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   342篇
  免费   9篇
  国内免费   5篇
安全科学   7篇
废物处理   20篇
环保管理   37篇
综合类   46篇
基础理论   85篇
环境理论   1篇
污染及防治   105篇
评价与监测   29篇
社会与环境   24篇
灾害及防治   2篇
  2023年   4篇
  2022年   6篇
  2021年   13篇
  2020年   8篇
  2019年   8篇
  2018年   13篇
  2017年   16篇
  2016年   24篇
  2015年   9篇
  2014年   22篇
  2013年   30篇
  2012年   21篇
  2011年   28篇
  2010年   25篇
  2009年   20篇
  2008年   15篇
  2007年   12篇
  2006年   12篇
  2005年   9篇
  2004年   12篇
  2003年   14篇
  2002年   5篇
  2001年   4篇
  2000年   8篇
  1999年   5篇
  1998年   5篇
  1997年   2篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1987年   2篇
排序方式: 共有356条查询结果,搜索用时 23 毫秒
351.
Within this paper, we analyze the fulfillment of the Kyoto emissions reduction commitment particularly in Germany and its implication on the long-term paths of all macro-variables. Germany, like all other industrial or Annex-B countries, must reduce its emissions by 2010 according to what we call a Kyoto Forever scenario. We specifically investigate tradable permits as reduction measures in a national overlapping generations (OLG) model, where we change the discounting technique by using generation adjusted discounting (GAD) in comparison to conventional OLG discounting. We show that within our model framework Germany is able to develop along growing paths of, for example, gross domestic product (GDP) in sharp contrast to conventional results of OLG simulations. At the same time, current generations must share higher burdens in terms of lower GDP, per capita consumption and employment which can be initially interpreted as contemporary costs for reaching sustainable paths and, second, contributions for internalizing external effects. However, all costs in terms of lower macro-variables for current living generations are re-compensated through higher future values. This effect can be interpreted as an intergenerational application of full cost bearance, or, in other words, the polluter pays principle which is oriented towards sustainability of greenhouse gases abatement.  相似文献   
352.
This study describes the deforestation impact from three settlements, 5 de Junio, El Tigre, and 30 de Agosto, near the Madidi National Park in Bolivia. First deforestation rates along the road that connects the settlements and then deforestation within each settlement are examined. Landsat Thematic Mapper (TM) imagery from 1987, 1997, and 2000 were used to measure the deforestation. Face-to-face interviews were also used to collect detailed social and land-use information. Road-building and farming have been the major causes of deforestation in this region. The TM measurements indicate a high increase in the deforestation rate along the road in the area of study. The results also show a rapidly escalating deforestation rate in 5 de Junio, a potential high future deforestation rate in El Tigre, and a gradual deforestation increase in 30 de Agosto. The information provided by the settlers about clearing was compared with the imagery analysis. Generally, the settlers estimates were lower than the deforestation as derived from the imagery.  相似文献   
353.
Pollen storage in a colony of Apis mellifera is actively regulated by increasing and decreasing pollen foraging according to the “colony's needs.” It has been shown that nectar foragers indirectly gather information about the nectar supply of the colony from nestmates without estimating the amount of honey actually stored in the combs. Very little is known about how the actual colony need is perceived with respect to pollen foraging. Two factors influence the need for pollen: the quantity of pollen stored in cells and the amount of brood. To elucidate the mechanisms of perception, we changed the environment within normal-sized colonies by adding pollen or young brood and measured the pollen-foraging activity, while foragers had either direct access to them or not. Our results show that the amount of stored pollen, young brood, and empty space directly provide important stimuli that affect foraging behavior. Different mechanisms for forager perception of the change in the environment are discussed. Received: 13 June 1998 / Accepted after revision: 25 October 1998  相似文献   
354.
Abstract: Recent water sector reforms and increased scarcity and vulnerability of water resources, combined with declining public funding available for large scale infrastructure investment in the sector, have led to a greater awareness by the Government of Vietnam for the need to analyze water resource allocation and use in an integrated fashion, at the basin scale, and from a perspective of economic efficiency. In this study we focus on the development, application, and selected policy analyses using an integrated economic hydrologic river basin model for the Dong Nai River Basin in southern Vietnam. The model framework depicts the sectoral structure and location of water users (agriculture, industry, hydropower, domestic, and the environment) and the institutions for water allocation in the basin. Water benefit functions are developed for the major water uses subject to physical limitations and to constraints of system control and policy. Based on this modeling framework, we will analyze policies that can affect water allocation and use at the basin level, including both basin-specific and general macroeconomic policies.  相似文献   
355.
