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   537篇
  免费   18篇
  国内免费   5篇
安全科学   26篇
废物处理   22篇
环保管理   99篇
综合类   82篇
基础理论   149篇
环境理论   4篇
污染及防治   125篇
评价与监测   24篇
社会与环境   21篇
灾害及防治   8篇
  2023年   8篇
  2022年   3篇
  2021年   7篇
  2020年   8篇
  2019年   15篇
  2018年   13篇
  2017年   25篇
  2016年   19篇
  2015年   13篇
  2014年   10篇
  2013年   59篇
  2012年   28篇
  2011年   37篇
  2010年   22篇
  2009年   26篇
  2008年   28篇
  2007年   30篇
  2006年   20篇
  2005年   18篇
  2004年   14篇
  2003年   23篇
  2002年   11篇
  2001年   8篇
  2000年   10篇
  1999年   7篇
  1998年   11篇
  1997年   5篇
  1996年   5篇
  1995年   7篇
  1994年   5篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1990年   6篇
  1989年   5篇
  1988年   3篇
  1987年   3篇
  1986年   6篇
  1985年   7篇
  1981年   2篇
  1980年   2篇
  1978年   4篇
  1976年   2篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1967年   1篇
  1966年   1篇
  1958年   1篇
  1954年   1篇
排序方式: 共有560条查询结果,搜索用时 281 毫秒
551.
Monitoring was carried out of particulate concentrations whilst simultaneously walking and driving 48 routes in London, UK. Monitoring was undertaken during May and June 2005. Route lengths ranged from 601 to 1351 m, and most routes were travelled in both directions. Individual journey times ranged from 1.5 to 15 min by car (average 3.7 min) and 7.3 to 30 min (average 12.8 min) whilst walking; car trips were therefore repeated up to 5 times for each single walking trip and the results averaged for the route. Car trips were made with windows closed and the ventilation system on a moderate setting. Results show that mean exposures while walking are greatly in excess of those while driving, by a factor 4.7 for the coarse particle mass (PM10-PM2.5), 2.2 for the fine particle mass (PM2.5-PM1), 1.9 for the very fine particle mass (相似文献   
552.
Watercraft collisions account for 25–30% of manatee deaths annually in Florida. Education and outreach interventions for boaters are strategies for reducing manatee mortality. We evaluated the effectiveness of the Manatee Watch program by surveying primary boat users whose boats were approached by Manatee Watch. We compared the attitudes, knowledge, and behavioral intentions of boaters who received Manatee Watch materials with a control group of boaters observed by the Florida Marine Research Institute in Tampa Bay during 1999–2001. Results of the 51-item telephone survey with 499 boaters indicated that the Manatee Watch intervention had little effect on boater’s attitudes, knowledge, and behaviors regarding manatees. However, individual attitude scores were positively correlated with safe boating behaviors in shallow waters including maintaining a slower speed and watching out for manatees. Overall knowledge about manatees was correlated with one manatee-safe boating behavior. To improve efficacy, educators should (a) incorporate evaluation into the planning stages of program development; (b) target messages to influence boaters’ attitudes toward manatees and ecosystem health, and their feelings of ownership and empowerment; (c) facilitate active participation of the boaters; and (d) increase the duration and variety of intervention.  相似文献   
553.
