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   146篇
  免费   12篇
  国内免费   1篇
安全科学   19篇
废物处理   6篇
环保管理   11篇
综合类   39篇
基础理论   72篇
污染及防治   7篇
评价与监测   1篇
社会与环境   1篇
灾害及防治   3篇
  2025年   1篇
  2024年   6篇
  2023年   6篇
  2022年   6篇
  2021年   2篇
  2020年   9篇
  2019年   2篇
  2018年   3篇
  2017年   4篇
  2016年   4篇
  2015年   5篇
  2014年   2篇
  2013年   3篇
  2012年   4篇
  2011年   2篇
  2010年   2篇
  2009年   10篇
  2008年   8篇
  2007年   17篇
  2006年   8篇
  2005年   3篇
  2004年   8篇
  2003年   2篇
  2002年   3篇
  2001年   4篇
  2000年   5篇
  1999年   3篇
  1998年   6篇
  1997年   4篇
  1996年   4篇
  1995年   10篇
  1994年   2篇
  1991年   1篇
排序方式: 共有159条查询结果,搜索用时 15 毫秒
91.
改革开放以来,中国经济发展水平不断提高,城市生活垃圾产量急剧增加。文章根据中国的实际情况,提出垃圾分类收集方案,运用层次分析法对垃圾分类收集方案进行了优化,确定出了垃圾分类收集最佳方案。即将生活垃圾分为厨房垃圾、客厅和卧室垃圾、厕所垃圾及有毒有害垃圾4类。  相似文献   
92.
Previous research has suggested that parental condition may affect offspring mortality patterns by affecting offspring testosterone levels. Accordingly, we hypothesized that there is a relationship between offspring testosterone concentration and survival during the early nestling period, and that both are influenced by parent age/experience and by prey availability. We tested our hypothesis on tawny owls Strix aluco in their first and third known breeding seasons, when they bred either in adverse or mild weather conditions, in Duna-Ipoly National Park, Hungary. Plasma testosterone concentrations of the nestlings were analyzed and related to parental condition, hatching order and nestling mortality. Inexperienced parents breeding in all weather conditions and experienced parents breeding in adverse conditions were both in poor condition compared to experienced parents breeding in mild conditions. Parents in poor condition produced broods with large between-sibling differences in testosterone concentrations and their later-hatched nestlings (which had low testosterone levels) died during the early nestling period, whereas parents in good condition produced broods with lower variation in offspring testosterone concentrations and all offspring survived the early nestling period. We discuss environmental influences on the amount of testosterone deposited in eggs, and also how maternal testosterone might induce those mechanisms producing testosterone in the nestlings.Communicated by M. Webster, T. Czeschlik  相似文献   
93.
    
Many birds hatch their offspring asynchronously, and the adaptive significance of this trait, if any, is controversial. David Lack suggested long ago that by facilitating brood reduction when resources are scarce, hatching asynchrony provides relief from the effects of overcrowding. Some field workers interpret this to mean that the growth and survival of survivors should rise following partial brood loss. Here we show in a 6-year study of red-winged blackbirds (Agelaius phoeniceus) that the presence or absence of marginal offspring in experimentally manipulated broods had virtually no effect upon the growth of core offspring, whereas alterations of the size of core brood had strong and significant effects. Nestling growth was, not surprisingly, slower in broods with partial brood loss. Intriguingly, marginal offspring showed significantly greater variation in mass. Core offspring are less sensitive to, but not exempt from, the inimical effects of resource shortfall than are marginal offspring. The phenotypic handicap appears to marginal offspring a caste of high-variance progeny whose fitness prospects rest upon levels of parental input (stochastic resources) and the size of the core brood (stochastic development). Received: 21 June 1999 / Revised: 5 June 2000 / Accepted: 25 June 2000  相似文献   
94.
胡彪  赵俊华  李健毅 《环境工程学报》2016,10(10):5855-5860
通过对近红外光谱(NIRS)识别分选混合废塑料的过程建立数学模型,将经过预处理的废塑料在传送带上的分布分为密集区和稀疏区两大类。以降低分选时间,提高分选效率为研究目的,对影响分选效率的因素进行分析,如分选机所能承受物料密集度上限值θ以及传送带的传输速度V等因素。比较不同θ和V的组合对总分选时间T的影响,通过数值计算并验证,求得最优组合解。研究结果表明:θ的大小影响密集区和稀疏区的面积在总面积中占有量的变化;分选总时间T在θ和V共同变化过程中存在极小值。  相似文献   
95.
