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   545篇
  免费   13篇
  国内免费   31篇
安全科学   80篇
废物处理   8篇
环保管理   97篇
综合类   195篇
基础理论   49篇
污染及防治   45篇
评价与监测   67篇
社会与环境   29篇
灾害及防治   19篇
  2024年   2篇
  2023年   6篇
  2022年   15篇
  2021年   18篇
  2020年   11篇
  2019年   12篇
  2018年   12篇
  2017年   14篇
  2016年   22篇
  2015年   16篇
  2014年   25篇
  2013年   27篇
  2012年   12篇
  2011年   30篇
  2010年   20篇
  2009年   32篇
  2008年   20篇
  2007年   26篇
  2006年   19篇
  2005年   22篇
  2004年   22篇
  2003年   17篇
  2002年   23篇
  2001年   17篇
  2000年   16篇
  1999年   25篇
  1998年   16篇
  1997年   19篇
  1996年   7篇
  1995年   11篇
  1994年   8篇
  1993年   10篇
  1992年   8篇
  1991年   5篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1986年   5篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
排序方式: 共有589条查询结果,搜索用时 78 毫秒
61.
In Lesotho, climate change adaptation funding is being managed and distributed by the same mechanisms which have traditionally operationalised humanitarian aid and international development assistance in the country. Lessons from the HIV/AIDS disaster, along with insights into the value of participatory approaches foregrounding the expertise of indigenous communities, must be heeded in order to ensure that those most affected by climate change have a say in how adaptation is carried out. This paper proposes that indigenous people have developed and actively maintained resilience strategies, encoded in social practices and farming techniques, designed out of long experience with climatic variability. Through case studies, indigenous resilience strategies are explored, with emphasis on the anarchistic, improvisational nature of traditional ecological knowledge. Future directions for policy-makers and practitioners dealing with climate change adaptation are suggested, namely the need to foreground indigenous knowledge and the experiences of frontlines experts in key policy arenas.  相似文献   
62.
Precipitation of calcium carbonate(Ca CO3) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one(scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and p H on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca2+was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80°C at p H 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of Ca CO3 changed from calcite to aragonite.  相似文献   
63.
An improved method for trace level quantification of dicyandiamide in stream water has been developed. This method includes sample pretreatment using solid phase extraction. The extraction procedure (including loading, washing, and eluting) used a flow rate of 1.0 mL/min, and dicyandiamide was eluted with 20 mL of a methanol/acetonitrile mixture (V/V = 2:3), followed by pre-concentration using nitrogen evaporation and analysis with high performance liquid chromatography–ultraviolet spectroscopy (HPLC–UV). Sample extraction was carried out using a Waters Sep-Pak AC-2 Cartridge (with activated carbon). Separation was achieved on a ZIC®-Hydrophilic Interaction Liquid Chromatography (ZIC-HILIC) (50 mm × 2.1 mm, 3.5 μm) chromatography column and quantification was accomplished based on UV absorbance. A reliable linear relationship was obtained for the calibration curve using standard solutions (R2 > 0.999). Recoveries for dicyandiamide ranged from 84.6% to 96.8%, and the relative standard deviations (RSDs, n = 3) were below 6.1% with a detection limit of 5.0 ng/mL for stream water samples.  相似文献   
64.
Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO2 is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO2 as a disinfecting agent, and the pathogen inactivation mechanism of CO2 treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO2 treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions (pressure, temperature, microorganism, water content, media …) suggest that most microorganisms are successfully inhibited under CO2 treatment. It will also be shown that the bacterial deaths under CO2 treatment can be explained by many different mechanisms. Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products (resulting from chlorination or ozone treatment).  相似文献   
65.
Little is known about the process of vegetation recovery and associated time frames in the Succulent Karoo Biome of southern Africa. This study investigated the recovery of vegetation on sites impacted by mining (different types of dumps and mined areas) in the arid succulent karoo. The main aim of this study was to determine the state of recovery, time frames, successional stages, and the influence of environmental factors on recovery of coastal dune and sand plain plant communities. For this purpose, vegetation was recorded on some 121 sites throughout a coastal strip of approximately 100 × 3 km in Namibia’s restricted diamond area (Sperrgebiet). Using the species pool concept to derive vegetation reference sites and dominance-diversity curves, recovery of vegetation (measured in terms of species richness and cover) in these altered landscapes reached about 46% on the oldest, 51-year-old mine dumps. However, based on species richness, richness levels similar to the undisturbed reference sites were recorded after 30 years, following a logarithmic trend. Successional stages of natural recovery were indicated in this dynamic coastal environment and Cladoraphis cyperoides and Galenia fruticosa appear to be early successional species. Scaling up of studies to landscape level and developing a target community using the species pool concept are discussed as means to measure recovery in dynamic biological communities. On these altered, man-made landforms, the availability of seed may be the bottleneck to achieve vegetation cover comparable to undisturbed vegetation in the surrounding. Hence, restoration efforts should focus on this aspect.  相似文献   
66.
