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   124篇
  免费   4篇
  国内免费   12篇
安全科学   12篇
废物处理   19篇
环保管理   5篇
综合类   25篇
基础理论   25篇
环境理论   3篇
污染及防治   39篇
评价与监测   4篇
社会与环境   7篇
灾害及防治   1篇
  2023年   2篇
  2022年   3篇
  2021年   2篇
  2019年   2篇
  2018年   4篇
  2017年   2篇
  2016年   6篇
  2015年   2篇
  2014年   5篇
  2013年   10篇
  2012年   7篇
  2011年   15篇
  2010年   8篇
  2009年   14篇
  2008年   12篇
  2007年   11篇
  2006年   7篇
  2005年   8篇
  2004年   6篇
  2003年   1篇
  2002年   4篇
  2001年   1篇
  2000年   3篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1958年   1篇
排序方式: 共有140条查询结果,搜索用时 15 毫秒
111.
112.
Long-term monitoring program of organisms is the most recommended for understanding changing processes on reefs. The video transect method presents advantages for that. Specialists state that it is important to make sure that the recorded coverage is always the same between campaigns, so that differences in results may be entirely attributed to environmental changes. This study aimed to test the capability of implementing this requirement through tracking simulation and its validity for monitoring the benthic communities of reefs using the video transect method. Ten transects 20 m long were established in Todos os Santos Bay coral reefs. Subsequent to the first transect capture, a second diver repeated the same track, simulating two different monitoring campaigns. Data were transformed and a matrix of similarity was generated using Bray–Curtis’ Index. ANOSIM analysis was performed to test the similarity of the ten transects and its repetitions. The result, R = 0.08 (P = 0.928), shows that reef monitoring using video transect, the way it is described in the literature, is appropriate, but it is important to consider some premises discussed in this work.  相似文献   
113.
Suspended particulate matter (SPM) and fine particulate matter (less than or equal to 2.5 μm: PM2.5) have generally been decreasing for the last decade in Tokyo, Japan. To elucidate the major cause of this decrease, the authors investigated the different trends of airborne particulates (both SPM and PM2.5 concentrations) by evaluating comparisons based on the location of the monitoring stations (roadside vs. ambient), days of the week (weekdays vs. Sundays), and daily fluctuation patterns (2002 vs. 2010). Hourly mean SPM and PM2.5 concentrations were obtained at four monitoring stations (two roadside stations, two ambient stations) in Tokyo, Japan. Annual mean concentrations of each day of the week and of each hour of the day from 2002 to 2010 were calculated. The results showed that (1) the daily differences in annual mean concentration decreased only at the two roadside monitoring stations; (2) the high hourly mean concentrations observed on weekdays during the daily rush hour at the two roadside monitoring stations observed in 2002 diminished in 2010; (3) the SPM concentration that decreased the most since 2002 was the PM2.5 concentration; and (4) the fluctuation of hourly concentrations during weekdays at the two roadside monitoring stations decreased. A decreasing trend of airborne particulates during the daily rush hour in Tokyo, Japan, was observed at the roadside monitoring stations on weekdays since 2002. The decreasing PM2.5 concentration resulted in this decreasing trend of airborne particulate concentrations during the daily rush hours on weekdays, which indicates fewer emissions were produced by diesel vehicles.
ImplicationsThe authors compared the trends of SPM and PM2.5 in Tokyo by location (roadside vs. ambient), days of the week (weekdays vs. Sundays), and daily fluctuation patterns (2002 vs. 2010). The high hourly mean concentrations observed at the roadside location during rush hour on weekdays in 2002 diminished in 2010. The SPM concentration that decreased during rush hour the most was the PM2.5 concentration. This significant decrease in the PM2.5 concentration resulted in the general decreasing trend of SPM concentrations during the rush hours on weekdays, which indicates fewer emissions were produced from diesel vehicles.  相似文献   
114.
Six products were formed by reaction of ethynylestradiol (EE2) with sodium hypochlorite in buffered solutions. 4-Chloroethynylestradiol (4-ClEE2) and 2,4-dichloroethynylestradiol (2,4-diClEE2) were identified as the two major reaction products, using preparative HPLC, MS, and NMR. When EE2 reacted with chlorine at different pHs (pH 5, 7, and 9) or chlorine concentrations (0.2, 1, 2, and 5 mmol/l, corresponding to molar ratios to EE2, 1, 5, 10, and 25, respectively), the formation of 4-ClEE2 and 2,4-diClEE2 was observed under the above conditions, and the highest yields were 20 and 52 mol%, respectively. EE2 was consumed almost completely within 5 min of chlorination by addition of chlorine of more than 1 mmol/l (molar ratio to EE2, 5). On the other hand, the two products existed in highly chlorinated solutions after 60 min (4ClEE2, 1-6 mol%; 2,4-diClEE2, 3-25 mol%). The estrogenic activities of 4-ClEE2 by estrogen receptor alpha or beta binding assay were similar to those of the parent EE2, and the activities of 2,4-diClEE2 were lower about 10 times.  相似文献   
115.