To investigate the effects of moist olive husks (MOH-residues) on soil respiration, microbial biomass, and enzymatic (o-diphenoloxidase, beta-glucosidase, dehydrogenase and alkaline phosphatase) activities, a silty clay soil was incubated with 0 (control), 8 x 10(3) (D), 16 x 10(3) (2D) and 80 x 10(3) (10D) kg ha-1 of MOH-residues on a dry weight basis. Soil respiration and microbial biomass data indicated that the addition of MOH-residues strongly increased microbial activity proportionally to the amounts added. Data of qCO2 suggested that the respiration to biomass ratio of the microbial population was strongly modified by MOH-residues additions during the first 90 days of incubation. The qCO2 data suggested a low efficiency in energy yields from C oxidation during the first 2 months of soil incubation. qFDA seemed to be relatively unaffected for treatments D and 2D as compared to the control, but was significantly lowered by the application of 10D, showing the lowest hydrolytic activity of microbial biomass in this treatment up to 360 days of incubation. o-Diphenoloxidase activity was delayed, and this delay was extended with the addition of larger quantities of MOH-residues. Alkaline phosphatase, beta-glucosidase and dehydrogenase activities were in line with the findings on microbial biomass changes and activities. The biological and biochemical data suggest that the addition of a large quantity of MOH-residues (80 x 10(3) kg ha-1) strongly modifies the soil characteristics affecting the r- and K-strategist populations, and that these changes last for at least the 360 days of incubation. The data also suggest that application rates exceeding 16 x 10(3) kg ha-1 are not recommended until the agro-chemical and -physical functions of the soil are further studied.  相似文献   
554.
The association between cerium status and risk of first acute myocardial infarction (AMI) was examined in a case-control study in 10 centres from Europe and Israel. Cerium in toenails was assessed by neutron activation analysis in 684 cases and 724 controls aged 70 years or younger. Mean concentrations of cerium were 186 and 173 microg/kg in cases and controls, respectively. Cerium was positively associated with low socio-economic status, smoking, mercury, zinc and scandium (p0.001). Cases had significantly higher levels of cerium than controls after adjustment for age and centre (case-control ratio 1.074; 95% CI 1.002-1.151) and increased in further adjustment for other cardiovascular risk factors 1.085; 95% CI 1.025-1.149. The risk after adjustment for age and centre was higher with increasing cerium levels (p for trend=0.02). After adjustment for BMI, history of hypertension, smoking, alcohol intake, diabetes, family history of CHD, beta-carotene, lycopene, alpha-tocopherol, selenium, mercury and scandium, the OR for the highest quintile was 1.43 (95% CI 0.85-2.41; p-trend 0.08). When we applied this same model in non-smokers the odds ratios in the 4th and 5th quintiles of cerium as compared with the lowest were 2.09 (95% CI 1.05-4.16) and 2.81 (95% CI 1.21-6.52), respectively, p-trend 0.011. Our results suggest that toenail cerium levels may be associated with an increased risk of AMI, but more research is warranted to shed further light and fully understand the plausibility and public health implications of these findings.  相似文献   
555.
Conkle JL  White JR  Metcalfe CD 《Chemosphere》2008,73(11):1741-1748
A number of pharmaceutically active compounds (PhACs) have been detected in the aquatic environment as a result of discharges of municipal wastewater. In the state of Louisiana, USA, many municipalities treat wastewater using natural systems, such as lagoons and wetlands, rather than conventional wastewater treatment technologies. Nearly all research to date has focused on the fate of PhACs in conventional treatment plants, not constructed and natural wetlands. In the wastewater treatment plant (WWTP) for Mandeville, Louisiana, USA, wastewater flows of 7600 m3 d−1 are treated in a series of aeration lagoons (basins), followed by a constructed wetland and UV disinfection, before being discharged into a natural forested wetland (i.e. Bayou Chinchuba) and eventually, Lake Pontchartrain. Thirteen out of the 15 PhACs investigated were detected in the wastewater inflow to the treatment plant. Only 9 of the 13 compounds were above the detection limits at the treatment plant effluent. The concentrations of most compounds were reduced by greater than 90% within the plant, while carbamazepine and sotalol were only reduced by 51% and 82%, respectively. The percent reductions observed in the Mandeville system were greater than reduction rates reported for conventional WWTPs; perhaps due to the longer treatment time (30 days). Most target PhACs were not completely removed before discharge into Lake Pontchartrain, although their collective annual loading was reduced to less than 1 kg and down to ppb with significant potential for dilution in the large lake.  相似文献   
556.
