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   79篇
  免费   1篇
  国内免费   5篇
废物处理   2篇
环保管理   12篇
综合类   34篇
基础理论   8篇
污染及防治   28篇
社会与环境   1篇
  2020年   2篇
  2019年   1篇
  2018年   2篇
  2016年   1篇
  2014年   2篇
  2013年   3篇
  2012年   3篇
  2011年   5篇
  2010年   3篇
  2009年   9篇
  2008年   4篇
  2007年   6篇
  2006年   1篇
  2005年   2篇
  2004年   1篇
  2002年   2篇
  2001年   1篇
  1999年   8篇
  1997年   1篇
  1993年   1篇
  1988年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1971年   1篇
  1969年   1篇
  1964年   2篇
  1962年   5篇
  1961年   1篇
  1960年   1篇
  1959年   1篇
  1958年   1篇
  1957年   1篇
  1955年   1篇
  1954年   1篇
  1952年   1篇
  1940年   2篇
  1936年   1篇
  1914年   1篇
  1913年   1篇
排序方式: 共有85条查询结果,搜索用时 0 毫秒
71.
72.
73.
典型夏季珠江三角洲地区植被的异戊二烯排放   总被引:9,自引:5,他引:9  
利用中巴卫星影像采用监督分类的方法对影像进行解译,并反演珠江三角洲4种主要的植被类型(PFT).利用自然排放气体和气溶胶模式——MEGAN(Model of Emissions of Gases and Aerosols from Nature),对典型夏季日珠江三角洲地区植被异戊二烯的排放进行了初步研究.结果显示:估算日珠江三角洲植被异戊二烯总的排放量为1.73×106kg(以C计,下同).异戊二烯的排放有明显的日变化特征,最大排放量出现在14:00,为2.39×105kg.广州、江门和惠州的异戊二烯平均排放速率最大,分别为45808·km-2·h-1、4250 g·km-2·h-1和4130 g·km-2h-1;同时江门和惠州也为异戊二烯日排放量的高值区,其日排放总量分别为4.60 ×105kg和4.29 ×105kg,排放贡献率分别为26.6%和24.8%.  相似文献   
74.
于2010年夏季,采用松弛涡度积累(Relaxed Eddy Accumulation)技术在长白山温带森林铁塔上测量了挥发性有机物(VOC)冠层尺度的排放通量,同步测量了气象参数、光合有效辐射(PAR)等,初步获得长白山阔叶林单萜烯的排放通量.同时,利用PAR能量守恒原理,建立了冠层尺度上单萜烯排放的经验模式.结果发现,模拟结果与测量结果比较一致,平均而言,模拟值高出测量值约20%~40%.采用不同方法对经验模式进行了检验,结果表明,采用比较各个采样时段平均值的方法可行,而且经验模式对于2010年夏季不同采样时段的平均值也给出了较好的模拟结果,其模拟值高出测量值约20%~24%.  相似文献   
75.
This study is aimed to investigation of the effect of modulated 450 MHz microwave radiation on the EEG inter-hemispheric asymmetry. Ten cycles of the microwave exposure (1 min off and 1 min on) at fixed modulation frequency were applied on two groups of healthy volunteers. The first group of 13 subjects was exposed to microwave radiation modulated at 14 Hz and the second group of 15 subjects at 40 Hz frequency. The peak specific absorption rate (SAR) average over 1 g was 0.303 W/kg. Differences in SAR between hemispheres were up to 20 dB. Rod antenna was located from the left side of the head. Differences of relative changes in EEG energy between symmetric channels FP1–FP2, T3–T4, P3–P4 and O1–O2 in exposed and sham conditions were analysed. The results showed increase in EEG energy from the left side caused by microwave exposure. Statistical analysis done for the whole group of subjects didn’t reveal significant differences in inter-hemispheres asymmetry between exposed and sham conditions. However, statistical analysis performed for individual subjects detected significant differences in asymmetry caused by exposure for 15–35% of individuals.  相似文献   
76.
77.
Landscape flux potentials for biogenic volatile organic compounds (BVOCs) were derived for three ecosystems in the continental U.S. (Fernbank Forest, Atlanta, GA; Willow Creek, Rhinelander, WI; Temple Ridge, CO). Analytical data from branch enclosure measurements were combined with ecological survey data for plant species composition and biomass. Other quantitative flux measurements at the leaf and landscape level were incorporated to scale the results from the enclosure measurements to the landscape level. Flux estimates were derived by using a one week ambient temperature and light record (30 min time resolution) and adjusting all emission rates to these conditions with temperature and light correction algorithms.  相似文献   
78.
79.
The prenatal social environment affects offspring development in most studied taxa with potentially lifelong consequences. To understand the adaptive significance of such maternal influences on offspring development, it is important to study their effects on fitness. In guinea pigs, social instability during pregnancy leads to delayed development of male offspring. This has been interpreted as an adaptation to high social densities, where young males need to queue for reproductive opportunities since they cannot out-compete older dominant males. The consequences for male reproductive success are, however, so far unknown. To study the effects of different prenatal social densities on offspring reproductive performance, we housed females individually or in small groups during late pregnancy. Offspring from both treatments were reared together in large groups until independence and thereafter housed in same-sex pairs of the same treatment. We then observed courtship, aggressive behavior, and reproductive success in a low-density context with one male from each treatment competing over access to two females. Sons born to individually housed females initiated more fights, had more social contacts, courted females more, and had a higher reproductive success than sons of group-housed females. Sons born to mothers experiencing low social densities before birth therefore perform better at low social group sizes, suggesting that male development may be adaptively adjusted to anticipated social densities, although performance under high densities still needs to be compared.  相似文献   
80.
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