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   1篇
  国内免费   2篇
安全科学   2篇
废物处理   5篇
环保管理   9篇
综合类   14篇
基础理论   32篇
污染及防治   42篇
评价与监测   16篇
社会与环境   6篇
灾害及防治   1篇
  2023年   1篇
  2022年   5篇
  2021年   8篇
  2020年   2篇
  2019年   4篇
  2018年   3篇
  2017年   4篇
  2016年   9篇
  2015年   7篇
  2014年   6篇
  2013年   9篇
  2012年   12篇
  2011年   5篇
  2010年   10篇
  2009年   4篇
  2008年   4篇
  2007年   8篇
  2006年   3篇
  2005年   1篇
  2004年   1篇
  2003年   5篇
  2002年   6篇
  2001年   2篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1991年   1篇
  1914年   1篇
  1913年   1篇
排序方式: 共有127条查询结果,搜索用时 31 毫秒
71.
72.
The present study investigated the existence of inter-individual and within-brood variability in the fatty acid (FA) profile of developing embryos of Nephrops norvegicus. In all surveyed females (n = 5), the quantitatively most important FAs were as follows: 22:6n-3 (20.8 ± 3.9% average of total FA ± standard error), 18:1n-9 (19.5 ± 2.0%), 16:0 (15.2 ± 3.4%), 20:5n-3 (10.2 ± 1.4%), 16:1n-7 (8.9 ± 1.6%), and 18:1n-7 (5.7 ± 1.3%). Differences in FA profiles of embryos in the same clutch were assessed using brooding chamber side (left and right) and pleopod (1st and 2nd, 3rd and 4th, and 5th) as predictive factors. There were no significant differences in the FA composition of embryos sampled from both sides of the brooding chamber in 4 of the 5 surveyed females. However, all females exhibited significant differences in the FA profiles of embryos sampled from different pleopods. Both saturated FA (SFA) and highly unsaturated FA (HUFA) present in developing embryos exhibited marked differences along the breeding chamber. Overall, FA reserves appeared to vary significantly within broods, which can ultimately be reflected on early larval survival. A potential cause for the within-brood variation recorded in the FA profile of developing embryos include (1) differential female investment during ovarian maturation, mainly due to variation in food quality/availability; (2) differential lipid catabolism during the incubation period of developing embryos, as a consequence of embryos position within the female’s brooding chamber; or (3) differential female investment during ovarian maturation amplified by differential lipid catabolism during the incubation period.  相似文献   
73.
Freshwater ecosystems provide irreplaceable services for both nature and society. The quality and quantity of freshwater affect biogeochemical processes and ecological dynamics that determine biodiversity, ecosystem productivity, and human health and welfare at local, regional and global scales. Freshwater ecosystems and their associated riparian habitats are amongst the most biologically diverse on Earth, and have inestimable economic, health, cultural, scientific and educational values. Yet human impacts to lakes, rivers, streams, wetlands and groundwater are dramatically reducing biodiversity and robbing critical natural resources and services from current and future generations. Freshwater biodiversity is declining rapidly on every continent and in every major river basin on Earth, and this degradation is occurring more rapidly than in terrestrial ecosystems. Currently, about one third of all global freshwater discharges pass through human agricultural, industrial or urban infrastructure. About one fifth of the Earth’s arable land is now already equipped for irrigation, including all the most productive lands, and this proportion is projected to surpass one third by midcentury to feed the rapidly expanding populations of humans and commensal species, especially poultry and ruminant livestock. Less than one fifth of the world’s preindustrial freshwater wetlands remain, and this proportion is projected to decline to under one tenth by midcentury, with imminent threats from water transfer megaprojects in Brazil and India, and coastal wetland drainage megaprojects in China. The Living Planet Index for freshwater vertebrate populations has declined to just one third that of 1970, and is projected to sink below one fifth by midcentury. A linear model of global economic expansion yields the chilling prediction that human utilization of critical freshwater resources will approach one half of the Earth’s total capacity by midcentury. Although the magnitude and growth of the human freshwater footprint are greater than is generally understood by policy makers, the news media, or the general public, slowing and reversing dramatic losses of freshwater species and ecosystems is still possible. We recommend a set of urgent policy actions that promote clean water, conserve watershed services, and restore freshwater ecosystems and their vital services. Effective management of freshwater resources and ecosystems must be ranked amongst humanity’s highest priorities.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01318-8) contains supplementary material, which is available to authorized users.  相似文献   
74.
75.
The coastal zone of the Brazilian state of Maranhão is an area characterized by a large variety of human activities and services, in particular in the Itaqui-Bacanga port complex (IBC). The IBC is an area prone to oil spills resulting from the processes of transportation, storage, and tank cleaning. The present study aimed to map the different physical environments adjacent to this complex and the socioeconomic profile of the local population that would be most vulnerable to this type of disaster. Vulnerability studies are essential as one of the first step in the development of an integrated coastal zone management. The variables analyzed in this study included geomorphological units, and the income, education, and dependence on fishing of the local population. The estimate of the vulnerability index was based on the relationships between these variables, which were used to generate a vulnerability map using GIS and the interpretation of high-resolution remote sensing, showing the areas of highest priority for intervention in the case of oil spills. The analysis of the natural and socioeconomic environments indicated that the areas of highest vulnerability correspond to the mangroves and the Vila Nova and Alto da Esperança neighborhoods, respectively. These neighborhoods have a direct relationship with fishing, and low levels of both income and education. By contrast, the lowest vulnerability was attributed to the coastal plateau and the central Anjo da Guarda neighborhood, which is occupied by residents with relatively high income and education, who do not depend on fishing.  相似文献   
76.
