982年   8篇
  1981年   5篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1976年   2篇
  1970年   2篇
  1962年   5篇
  1961年   2篇
排序方式: 共有2088条查询结果,搜索用时 15 毫秒
131.
This study aimed to analyze the spectral trend of vegetation with rainfall in El Niño-Southern Oscillation events (ENSO) in the Atlantic Forest, Brazil. Monthly rainfall data were collected from 85 conventional meteorological stations (EMC), data from the Enhanced Vegetation Index 2 (EVI2) and ENSO events (El Niño, La Niña, and Neutral) in the period from 2001 to 2013. Afterwards, state cluster analysis was performed using the results of non-parametric tests. The Mann-Kendall (MK) non-parametric test did not identify a trend pattern in rainfall distribution in the Atlantic Forest. The results for EVI2 by state and region showed that the trend is decreasing in the Northeast Region, except for the states of Alagoas and Pernambuco. Southeast region showed an increasing trend of EVI2 (except for Rio de Janeiro and São Paulo), while the South region showed a decreasing trend. In the Midwest, the trend was significantly decreasing. In the prognosis elaborated for the future, the regions with significant declines of the vegetation were the Northeast and Midwest. This study shows that the Atlantic Forest in some regions of Brazil has been suffering from the growing urbanization process and there is a trend of soil degradation.  相似文献   
132.
In lakes, the littoral habitat and its invertebrate communities are often exposed to water-level fluctuations. We examined the effects of seasonal changes on water level, substrata availability and benthic fauna in the littoral zone of Peri Lake, a shallow lake that has experienced a strong reduction in water level due to changes in rainfall. In this study, we also examined whether the abundance and composition of aquatic invertebrates differed among the four substrata. Our main objective was to assess the effect of seasonal changes on water level and benthic invertebrates inhabiting the different types of substrata. Benthic invertebrates were sampled four different substrata (Schoenoplectus californicus, sand and stones, allochthonous leaf litter, and macrophyte stands), and we also measured meteorological, physical and chemical variables. We found that complex habitats, such as allochthonous leaf litter and aquatic macrophyte, stand to be colonised by a larger number of macroinvertebrates because they provide more habitats or potential niches for colonisation by different species. In addition, we observed that during periods of low water level, the presence of substrata in the littoral zone decreased, as did the associated biota. Therefore, our results suggest that water level changes have a major functional impact on the littoral zone of the lake, and can affect substratum availability, which also impacts invertebrate communities.  相似文献   
133.
134.
This paper investigates multi-stakeholder arrangements initiated by businesses and NGOs from the North that aim to enhance a more sustainable agricultural production at specific localities in Southern countries. We aim to better understand the search for concerted action in multi-actor arrangements. Therefore, this paper presents a diagnostic framework with three strategic challenges the partnership projects are facing: linking global economic objectives to local needs, values and interests; bridging public and private interests and responsibilities; and seeking trade-offs between social, environmental and economic values. Starting from the partnerships’ Theory of Change, this diagnostic framework is applied to comparative case studies of partnership projects in the cocoa sector in Indonesia, which are part of a Northern-based public–private partnership to improve farmers’ prospective. It is concluded that the economic reality faced by the farmers differs from that of the Northern actors; collaboration with governments is difficult because of different organizational cultures; and the partnership projects underestimate the strength of vested social relations the smallholders are part of. Overall, the initiators of the partnerships seem to work with a too restricted economic interpretation of the local reality.  相似文献   
135.
Fermentation can use renewable raw materials as substrate, which makes it a sustainable method to obtain H2. This study evaluates H2 production by a mixed culture from substrates such as glucose and derivatives from sugarcane processing (sucrose, molasses, and vinasse) combined with landfill leachate. The leachate alone was not a suitable substrate for biohydrogen production. However, leachate blended with glucose, sucrose, molasses, or vinasse increased the H2 production rate by 2.0-, 2.8-, 4.6-, and 0.5-fold, respectively, as compared with the substrates without the leachate. Determination of metals (Cu, Cd, Pb, Hg, Ni, and Fe) at the beginning and at the end of the fermentative assays showed how they were consumed during the fermentation and demonstrated improved H2 production. During fermentation, Cu, Fe, and Cd were the most consumed leachate metals. The best substrate combination to produce H2 was molasses and leachate, which gave high volumetric productivity—469 ml H2/l h. However, addition of the leachate to the substrates stimulated lactic acid formation pathways, which lowered the H2 yield. The use of leachate combined with sugarcane processing derivatives as substrates could add value to the leachate and reduce its polluting power, generating a clean energy source from renewable raw materials.  相似文献   
136.
