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   1667篇
  免费   147篇
  国内免费   289篇
安全科学   160篇
废物处理   23篇
环保管理   269篇
综合类   984篇
基础理论   212篇
环境理论   2篇
污染及防治   103篇
评价与监测   62篇
社会与环境   213篇
灾害及防治   75篇
  2024年   3篇
  2023年   26篇
  2022年   29篇
  2021年   45篇
  2020年   52篇
  2019年   51篇
  2018年   45篇
  2017年   79篇
  2016年   69篇
  2015年   76篇
  2014年   75篇
  2013年   135篇
  2012年   142篇
  2011年   150篇
  2010年   111篇
  2009年   116篇
  2008年   90篇
  2007年   121篇
  2006年   118篇
  2005年   89篇
  2004年   65篇
  2003年   50篇
  2002年   58篇
  2001年   36篇
  2000年   35篇
  1999年   36篇
  1998年   23篇
  1997年   24篇
  1996年   25篇
  1995年   28篇
  1994年   14篇
  1993年   15篇
  1992年   16篇
  1991年   16篇
  1990年   5篇
  1989年   10篇
  1988年   4篇
  1986年   2篇
  1985年   2篇
  1984年   4篇
  1983年   1篇
  1981年   4篇
  1980年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1972年   2篇
  1971年   1篇
  1969年   1篇
排序方式: 共有2103条查询结果,搜索用时 99 毫秒
671.
Ecological accounting is concerned with providing information to assist managers with performance appraisal, control, decision-making and reporting for an organisation or region. It is based on ecological concepts and on ecological measures and values in addition to the familiar economics ones. The implementation of sustainable development requires a cultural change and ecological accounting would represent a part of this change within both organisations and wider society. In many ways, ecological accounting could help bring sustainable development into common sense and give it a place as a day-to-day business goal.  相似文献   
672.
食品应急储备配置比例及方法研究   总被引:1,自引:0,他引:1       下载免费PDF全文
为提升食品应急储备的科学性、合理性,在总结分析食品应急储备的种类、形式与影响因素的基础上,以我国官方发布的食物与营养发展目标为依据,确定了八大类应急储备食品的基础配置比例,并提出了食品大类配置比例的修正方法,随后综合考虑生产周期、保质期、易储性和储备成本,给出实物储备和产能储备的配置方法,最后提出了单类食品实物储备模式下单品的配置原则和方法,并以单价修正为例对单品选择性修正方法进行了说明,对不断提高突发事件应急保障工作的水平,提升应对突发事件的保障能力,实现受灾群众更科学合理的饮食结构有重要意义。  相似文献   
673.
劳动负荷的提高会导致作业疲劳,但适当的劳动负荷对作业能力的提高可能有一定促进作用。设计实验,分析了RPE值和相对心率的相关性,并以相对心率和RPE值为解释变量,分析了它们和反应时、两点阈之间的关系,发现反应时和两点阈在负荷增加过程中存在一个最小值点,而导致这个点出现的劳动负荷即为最佳负荷。以此最佳负荷量安排作业对合理利用劳动力,提高劳动效率,保护劳动者有一定的意义。  相似文献   
674.
中国环渤海地区县域土地适度非农化研究   总被引:7,自引:5,他引:2  
基于土地非农化与经济发展阶段耦合规律的理论分析,应用承载力模型,开展了2008年环渤海地区县域土地非农化适度性的评价和土地适度非农化阈值的界定。结果表明:①受区域土地资源禀赋与经济社会需求的影响,经济社会发展对非农建设用地的需求与建设用地供给之间呈现为正反双向的"S"型曲线,两者之间的耦合变化规律以工业化完成阶段最为显著;②工业化初期至后期阶段土地非农化趋势表现为缓慢增长,土地适度非农化阈值为10.0%~17.5%;③工业化与城镇化驱动作用强度决定着土地非农化规模的区域差异。因地制宜、科学调控土地非农化进程是区域可持续发展的重要保障。  相似文献   
675.
Resilience to natural hazards: How useful is this concept?   总被引:1,自引:0,他引:1  
Resilience is widely seen as a desirable system property in environmental management. This paper explores the concept of resilience to natural hazards, using weather-related hazards in coastal megacities as an example. The paper draws on the wide literature on megacities, coastal hazards, hazard risk reduction strategies, and resilience within environmental management. Some analysts define resilience as a system attribute, whilst others use it as an umbrella concept for a range of system attributes deemed desirable. These umbrella concepts have not been made operational to support planning or management. It is recommended that resilience only be used in a restricted sense to describe specific system attributes concerning (i) the amount of disturbance a system can absorb and still remain within the same state or domain of attraction and (ii) the degree to which the system is capable of self-organisation. The concept of adaptive capacity, which has emerged in the context of climate change, can then be adopted as the umbrella concept, where resilience will be one factor influencing adaptive capacity. This improvement to conceptual clarity would foster much-needed communication between the natural hazards and the climate change communities and, more importantly, offers greater potential in application, especially when attempting to move away from disaster recovery to hazard prediction, disaster prevention, and preparedness.  相似文献   
676.
