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   20758篇
  免费   171篇
  国内免费   118篇
安全科学   470篇
废物处理   774篇
环保管理   2079篇
综合类   6501篇
基础理论   4327篇
环境理论   10篇
污染及防治   5017篇
评价与监测   1038篇
社会与环境   764篇
灾害及防治   67篇
  2018年   273篇
  2017年   263篇
  2016年   371篇
  2015年   296篇
  2014年   414篇
  2013年   1332篇
  2012年   461篇
  2011年   680篇
  2010年   597篇
  2009年   665篇
  2008年   756篇
  2007年   755篇
  2006年   659篇
  2005年   573篇
  2004年   593篇
  2003年   545篇
  2002年   552篇
  2001年   682篇
  2000年   467篇
  1999年   321篇
  1998年   239篇
  1997年   230篇
  1996年   229篇
  1995年   262篇
  1994年   278篇
  1993年   228篇
  1992年   259篇
  1991年   261篇
  1990年   275篇
  1989年   252篇
  1988年   200篇
  1987年   193篇
  1986年   200篇
  1985年   197篇
  1984年   214篇
  1983年   204篇
  1982年   210篇
  1981年   225篇
  1980年   182篇
  1979年   196篇
  1978年   167篇
  1973年   167篇
  1968年   166篇
  1967年   206篇
  1966年   177篇
  1965年   190篇
  1964年   178篇
  1963年   174篇
  1961年   163篇
  1955年   165篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
331.
 Volatiles from leaves or bark of nonhost birch (Betula pendula) and Norway spruce (Picea abies) dramatically reduced the attraction of the bark beetle, Pityogenes bidentatus (Coleoptera: Scolytidae), to their aggregation pheromone components (cis-verbenol and grandisol) in the field. In addition, odors from both the needles and bark of the host Scots pine (Pinus sylvestris) similarly inhibited attraction. Monoterpenes of pine and spruce (α-pinene, β-pinene, terpinolene, and 3-carene) as well as ethanol, chalcogran and some nonhost green leaf alcohols [(Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, and 1-hexanol], also reduced catches. Collections of volatiles from the field-tested plant tissues indicated they released monoterpenes in amounts similar to the synthetics that inhibited responses. The various plant and insect sources of these inhibitory compounds indicate that P. bidentatus bark beetles have evolved several strategies to increase their fitness by avoiding nonhost and unsuitable host trees in a complex olfactory landscape. Received: 6 June 2000 / Accepted in revised form: 25 September 2000  相似文献   
332.
The present paper describes heavy metal contamination of soils and crops resulting from auto traffic, sewage sludge, pig manure and chemical fertilizers, in three separate experiments.The first experiment revealed that although the ADDT (average annual daily traffic) value of the Agricultural Area was lower, higher concentrations of Cu, Cd, Zn, Pb and Mn were obtained in soil when compared with the Commercial-Residential Area. Contaminations of trace metals from various source, e.g., chemical fertilizer, animal manure, night soil and pesticides of the nearby agricultural land were suspected.The second experiment compared the effects of adding a commercial fertilizer and digested sludge which contain substantial amounts of various trace metals to a sandy loam for growing Chinese radish. The results indicated that repeated applications of the fertilizer elevated the contents of various trace metals in the roots of Chinese radish. The phenomenon was further aggravated when digested sludge was also incorporated.The third experiment compared the contents of trace metals in the root and leaf tissues of tree seedlings (Acacia confusa) added with a single dose of the trace metalenriched fertilizer, and different portions of pig manure compost. It was revealed that the fertilizer-treated tree seedlings had a higher content of trace metals in the tissues than those amended with manure compost. Although the metal contents of soil increased as more manure compost was added, the contents in plant tissues did not increase correspondingly.  相似文献   
333.
334.
335.
336.
337.
338.
339.
340.
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