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   473篇
  免费   1篇
安全科学   11篇
废物处理   47篇
环保管理   34篇
综合类   50篇
基础理论   72篇
环境理论   1篇
污染及防治   108篇
评价与监测   133篇
社会与环境   14篇
灾害及防治   4篇
  2023年   21篇
  2022年   30篇
  2021年   17篇
  2020年   5篇
  2019年   8篇
  2018年   22篇
  2017年   17篇
  2016年   29篇
  2015年   14篇
  2014年   41篇
  2013年   62篇
  2012年   11篇
  2011年   13篇
  2010年   35篇
  2009年   34篇
  2008年   22篇
  2007年   15篇
  2006年   15篇
  2005年   13篇
  2004年   2篇
  2003年   6篇
  2002年   4篇
  2001年   6篇
  2000年   3篇
  1999年   1篇
  1998年   3篇
  1995年   4篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
  1981年   2篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
  1969年   1篇
  1960年   2篇
  1959年   1篇
  1956年   1篇
  1943年   1篇
  1942年   1篇
  1937年   1篇
  1936年   1篇
  1923年   1篇
  1920年   1篇
  1919年   1篇
排序方式: 共有474条查询结果,搜索用时 15 毫秒
451.
Lead (Pb) in the environment is derived from both naturaland anthropogenic sources. The aim of this study is to estimate the isotopic signature of anthropogenic Pb in sediments from a highly contaminated area (Stockholm), to discuss the influence of different sources on this signature, and to suggest natural Pb background concentrations. Also distribution patterns and differences between different water areas in Stockholm have been studied, both by total Pb and stable Pb isotopes. In 1993, sediment samples were collected at 24 stations in the Stockholm area and analysed for total Pb, zirconium (Zr), scandium (Sc) and stable Pb isotopes (204, 206-208Pb). Total Pb data show that the Stockholm sediments are severely contaminated by Pb. The contamination seems to be rather local since the small lakes surrounding the central parts of Stockholm are much less effected than the central parts. Stockholm is clearly influenced by anthropogenic and natural sources, but in some of the small lakes also by Pb in zircons from the geological basement. The anthropogenic Pb in Stockholm has typical 207Pb/206Pb ratios of 0.85–0.89 and 208Pb/204Pb ratios of 36–38, which are distinct from natural sources. Pb/Sc ratios suggest that the natural background Pb concentration is 10–20 mg kg-1 d.w.  相似文献   
452.
The aim of this study is to determine the contents of aluminum, iron, manganese, nickel, copper, zinc, chromium, cadmium, lead, and mercury in sediments at 1–30?m depths of the Band?rma and Erdek Gulfs in the Southern Inner Shelf of the Marmara Sea. Sediment samples were collected from different depths (1?m, 5?m, 10?m, 20?m, 30?m) at each region in February 2008. Primary hydrographic conditions, such as temperature (6.6–14.5°C), salinity (22.6–26.875 psu), percentage of dissolved oxygen saturation (35–83 %), and pH (8.0–8.4) were recorded for each sampling point. Moreover the total organic carbon (0.5–2.9%) and the total calcium carbonate contents (0.8–60%) of sediment samples were determined. In surface sediments of both gulfs, Pb (21–62?mg?kg?1) and Cd (0.52–0.86?mg?kg?1) contents were determined to be higher than the shale average (Pb 20?mg?kg?1, Cd 0.2?mg?kg?1) while the other metal contents were measured to be lower in general. On the other hand, generally Hg (0.06–1.1?mg?kg?1) contents were higher than the shale average (0.3?mg?kg?1)at all of the examined stations in the Band?rma Gulf and lower than the shale average in the Erdek Gulf.  相似文献   
453.
Italy is an earthquake‐prone country and its disaster emergency response experiences over the past few decades have varied greatly, with some being much more successful than others. Overall, however, its reconstruction efforts have been criticised for being ad hoc, delayed, ineffective, and untargeted. In addition, while the emergency relief response to the L'Aquila earthquake of 6 April 2009—the primary case study in this evaluation—seems to have been successful, the reconstruction initiative got off to a very problematic start. To explore the root causes of this phenomenon, the paper argues that, owing to the way in which Italian Prime Minister Silvio Berlusconi has politicised the process, the L'Aquila reconstruction endeavour is likely to suffer problems with local ownership, national/regional/municipal coordination, and corruption. It concludes with a set of recommendations aimed at addressing the pitfalls that may confront the L'Aquila reconstruction process over the next few years.  相似文献   
454.
The boundaries as well as the macro-epibenthic biomass distribution and composition of a North Adriatic benthic community, dominated by the brittle star Ophiothrix quinquemaculata (D.Ch.), the sponges Reniera ssp., and the ascidians Microcosmus ssp. were determined. Transects totalling more than 80 km (i.e., a recorded area of approximately 150 000 m2) were taken by means of a combined TV- and photocamera sled. The observations, TV-recordings, and photos, together with 392 diver-collected quantitative samples were evaluated. The biomass values were used to establish isobenths. Within the community, the mean biomass, measured as wet weight, amounted to 370 (±73) g/m2 with maxima of more than 1000 g/m2. 64% of the biomass was due to the designating group Ophiothrix-Reniera-Micrcosmus, 87.5% were represented by filter- and suspension-feeding species alone. The mean biomass in the peripheral areas was evaluated at 166 (±62) g/m2. Biomass distribution and composition is examined, and the ecological function and meaning of the observed patterns is discussed.This investigation was carried out within the frame of a joint programme between the Lehrkanzel für Meeresbiologie, University of Vienna, and the Marine Biological Station, Portoroz, University of Ljubljana.  相似文献   
455.
