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   92114篇
  免费   1228篇
  国内免费   1118篇
安全科学   3803篇
废物处理   3339篇
环保管理   14148篇
综合类   21123篇
基础理论   26508篇
环境理论   72篇
污染及防治   15457篇
评价与监测   5577篇
社会与环境   3872篇
灾害及防治   561篇
  2022年   806篇
  2021年   799篇
  2020年   649篇
  2019年   857篇
  2018年   1154篇
  2017年   1207篇
  2016年   2159篇
  2015年   1822篇
  2014年   2569篇
  2013年   9244篇
  2012年   2276篇
  2011年   2604篇
  2010年   3284篇
  2009年   3458篇
  2008年   2164篇
  2007年   2044篇
  2006年   2425篇
  2005年   2359篇
  2004年   2629篇
  2003年   2522篇
  2002年   2035篇
  2001年   2362篇
  2000年   2027篇
  1999年   1537篇
  1998年   1377篇
  1997年   1367篇
  1996年   1493篇
  1995年   1596篇
  1994年   1470篇
  1993年   1324篇
  1992年   1333篇
  1991年   1292篇
  1990年   1257篇
  1989年   1226篇
  1988年   1055篇
  1987年   984篇
  1986年   994篇
  1985年   1068篇
  1984年   1158篇
  1983年   1179篇
  1982年   1178篇
  1981年   1097篇
  1980年   945篇
  1979年   939篇
  1978年   820篇
  1977年   724篇
  1976年   644篇
  1974年   625篇
  1973年   648篇
  1972年   663篇
排序方式: 共有10000条查询结果,搜索用时 47 毫秒
221.
We describe the first prenatally detected case of a small de novo interstitial duplication of chromosome 16q. This chromosomal aberration is extremely rare. Amniocentesis was indicated by advanced maternal age only. Ultrasound examinations of the foetus showed no abnormalities. Conventional and molecular cytogenetic analyses on cultured amniocytes by comparative genomic hybridisation (CGH) and fluorescence in situ hybridisation (FISH) using partial chromosome paints and a locus-specific YAC clone revealed a de novo direct duplication of the chromosomal region 16q11.2-q13 leading to a partial trisomy 16q (46,XX,dup(16)(q11.2q13)). There are only five postnatal reports of comparable duplications involving this chromosomal region. These patients presented with little or no associated dysmorphic features but with significant neurodevelopmental delay and severe behavioural problems. After genetic counselling, the parents opted for termination of pregnancy. Post-mortem examination showed slight facial dysmorphic signs, minor dysgenesis of the ovaries and an atypical outflow of the arteria thyroidea ima. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
222.
The components of an environmental decision support system (EDSS) were outlined in Part 1 of this paper. Here, an example application is given using a range of data from the database in order to assess the utility of one specific model chosen from the modelbase: the one-dimensional thermal stratification model, EDD1. The model is applied to a range of lake types worldwide.  相似文献   
223.
224.
225.
226.
Critical loads offer a unique way of evaluating impacts of acid deposition by quantifying environmental sensitivity. The critical loads of acidity for UK peat soils have been based upon an arbitrary reduction in pH of 0.2 units. This chemical shift needs to be better related to adverse effects on sensitive biological receptors. It is known that effective precipitation pH equates closely to soil solution pH, and the latter is directly linkable to biotic effects of pH change. On continuation of a long-term experiment assessing impacts of simulated acid rain on peat microcosms in a realistic outdoor environment, Calluna vulgaris continued to flourish at acid deposition loads well above the existing critical load. Calluna plants were harvested and analysed, and acid deposition treatments to the microcosms continued to allow natural vegetation to regenerate. A diverse mixture of moorland plants and bryophytes established at acidity treatments well above the existing critical load, and only a very high acid load resulted in no natural regeneration. A critical effective rain pH value of 3.6 is suggested as a basis for setting critical loads. At this pH, Calluna grows well, and a healthy diverse vegetation community re-establishes when harvested. It is suggested that the peat critical load should be set at the acid load that, at any specific site, would result in a mean effective precipitation pH of 3.6.  相似文献   
227.
A new methodological approach to the development of biological and technological safety standards for the impact of underground mining on the natural biota is proposed.  相似文献   
228.
New experimental data on biological productivity of plant communities in oligotrophic and mesotrophic bogs of the middle taiga subzone over the past five years are presented. The relationship between net primary production and the stock of live phytomass is estimated. The stock of necromass in oligotrophic bog ecosystems increases from west to east, while the stock of live phytomass and net primary production decrease.  相似文献   
229.
Heavy metal accumulation by plant communities has been studied in different zones of impact of gas field development. The contents of heavy metals in different blocks of plant communities has proved to depend not only on the location of phytocenosis but also on its species composition. Communities dominated by species of the family Poaceae contain smaller amounts of heavy metals than those dominated by species of the family Asteraceae, especially of the genus Artemisia. The order of precedence in the accumulation of heavy metals in different blocks of plant communities has been revealed.  相似文献   
230.
要保护公园的生态、社会、经济和文化价值 ,游客管理具有根本的重要性 . 政府要求公园进一 步在财政上自给自足 . 正在制定一个更加完善的管理方法代替单纯地限制游客的数量 . 这种 方法鼓励公众参与公园的目标设定和游客满意度评价 ,并奖励胜任的财务管理 .  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