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   20570篇
  免费   186篇
  国内免费   202篇
安全科学   559篇
废物处理   995篇
环保管理   2465篇
综合类   2686篇
基础理论   5360篇
环境理论   4篇
污染及防治   5648篇
评价与监测   1659篇
社会与环境   1459篇
灾害及防治   123篇
  2023年   94篇
  2022年   220篇
  2021年   224篇
  2020年   143篇
  2019年   180篇
  2018年   332篇
  2017年   325篇
  2016年   533篇
  2015年   374篇
  2014年   579篇
  2013年   1759篇
  2012年   683篇
  2011年   871篇
  2010年   809篇
  2009年   797篇
  2008年   895篇
  2007年   986篇
  2006年   881篇
  2005年   725篇
  2004年   730篇
  2003年   710篇
  2002年   676篇
  2001年   915篇
  2000年   634篇
  1999年   403篇
  1998年   276篇
  1997年   254篇
  1996年   297篇
  1995年   274篇
  1994年   255篇
  1993年   237篇
  1992年   244篇
  1991年   210篇
  1990年   216篇
  1989年   219篇
  1988年   199篇
  1987年   160篇
  1986年   128篇
  1985年   139篇
  1984年   170篇
  1983年   154篇
  1982年   193篇
  1981年   135篇
  1980年   120篇
  1979年   152篇
  1978年   119篇
  1977年   109篇
  1976年   100篇
  1975年   83篇
  1974年   88篇
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
971.
972.
The situation and the latest findings of forest damage research in Germany are discussed. A newly developed concept for this research is described. This concept allows to identify the drawbacks of the recent damage research concept but also the integration of results compiled up to now. The importance for including natural occurring stress factors such as climate, soil conditions or local situation of individual species is outlined.  相似文献   
973.
Thin-layer chromatography plates were exposed at three different locations in Bavaria for 3-week periods during the growing season of maize. The adsorption of traces of atrazine was detected by thin-layer chromatography, GC-MS, and by an enzyme immunoassay. It was restricted to the sowing season, which coincides with the application of atrazine. The herbicide could not be detected after this time. The simplicity of the adsorption device, combined with a serological assay, render this procedure suitable for detecting airborne organic pollutants.  相似文献   
974.
Intrapopulation diversity and correlations of 30 volatile compounds in needles have been studied in Scots pine populations of southern Siberia. Significant differences between populations have been revealed in the correlation pattern of relative terpenoid contents in needle samples. Stable combinations of closely associated mono- and sesquiterpenes and specific features of the general pattern of correlations between relevant characters have been determined.  相似文献   
975.
Concentrations of eleven metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) were determined in the brown seaweed Fucus vesiculosus collected from the Archipelago of Stockholm. Several factors which influence the metal content in the seaweed have been studied, including errors caused by epiphytes, sea exposure and differences depending on which part of the seaweed is analysed. It is concluded that, if all these factors are considered, Fucus vesiculosus plants are excellent bio-indicators of metal pollution. This is also demonstrated by a significant increase in metal content in transplanted Fucus vesiculosus near the city of Stockholm. The results from this investigation also indicate increasing metal concentrations, especially Cd, in samples from the northern parts of the Archipelago and the reason for this is discussed.  相似文献   
976.
Environmental Science and Pollution Research - Formation of oil-suspended sediment aggregates (OSAs) is believed to be one of the natural cleaning processes in the marine environment. In this...  相似文献   
977.
Chirostoma charari and C. compressum, and they are presumed extinct. Twelve (63%) of the remaining species had declines in distribution. Sixteen (80%) of the 20 localities sampled had lost species. The greatest declines occurred in Lago de Cuitzeo proper and in the lower portion of the Río Grande de Morelia watershed. Species losses from the lake were attributable to drying and hypereutrophication of the lake because of substantial reductions in the amount and quality of tributary inputs, whereas losses from the Río Grande de Morelia watershed were the result of pollution from agricultural, municipal, and industrial sources, especially in the region around the city of Morelia. Three localities in the upper portion of the Río Grande de Morelia watershed—Cointzio reservoir, La Mintzita spring, and Insurgente Morelos stream—contained most of the remaining fish species diversity in the basin and deserve additional protection. Fish faunal changes indicated major declines in the health of aquatic ecosystems in the Morelia–Cuitzeo basin.  相似文献   
978.
Environmental Science and Pollution Research - We studied the removal of 61 emerging micropollutants, including illicit drugs, in a biofilter wastewater treatment plant located in the French Indies...  相似文献   
979.
980.
Chronic fluoride toxicity in the form of dental fluorosis was observed in cattle from nine (9) villages under two (2) blocks of Nayagarh district of Orissa. Out of 1117 cattle, 221 (18.09%) showed the signs of dental fluorosis. In all affected villages, the prevalence of dental fluorosis in calves (< 1 year age) was greater than adults. There was significant difference in prevalence in respect to age. The commonly observed signs of dental fluorosis were brown discoloration, mottling, attrition or uneven wearing of teeth with or without pitting. None of the affected animals showed characteristic signs of osteofluorosis. The mean serum and urine fluoride concentration of affected animals were significantly (P < 0.05) higher than those of control animals. Fluoride levels (mean) of ground water and surface water in two blocks were 1.30 +/- 0.16 ppm, 0. 66 +/- 0.08 ppm and 1.12 +/- 0.19 ppm, 0. 48 +/- 0.05 ppm respectively. The fluoride content of grass samples of affected and control (non-endemic) area was comparable. There was a highly positive correlation (r = + 0.664) between prevalence of dental fluorosis and fluoride content of ground water. It was concluded that fluoride intake through the water especially ground water contributed to the development of fluorosis in cattle.  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