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   619篇
  免费   30篇
  国内免费   239篇
安全科学   43篇
废物处理   50篇
环保管理   44篇
综合类   320篇
基础理论   130篇
污染及防治   222篇
评价与监测   26篇
社会与环境   25篇
灾害及防治   28篇
  2024年   1篇
  2023年   13篇
  2022年   29篇
  2021年   23篇
  2020年   15篇
  2019年   18篇
  2018年   21篇
  2017年   25篇
  2016年   27篇
  2015年   48篇
  2014年   51篇
  2013年   69篇
  2012年   47篇
  2011年   59篇
  2010年   40篇
  2009年   29篇
  2008年   34篇
  2007年   48篇
  2006年   33篇
  2005年   24篇
  2004年   17篇
  2003年   23篇
  2002年   19篇
  2001年   17篇
  2000年   21篇
  1999年   27篇
  1998年   17篇
  1997年   16篇
  1996年   15篇
  1995年   9篇
  1994年   9篇
  1993年   9篇
  1992年   10篇
  1991年   7篇
  1990年   7篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1982年   2篇
  1981年   1篇
排序方式: 共有888条查询结果,搜索用时 15 毫秒
121.
Epidemiological survey of 573 families, clinical examination of 2593 persons, and X-ray examination of 1136 persons (in 16 typical endemic villages) were conducted, based on the classification of endemiology for KBD disease areas, i.e, mountain type, loess plateau type, plateau type, and flatlands type. It was revealed that the KBD disease areas exhibited the regular pattern of corming-into-being, development and passing-away and the characteristics of growth and decline. Further, it was found clinically that the disease areas may be divided into 4 types, i.e., recent onset, developing, stable, and historical. This division is simple and easy, practical, scientific, and reliable and can be applied by medical personnel at different levels.  相似文献   
122.
DBD降解CF2ClBr过程中自由基与电子能量   总被引:1,自引:1,他引:1  
利用介质阻挡放电方法对环境污染物CF2ClBr进行了等离子体降解的研究.在前人对该体系的降解产物分析及活性粒子推测的基础上,采用动态反应装置得到了等离子体的发射光谱,进一步确证了等离子体系中出现的CF2、CFCl、F、Cl、Br等主要自由基,并从中推出了等离子态气体可能发生的自由基反应.同时通过发射光谱的分析,近似得到该体系的平均电子能量约为2.42eV  相似文献   
123.
Dry deposition velocity of total suspended particles (TSP) is an effective parameter that describes the speed of atmospheric particulate matter deposit to the natural surface. It is also an important indicator to the capacity of atmosphere self-depuration. However, the spatial and temporal variations in dry deposition velocity of TSP at different urban landscapes and the relationship between dry deposition velocity and the meteorological parameters are subject to large uncertainties. We concurrently investigated this relationship at four different landscapes of Guangzhou, from October to December of 2009. The result of the average dry deposition velocity is (1.49 ± 0.77), (1.44 ± 0.77), (1.13 ± 0.53) and (1.82 ± 0.82) cm/sec for urban commercial landscape, urban forest landscape, urban residential landscape and country landscape, respectively. This spatial variation can be explained by the difference of both particle size composition of TSP and meteorological parameters of sampling sites. Dry deposition velocity of TSP has a positive correlation with wind speed, and a negative correlation with temperature and relative humidity. Wind speed is the strongest factor that affects the magnitude of TSP dry deposition velocity, and the temperature is another considerable strong meteorological factor.We also find out that the relative humidity brings less impact, especially during the dry season. It is thus implied that the current global warming and urban heat island effect may lead to correlative changes in TSP dry deposition velocity, especially in the urban areas.  相似文献   
124.
活性半焦用于油田含油污水除油的研究   总被引:3,自引:0,他引:3  
以经济廉价的半焦为原料,制备用于处理油田含油污水的吸附剂。采用高温焙烧活化、水蒸气活化、高压水热活化以及硝酸、氢氧化钾活化等方法对半焦进行活化处理,通过静态吸附实验测定除油率来评价活化效果,重点讨论了氢氧化钾活化条件对除油效果的影响。结果表明:KOH与半焦质量比为6∶1,80℃浸渍3 h,550℃焙烧1.5 h时,制备的活性半焦吸附除油效果最好,除油率可以达到75.6%;活性半焦对油的吸附符合Freund lich吸附方程。利用酸碱滴定法对样品表面酸碱官能团进行分析,发现KOH活化后半焦表面碱性亲油官能团明显增多;通过SEM对半焦的微观结构进行分析,发现KOH活化后半焦产生大量有利于吸附的孔结构。  相似文献   
125.
