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   674篇
  免费   16篇
  国内免费   11篇
安全科学   34篇
废物处理   17篇
环保管理   166篇
综合类   107篇
基础理论   187篇
环境理论   1篇
污染及防治   113篇
评价与监测   32篇
社会与环境   28篇
灾害及防治   16篇
  2023年   10篇
  2022年   10篇
  2021年   25篇
  2020年   13篇
  2019年   28篇
  2018年   20篇
  2017年   30篇
  2016年   32篇
  2015年   21篇
  2014年   19篇
  2013年   55篇
  2012年   37篇
  2011年   37篇
  2010年   33篇
  2009年   28篇
  2008年   38篇
  2007年   30篇
  2006年   31篇
  2005年   24篇
  2004年   25篇
  2003年   18篇
  2002年   26篇
  2001年   16篇
  2000年   8篇
  1999年   9篇
  1998年   3篇
  1997年   4篇
  1996年   5篇
  1995年   7篇
  1994年   4篇
  1993年   5篇
  1992年   3篇
  1991年   5篇
  1990年   1篇
  1989年   2篇
  1988年   2篇
  1987年   6篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1983年   5篇
  1982年   6篇
  1981年   5篇
  1980年   1篇
  1979年   2篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
排序方式: 共有701条查询结果,搜索用时 375 毫秒
411.
The preparation and dissemination of policy statements are necessary but insufficient to prevent the inappropriate use of infant-feeding products in emergencies. The widespread failure of humanitarian agencies operating in the Balkan crisis to act in accordance with international policies and recommendations provides a recent example of the failure to translate infant-feeding policies into practice. This article explores the underlying reasons behind the failures which include: (1) the weak institutionalisation of policies; (2) the massive quantities of unsolicited donations of infant-feeding products: (3) the absence of monitoring systems; (4) inadequate co-ordination mechanisms; (5) the high costs of correcting mistakes; and (6) the cumulative effects of poor practice. Efforts to uphold best practice during the crisis are also documented. Finally, the article identifies actions that could be undertaken in advance of and during future emergencies to enhance the application of infant feeding policies in emergencies.  相似文献   
412.
413.
414.
Agrochemical spray drift; assessment and mitigation--a review   总被引:1,自引:0,他引:1  
During application of agrochemicals spray droplets can drift beyond the intended target to non-target receptors, including water, plants and animals. Factors affecting this spray drift include mode of application, droplet size, which can be modified by the nozzle types, formulation adjuvants, wind direction, wind speed, air stability, relative humidity, temperature and height of released spray relative to the crop canopy. The rate of fall of spray droplets depends upon the size of the droplets but is modified by entrainment in a mobile air mass and is also influenced by the rate of evaporation of the liquid constituting the aerosol. The longer the aerosol remains in the air before falling to the ground (or alternatively striking an object above ground) the greater the opportunity for it to be carried away from its intended target. In general, all size classes of droplets are capable of movement off target, but the smallest are likely to move the farthest before depositing on the ground or a non-target receptor. It is not possible to avoid spray drift completely but it can be minimized by using best-management practices. These include using appropriate nozzle types, shields, spray pressure, volumes per area sprayed, tractor speed and only spraying when climatic conditions are suitable. Field layout can also influence spray drift, whilst crop-free and spray-free buffer zones and windbreak crops can also have a mitigating effect. Various models are available to estimate the environmental exposure from spray drift at the time of application.  相似文献   
415.
Bhadha, Jehangir H., Casey Schmidt, Robert Rooney, Paul Indeglia, Ruben Kertesz, Elizabeth Bevc, and John Sansalone, 2009. Granulometric and Metal Distributions for Post‐Katrina Surficial Particulate Matter Recovered From New Orleans. Journal of the American Water Resources Association (JAWRA) 45(6):1434‐1447. Abstract: Hurricane Katrina and the resulting failure of the levees that surrounded and protected New Orleans generated a significant detained volume of stormwater within the urban area of New Orleans. Between the inundation resulting from levee failure and eventual pumped evacuation of stormwater from the urban area of New Orleans, a large mass of storm‐entrained particulate matter (PM) was deposited in the inundated areas. This study examined the granulometry and granulometric distribution of metals for post‐Katrina surficial PM deposits recovered from 15 sites (10 inundated and 5 non‐inundated) in New Orleans. Results of this examination were compared to pre‐Katrina data from New Orleans. While post‐Katrina analysis of PM indicates that Pb, Zn, and Cu concentrations for PM are reduced for all sites, inundated sites had higher Cu, Pb, and Zn concentrations for the settleable (~25‐75 μm) and sediment (>75 μm) size fractions. A comparison between total metal concentration and the bioavailable (leachable) fraction for PM reveals that inundated sites had up to 19% higher leachable metal concentration compared to non‐inundated sites. The reduction in PM‐bound total metal concentrations for recovered PM can be explained through a combination of scouring (and therefore change in granulometry from pre‐Katrina) that resulted from transport of suspended PM by storm flows and pumped evacuation; as well as leaching and PM‐based redistribution from extended contact with rainfall and during stormwater detention. New Orleans has been exposed to elevated levels of metals through decades of activities that include vehicular transportation, chemical, industrial, and oil production facilities resulting in higher metal concentrations for urban soil‐residual complexes. As a result, the influent storm flows associated with Katrina as an episodic event cannot solely explain the distribution and fate of PM‐associated metal concentrations.  相似文献   
416.