为研究甘肃南部城镇PM2.5及水溶性离子(WSIIs)浓度水平,于2019年4月—2020年2月在甘肃成县按季度进行PM2.5样品采集,分析了其变化特征,并运用相关和主成分分析法进行来源解析.结果表明:采样期间甘肃成县PM2.5年平均质量浓度为(57.2±26.9) μg·m-3,表现为冬季>春季>秋季>夏季的季节变化特征,冬季质量浓度约为夏季的1.9倍,全年空气质量优良率为81%,其中夏季达100%.WSIIs质量浓度呈现SO42->NO3->Na+>NH4+>Ca2+> K+>Cl->Mg2+的特征.SNA是浓度水平最高的3种水溶性离子,占8种主要水溶性离子浓度的70.1%.ρ(NO3-)/ρ(SO42-)平均值为0.6,表明工农业生产及化石燃料燃烧排放等固定源是颗粒物污染的主要来源.新型冠状病毒疫情期间人员管控对PM2.5和水溶性离子中SNA质量浓度影响显著,PM2.5平均质量浓度降幅达44.2%.源解析表明,PM2.5中WSIIs主要来自化石燃料燃烧、生物质燃烧及二次源和道路建筑扬尘等.  相似文献   
67.
本文主要对官地水电站高陡边坡植被混凝土前期绿化试验成果进行分析,以寻求在干湿季节明显、雨量集中、干旱季节漫长、温度高、蒸发量大等干热河谷气候特征条件下的最佳生境构筑方法,为官地水电站乃至雅砻江流域水电工程高陡边坡生态恢复提供技术依据。  相似文献   
68.
常用中药中以药用植物占多数,几乎凡具有特殊化学成分及生理作用的植物均可以作为药用植物利用。统计表明,冀南野生药用植物资源丰富,约170种。主要分布在西部山区。本文对其中部分重要药用资源植物的成分、功效作较详细介绍,其它只作一般性介绍:一、冀南重要野生药用植物  相似文献   
69.
王倩  邱俊杰  余劲 《自然资源学报》2019,34(7):1376-1390
山区移民搬迁是否加剧耕地撂荒关系到移民稳定性及国家粮食安全,具有重要的研究价值。基于陕西省南部地区商洛、安康、汉中3市8县(区)1578户农户调查数据,运用面板Logit和Tobit模型回归得出,移民年数对是否撂荒、撂荒面积及撂荒耕地占比在1%的水平上有正向影响;仅当移民距离超过0.5 km时,农户耕地撂荒面积及撂荒耕地占比显著增加;不同移民类型中,工程移民对耕地撂荒的影响程度最大,避灾移民影响程度最小;另外,户主特征、家庭特征、资源禀赋特征、农地流转特征显著影响了农户的耕地撂荒行为。可以得出,移民搬迁加剧了山区耕地撂荒,城镇生活的转变及务农时间机会成本的增加是耕地撂荒的主要原因。建议政府对工程移民农户进行有土安置,加大生态移民区退耕还林支持力度,扶持扶贫、避灾移民农户发展特色产业,加快农地流转信息平台建设。  相似文献   
70.
闽三角城市群自然资本损失评估   总被引:3,自引:1,他引:2  
在快速城镇化进程中,城市群发展在促进区域经济竞争与合作的同时,也在一定程度上造成人地关系矛盾的加剧,生态系统服务水平下降。为了量化城镇化对自然资本产生的变动,揭示人类资源消耗过程对区域生态系统服务的影响机制,以快速城镇化的典型区域——闽三角城市群为例,运用能值分析方法与GIS技术,分析了2000-2015年闽三角城市群可更新资源时空演变特征,城镇化进程中生态环境价值演变规律以及土地转化过程中的自然资本损失。研究结果表明:(1)闽三角城市群可更新资源在时间上呈波动减小趋势,空间上自沿海区域向内陆区域逐渐升高;(2)高环境质量等级中城镇用地面积占比呈显著增加趋势,由0增加到10.63%,人类活动导致区域生态环境价值的损失逐渐上升;(3)城镇化过程中由于城市空间扩张,使部分自然用地与农业用地转化为城镇用地,转化过程造成的自然资本损失总量为1.27×1022 seJ,货币价值超过6.30×109元。研究有助于完善城镇化影响下的生态环境效应研究,为城市群或区域生态环境管理与修复提供决策参考。  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