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   383篇
  免费   1篇
  国内免费   1篇
安全科学   1篇
废物处理   9篇
环保管理   11篇
综合类   221篇
基础理论   37篇
污染及防治   68篇
评价与监测   29篇
社会与环境   9篇
  2017年   5篇
  2016年   5篇
  2014年   6篇
  2013年   15篇
  2012年   6篇
  2011年   8篇
  2010年   6篇
  2009年   4篇
  2008年   22篇
  2007年   12篇
  2006年   6篇
  2005年   5篇
  2004年   11篇
  2003年   9篇
  2002年   7篇
  1997年   4篇
  1994年   6篇
  1993年   4篇
  1992年   5篇
  1991年   5篇
  1990年   6篇
  1989年   6篇
  1988年   8篇
  1987年   6篇
  1985年   5篇
  1984年   4篇
  1979年   5篇
  1978年   7篇
  1977年   4篇
  1976年   6篇
  1969年   3篇
  1968年   9篇
  1967年   8篇
  1966年   5篇
  1965年   6篇
  1964年   6篇
  1963年   5篇
  1961年   5篇
  1958年   3篇
  1957年   3篇
  1956年   5篇
  1954年   6篇
  1952年   4篇
  1943年   5篇
  1934年   3篇
  1924年   4篇
  1919年   3篇
  1918年   4篇
  1917年   4篇
  1913年   4篇
排序方式: 共有385条查询结果,搜索用时 15 毫秒
201.
An accidental exposition of 25 persons to beryllium dust was used to follow up trace analytical and clinical parameters over a period of 10 months. Although no exposed person shows any symptoms of an acute beryllium intoxication, up to 5‐fold increased beryllium concentrations could be analysed in serum samples about 10 hours after exposition. The beryllium clearance shows a biological half time in the range of 2 to 8 weeks. The beryllium determination in the nanogram range was carried out using a combined method by flameless a.a.s. with a detection limit of 0.6 ppb Be and a relative standard deviation from 20 to 4% in relation to the concentration range of beryllium measurement.

Beryllium analyses are completed by thorax X‐ray, spirometry, y‐globulins and liver enzymes (SGOT, SGPT), which have shown no pathological values. Because it is known for beryllium to sensitize the cellular immune response, neopterin measurement was used to determine the activity of the immune system. Neopterin, a pteridine synthesized by activated macrophages after stimulation by gamma‐interferon derived from sensitized T‐lymphocytes, was determined in urine samples by HPLC combined with an fluorescence detector. Only in two cases a slight increase of neopterin has been found. As a result of this study it can be summarized, that a short‐time exposure to beryllium (10–20 h), which results in a increase of beryllium in serum to the fivefold normal beryllium level, does not initiate any symptoms of an acute beryllium intoxication. The exposed persons are controlled in future to evaluate the further course.  相似文献   
202.
203.
204.
205.
206.
The metabolism of 4,4′-dichlorobiphenyl by mixed cultures of bacteria, isolated from activated sludge, was studied in shake cultures and in soil, both in presence and absence of alternative carbon sources. When 4,4′-dichlorobiphenyl was used as sole carbon source, 4-chlorobenzoic acid and 4,4′-dichloro-2,3-biphenyldiol could be isolated from the culture medium. Polar metabolites however, could not be detected in soil and in media in which alternative carbon sources such as glucose, glycerol, peptone, yeast-extract, humic acid or activated sludge were present. No hydroxylated or carboxylic acid derivatives could be isolated when 2,4′, 5-tri-, 2,2′,5,5′,-textra-, 2,2′,3,4,5′-penta-, 2,2′,3,4,5,5′-hexa- and decachlorobiphenyl were used as the sole carbon sources for incubation with bacteria in shake culture.  相似文献   
207.
Wetlands constitute a significant source of life since they incorporate unique habitats with endemic and migrant species. They also contribute to the preservation of high global biodiversity and they are under protection according to EU legislation. Nevertheless, during the last century, significant degradation has been observed in wetlands, mainly due to intensification of agriculture and poor water management practices. Calcareous fens habitat with the endangered species Cladium mariscus and Carex spp. is an ecologically significant wetland that undergoes great ecological stresses globally, due to the irrational use of water resources. In Trichonis lake, Western Greece, this habitat has been under deterioration during the last 50 years due to the lack of a sustainable water management plan that has caused destabilization of the hydrologic balance and high water level fluctuations. This human induced hydrologic regime has led to seasonal shifting between drought and flooding which constitute unfavorable conditions for this fen habitat and as a result significant elimination of this ecosystem extent has occurred. This study has adopted technologically advanced scientific methods such as GIS applications and remote sensing techniques to quantify the existing water resources and formulate a sustainable management scheme by considering both anthropogenic water uses and environmental protection.  相似文献   
208.
209.
210.
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