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   528篇
  免费   1篇
  国内免费   6篇
安全科学   10篇
废物处理   12篇
环保管理   32篇
综合类   306篇
基础理论   80篇
环境理论   1篇
污染及防治   80篇
评价与监测   9篇
社会与环境   5篇
  2021年   5篇
  2013年   13篇
  2012年   17篇
  2011年   10篇
  2010年   10篇
  2009年   9篇
  2008年   9篇
  2007年   15篇
  2006年   8篇
  2005年   5篇
  2004年   8篇
  2003年   11篇
  2002年   9篇
  2001年   13篇
  2000年   18篇
  1999年   6篇
  1998年   6篇
  1997年   9篇
  1996年   9篇
  1995年   12篇
  1994年   10篇
  1993年   10篇
  1990年   11篇
  1984年   5篇
  1975年   5篇
  1969年   6篇
  1968年   6篇
  1966年   6篇
  1965年   6篇
  1964年   6篇
  1963年   9篇
  1962年   6篇
  1961年   11篇
  1960年   13篇
  1959年   9篇
  1958年   13篇
  1957年   8篇
  1955年   11篇
  1954年   6篇
  1943年   5篇
  1941年   5篇
  1938年   5篇
  1937年   4篇
  1935年   4篇
  1934年   4篇
  1928年   5篇
  1923年   6篇
  1919年   5篇
  1914年   6篇
  1913年   5篇
排序方式: 共有535条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
Growth as an integrative parameter of all physiological processes was measured in young sporophytes of temperate Laminaria digitata, Laminaria saccharina and Laminaria hyperborea exposed in the laboratory to irradiance consisting of either only photosynthetically active radiation (PAR) or to a spectrum including ultraviolet radiation (UVR) (PAR+UVA+UVB) by use of cut-off glass filters. Size increment was measured every 10 min over a period of 18–21 days using growth chambers with on-line video measuring technique. In the chamber, plants were grown at 10±2°C and 16:8 h light–dark cycles with 6 h additional UVR exposure in the middle of the light period. Tissue morphology and absorption spectra were measured in untreated young sporophytes while chlorophyll a content and DNA damage were measured in treated thalli at the end of the experiment. Sensitivity of growth under UVR was found to be related to the observed upper depth distribution limit of the upper sublittoral L. digitata, upper to mid sublittoral L. saccharina and lower sublittoral L. hyperborea. Tissue DNA damage is, however, dependent on thallus thickness which minimizes UVR effect where outer cell layers shade inner cells and provide longer pathlength for UVR. Exposure to UVR causes cellular, enzymatic and molecular damage. Presence of UV-absorbing compounds further reduces effective UVR from reaching physiological targets. The cost of producing higher amount of UV-absorbing compounds and effective DNA repair mechanism can, however, divert photosynthate at the expense of growth. Tissue chlorophyll a content was not significantly different between treatments suggesting a capacity for acclimation to moderate UVR fluence. Growth acclimation to repeated UVR exposure was observed within a period of 12 days while growth inhibition was observed after a longer UVR exposure period of 21 days. The results give further insight into the effects of UVR on the cellular level and show how ecological parameters such as the upper depth distribution limit are dependent on cellular processes.  相似文献   
67.
68.
69.
We present an in-depth decompositionanalysis using physical indicators oftrends in Carbon dioxide (CO2) emissions in the cementindustry in Brazil, China, South Korea andthe United States. Physical indicatorsallow a detailed analysis of intra-sectoraltrends, in contrast to the often usedmonetary indicators. We assess thecontribution of different factors affectingCO2 emissions in the cement industry,including change in product mix, efficiencyof power generation, changes in fuel mixand changes in energy efficiency. Thedecomposition results show that in allexamined countries, increased productionwas the main contributor to the increase intotal CO2 emissions. Energy-efficiencyimprovement is the most important factorthat led to the reduction of emissionintensities for all countries except Korea.For Korea, structural change in the productmix is the most important factorcontributing to the emission intensityreduction.  相似文献   
70.
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