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   197篇
  免费   21篇
  国内免费   42篇
安全科学   10篇
废物处理   7篇
环保管理   14篇
综合类   79篇
基础理论   91篇
污染及防治   39篇
评价与监测   4篇
社会与环境   1篇
灾害及防治   15篇
  2023年   5篇
  2022年   3篇
  2021年   8篇
  2020年   8篇
  2019年   4篇
  2018年   5篇
  2017年   8篇
  2016年   12篇
  2015年   11篇
  2014年   14篇
  2013年   28篇
  2012年   21篇
  2011年   17篇
  2010年   11篇
  2009年   19篇
  2008年   11篇
  2007年   15篇
  2006年   15篇
  2005年   14篇
  2004年   4篇
  2003年   4篇
  2002年   3篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   4篇
  1984年   2篇
  1982年   1篇
  1980年   1篇
排序方式: 共有260条查询结果,搜索用时 15 毫秒
231.
Oral vaccination of foxes (OVF) is a powerful tool to combat rabies in wildlife, and large parts of western Europe have been freed from rabies using this tool. Nevertheless, the success of OVF, given with the number of campaigns needed to eliminate the disease, depends on many factors. This article for the first time focuses on and assesses difference in OVF with respect to the spatial setting of vaccinated areas with time. The size of the areas vaccinated with time and the size of the overlapping area of consecutively vaccinated areas are particularly considered. In order to integrate these two aspects into one single figure, an Area Index is proposed ranging between 0 and 1. A statistical analysis indicates that the number of campaigns needed for rabies elimination significantly decreases on condition that the total rabies endemic area is consecutively treated right from the beginning of oral vaccination. Hence, from an economical and environmental point of view, vaccination areas should be selected the way that guarantees an Area Index close to 1. The concept of an Area Index, as described here, is a useful tool not only in the context of OVF, but it could also be used for other control schemes against infectious diseases in wildlife.  相似文献   
232.
ABSTRACT: The 1950 flood disaster in the Red River Valley, Manitoba, and particularly in Winnipeg made all levels of government aware of the need for control measures. The principal elements of the system which was implemented were two large excavated diversion channels, a storage reservoir, and ring dykes around several small communities. In terms of cost and size, the flood control system is the largest in Canada and despite Federal contributions amounting to nearly 60 percent of the final cost, it represented a considerable fiscal burden for the comparatively small population of Manitoba. Between the opening of the Red River Floodway in 1968 and 1979, a series of exceptional spring peak flows on the Red and Assiniboine Rivers demonstrated the benefits of such a system to a degree which could not have been anticipated at the time the projects were being considered. Furthermore, maximum spring discharges from 1913 to 1978 show a clear rising trend, indicating that the flood hazard is becoming even more severe than was initially assumed; if this trend continues, future benefits will continue to exceed expectations. The overall effectiveness of the hazard reduction program in the Red River Valley, however, has suffered from continued development in unprotected areas. Recent federal-provincial agreements have been reached which will substantially reduce this problem and place greater emphasis on improving the non-structural components of an overall flood hazard reduction program.  相似文献   
233.
Globally, many invasive alien species have caused extensive ecological and economic damage from either accidental or intentional introduction. The red imported fire ant, Solenopsis invicta, has created billions of dollars in costs annually, spreading as an invasive species across the southern United States. In 1998, the red imported fire ant spread into California creating a highly probable future introduction via shipped products to Hawaii. This paper presents the estimation of potential economic impacts of the red imported fire ant (RIFA) to the state of Hawaii. Evaluation of impacts focuses on the economic sectors of (1) households, (2) agriculture (cattle and crop production), (3) infrastructure (cemeteries, churches, cities, electrical, telephone, and cable services, highways, hospitals and schools), (4) recreation, tourism and business (hotels/resort areas, golf courses, commercial businesses and tourists), and (5) government expenditures (with minimal intervention). The full annual economic costs of the red imported fire ant to Hawaii are estimated (in US$ 2006) to be $211 million/year, comprised of $77 million in damages and expenditures and $134 million in foregone outdoor opportunities to households and tourists. The present value of the projected costs of RIFA over a 20-year period after introduction total $2.5 billion. RIFA invasions across the globe indicate that economic cost-effective action in Hawaii entails implementation of prevention, early detection and rapid response treatment programs for RIFA.  相似文献   
234.
The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation.  相似文献   
235.
Where floods are prevalent, decisions on how to mitigate vulnerability are made within a social-cultural context that includes values (and related customs, norms, beliefs, technology) of local people, which have evolved through interactions with the physical environment. Consequently, the success of floodplain management and flood mitigation activities is determined, at least in part, by the nature of values that impact the decision-making process. This paper explores this contention by considering the community values context surrounding flood risk management in two small Canadian communities in the Red River Basin.

Using a qualitative methodology that includes semi-structured interviews with residents, community values are identified and accounted for in the context of flood vulnerability. Values discussions are organized around seven broad categories: community identity and community attributes; community economic development; technical and nonstructural approaches; civic engagement; flood legacy; personal rights and liberties; and shared values. Challenges posed by key identified values and their policy implications are considered. Some values are found to act as constraints if sustainable floodplain management practices are to be realized.  相似文献   
236.