大气颗粒物对肺免疫系统有潜在毒性作用,打破免疫系统平衡,大气颗粒物成分中危害首当其冲的是大气细颗粒物(PM_(2.5)),为研究大气细颗粒物引起的机体T淋巴细胞中Th1/Th2免疫失衡方向。本研究通过免疫组化实验方法检测暴露后小鼠肺组织中T淋巴细胞的表达,进一步采用流式细胞术检测大气细颗粒物气管滴注后小鼠肺脏淋巴细胞中Th1/Th2比例。暴露组小鼠肺组织免疫组化研究结果提示浸润细胞区有大量的CD4~+T细胞,中高剂量暴露组小鼠肺组织中淋巴细胞亚群Th1/Th2比例向Th1偏移。大气细颗粒物影响免疫失衡,使T淋巴细胞向Th1漂移。  相似文献   
126.
结合基于遥感数据获得的土地利用结果与SCS模型,在GIS环境下模拟了上海浦东新区不同阶段的土地利用/覆被变化对地表径流的影响.结果表明:土地利用结构与格局的变化使地表径流深度趋于增大;同时,在浦东新区城市化的不同时期,由土地利用/覆被变化引起的地表平均径流深度变化也不相同.  相似文献   
127.
Abstract

Agglomeration of the Yangtze Delta (UAYD), one of the most developed regions of China, has witnessed an increasing prevalence in building ecological cities when the ecological cities are pursued by many modern cities, and great achievements have been made in this regard. It is inevitable, however, that certain problems exist during the construction of ecological city, which include but not limited to non-harmonious development of urban complex ecosystem, and the difficulty in quantifying eco-city construction or incomplete quantification in assessing the construction of present and future eco-city. Based on the analysis on social-economic conditions and regional conditions of the UAYD, this paper attempts to set up an index system of eco-cities combining with local characteristics, and to adopt the indices of eco-city, urban harmony, and eco-city colligate to evaluate the ecological level, urban harmonious development and eco-city construction of cities within the UAYD. Results indicate that among 15 cities in UAYD, Suzhou City ranks the highest in terms of eco-city construction, whereas Nantong ranks relatively lower; sustainable eco-city construction is possible only when cities are developed in every respect of harmony.  相似文献   
128.
Knowledge about carbon and nitrogen in plants and soils and response to fence and graze in alpine ecosystems is still rudimentary because of extremely geographic situation. The purpose of this study was to compare the difference among carbon, nitrogen concentration, and content of unit area and dynamics of above- and below-ground biomass, soil organic carbon and total nitrogen between fencing and grazing alpine meadow. The results showed that total carbon and C: N radio in the aboveground tissue were significantly higher in fenced and ungrazing grassland (FU) than those in free grazing grassland (FG). In addition, the order of total carbon and nitrogen concentration of aboveground tissue of different function groups were not identical between them; The total carbon storage (TCS) per unit of aboveground tissue, roots and 0–30 cm soil layer increased after being fenced for 5 years from free grazing grassland (9255.17 g/m2) to fenced and ungrazing grassland (12637.10 g/m2) by 26.79%. The corresponding total nitrogen storage (TNS) increased by 751.42 g/m2. Furthermore over 95% TCS (TNS) come from 0–30 cm soil layer. However there were no significant differences between fenced and ungrazing grasslands of 10 years and 5 years. Therefore fenced to exclude grazing by Tibetan sheep and yaks was an alternative approach to sequester C to the soil in alpine meadow systems.  相似文献   
129.
A pot experiment was conducted to investigate the influence of citric and oxalic acids effect on Pb and Zn uptake by corn and winter wheat. The experiment was employed with citric acid (CA) applied at 3 rates (0, 1.5 and 3.0 mmol kg-1 soil), oxalic acid (OA) at 3 rates (0, 1.5 and 3.0mmol kg-1 soil) and citric acid combined with oxalic acid (1.5 mmol citric acid combined with 1.5 mmol oxalic acid kg-1). Two types of soil were chose in the experiment. One was collected from the agricultural soil near a battery-recycling factory in Anhui province, China (site A) and the other was collected from a Pb-Zn mine residues in Hunan province, China (site B). The results showed that soil pH varied with the different treatment of citric and oxalic acids. However, there were no differences in all the treatments. 3.0mmol CA kg-1 soil addition significantly increased the concentrations of the CaCI2-extractable Pb and Zn and other treatments have no significantly increased. The highest shoot concentrations of Pb and Zn  相似文献   
130.
搞好综合开发是建设现代化农业的战略措施之一,而要搞好综合开发,必先搞好农业区域开发规划。本文根据涟水地区的自然资源、社会经济条件和市场对农副产品及其制品需求出发,把涟水县域划分为2个开发区域,从分析开发的潜力入手,通过投资和效益的分析,提出了区域近、远期的开发目标、步骤和相应的开发措施。  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