The suitability of a granulated zero valent iron (ZVI) permeable reactive barrier (PRB) remediation strategy was investigated for tribromoethene (TriBE), cis-1,2-dibromoethene (c-DBE), trans-1,2-dibromoethene (t-DBE) and vinyl bromide (VB), via batch and large-scale column experiments that were subsequently analysed by reactive transport modelling.The brominated ethenes in both batch and large-scale column experiments showed rapid (compared to controls and natural attenuation) degradation in the presence of ZVI. In the large-scale column experiment, degradation half-lives were 0.35 days for TriBE, 0.50 days for c-DBE, 0.31 days for t-DBE and 0.40 days for VB, under site groundwater flow conditions, resulting in removal of brominated ethenes within the first 0.2 m of a 1.0 m thick ZVI layer, indicating that a PRB groundwater remediation strategy using ZVI could be used successfully.In the model simulations of the ZVI induced brominated ethene degradation, assuming a dominant reductive β-elimination pathway via bromoacetylene and acetylene production, simulated organic compound concentrations corresponded well with both batch and large-scale column experimental data. Changes of inorganic reactants were also well captured by the simulations. The similar ZVI induced degradation pathway of TriBE and TCE suggests that outcomes from research on ZVI induced TCE remediation could also be applied to TriBE remediation.  相似文献   
417.
A study of carbonaceous particulate matter (PM) was conducted in the Middle East at sites in Israel, Jordan, and Palestine. The sources and seasonal variation of organic carbon, as well as the contribution to fine aerosol (PM2.5) mass, were determined. Of the 11 sites studied, Nablus had the highest contribution of organic carbon (OC), 29%, and elemental carbon (EC), 19%, to total PM2.5 mass. The lowest concentrations of PM2.5 mass, OC, and EC were measured at southern desert sites, located in Aqaba, Eilat, and Rachma. The OC contribution to PM2.5 mass at these sites ranged between 9.4% and 16%, with mean annual PM2.5 mass concentrations ranging from 21 to 25 ug m?3. These sites were also observed to have the highest OC to EC ratios (4.1–5.0), indicative of smaller contributions from primary combustion sources and/or a higher contribution of secondary organic aerosol. Biomass burning and vehicular emissions were found to be important sources of carbonaceous PM in this region at the non-southern desert sites, which together accounted for 30%–55% of the fine particle organic carbon at these sites. The fraction of measured OC unapportioned to primary sources (1.4 μgC m?3 to 4.9 μgC m?3; 30%–74%), which has been shown to be largely from secondary organic aerosol, is relatively constant at the sites examined in this study. This suggests that secondary organic aerosol is important in the Middle East during all seasons of the year.  相似文献   
418.
A wide range of goals and objectives have to be taken into account in natural resources management. Defining these objectives in operational terms, including dimensions such as sustainability, productivity, and equity, is by no means easy, especially if they must capture the diversity of community and stakeholder values. This is especially true in the coastal zone where land activities affect regional marine ecosystems. In this study, the aim was firstly to identify and hierarchically organise the goals and objectives for coastal systems, as defined by local stakeholders. Two case study areas are used within the Great Barrier Reef region being Mackay and Bowen–Burdekin. Secondly, the aim was to identify similarities between the case study results and thus develop a generic set of goals to be used as a starting point in other coastal communities. Results show that overarching high-level goals have nested sub-goals that contain a set of more detailed regional objectives. The similarities in high-level environmental, governance, and socio-economic goals suggest that regionally specific objectives can be developed based on a generic set of goals. The prominence of governance objectives reflects local stakeholder perceptions that current coastal zone management is not achieving the outcomes they feel important and that there is a need for increased community engagement and co-management. More importantly, it raises the question of how to make issues relevant for the local community and entice participation in the local management of public resources to achieve sustainable environmental, social, and economic management outcomes.  相似文献   
419.
Ferris E  Ferro-Ribeiro S 《Disasters》2012,36(Z1):S43-S63
Humanitarian actors have sought increasingly not only to assist people affected by natural disasters but also to protect them. This paper examines the efforts of international humanitarian actors to protect Haitians affected by the devastating earthquake of 12 January 2010. It begins with an analysis of the particular difficulties of conceptualising and operationalising protection in an urban environment and traces the efforts of international actors on the ground to develop appropriate protection strategies. The particular difficulties of working with camps and spontaneous settlements in urban areas are explored as are the challenges that stemmed from working with different levels of governmental authorities and a multitude of humanitarian actors. The paper concludes by highlighting some of the lessons learned from the successes and failures of international protection efforts in Haiti. It is hoped that these may assist future efforts to protect people living in urban environments.  相似文献   
420.
Common vetch (Vicia sativa L.) is a legume species with an extensive agricultural use. However, the phytoremediation potentiality of this species has not been sufficiently explored because little is known about its resistance to inorganic and organic pollutants. In the present work, phenol tolerance of common vetch was assayed at different stages of growth. Germination index and germination rate decreased only at high phenol concentrations (250 and 500 mg L(-1)), whereas 30-day-old plants were able to tolerate this pollutant, with high removal efficiencies. The activities of antioxidative enzymes, such as peroxidase (POD) and ascorbate peroxidase, increased significantly with the highest phenol concentration, whereas superoxide dismutase activity, malondialdehyde, and H(2)O(2) levels remained unaltered. Besides, an increase in two basic isoforms of POD was observed in plants treated with phenol. The results suggested that common vetch has an efficient protection mechanism against phenol-induced oxidative damage. Moreover, it could tolerate and remove high phenol concentrations, avoiding serious phytotoxic effects. Thus, V. sativa could be considered an interesting tool in the field of phytoremediation.  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