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   19218篇
  免费   245篇
  国内免费   175篇
安全科学   607篇
废物处理   806篇
环保管理   2552篇
综合类   2975篇
基础理论   5214篇
环境理论   7篇
污染及防治   4889篇
评价与监测   1343篇
社会与环境   1114篇
灾害及防治   131篇
  2022年   162篇
  2021年   147篇
  2020年   151篇
  2019年   166篇
  2018年   276篇
  2017年   340篇
  2016年   451篇
  2015年   368篇
  2014年   576篇
  2013年   1509篇
  2012年   663篇
  2011年   900篇
  2010年   773篇
  2009年   763篇
  2008年   864篇
  2007年   914篇
  2006年   775篇
  2005年   674篇
  2004年   664篇
  2003年   638篇
  2002年   617篇
  2001年   736篇
  2000年   539篇
  1999年   312篇
  1998年   219篇
  1997年   266篇
  1996年   252篇
  1995年   286篇
  1994年   288篇
  1993年   223篇
  1992年   232篇
  1991年   212篇
  1990年   231篇
  1989年   211篇
  1988年   169篇
  1987年   177篇
  1986年   170篇
  1985年   178篇
  1984年   166篇
  1983年   166篇
  1982年   145篇
  1981年   150篇
  1980年   134篇
  1979年   140篇
  1978年   113篇
  1977年   116篇
  1975年   92篇
  1974年   90篇
  1973年   98篇
  1972年   90篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
The possible effects of landscape structure on starling roost distribution were investigated in western France using GIS analysis at different radii (2, 4, 8 and 10 km). Composition (11 land use classes) and configuration (patch size, diversity index) of the landscapes surrounding 97 roost sites used by starlings from 1981 to 2002 and surrounding 50 random points not used as roost sites were compared. Significant results suggested that starling roosts were established preferentially in the centre of an agricultural landscape where large units of pastures and arable land predominated and where natural areas were lacking both in large patches (forests or wetland classes) and in small patches such as woods in the mixed land class. A varied farmland landscape with natural areas and small patches should be promoted to limit the starling damage in wintering regions and also to favour their reproduction in regions where it has declined.  相似文献   
93.
94.
95.
96.
97.
The main objective of this project was to evaluate the possibility of reducing the quantity of fibre wasted at one of many hydrocyclone (centrifugal) cleaning processes in a paper mill. It was found that the application of elutriation water to both the tertiary and quaternary cleaners was essential to minimise the fibre discharged to the sewer, and the pressure of this elutriation water had a dramatic effect of reducing the fibre wastage. Accordingly, it has been shown that 150–160 kPa as the optimum pressure range to apply elutriation water to minimise the product grade fibre wasted whilst sending undesired shive fibre to the sewer. Also, monitoring of the press uhle box wastewater revealed that the paper mill has the potential to make substantial cost savings by reducing the waste stream. Further investigation is necessary to determine the types of fibre that are being wasted, and the viability of a screen to recycle the wasted fibre to the process. However, these fibres may be unsuitable to reuse in the process and alternative uses must be found.  相似文献   
98.
99.
100.
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   
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