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   121篇
  免费   2篇
  国内免费   2篇
安全科学   2篇
废物处理   4篇
环保管理   9篇
综合类   36篇
基础理论   28篇
污染及防治   29篇
评价与监测   10篇
社会与环境   4篇
灾害及防治   3篇
  2023年   4篇
  2022年   1篇
  2021年   2篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2017年   4篇
  2016年   7篇
  2015年   3篇
  2014年   3篇
  2013年   8篇
  2012年   7篇
  2011年   6篇
  2010年   7篇
  2009年   5篇
  2008年   5篇
  2007年   7篇
  2006年   6篇
  2004年   6篇
  2003年   1篇
  2002年   3篇
  2001年   5篇
  2000年   2篇
  1999年   2篇
  1996年   2篇
  1995年   1篇
  1984年   1篇
  1977年   1篇
  1974年   2篇
  1971年   1篇
  1967年   2篇
  1965年   1篇
  1958年   3篇
  1956年   2篇
  1955年   1篇
  1954年   1篇
  1953年   1篇
  1952年   1篇
  1949年   1篇
  1947年   1篇
  1944年   1篇
  1938年   1篇
  1935年   1篇
排序方式: 共有125条查询结果,搜索用时 379 毫秒
11.
The European Operational Smog (EUROS) integrated air quality modelling system has been extended to model fine particulate matter (PM). From an extended literature study, the Caltech Atmospheric Chemistry Mechanism and the Model of Aerosol Dynamics, Reaction, Ionisation and Dissolution were selected and recently coupled to EUROS. Currently, modelling of mass and chemical composition of aerosols in two size fractions (PM2.5 and PM10–2.5) is possible. The chemical composition is expressed in terms of seven components: ammonium, nitrate, sulphate, elementary carbon, primary inorganic compounds, primary organic compounds and secondary organic compounds. Calculated PM10 concentrations and chemical composition are presented for two summer months of the year 2003 (1 July to 31 August).  相似文献   
12.
A large area of plantations has been established worldwide and especially in China. Evaluating the restoration status of these plantations is essential for their long-term management. Based on our previous work, we used an ecological memory (EM) approach to evaluate four 26-year-old plantations that represent four common kinds of plantations in subtropical China, i.e., mixed broad-leaved plantation (MBP), mixed coniferous plantation (MCP), eucalyptus plantation (EP), and mixed legume plantation (MLP). Comparing them with the regional climax community, i.e., monsoon evergreen broad-leaved forest (BF), all four plantations accumulated nearly the same pattern of EM during succession. EM was >50 % for soil minerals, light conditions, soil age, soil animals, and soil microbes. EM was about 25 % for soil pollen and 10 % for birds, soil seed bank, and plant species. The total EM value of the four plantations ranged from 50.96 to 52.54, which indicated that all four plantations were in the regional, natural trajectory of succession and between the early and medium successional stages. The results indicated that natural succession processes are unlikely to be accelerated by planting late-stage tree species without sufficient EM. The results also demonstrated that all four plantations were in positive successional trajectories, and the positive succession dynamics were greater in the MLP and MCP. We suggest that the entire natural succession trajectory be used to evaluate the restoration of a site and that the ultimate restoration target be divided into several milestones along the reference trajectory to monitor progress. Forest restoration may be accelerated by starting with a minimum dynamic unit supporting sufficient EM.  相似文献   
13.
This study investigates how environmental strategies change over time. We submit evidence from the US steel industry that firms have modified their strategies over time. We offer that US industry passed through three stages--cost minimization, cost-effective compliance, and beneficial environmental controls. We compare typologies of environmental strategies and choose that of C. Oliver as the most appropriate. We investigate how environmental strategies in the steel industry changed over time a 4-year period. We offer that a further understanding of Oliver's strategies may increase understanding of the relationship between business and government on environmental issues. One over-arching problem in our field is the need to adequately operationalize how firms change strategies and pass through different stages. We hope that our study will help future researchers and practitioners better articulate the concepts of environmental strategies over time. Our study focused on the steel industry in the United States. We chose the US steel industry as one of the major environmental actors in the United States. The United States Environmental Protection Agency ranks the iron and steel industry as the largest industrial source of toxic environmental contamination. We encourage researchers to evaluate and test our methodology and findings in other contexts--both in other nations and different industries.  相似文献   
14.
Felimare californiensis (=Hypselodoris californiensis) was once common throughout the Southern California Bight (SCB) and California Channel Islands. This well-known shallow-water nudibranch, which specializes on dysideid sponges, has persisted for decades in Mexico, but in California disappeared from its entire range by 1984. Since reappearing in 2003, it has been found only at Santa Catalina Island, plus sightings of single individuals in 2011 at Santa Cruz Island and San Diego. The decline of F. californiensis in California was documented using published historical records, museum collections, unpublished field accounts, and images posted online. The loss of this emblematic species is unique among Californian nudibranchs, including (1) its congener Felimare porterae (=Mexichromis porterae), with which it appears to overlap in diet, and (2) opisthobranch species with similar historical geographic ranges and mode of development. The decline in F. californiensis is not predicted by warming trends and climate variation over the past 40 years, including the strong El Niño events of 1983 and 1998. Coastal pollution from the large human population in southern California may have impacted Dysidea amblia, the primary reported prey of F. californiensis. Historical overcollecting of the nudibranch and habitat loss through the development of major ports likely also contributed to its decline. Sightings since 2003 are consistent with a nascent recovery, as elements of water quality have improved in the SCB in recent decades.  相似文献   
15.
16.
17.
This paper presents evidence relating to a forecast-based cash and non-food item distribution among vulnerable herder households during the 2017–18 dzud (extreme winter) season in Mongolia, and analyses the results of a quasi-experimental study evaluating its impacts. An innovative approach in disaster risk reduction, forecast-based financing (FbF) can have short- and long-term benefits to vulnerable households but remains understudied. The paper contributes information on a multimodal FbF programme offering one-off cash grants and in-kind veterinary kits. The data found significant effects of reduced mortality and increased offspring survival in some types of livestock, and that the timing of FbF assistance is crucial, as reported early assistance correlated to positive outcomes in terms of reduced animal mortality. These findings can be used to design more effective FbF interventions, to understand better the appropriateness of FbF designs, and to use early warnings and early actions to help people prepare and withstand disasters such as dzuds.  相似文献   
18.
19.
Metabolic scaling laws predict a variety of emergent properties of biological systems based on relationships among temperature, body size, and rates of physiological processes. These models have been criticized as being overly simplistic and not accounting for directional variability arising from evolutionary tradeoffs. I measured hatch success and egg development time at six temperatures for 12 populations throughout the latitudinal range of two broadly distributed topminnows (Fundulus). I asked if hatch success and development time differed between the species and northern and southern populations. Hatch success reaction norms suggested that the more broadly (and northern) distributed Fundulus notatus was more eurythermic with a lower optima and broader performance breadth than Fundulus olivaceus. Temperature explained most variability in mass-corrected development time. Development time differed between the species, but not northern and southern populations. Deviations from predictions of universal scaling laws were most pronounced away from specie's thermal optima.  相似文献   
20.
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