Benzo[a]pyrene, a high molecular weight (HMW) polycyclic aromatic hydrocarbon (PAH) was removed from solution by Sphingomonas yanoikuyae JAR02 while growing on root products as a primary carbon and energy source. Plant root extracts of osage orange (Maclura pomifera), hybrid willow (Salix albaxmatsudana), or kou (Cordia subcordata), or plant root exudates of white mulberry (Morus alba) supported 15-20% benzo[a]pyrene removal over 24 h that was similar to a succinate grown culture and an unfed acetonitrile control. No differences were observed between the different root products tested. Mineralization of (14)C-7-benzo[a]pyrene by S. yanoikuyae JAR02 yielded 0.2 to 0.3% (14)CO(2) when grown with plant root products. Collectively, these observations were consistent with field observations of enhanced phytoremediation of HMW PAH and corroborated the hypothesis that co-metabolism may be a plant/microbe interaction important to rhizoremediation. However, degradation and mineralization was much less for root product-exposed cultures than salicylate-induced cultures, and suggested the rhizosphere may not be an optimal environment for HMW PAH degradation by Sphingomonas yanoikuyae JAR02.  相似文献   
557.
Environment Systems and Decisions - ‘Science’ is a proportionately small but recurring constituent in the rhetorical lexicon of political leaders. To evaluate the use of science-related...  相似文献   
558.
With the intention of securing industry-free land and seascapes, protecting wilderness entered international policy as a formal target for the first time in the zero draft of the Post-2020 Global Biodiversity Framework under the Convention on Biological Diversity. Given this increased prominence in international policy, it is timely to consider the extent to which the construct of wilderness supports global conservation objectives. We evaluated the construct by overlaying recently updated cumulative human pressure maps that offer a global-scale delineation of industry-free land as wilderness with maps of carbon stock, species richness, and ground travel time from urban centers. Wilderness areas took variable forms in relation to carbon stock, species richness, and proximity to urban centers, where 10% of wilderness areas represented high carbon and species richness, 20% low carbon and species richness, and 3% high levels of remoteness (>48 h), carbon, and species richness. Approximately 35% of all remaining wilderness in 2013 was accessible in <24 h of travel time from urban centers. Although the construct of wilderness can be used to secure benefits in specific contexts, its application in conservation must account for contextual and social implications. The diverse characterization of wilderness under a global environmental conservation lens shows that a nuanced framing and application of the construct is needed to improve understanding, communication, and retention of its variable forms as industry-free places.  相似文献   
559.
Environmental and Ecological Statistics - Within the field of geostatistics, Gaussian processes are a staple for modelling spatial and spatio-temporal data. Statistical literature is rich with...  相似文献   
560.
2010—2016年上海城区臭氧长时间序列变化特征初探   总被引:4,自引:0,他引:4       下载免费PDF全文
基于2010—2016年上海城区近地面大气臭氧(O3)的连续在线观测数据,研究了上海城区O3长时间序列变化规律和污染特征.结果表明,近7年来上海城区O3污染逐渐凸显,但总体以轻度污染为主,7—8月高温炎热季节以中度污染居多.城区O3-8 h(臭氧日最大8 h滑动平均)年均增速为3.81 μg·m-3·a-1,99%和95%分位值增速较快,分别为6.65和4.94 μg·m-3·a-1;25%、50%和75%分位值的增速在3.06~4.45 μg·m-3·a-1之间.春季O3浓度均值较高,年际变化小;夏季极值较高,且污染超标情况最为突出;秋季O3浓度次于春、夏季,冬季最低;夏、秋和冬季O3浓度总体呈上升态势.O3日变化呈"单峰型",最大值出现在13:00左右,且峰值逐年增加,污染持续时间变长,最小值出现在早晨7:00.城区O3"周末效应"逐渐减弱.基于KZ过滤器方法的数据分析结果表明,上海城区O3-8 h长期变化主要受O3-BF(O3-8 h的基准组分)影响;O3-SF(O3-8 h的天气影响组分)在5—9月对O3-8 h影响较大,其范围为-98.85~139.60 μg·m-3.  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