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   949篇
  免费   42篇
  国内免费   70篇
安全科学   80篇
废物处理   14篇
环保管理   302篇
综合类   154篇
基础理论   322篇
环境理论   1篇
污染及防治   75篇
评价与监测   48篇
社会与环境   47篇
灾害及防治   18篇
  2023年   15篇
  2022年   10篇
  2021年   28篇
  2020年   25篇
  2019年   18篇
  2018年   10篇
  2017年   17篇
  2016年   33篇
  2015年   26篇
  2014年   22篇
  2013年   61篇
  2012年   24篇
  2011年   69篇
  2010年   44篇
  2009年   77篇
  2008年   56篇
  2007年   49篇
  2006年   67篇
  2005年   46篇
  2004年   34篇
  2003年   31篇
  2002年   29篇
  2001年   22篇
  2000年   22篇
  1999年   12篇
  1998年   23篇
  1997年   16篇
  1996年   14篇
  1995年   15篇
  1994年   9篇
  1993年   9篇
  1991年   4篇
  1990年   7篇
  1989年   8篇
  1988年   6篇
  1987年   10篇
  1986年   6篇
  1985年   7篇
  1984年   4篇
  1983年   6篇
  1981年   9篇
  1980年   7篇
  1979年   12篇
  1978年   6篇
  1977年   5篇
  1975年   3篇
  1973年   5篇
  1972年   7篇
  1971年   5篇
  1970年   3篇
排序方式: 共有1061条查询结果,搜索用时 281 毫秒
881.
Normal theory procedures for calculating upper confidence limits (UCL) on the risk function for continuous responses work well when the data come from a normal distribution. However, if the data come from an alternative distribution, the application of the normal theory procedures may lead serious over- or under-coverage depending upon the alternative distribution. In this paper we conduct simulation studies to investigate the sensitivity of three normal theory UCL procedures to departures from normality. Data from several gamma, reciprocal gamma, and lognormal distributions are considered. The normal theory procedures are applied to both the raw data and the log-transformed data.  相似文献   
882.
通过对兵团土地利用空间格局变化分析,选择合适的土地利用政策保护生态环境。运用RS和GIS技术对兵团近10年土地利用/覆被变化及景观格局空间变化进行分析,并在此基础上运用Markov模型对未来30年土地利用变化进行预测。2000—2010年,新疆生产建设兵团景观多样性升高,连通性增强,形状愈来愈简单,景观格局整体变化不大;草地、灌丛、湿地、荒漠和冰川/永久积雪面积减少,耕地和城镇面积增加,森林保持稳定;人为干扰对土地利用结构的变化具有重要作用,土地利用强度受人为活动影响的同时受土地利用政策影响;在未来30年间耕地和城镇面积继续增加,除森林基本保持不变外其他土地利用类型均减小。兵团城镇用地与草地和耕地之间的矛盾逐渐显现,势必引起兵团生态格局的变化。因此,必须实行合适的土地利用政策保护环境。  相似文献   
883.
884.
Stirzaker R  Biggs H  Roux D  Cilliers P 《Ambio》2010,39(8):600-607
Decision makers responsible for natural resource management often complain that science delivers fragmented information that is not useful at the scale of implementation. We offer a way of negotiating complex problems by putting forward a requisite simplicity. A requisite simplicity attempts to discard some detail, while retaining conceptual clarity and scientific rigor, and helps us move to a new position where we can benefit from new knowledge. We illustrate the above using three case studies: elephant densities and vegetation change in a national park, the use of rules of thumb to support decision making in agriculture, and the management of salt in irrigation. We identify potential requisite simplicities that can allow us to generate new understanding, lead to action and provide opportunities for structured learning.  相似文献   
885.
生物质活性炭的制备及其染料废水中的应用   总被引:8,自引:0,他引:8  
以城市污水厂活性污泥为原料,用3 mol/L ZnCl2溶液活化,通入水蒸气作活化气制备活性炭吸附剂.实验结果表明,温度为600℃条件下,活化时间为1 h,制得的活性炭其碘吸附值为374.10 mg/g,比表面积为381.62 m2/g,孔容积为0.25 cm3/g,微孔容积为0.11cm3/g.并进一步将生物质活性炭应用于染料废水的处理,考察了吸附时间、活性炭投加量和pH对色度及TOC的脱除效果的影响.室温下,酸性大红GR染料废水初始浓度为300 mg/L,污泥活性炭的最佳投加量为2%(质量分数),吸附15min,废水色度脱除率可达99.6%,TOC去除率可达99.7%,利用等温吸附实验作吸附等温线,吸附等温线可以用Freundlich或Langmuir方程描述.  相似文献   
886.
