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   4407篇
  免费   73篇
  国内免费   37篇
安全科学   137篇
废物处理   145篇
环保管理   673篇
综合类   1175篇
基础理论   996篇
环境理论   9篇
污染及防治   947篇
评价与监测   223篇
社会与环境   163篇
灾害及防治   49篇
  2021年   43篇
  2020年   25篇
  2019年   34篇
  2018年   85篇
  2017年   87篇
  2016年   86篇
  2015年   96篇
  2014年   106篇
  2013年   276篇
  2012年   185篇
  2011年   229篇
  2010年   170篇
  2009年   185篇
  2008年   196篇
  2007年   232篇
  2006年   232篇
  2005年   178篇
  2004年   140篇
  2003年   133篇
  2002年   140篇
  2001年   77篇
  2000年   68篇
  1999年   54篇
  1998年   61篇
  1997年   64篇
  1996年   51篇
  1995年   67篇
  1994年   61篇
  1993年   38篇
  1992年   38篇
  1991年   28篇
  1990年   30篇
  1986年   23篇
  1985年   22篇
  1984年   24篇
  1983年   25篇
  1980年   22篇
  1979年   28篇
  1978年   23篇
  1965年   25篇
  1964年   22篇
  1963年   32篇
  1962年   24篇
  1960年   27篇
  1959年   29篇
  1957年   26篇
  1955年   31篇
  1954年   36篇
  1953年   21篇
  1951年   26篇
排序方式: 共有4517条查询结果,搜索用时 343 毫秒
51.
52.
53.
54.
The printed circuit board (PCB) manufacturers face several problems regarding the waste they generate. In Austria, a detailed study for waste minimization was carried out with three PCB manufacturers and one electroplating company. In this project a lot of ecologically and economically effective options were found and implemented. The ecological evaluation of processes is still an unsolved problem. Several evaluation models are tested on selected processes of the project.  相似文献   
55.
Developing a relationship between pest abundance and damage to crops is essential for the calculation of economic injury levels (EIL) leading to informed management decisions. The crop modelling framework, APSIM, was used to simulate the impact of mouse damage on yield loss on wheat where a long-term dataset on the density of mice was available (1983–2003). The model was calibrated using results from field trials where wheat plants were hand clipped to imitate mouse damage. The grazing effect of mice was estimated using the population density, daily intake per mouse and the proportion of wheat grain and plant tissue in the diet to determine yield loss. The mean yield loss caused by mice was 12.4% (±5.4S.E.; range −0.5 to 96%). There were 7/21 years when yield loss was >5%. A damage/abundance relationship was constructed and a sigmoidal curve explained 97% of variation when accounting for different trajectories of mouse densities from sowing to harvest. The majority of damage occurred around emergence of the crop when mouse densities were >100 mice ha−1. This is the first time that field data on mouse density and a crop simulation model have been combined to estimate yield loss. The model examines the efficacy of baiting and how to estimate EILs. Because the broadscale application of zinc phosphide is cheap and effective, the EIL is very low (<1% yield loss). The APSIM model is highly flexible and could be used for other vertebrate pests in a range of crops or pastures to develop density/damage relationships and to assist with management.  相似文献   
56.
Twelve second-trimester fetuses with cystic hygroma underwent fetal blood sampling for rapid karyotyping, haematologic evaluation, and blood gas analysis. An abnormal karyotype was found in seven cases: monosomy X in five, trisomy 21 in one, and trisomy 13 in the other. Eight often fetuses undergoing blood gas analysis showed hypoxaemia, five of which were growth-retarded. Nine pregnancies were terminated. Of the remaining three, only one fetus survived the perinatal period.  相似文献   
57.
58.
59.
Letter to the Editors   总被引:1,自引:0,他引:1  
  相似文献   
60.
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