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   11601篇
  免费   207篇
  国内免费   377篇
安全科学   437篇
废物处理   537篇
环保管理   1475篇
综合类   1783篇
基础理论   2912篇
环境理论   2篇
污染及防治   3388篇
评价与监测   827篇
社会与环境   745篇
灾害及防治   79篇
  2023年   77篇
  2022年   174篇
  2021年   136篇
  2020年   110篇
  2019年   105篇
  2018年   192篇
  2017年   209篇
  2016年   292篇
  2015年   232篇
  2014年   329篇
  2013年   917篇
  2012年   413篇
  2011年   575篇
  2010年   463篇
  2009年   488篇
  2008年   583篇
  2007年   589篇
  2006年   517篇
  2005年   451篇
  2004年   388篇
  2003年   441篇
  2002年   394篇
  2001年   584篇
  2000年   377篇
  1999年   230篇
  1998年   149篇
  1997年   160篇
  1996年   150篇
  1995年   175篇
  1994年   136篇
  1993年   110篇
  1992年   134篇
  1991年   131篇
  1990年   135篇
  1989年   133篇
  1988年   99篇
  1987年   93篇
  1986年   69篇
  1985年   94篇
  1984年   92篇
  1983年   91篇
  1982年   85篇
  1981年   80篇
  1980年   62篇
  1979年   69篇
  1977年   54篇
  1976年   48篇
  1975年   53篇
  1974年   51篇
  1973年   54篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
131.
132.
Boundaries between different forest types in Changbai Mountain Eatern China are results from complex interactions between forest ecosystems,topogrphy,and geomorphology.Detecting and quantifying the transitional zones are highly important since high environmental beterogeneity and biodiversity are ofter found within these zpmes.In this study,we used GIS and multivariate statistics techniques(PCA and MSWA) to analyze data from Landsat TM satellite imageries and quantitatively determined the positions and widths of the landscape boundary betweeen mountain birch and evergreen coniferous forests in the northern slope of Changbai Mountain.The results showed that the widths of the landscape boundary ranges from 30-50 m while using the MWW A or/and PC method.Such detected widths are consistent with field transect data that suggest a 50m tranistional zone width.The results further suggest that TM data can be used in combination with GIS and statistical techniques in determining forest landscape boundaries.MSWA is more reliable than PCA,while PCA can also be used to determine the landscape boundary when transects are properly located.  相似文献   
133.
水解酸化+两级生物接触氧化处理高盐度水产品加工废水   总被引:1,自引:0,他引:1  
介绍了“水解酸化+两级生物接触氧化”处理水产品加工废水的运行效果和工程实例,结果表明:对C1^-浓度平均6000mg/L的高盐度水产品加工废水,系统对COD、SS、氨氮的去除率分别超过了88%、90%、85%,出水COD、SS、氨氮分别低于100mg/L、70mg/L、15mg/L,出水完全可以达到《污水综合排放标准》(GB8978—1996)一级排放标准。  相似文献   
134.
135.
In this paper we deal with the problem of identifying environmental principles for the design and operation of supply chains. The operations that are included in supply chains are briefly described along with the approaches that are applied in order to improve their environmental performance. A background of environmental principles for achieving eco-efficiency and building of environmentally friendly organizational systems is presented and emphasis is put on the application of such principles “from cradle to grave”. Then, environmental principles applicable to particular objects of logistics networks planning are identified and commented upon. In addition, selective case studies from the literature, which show the applicability of the formulated principles and their relevance to practice, are discussed. The paper concludes with some remarks regarding the benefits for companies and societies, in general, that occur as a result of the application of the formulated principles.  相似文献   
136.
 In Hydra vulgaris at the level of dissociated single cells endodermal cells adhere to each other more readily than to ectodermal cells at the initial adhesion. The time required for adhesion to occur between two adjacent cells is shorter for both endodermal and ectodermal homotypic cell adhesions once the initial adhesion of the first pair of cells has been established. It is confirmed that contact of an aggregated pair with additional homotypic cells facilitates the occurrence of homotypic adhesions; heterotypic adhesions are discouraged. This suggests that adhesion of homotypic cells contributes to an increased readiness for subsequent homotypic cells to adhere. Received: 25 August 1999 / Accepted in revised form: 11 January 2000  相似文献   
137.
138.
139.
140.
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