核辐射事故以及随后的应急响应和恢复行动都会产生大量的废物,对这些废物的安全管理至关重要,有必要对核或辐射应急过程中产生的废物管理可能遇到的困难和挑战进行分析,提出在应急准备中需要注意的问题,对我国目前相关的法律条文进行梳理并提出建议。  相似文献   
137.
Economic values of water for the main Public Irrigation Schemes in the sub-middle region of the São Francisco River Basin, in northeastern Brazil, are determined in this study using an integration of a global agro-economic land and water use (MAgPIE) with a local economic model (Positive Mathematical Programming). As in the latter, the water values depend on the crops grown, and as Brazilian agriculture is strongly influenced by the global market, we used a regionalized version of the global model adapted to the region in order to simulate the crop land use, which is in turn determined by changes in global demand, trade barriers, and climate. The allocation of sugarcane and fruit crops projected with climate change by the global model, showed an impact on the average yields and on the water costs in the main schemes resulting in changes in the water values locally. The economic values for all schemes in the baseline year were higher than the water prices established for agricultural use in the basin. In the future, these water values will be higher in all the schemes. The highest water values currently and in the future were identified in municipalities with a significant proportion of area growing irrigated sugarcane. Being aware of current water values of each user in a baseline year and in a projected future under global climate and socioeconomic changes, decision makers should improve water allocation policies at local scale, in order to avoid conflicts and unsustainable development in the future.  相似文献   
138.
This study was undertaken to evaluate the effectiveness of several household practices (washing with water or acidic, alkaline, and oxidizing solutions, and peeling) in minimizing pesticide residue contamination of tomatoes, as well as the impact on the quality of the treated fruit. Tests were performed using two systemic fungicides (azoxystrobin and difenoconazole) and one contact fungicide (chlorothalonil). Solid-liquid extraction with low temperature partition (SLE/LTP) and liquid-liquid extraction with low temperature partition (LLE/LTP) were used to prepare the samples for pesticides determination by gas chromatography. Washing the tomatoes with water removed approximately 44% of chlorothalonil, 26% of difenoconazole, and 17% of azoxystrobin. Sodium bicarbonate (5%) and acetic acid (5%) solutions were more efficient, removing between 32 and 83% of the residues, while peeling removed from 68 to 88% of the pesticides. The washing solutions altered some fruit quality parameters, including acidity and chroma, and also caused weight loss. Acetic acid (0.15 and 5%) and hypochlorite (1%) solutions had the greatest effect on these parameters.  相似文献   
139.
In the last two decades, there has been a rich debate about the environmental degradation that results from exposure to solid urban waste. Growing public concern with environmental issues has led to the implementation of various strategic plans for waste management in several developed countries, especially in the European Union. In this paper, the relationships were assessed between economic growth, renewable energy extraction and greenhouse gas (GHG) emissions in the waste sector. The Environmental Kuznets Curve hypothesis was analysed for the member states of the European Union, in the presence of electricity generation, landfill and GHG emissions for the period 1995 to 2012. The results revealed that there is no inverted-U-shaped relationship between income and GHG emissions in European Union countries. The renewable fuel extracted from waste contributes to a reduction in GHG, and although the electricity produced also increases emissions somewhat, they would be far greater if the waste-based generation of renewable energy did not take place. The waste sector needs to strengthen its political, economic, institutional and social communication instruments to meet its aims for mitigating the levels of pollutants generated by European economies. To achieve the objectives of the Horizon 2020 programme, currently in force in the countries of the European Union, it will be necessary to increase the share of renewable energy in the energy mix.  相似文献   
140.

The present study assessed the DNA damage in environmentally exposed volunteers living in seven municipalities in an industrial coal region, through the use of the comet assay with blood cells and the micronucleus test with buccal cells. Blood and buccal smears were collected from 320 male volunteers living in seven cities inserted in a coal region. They were ages of 18 and 50 years and also completed a questionnaire intended to identify factors associated with DNA damage through a Poisson regression analysis. The comet assay detected significant differences in DNA damage in volunteers from different municipalities, and neighboring cities (Pedras Altas, Aceguá, and Hulha Negra) had a higher level of DNA damage in relation to control city. Some of the risk factors associated with identified DNA lesions included residence time and life habits. On the other hand, the micronucleus test did not identify differences between the cities studied, but the regression analysis identified risk factors such as age and life habits (consumption of mate tea and low carbohydrates diet). We conclude that there are differences in the DNA damage of volunteers from different cities of the carboniferous region, but the presence of micronuclei in the oral mucosa does not differ between the same cities. Furthermore, we alert that some related factors may increase the risk of genotoxicity, such as residence location and time, and living and food habits. Finally, we suggest the need for continuous biomonitoring of the population, as well as for investing in health promotion in these vulnerable populations.

  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