餐厨垃圾含丰富有机质,是潜在的廉价优质生物质资源;丁醇是继乙醇后的一种极具潜力的新型生物燃料。探索了以餐厨垃圾糖化液为原料,通过微生物发酵制取生物燃料丁醇。首先从实验室现有5株产丁醇梭菌中,优选出Clostridium beijerinckii NCIMB 8052作为丁醇生产菌,并考察在未添加任何营养物质,且不调节pH的条件下(简称非调控状态),以糖化液作为底物进行丁醇发酵的可行性。结果表明:非调控状态发酵的丁醇产量仅为5.96 g/L,并产生"酸崩"抑制;添加0.3%(w/V)Ca CO_3提高了糖化液pH缓冲能力,可解决"酸崩"问题,并将丁醇产量、总溶剂产量及丁醇生产速率分别提高了57.8%、53.1%和90.6%。这证明餐厨垃圾做为原料用于燃料丁醇生产是完全可行的。  相似文献   
116.
Biodegradationofsyntheticsurfactantsbyrivermicroorganisms¥HideakiMaki;KenrouTokuhiro;YasuhiroFujiwara;MichihikoIke;KenjiFuruk...  相似文献   
117.
为了定量分析大气总悬浮颗粒物(TSP)对居民呼吸系统疾病死亡率的影响,采用单因素泊松(Poisson)回归分析法,研究了辽宁省抚顺市城区TSP浓度变化与市区1999~2003年呼吸系统疾病死亡率的相关关系.结果发现,在消除了时间、气象等因素影响后,滞后4日TSP浓度每增加50μg·m-3,呼吸系统疾病总人群组死亡率相对危险度(OR)增加1.02195(95%CI=1.00195~1.04245),即滞后4日TSP浓度变化造成总人群组呼吸系统疾病死亡率明显增加的超额死亡率为2.195%.抚顺城区大气TSP污染可能是市区居民呼吸系统疾病死亡率增加的原因之一.  相似文献   
118.
Although traditional sexual selection theories for the evolution of ornamental male traits often assume consistency in female preferences for the traits over time, recent theories predict plasticity in female mate preferences and the contribution of plastic female preferences to the maintenance of polymorphism in male sexual ornaments. However, the plasticity of female preferences and its influences on male ornaments are almost unknown in natural populations. Here we examined both the intensity of female preferences and the exaggeration of a male ornament (relative area of orange spots) in a wild population of the guppy (Poecilia reticulata) every few months over a period of 3 years. Results indicated that female preference intensity was negatively correlated with the relative area of orange spots of males. In addition, we found a positive correlation between female preference intensity and the relative area of orange spots of males of their offspring generation. Because the relative area of orange spots of male guppies is a heritable trait, female preferences might have a strong influence on male orange spot size in the next generation. This study provides the first evidence of plastic female preferences depending on the scarcity of males with large ornaments in a natural population. Results of this study imply a possible contribution of female preferences for the maintenance of variation in male ornamentation.  相似文献   
119.
Steam gasification in the presence of carbonate compounds is an effective method to recover useful materials from electronic waste streams by converting plastics into gaseous products that can be used for energy production and avoiding the expensive manual disassembly process. We investigated steam gasification of activated carbon in the presence of various mixtures of lithium carbonate, sodium carbonate, and potassium carbonate. The activated carbon was almost completely converted into hydrogen and carbon dioxide at 700°C under 0.1 MPa pressure in the presence of carbonate mixtures. Carbon dioxide was also derived from partial decomposition of lithium carbonate. Steam gasification was accelerated in the presence of various carbonate mixtures and at increasing steam partial pressures. These experimental results show that fluidity of carbonates, the potassium content of the carbonate, and the steam partial pressure are important factors in accelerating steam gasification.  相似文献   
120.
日本企业安全培训现状及对中国的启示   总被引:2,自引:2,他引:0  
依据中日合作项目<加强中国国家安全生产科学技术能力计划>成果,系统介绍了日本企业安全培训相关法规要求、班组长培训讲师培养、安全培训指导方案编制等.同时,分析了中国安全培训现状,提出了开展企业内安全培训讲师培养,加强中国企业安全培训能力的建议,并对堵训目的、培训对象、培训讲师主要工作、培训主要内容等要点进行了阐述.本文对完善和提高中国企业安全培训具有重要的指导和参考意义.  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