The early phases of a project to design and make operational an ombudsman for humanitarian assistance (HAO) are described in this paper. Beginning with a brief historical overview of the ombudsman concept, it then outlines seven key features of a potential HAO that were identified in the initial feasibility study. The main conclusion from the feasibility study was that, in principle, it is possible to design an HAO by adapting the operational frameworks of existing ombudsman schemes so as to match the needs of the humanitarian sector. Although this seems possible in theory, there still remain some major challenges requiring practical testing in a pilot phase. The most fundamental of these is how to enable the beneficiaries of aid to make their voices heard and register their views on the management of the emergency that is affecting them. Important also, are the issues of ensuring an international jurisdiction and finding sustainable ways of financing the scheme. Finally, the paper alludes to the framework of the pilot itself and how to address the main challenges ahead.  相似文献   
237.
The influence of a Reactive Brilliant Red X-3B (RBR X-3B) dye on the peroxidase isoenzyme of Phanerochaete chrysosporium was determined, and the biofilm structure in a white rot fungal continuous membrane bioreactor (MBR) was also investigated by scanning electron microscope (SEM). The variation of peroxidase isoenzyme and the decolorization rate in the continuous MBR were evaluated. The results showed that the 100 mg/L RBR X-3B could stimulate the production of the peroxidase isoenzyme in the shaking-flask culture. In addition, two new peroxidase isoenzyme bands with relative mobility (Rf) value of 0.27 and 0.28 appeared, but the activity was lower than the blank control of 11 d. In the continuous MBR, the system worked stably during the first 60 d, the main peroxidase isoenzyme bands existed and three new bands with Rf value of 0.10, 0.27, and 0.28 appeared. Meanwhile, the biofilm grew well and the average decolorization rate could reach 90.6%. But the bands of peroxidase isoenzyme decreased rapidly at day 65, only two bands with Rf value 0.24 and 0.26 existed, and the decolorization rate decreased to 78.3%. Therefore, 5 bottles of P. chrysosporium mycelial pellet were added into the MBR, and then the activity of the peroxidase isoenzyme and the decolorization rate had a slight recovery. Finally, the decolorization rate finally decreased to 75.2%. These results contribute to a comprehensive understanding of the variation of peroxidase isoenzyme and biofilm in continuous MBR by white rot fungi.  相似文献   
238.
基于紫外辐照/硼氢化钾/亚硫酸氢钠(UV/KBH4/NaHSO)3体系下对活性艳红X-3B进行还原脱色反应,重点探讨了该体系下还原降解活性艳红X-3B的反应机理,考察了硼氢化钾和亚硫酸氢钠的摩尔比(B/S)、辐射光强对其反应机理的影响。结果发现,UV/KBH4/NaHSO3处理染液具有明显协同作用,初步推测光助硼氢化钾和亚硫酸氢钠还原活性艳红X-3B的脱色反应是SO2-参与的自由基反应;脱色反应的B/S最佳摩尔比为1:30;增加辐射光的强度对染液的还原脱色反应过程具有明显的促进作用。  相似文献   
239.
National Oceanic and Atmospheric Administration's National Weather Service (NWS) flash flood warnings are issued by Weather Forecast Offices and are underpinned by information from the Flash Flood Guidance (FFG) system operated by the River Forecast Centers (RFCs). This study focuses on the quantitative evaluation and limitations of the FFG system using reported flash flood cases in 2010 and 2011. The flash flood reports were obtained from the NWS Storm Event database for the Arkansas‐Red Basin RFC (ABRFC). The current FFG system at the ABRFC provides gridded flash flood guidance (GFFG) system using the NWS Hydrology Laboratory‐Research Distributed Hydrologic Model to translate the upper zone soil moisture to estimates of Soil Conservation Service Curve Numbers. Comparisons of the GFFG and real‐time Multisensor Precipitation Estimator‐derived Quantitative Precipitation Estimate for the same duration and location were used to analyze the success of the system. Typically, the six‐hour duration was characterized by higher probability of detection values than the three‐hour duration, which highlights the difficulty of hydrologic process estimation for shorter time scales. The current system does not take into account physical characteristics such as land use, including irrigated agricultural farm and urban areas, hence, overly dry soil moisture estimates over these areas can lower the success rate of the GFFG product.  相似文献   
240.
玻璃纤维负载P25光催化接触氧化活性艳红X-3B   总被引:12,自引:2,他引:12  
汤心虎  韦朝海  原炜明  张娜 《环境科学》2005,26(5):124-124-127
在玻璃纤维上焙烧P25制备了负载型TiO2光催化剂,探讨了焙烧温度对催化活性的影响,设计了光催化接触氧化反应器,并以活性艳红X-3B为模型污染物,考察溶液pH值、共存阴离子(CO32-、SO42-、Cl-)对光催化反应的影响.结果表明,焙烧温度直接影响负载后催化剂的活性,300℃负载时活性最高,SEM照片显示此时P25与载体结合牢固、负载颗粒均匀.酸性条件对活性艳红X-3B的降解有利,当溶液初始pH由2.0上升到10.0时,活性艳红X-3B的降解率从90.06%下降至42.71%.共存的CO32-、SO42-对活性艳红X-3B降解的影响不大,但Cl-对氧化过程有明显的抑制,使活性艳红X-3B的降解率下降17.03%.利用成熟的光催化剂P25,通过烧结的方法制备负载型催化剂是当前替代粉末催化剂的较为可行的方案.  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