Biological control at the larval stages of development of mosquitoes is one of the techniques that afford a non-expensive, easy-to-use, and environment-friendly method for mosquito control. In this study, investigations were undertaken on microbial product to develop a strategy to control mosquito larval and pupal population in the lab and field. Highest larval mortality was evident in the lab with LC50 and LC90 at 0.25 and 0.5 at 24?h for Aedes aegypti. In the field study, to kill mosquito larval population resulting in 100% mortality of A. aegypti required 5 days duration. The dose-dependent mortality was calculated using a lethal time of approximately 1–5 days test period. The number of mosquito bites (%) (vectorial capacity) decreased at increasing concentration of fungal insecticide. Data indicate that the fungal pathogen interacting with mosquito larvae controlled mosquitoes in the lab and field.  相似文献   
677.
上海淀山湖水环境容量评估   总被引:4,自引:0,他引:4       下载免费PDF全文
淀山湖是上海市重要的饮用水源保护区和生态涵养区.近10年来水质富营养化程度急剧增加,藻类水华频发,对上海饮用水源地水质安全构成了巨大威胁.为水污染控制和水质改善提供科学依据,利用已有评估模型评估了不同水质目标情景下淀山湖对COD、TN 和TP的最大容量,结果表明,在保持现状水质条件下,COD、TN和TP的环境容量分别为47213,8337.7,476.3t/a;水质控制目标为II类时,其环境容量分别为46325,1191.1,59.5t/a;水质目标为III类时,环境容量分别为68547,2382.2,119.1t/a.为IV类水质目标时,TN、TP的环境容量分别为3573.3,238.2t/a.  相似文献   
678.
Abstract

A series of mesocosms was exposed to a suite of light treatments and nutrient enrichment in order to generate algal communities of varying biomass. the influence of this biomass on the speciation of copper (II) was studied. Distribution coefficients ( Kd,Lkg?1) were relatively high (log Kd = 5 to 7), indicative of robust trace metal sequestration, and were likely controlled by the particulate organic carbon content (foc). Differences in Kd over time and among treatments were significant, as was the relationship between Kd and foc. Fluorescence quenching was used to determine binding capacities ( Lt , M) and their associated binding constants ( Kcond ,M?1) in order to model the solid phase copper speciation. the Kcond ranged between 2.1 and 5.2 × 1012M?1, indicating a very strong copper-ligand complex, and was higher in mesocosms that received more light. the light Lt increased over time, dramatically after the nutrient enrichment, but did not vary systematically among light treatments. Lt ranged from 7.2 × 10? 7 to 4.9 × 10? 5 M. the large magnitudes of Kd , Kcond and Lt ensured that greater than 97% of total copper in the mesocosms was complexed by organic matter. the total copper concentration ([Cu]T, M) needed to reach a target dissolved copper concentration of 10?12.5 M (pCu = 12.5) was determined for each mesocosm over time. [Cu]T was between 8.02 × 10?5 and 3.41 × 10?2 M, and increased over time. the [Cu]T normalized to the target pCu (Effective Dose Ratio, EDR) increased directly with increases in algal biomass, indicating a direct link between system productivity and copper exposure. Approximately 45% of the variance in EDR was explained by variance in total biomass, while the residual variance in EDR was due likely to differences in the strengths of particle associations and magnitude of binding capacities.  相似文献   
679.
为探讨红花荷(Rhodoleia championii)等12种园林植物抗SO2和NO2污染能力,以1~2年生实生苗为材料,通过人工气候室的盆栽实验,研究不同SO2和NO2混合气体胁迫对园林植物苗木光合参数和相对叶绿素含量的影响,并利用隶属函数法及系统聚类分析法对其抗SO2和NO2污染能力进行了综合评价。结果表明,植物叶片净光合速率、气孔导度、蒸腾速率和相对叶绿素含量基本上随着SO2和NO2胁迫的加剧而逐渐降低,但水分利用效率受净光合速率和蒸腾速率变化的影响规律不明显。综合隶属函数和聚类分析可知,红花荷和红千层(Callistemon rigidus)抗污染能力强,杜鹃红山茶(Camellia azalea)和粉红羊蹄甲(Bauhinia blakeana)抗污染能力较强,红花银桦(Grevillea robusta)和无忧树(Saraca divespierre)抗污染能力中等,大叶紫薇(Lagerstroemia speciosa)、金花风铃木(Tabebuia chrysantha)和腊肠树(Cassia fistula)抗污染能力较弱,而本地火焰木(Spathodea nilotica)、复羽叶栾树(Koelreuteria bipinnata)和樱花(Prunus serrulata)抗污染能力弱。研究结果为火电厂、陶瓷厂、钢铁厂、石化厂等重度酸污染地区植物选择提供参考。  相似文献   
680.
根据承载力确定土地资源安全度--以江苏省为例   总被引:13,自引:0,他引:13  
土地资源安全维系着国民经济的可持续发展,而可持续发展是在不超过生态系统承载力情况下的一种安全发展模式.因此,通过土地资源承载力分析,可以了解土地资源的安全度.由于人类种群的增长可用Logstic模型(DN)/(dt)=r*N*(\{K-N\})/(K)加以描述.运用熵理论推导证明(K)/(2)≤N<1 (1)/(3)*(K)/(2)为模型的全局解,可作为区域土地资源的人口安全区间.以江苏省为例,在确定人口承载力的基础上,分别给出了温饱型、小康型和富裕型等三种生活水平下的土地资源安全评价标准.结果表明:目前江苏省土地资源在三种生活水平下均处于安全状况,但在富裕生活水平下人口已接近安全上限,必须控制人口,保护土地资源;提出进一步研究土地资源安全度应解决的几个问题.  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