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   398篇
  免费   7篇
  国内免费   4篇
安全科学   4篇
废物处理   10篇
环保管理   28篇
综合类   217篇
基础理论   73篇
污染及防治   48篇
评价与监测   12篇
社会与环境   16篇
灾害及防治   1篇
  2022年   5篇
  2021年   8篇
  2020年   5篇
  2018年   7篇
  2017年   5篇
  2016年   4篇
  2015年   9篇
  2014年   8篇
  2013年   13篇
  2012年   11篇
  2011年   13篇
  2010年   19篇
  2009年   12篇
  2008年   11篇
  2007年   11篇
  2006年   9篇
  2005年   8篇
  2004年   5篇
  2003年   6篇
  2002年   11篇
  2001年   5篇
  2000年   8篇
  1997年   5篇
  1995年   4篇
  1985年   4篇
  1980年   4篇
  1977年   4篇
  1972年   4篇
  1970年   5篇
  1966年   5篇
  1965年   4篇
  1964年   7篇
  1963年   5篇
  1962年   4篇
  1961年   4篇
  1960年   11篇
  1959年   5篇
  1958年   6篇
  1957年   6篇
  1956年   8篇
  1955年   4篇
  1954年   4篇
  1953年   6篇
  1933年   5篇
  1932年   4篇
  1930年   4篇
  1929年   5篇
  1926年   4篇
  1914年   3篇
  1913年   4篇
排序方式: 共有409条查询结果,搜索用时 15 毫秒
41.
Previous studies show that conservation actions have prevented extinctions, recovered populations, and reduced declining trends in global biodiversity. However, all studies to date have substantially underestimated the difference conservation action makes because they failed to account fully for what would have happened in the absence thereof. We undertook a scenario‐based thought experiment to better quantify the effect conservation actions have had on the extinction risk of the world's 235 recognized ungulate species. We did so by comparing species’ observed conservation status in 2008 with their estimated status under counterfactual scenarios in which conservation efforts ceased in 1996. We estimated that without conservation at least 148 species would have deteriorated by one International Union for Conservation of Nature (IUCN) Red List category, including 6 species that now would be listed as extinct or extinct in the wild. The overall decline in the conservation status of ungulates would have been nearly 8 times worse than observed. This trend would have been greater still if not for conservation on private lands. While some species have benefited from highly targeted interventions, such as reintroduction, most benefited collaterally from conservation such as habitat protection. We found that the difference conservation action makes to the conservation status of the world's ungulate species is likely to be higher than previously estimated. Increased, and sustained, investment could help achieve further improvements.  相似文献   
42.
The Science of Nature -  相似文献   
43.
This report summarizes the results of two studies of electricity supply for Europe (EU), the Middle East (ME) and North Africa (NA) up to the year 2050. It shows that a transition to competitive, secure and sustainable supply of electricity and water is possible using renewable energy sources, efficiency gains and fossil fuel backup for balancing power. A strong cooperation between the EU and MENA for the market introduction of renewable energy and the interconnection of the electricity grids by high-voltage direct-current transmission are keys to the success and survival of the whole region. However, the necessary measures will take at least two decades to become effective. Therefore, adequate policy and economic frameworks for their realization must be introduced immediately. The importance of sustainable energy for the security of freshwater supplies in MENA is also described.
Hans Müller-SteinhagenEmail:
  相似文献   
44.
The concentrations of environmental tobacco smoke (ETS) constituents including benzene were measured in the living rooms of 10 nonsmoking households and 20 households with at least one smoker situated in the city and suburbs of Munich. In the city, the median benzene levels during the evening, when all household members were at home, were 8.1 and 10.4 μg/m3 in nonsmoking and smoking homes, respectively. The corresponding levels of 3.5 and 4.6 μg/m3 were considerably lower in the suburbs. Median time-integrated 1-week benzene concentrations in the city were 10.6 μg/m3 in nonsmoking homes and 13.1 μg/m3 in smoking homes. In the suburbs, the corresponding values were 3.2 and 5.6 μg/m3. While the benzene concentrations in nonsmoking homes located in the city were significantly higher (p < 0.05) than in suburban nonsmoking households, no difference was found between smoking and nonsmoking households located either in the city or in the suburbs. Individual exposures to benzene and to specific markers for tobacco smoke of all household members (82 nonsmokers and 32 smokers) were determined by questionnaire, personal monitoring, and biomonitoring. Within the city, the benzene exposure determined by personal samplers was 11.8 μg/m3 for nonsmokers living in nonsmoking homes and 13.3 μg/m3 for nonsmokers in smoking homes. The corresponding values for nonsmokers living in the suburbs were 5.9 and 6.9 μg/m3, respectively. Neither difference was statistically significant. Nonsmokers living in nonsmoking households in the city had significantly higher exposure to benzene compared to their counterparts living in the suburbs (personal samplers: 11.8 vs 5.9 μg/m3, p < 0.001; benzene in exhalate: 2.4 vs. 1.1 μg/m3, p < 0.05; trans,trans-muconic acid excretion in urine: 92 vs. 54 μg/g creatinine, p < 0.05). Nonsmokers from all households with smokers were significantly more exposed to benzene than nonsmokers living in the nonsmoking households (personal samplers: 13.2 vs. 7.0 μg/m3, p < 0.05; benzene in exhalate: 2.6 vs. 1.8 μg/m3, p < 0.01; trans,trans-muconic acid excretion in urine: 73 vs. 62 μg/g creatinine), but the contribution of ETS to the total benzene exposure was relatively low compared to that from other sources. Analysis of variance showed that at most 15% of the benzene exposure of nonsmokers living in smoking homes was attributable to ETS. For nonsmokers living in nonsmoking households benzene exposure from ETS was insignificant.  相似文献   
45.
46.
47.
48.
49.
50.
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