垃圾分类制度的推行,实现了湿垃圾(厨余垃圾)从混合垃圾中的分出,垃圾产生特征与流向随之发生变化,进而对后续处理过程环境表现带来影响.针对受分类制度影响最大的干、湿垃圾组分,基于生命周期思想提出了碳排放量核算方法,并以垃圾分类典型城市上海市为例,探究分类前后混合垃圾与分类垃圾处理的生命周期碳排放特征.结果显示,随着垃圾分类制度的实施,干湿垃圾处理系统整体碳排放量明显下降,减排程度受干湿垃圾分出水平和垃圾组分变化影响.对比垃圾分类前后单位垃圾处理碳排放量发现,排放量由分类前的300.4 kgCO2eq·t-1降至分类后的200.3~244.1 kgCO2eq·t-1,最多降低了 33.3%.从碳排放来源来看,垃圾焚烧带来碳排放量贡献最大,其中又以焚烧直接碳排放占比最大.相比之下,湿垃圾处理总体排放强度较小,厌氧消化残渣处理方式是影响湿垃圾处理碳排放的关键.综合来看,湿垃圾的有效分出和低碳化处理是干湿垃圾处理系统碳排放量降低的关键.对干湿垃圾资源化处理工艺开展减排潜力分析发现,综合采用干垃圾焚烧热电联产和湿垃圾残渣作土壤改良剂可进一步实现碳减排.  相似文献   
96.
The reproductive biology of spiny lobster, Panulirus penicillatus, was studied based on 2,068 lobsters, ranging from 34.28 to 131.60 mm carapace length (CL), sampled in Taitung coastal waters from September 2003 to December 2004. The overall sex ratio approximated 1:1 (χ2 = 0.02, P > 0.05), but the monthly sex ratios in 2004 showed significant differences and males were predominant in sizes larger than 80 mm CL. Reproductive activity, assessed using histology, a gonadosomatic index and percentage of ovigerous females, indicated that the mature females could be found in every month and that the major spawning occurred from May to September. The presence of re-developing/re-ripe ovaries by month and size-specific spawning time suggest that larger mature females (>60 mm CL) spawn at least three times a year while smaller new mature females spawn at least once a year. For females, the estimated sizes at 50% physiological and functional maturity were (mean ± SE) 56.46 ± 0.56 mm CL and 66.63 ± 1.07 mm CL. The estimated sizes at functional maturity were between 72 and 74 mm CL for males. The number of eggs per spawning event (brood size, BS) was related to CL by the equation Y BS = 2.4 × 10-3CL4.18 (r 2 = 0.902, n = 12). Female lobsters with CL ranging from 60 to 80 mm made the greatest contributions to egg production because of their high brood size and active reproductive activity. A minimum legal size should be established for the fishery to protect egg production potential of lobster population in the southeastern coastal waters off Taiwan.  相似文献   
97.
基于非结构模糊决策的中国药品安全管理体系研究   总被引:1,自引:0,他引:1  
基于安全管理理论和中国药品管理实践,通过专家意见和社会调查,确定中国药品安全管理的要素和决策标准;运用非结构模糊决策方法确定中国药品安全管理中各重要要素的权重,从而探索中国药品安全管理体系;对体系的不同要素进行排序.研究表明:影响中国药品安全管理的主要要素有,安全交易、许可制度、药品利润率、可追溯体系、药物警戒、应急管理;决策标准是,成本、经济水平、硬件条件、从业人员素质、消费者观念;重要性排序是,可追溯体系、许可制度、药物警戒、应急管理、安全交易、药品利润率.药品安全管理体系的建立和要素排序为政府监管提供了科学依据.  相似文献   
98.
结合当前国内外对高速铁路动车组运用的相关研究,给出了动车组周转这一特大型组合优化问题的数学描述并建立神经网络模型,提出了基于分层聚类思想与模拟退火算法相结合的解决方案,降低了算法的时间复杂度,达到了减少车底在车站的停留时间,提高了车底利用效率,为优化我国在建和拟建的高速铁路、城际客运专线的动车组周转及计算机自动编制车底运用计划提供理论支持,并结合实际客运专线运用计算机模拟进行检算,证实了算法的可行性、实用性.  相似文献   
99.
广州市城市木质废弃物资源化利用的初步探讨   总被引:1,自引:0,他引:1  
目前,广州市已全面实施垃圾分类工作,将城市垃圾中占一定比重的木质废弃物进行资源化利用对解决城市垃圾减量问题具有重大意义。提出总体布局回收网络,规划分拣中心,整合资源化利用平台,推动公共政策服务规范化和标准化的思路和构想,推进木质废弃物资源化利用,为实现广州市垃圾减量和推动循环经济发展提供参考。  相似文献   
100.
The relationship between the pattern of pollutant releases and neighborhood characteristics has been in the center of environmental justice debates for the last decades. One part of the discourse revolves around the question if the siting decision of polluting firms or the sorting decision of households is the explanatory factor for the pattern of pollutant releases. The aim of this study is to contribute to the discussion by investigating the potential correlation between polluting facilities and socioeconomic characteristics of neighborhoods in Ontario, Canada, using data from the Canadian census and National Pollutant Release Inventory. The analysis shows that when the results are considered from the perspectives of the siting decision of firms and sorting decision of households’ hypotheses, the results weigh in favor of the sorting decision of households.  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