Governments often impose new energy strategies to support new CO2 emission-reducing technologies without affecting economic growth. Hence, this study aims to re-investigate the relationship between economic growth, renewable energy use, and CO2 emissions in Algeria from 1990 to 2018. Motivated by the mixed findings of the existing literature, which ignore the Fourier function and bootstrap test and apply the newly developed Fourier bootstrap autoregressive distributed lag model (FARDL). Our findings indicate that renewable energy use and growth have a long-run relationship with CO2 emissions and do not accept the existence of the Environmental Kuznets Curve (EKC) hypothesis for CO2 emissions in Algeria. In the long term, the results show that renewable energy use has a negative and significant impact, and growth has a positive and statistically significant effect on CO2 emissions. In the short run, the findings indicate that renewable energy use reduces CO2 emissions, while both the growth and squared growth had positive and statistically insignificant impacts on CO2 emissions, confirming the lack of evidence supporting the EKC hypothesis. Moreover, the causality test indicates a one-way causation from growth to renewable energy use, confirming the conservation hypothesis for Algeria and from growth to CO2 emissions. Interestingly, we found one-way causality from CO2 emissions to renewable energy use, attributing this to the fact that renewable energy usage has yet to reach a point that it can significantly cause a CO2 emissions reduction. Based on the results, we recommend that policymakers design appropriate policies to decarbonize energy consumption, e.g., increasing fossil fuel costs and implementing a carbon tax. In contrast, Algeria should promote new CO2 emission-reducing technologies without affecting economic growth, e.g., tax exemptions and reductions for enterprise owners in the renewable energy industry.  相似文献   
887.
十三陵抽水蓄能电站施工期间排放废水,造成了对周围地下水的污染。本工作沿地下水流动方向4.4km^2的范围内,进行了地下水的环境质量调查,分析和评价,查明了地下水污染因子和污染程度及范围,通过消除污染源,建设污水处理站等一系列水质恢复措施后,该地区地下水水质明显好转。  相似文献   
888.
Introduction: Rear-end crashes are one of the most frequent crash types in China, leading to significant economic and societal losses. The development of active safety systems – such as Automatic Emergency Braking System (AEBS) – could avoid or mitigate the consequences of these crashes in Chinese traffic situations. However, a clear understanding of the crash causation mechanisms is necessary for the design of these systems. Method: Manually coded variables were extracted from a naturalistic driving study conducted with commercial vehicles in Shanghai. Quantitative analyses of rear-end crashes and near crashes (CNC) were conducted to assess the prevalence, duration, and location of drivers’ off-path glances, the influence of lead vehicle brake lights on drivers’ last off-path glance, and driver brake onset, and the influence of off-path glances and kinematic criticality on drivers’ response to conflicts. Results: The results indicate that the Chinese truck drivers in our study rarely engage in distracting activities involving a phone or other handheld objects while driving. Instead, they direct their off-path glances mainly toward the mirrors, and the duration of off-path glances leading to critical situations are shorter compared to earlier analyses performed in Western countries. The drivers also often keep small margins. Conclusions: Overall, the combination of short time headway with off-path glances directed toward the mirror originates visual mismatches which, associated to a rapid change in the kinematic situation, cause the occurrence of rear-end CNC. When drivers look back toward the road after an off-path glance, a fast response seems to be triggered by lower values of looming compared to previous studies, possibly because of the short time headways. Practical Application: The results have practical implications for the development of driver models, for the design of active safety systems and automated driving, and for the design of campaigns promoting safe driving.  相似文献   
889.
Zeolitic materials have been prepared from coal fly ash as well as from a SiO2–Al2O3 system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni2+, Cu2+, Cd2+ and Pb2+ were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin–Kaganer–Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model.  相似文献   
890.
Household water use behavior: An integrated model   总被引:1,自引:0,他引:1  
Water authorities are dealing with the challenge of ensuring that there is enough water to meet demand in the face of drought, population growth and predictions of reduced supply due to climate change. In order to develop effective household demand management programs, water managers need to understand the factors that influence household water use. Following an examination and re-analysis of current water consumption behavioral models we propose a new model for understanding household water consumption. We argue that trust plays a role in household water consumption, since people will not save water if they feel others are not minimizing their water use (inter-personal trust). Furthermore, people are less likely to save water if they do not trust the water authority (institutional trust). This paper proposes that to fully understand the factors involved in determining household water use the impact of trust on water consumption needs investigation.  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