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   1177篇
  免费   8篇
  国内免费   5篇
安全科学   18篇
废物处理   45篇
环保管理   70篇
综合类   691篇
基础理论   141篇
污染及防治   172篇
评价与监测   33篇
社会与环境   18篇
灾害及防治   2篇
  2017年   14篇
  2015年   10篇
  2014年   10篇
  2013年   39篇
  2012年   33篇
  2011年   30篇
  2010年   23篇
  2009年   33篇
  2008年   24篇
  2007年   27篇
  2006年   29篇
  2005年   32篇
  2004年   37篇
  2003年   33篇
  2002年   26篇
  2001年   14篇
  2000年   9篇
  1998年   11篇
  1995年   14篇
  1994年   12篇
  1993年   9篇
  1989年   9篇
  1978年   10篇
  1966年   10篇
  1965年   15篇
  1964年   15篇
  1963年   25篇
  1962年   21篇
  1961年   14篇
  1960年   23篇
  1959年   24篇
  1958年   16篇
  1957年   16篇
  1956年   15篇
  1955年   27篇
  1954年   33篇
  1953年   19篇
  1952年   14篇
  1951年   24篇
  1948年   9篇
  1947年   11篇
  1943年   11篇
  1941年   10篇
  1939年   9篇
  1938年   13篇
  1935年   10篇
  1933年   10篇
  1931年   12篇
  1930年   13篇
  1929年   13篇
排序方式: 共有1190条查询结果,搜索用时 15 毫秒
121.
In 1996 the Swedish Poisons Information Centre performed a follow-up study concerning poisonings related to ‘do-it-yourself’ activities. The study was supported by the National Institute of Public Health in Sweden. The objectives were to investigate and define monthly variations, route of exposure, type of products and, in particular, exposures to corrosives, age and sex groups, place of treatment, severity of symptoms, place of the accident, special risk products and risk situations. The Poisons Information Centre was contacted concerning 1609 cases, with a peak during the summer months. There was no or uncertain connection between exposure and symptoms in 117 cases. This means that 1492 cases were left to study. Inhalation and eye exposure were the predominant routes, followed by skin exposure and ingestion. Cleaning agents were the most common type of products involved. Of the 1492 cases included in the study 1033 were possible to follow up. Among these, 20–29 year olds and 30–39 year olds predominated, and there was a dominance for men. In total, 28% of those exposed were subject to medical attention, either in hospital or in outpatient clinics. According to the Poisoning Severity Score 78% had mild (grade 1) and 7% moderate (grade 2) symptoms. There were no severe intoxications and no deaths. Severity grade 2 occurred 3.6 times more often among those with exposures involving risk of corrosive damage than among others in the study population. Most accidents occurred in the home. Special risk products and risk situations were exposure to corrosive products, release of chlorine when mixing hypochlorite and acid, ‘fire-eating’, siphoning gasoline and diesel fuel, welding, and inhalation of carbon monoxide from exhaust gases. The Swedish Poisons Information Centre registered 1609 cases of poisoning accidents during ‘do-it-yourself’ activities, which means an average of four to five cases per day. Although this type of accidents is not uncommon, significant poisoning seems to be rare. Some special risk situations were identified.  相似文献   
122.
123.
124.
125.
A mathematical model has been developed to study the distribution and abundance of benthic algae species in a Norwegian fjord. The main forcing functions are the physical factors which have well defined gradients in this area, but biotic interactions are also accounted for in the model.The distribution of algae along vertical transects in the intermediate fjord area has been simulated, and the observed distribution is reproduced fairly well. This indicates that the major factors determining the equilibrium elevation between intertidal and subtidal vegetations in this area are adequately represented in the model.Based on observations in a fjord branch with a high level of freshwater influx and polluted by heavy metals, assumptions are made of the combined influence of these contaminants on growth characteristics of the species considered. The resulting effects on community development and community patterns are simulated. For a certain level of contamination, the decrease in abundance, community development rate and species separation have been determined. It is also shown that the fluctuations in biomass during a year are more pronounced than under unaffected conditions.The relative importance of external growth regulating factors and self-shading is demonstrated for different degrees of community development, and we have indicated that this may be an important factor in the assessment of transient and long-term responses to “natural” and man-made influences on the shore-line vegetation.One of the main problems during model development was the formulation of the interaction function for factors influencing growth parameters. Several alternatives were examined.The differences between the most frequently used forms were small with respect to abundance and not very large with respect to possible changes in distribution. It was noted that even by including only the most limiting factor at each instant, (Liebig's form) a high percentage of the potentially limiting factors did actually limit growth during periods of the year.The model is intended as a working tool for the studies of changes in the shore-line vegetation caused by man-made interferences like heavy metal and oil pollution, and we believe that the results presented demonstrate that it can successfully be used for this purpose.  相似文献   
126.
127.
128.
In recent years several hitherto unknown types of celestial objects related to star formation and early stellar evolution have been discovered by infrared and radio observations. New stars are born within large and massive interstellar molecular clouds. The onset of star formation in these clouds seems to be triggered by external forces.  相似文献   
129.
Based on a feasibility study, we have recently proposed a multivariate regression model for the impact of air pollution on the mortality of a long-term exposed population. This article proceeds by providing some experimental results, since this model has been fitted to data on a cross sectional basis for 41 census tracts in the Munich metropolitan area. The results obtained so far could be supportive to more detailed epidemiological studies of air pollution which have been conducted in many industrial countries; unfortunately, only relatively few have been conducted in West Germany.  相似文献   
130.
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