The REDD-ALERT (Reducing Emissions from Deforestation and Degradation from Alternative Land Uses in the Rainforests of the Tropics) project started in 2009 and finished in 2012, and had the aim of evaluating mechanisms that translate international-level agreements into instruments that would help change the behaviour of land users while minimising adverse repercussions on their livelihoods. Findings showed that some developing tropical countries have recently been through a forest transition, thus shifting from declining to expanding forests at a national scale. However, in most of these (e.g. Vietnam), a significant part of the recent increase in national forest cover is associated with an increase in importation of food and timber products from abroad, representing leakage of carbon stocks across international borders. Avoiding deforestation and restoring forests will require a mixture of regulatory approaches, emerging market-based instruments, suasive options, and hybrid management measures. Policy analysis and modelling work showed the high degree of complexity at local levels and highlighted the need to take this heterogeneity into account—it is unlikely that there will be a one size fits all approach to make Reducing Emissions from Deforestation and Degradation (REDD+) work. Significant progress was made in the quantification of carbon and greenhouse gas (GHG) fluxes following land-use change in the tropics, contributing to narrower confidence intervals on peat-based emissions and their reporting standards. There are indications that there is only a short and relatively small window of opportunity of making REDD+ work—these included the fact that forest-related emissions as a fraction of total global GHG emissions have been decreasing over time due to the increase in fossil fuel emissions, and that the cost efficiency of REDD+ may be much less than originally thought due to the need to factor in safeguard costs, transaction costs and monitoring costs. Nevertheless, REDD+ has raised global awareness of the world’s forests and the factors affecting them, and future developments should contribute to the emergence of new landscape-based approaches to protecting a wider range of ecosystem services.  相似文献   
456.
The aim of this study is to evaluate the metal removal ability of three different plants from metal processing sludge containing Pb, Cd, and Zn. Therefore, phytoremediation and pyrolysis were sequentially applied. In the phytoremediation applications, sunflower (Helianthus annuus), corn (Zea mays), and rape (Brassica napus) seeds were sown in sludge/soil mixtures at four different levels (25/75, 50/50, 75/25, 100/0). The chelating agent, ethylenediaminetetraacetic acid, was added to the mixtures for plant uptake during phytoremediation. At the phytoremediation stage, it was noted that rape was the most effective plant for the mixture of 75/25 sludge/soil, with metal removal efficiencies ranging between 80%–90%. At the pyrolysis stage, after harvesting, contaminated plants grown in a 75/25 sludge/soil mixture were pyrolyzed at 500 °C, with a heating rate of 35 °C/min. The results show that 60%–90% of the initial metal content was held by the solid product. In addition to this, it can be concluded that pyrolysis stabilizes metals into a solid product and that this solid product can be safely landfilled as inert waste since its toxicity leaching value is lower than the limit values.  相似文献   
457.
Yttrium oxide nanoflowers were prepared by a hydrothermal technique, and X-ray diffraction and scanning electron microscopy were used to determine their structures. The cytotoxic and genotoxic potentials of aqueous dispersions of the nanoflowers to cultured primary rat hepatocytes were examined at concentrations up to 500 mg L?1 for 72 h. Cell viability was determined by monitoring the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, release of lactate dehydrogenase, and uptake of neutral red. Genotoxicity was assessed by the liver micronucleus assay. Exposure to Y2O3 nanoflowers at concentrations lower than 100 mg L?1 did not lead to any cytotoxicity or genotoxicity. At higher concentrations (200, 400, and 500 mg L?1), cell viability decreased and induction of micronuclei increased (400 and 500 mg L?1).  相似文献   
458.
English is widely recognized as the language of science, and English-language publications (ELPs) are rapidly increasing. It is often assumed that the number of non-ELPs is decreasing. This assumption contributes to the underuse of non-ELPs in conservation science, practice, and policy, especially at the international level. However, the number of conservation articles published in different languages is poorly documented. Using local and international search systems, we searched for scientific articles on biodiversity conservation published from 1980 to 2018 in English and 15 non-English languages. We compared the growth rate in publications across languages. In 12 of the 15 non-English languages, published conservation articles significantly increased every year over the past 39 years, at a rate similar to English-language articles. The other three languages showed contrasting results, depending on the search system. Since the 1990s, conservation science articles in most languages increased exponentially. The variation in the number of non-English-language articles identified among the search systems differed markedly (e.g., for simplified Chinese, 11,148 articles returned with local search system and 803 with Scopus). Google Scholar and local literature search systems returned the most articles for 11 and 4 non-English languages, respectively. However, the proportion of peer-reviewed conservation articles published in non-English languages was highest in Scopus, followed by Web of Science and local search systems, and lowest in Google Scholar. About 20% of the sampled non-English-language articles provided no title or abstract in English; thus, in theory, they were undiscoverable with English keywords. Possible reasons for this include language barriers and the need to disseminate research in countries where English is not widely spoken. Given the known biases in statistical methods and study characteristics between English- and non-English-language studies, non-English-language articles will continue to play an important role in improving the understanding of biodiversity and its conservation.  相似文献   
459.
Journal of Polymers and the Environment - Poly ε-caprolactone (PCL) synthesized by ring-opening polymerization method, and then it blended with polylactic acid (PLA). The blend was loaded with...  相似文献   
460.
Journal of Polymers and the Environment - This study is the first report of the preparation of hydroxyethyl starch (HES) hydrogels rapidly crosslinked with divinyl sulfone in a single step and...  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