Factors influencing households' participation in recycling   总被引:2,自引:0,他引:2  
The success of a recycling programme depends on the active and sustained participation of citizens in the correct separation and collection of recyclable waste. An effective study of strategies aimed at augmenting people's involvement in recycling involves understanding which factors influence the decision to co-operate with a recycling programme. This research investigates the influence of attitudes, incentives, presence of children in household and information through direct media, on households' participation in recycling. The results suggest that positive attitudes toward recycling and information are important factors in explaining recycling participation. Some guidelines that may be considered in future communication and intervention strategies designed to promote recycling participation are discussed.  相似文献   
77.
Monitoring agricultural products requires the periodic determination of land cover and the production of land use policies in an optimum way. The hazelnut is one of the important Turkish agricultural exports and Turkey provides 77% of the world's hazelnuts. In Turkey, hazelnut production exceeds the demand; new regulations have been enacted to create new land use policies. By putting into practice regulations restricting hazelnut plantation areas, a more efficient and productive hazelnut harvest policy could be created. Therefore, more information on existing land cover is required to determine optimum (or ideal) potential hazelnut areas (PHA) and to forecast future crop production. The principle aim of this study is to create a methodology for determining existing PHA, using Geographic information system (GIS) and remote sensing (RS) techniques regarding to support hazelnut policy developers and economists. This study was basically carried out in the province of Trabzon, which is one of the most important hazelnut production areas in Turkey. Landsat ETM+ image was used to generate a current land cover classification. Using the supervised classification method, overall accuracy was determined to be 84.7%. Suitable hazelnut areas were determined according to criteria settled by government regulations.  相似文献   
78.
In 1996 a program was started, financed by the Environmental Ministry of Portugal and IAEA, aiming to study the inorganic atmospheric pollutant dispersion in Sado Estuary. Gent PM10 air samplers were used for air particulate matter sampling. Three sampling sites were chosen, forming a triangle around the fuel power station of Setúbal. Transplants of Parmelia sulcata Taylor were suspended in nylon bags within a rectangle 15 km wide and 25 km long on a 2.5 x 2.5 km grid. Two sets of four transplants were hung in each of the 47 locations, one set facing the wind and the other set opposing the wind. The transplants were suspended in December 1997 for a 1-year period; every 3 months, one transplant of each set was collected. Both lichen transplants and PM10 filters were analysed by INAA and PIXE. A comparative study of results obtained for the two sampling procedures is presented in this work.  相似文献   
79.
Transformational leadership is associated with a range of positive outcomes. Yet, according to substitutes for leadership theory, there may be circumstances under which it is difficult, if not impossible, for leaders to inspire and challenge their employees. Therefore, we hypothesize that transformational leadership behaviors as well as employee self‐leadership strategies contribute to employee work engagement and job performance. Furthermore, we hypothesize that transformational leadership behaviors are more effective when employees have a high need for leadership, whereas self‐leadership strategies are more effective when employees have a low need for leadership. A sample of 57 unique leader–employee dyads filled out a quantitative diary survey at the end of each week, for a period of five weeks. The results of multilevel structural equation modeling showed that employees were more engaged in their work and received higher performance ratings from their leader when leaders used more transformational leadership behaviors, and when employees used more self‐leadership strategies. Furthermore, we showed that transformational leadership behaviors were more effective when employees had a high (vs. low) need for leadership and that the opposite was true for employee self‐leadership. These findings contribute to our understanding of the role of employees in the transformational leadership process. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
80.
Solid waste presents the potential for contamination of the soil when it is improperly managed. One of the great challenges of today's society is to promote the proper disposal of municipal solid waste in order to guarantee the safety of public health and to avoid risks to the environment. In this context, the objective of this study is to analyze the concentration profiles of heavy metals and aromatic hydrocarbons of risk that human health in landfill soil. Such works provides an important tool to evaluate the possible presence of contaminants from inappropriate waste disposal, as well as to assist in the management of waste and to prevent environmental contamination. In order to analyze cadmium (Cd), lead (Pb), nickel (Ni), arsenic (As), and mercury (Hg), which are toxic elements, and aromatic hydrocarbons, including benzene, toluene, ethylbenzene, o‐xylene, m‐xylene, and p‐xylene, soil samples were collected at different sites and depths. Neither Cd nor As was detected in any of the samples that were analyzed. Pb levels ranged from 5.34 milligrams per kilograms (mg/kg) to 7.40 mg/kg, Ni levels ranged from 2.17 mg/kg to 3.00 mg/kg, and Hg levels ranged from 75.4 micrograms per kilograms (μg/kg) to 88.3 μg/kg. The aromatic hydrocarbon compounds of benzene, toluene, ethylbenzene, and o‐xylene were below 5.5 μg/kg, and m‐, p‐xylene was below 11 μg/kg. The analysis of heavy metals and aromatic hydrocarbons present in the landfill soil showed concentrations below the soil quality guideline values of the Brazilian National Environment Council (CONAMA) Resolution 420, which has criteria for the presence of chemical substances in soil for Brazil. Therefore, the low levels of chemicals may be related to the operational time of the landfill or to the population profile of the municipality, which is predominantly composed of persons involved in family‐based agriculture.  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