Winfried Schröder  Stefan Nickel  Simon Schönrock  Michaela Meyer  Werner Wosniok  Harry Harmens  Marina V. Frontasyeva  Renate Alber  Julia Aleksiayenak  Lambe Barandovski  Alejo Carballeira  Helena Danielsson  Ludwig de Temmermann  Barbara Godzik  Zvonka Jeran  Gunilla Pihl Karlsson  Pranvera Lazo  Sebastien Leblond  Antti-Jussi Lindroos  Siiri Liiv  Sigurður H. Magnússon  Blanka Mankovska  Javier Martínez-Abaigar  Juha Piispanen  Jarmo Poikolainen  Ion V. Popescu  Flora Qarri  Jesus Miguel Santamaria  Mitja Skudnik  Zdravko Špirić  Trajce Stafilov  Eiliv Steinnes  Claudia Stihi  Lotti Thöni  Hilde Thelle Uggerud  Harald G. Zechmeister 《Environmental science and pollution research international》2016,23(11):10457-10476
For analysing element input into ecosystems and associated risks due to atmospheric deposition, element concentrations in moss provide complementary and time-integrated data at high spatial resolution every 5 years since 1990. The paper reviews (1) minimum sample sizes needed for reliable, statistical estimation of mean values at four different spatial scales (European and national level as well as landscape-specific level covering Europe and single countries); (2) trends of heavy metal (HM) and nitrogen (N) concentrations in moss in Europe (1990–2010); (3) correlations between concentrations of HM in moss and soil specimens collected across Norway (1990–2010); and (4) canopy drip-induced site-specific variation of N concentration in moss sampled in seven European countries (1990–2013). While the minimum sample sizes on the European and national level were achieved without exception, for some ecological land classes and elements, the coverage with sampling sites should be improved. The decline in emission and subsequent atmospheric deposition of HM across Europe has resulted in decreasing HM concentrations in moss between 1990 and 2010. In contrast, hardly any changes were observed for N in moss between 2005, when N was included into the survey for the first time, and 2010. In Norway, both, the moss and the soil survey data sets, were correlated, indicating a decrease of HM concentrations in moss and soil. At the site level, the average N deposition inside of forests was almost three times higher than the average N deposition outside of forests.  相似文献   
356.
Biomass burning is a common agricultural practice, because it allows elimination of postharvesting residues; nevertheless, it involves an inefficient combustion process that generates atmospheric pollutants emission, which has implications on health and climate change. This work focuses on the estimation of emission factors (EFs) of PM2.5, PM10, organic carbon (OC), elemental carbon (EC), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) of residues from burning alfalfa, barley, beans, cotton, maize, rice, sorghum, and wheat in Mexico. Chemical characteristics of the residues were determined to establish their relationship with EFs, as well as with the modified combustion efficiency (MCE). Essays were carried out in an open combustion chamber with isokinetic sampling, following modified EPA 201-A method. EFs did not present statistical differences among different varieties of the same crop, but were statistically different among different crops, showing that generic values of EFs for all the agricultural residues can introduce significant uncertainties when used for climatic and atmospheric pollutant inventories. EFs of PM2.5 ranged from 1.19 to 11.30 g kg?1, and of PM10 from 1.77 to 21.56 g kg?1. EFs of EC correlated with lignin content, whereas EFs of OC correlated inversely with carbon content. EFs of EC and OC in PM2.5 ranged from 0.15 to 0.41 g kg?1 and from 0.33 to 5.29 g kg?1, respectively, and in PM10, from 0.17 to 0.43 g kg?1 and from 0.54 to 11.06 g kg?1. CO2 represented the largest gaseous emissions volume with 1053.35–1850.82 g kg?1, whereas the lowest was CH4 with 1.61–5.59 g kg?1. CO ranged from 28.85 to 155.71 g kg?1, correlating inversely with carbon content and MCE. EFs were used to calculate emissions from eight agricultural residues burning in the country during 2016, to know the potential mitigation of climatic and atmospheric pollutants, provided this practice was banned.

Implications: The emission factors of particles, short-lived climatic pollutants, and atmospheric pollutants from the crop residues burning of eight agricultural wastes crops, determined in this study using a standardized method, provides better knowledge of the emissions of those species in Latin America and other developing countries, and can be used as inputs in air quality models and climatic studies. The EFs will allow the development of more accurate inventories of aerosols and gaseous pollutants, which will lead to the design of effective mitigation strategies and planning processes for sustainable 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