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   25374篇
  免费   262篇
  国内免费   207篇
安全科学   716篇
废物处理   1015篇
环保管理   3427篇
综合类   5085篇
基础理论   6141篇
环境理论   14篇
污染及防治   6345篇
评价与监测   1533篇
社会与环境   1399篇
灾害及防治   168篇
  2022年   198篇
  2021年   202篇
  2020年   156篇
  2019年   191篇
  2018年   324篇
  2017年   345篇
  2016年   516篇
  2015年   418篇
  2014年   562篇
  2013年   2024篇
  2012年   738篇
  2011年   994篇
  2010年   792篇
  2009年   898篇
  2008年   975篇
  2007年   1077篇
  2006年   985篇
  2005年   798篇
  2004年   800篇
  2003年   810篇
  2002年   716篇
  2001年   898篇
  2000年   682篇
  1999年   419篇
  1998年   287篇
  1997年   296篇
  1996年   302篇
  1995年   350篇
  1994年   335篇
  1993年   309篇
  1992年   316篇
  1991年   323篇
  1990年   309篇
  1989年   278篇
  1988年   266篇
  1987年   227篇
  1986年   229篇
  1985年   244篇
  1984年   269篇
  1983年   268篇
  1982年   259篇
  1981年   240篇
  1980年   231篇
  1979年   235篇
  1978年   183篇
  1977年   191篇
  1975年   152篇
  1974年   196篇
  1973年   148篇
  1972年   165篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
171.
172.
Abstract: Over the past 50 years, human agents of deforestation have changed in ways that have potentially important implications for conservation efforts. We characterized these changes through a meta‐analysis of case studies of land‐cover change in the tropics. From the 1960s to the 1980s, small‐scale farmers, with state assistance, deforested large areas of tropical forest in Southeast Asia and Latin America. As globalization and urbanization increased during the 1980s, the agents of deforestation changed in two important parts of the tropical biome, the lowland rainforests in Brazil and Indonesia. Well‐capitalized ranchers, farmers, and loggers producing for consumers in distant markets became more prominent in these places and this globalization weakened the historically strong relationship between local population growth and forest cover. At the same time, forests have begun to regrow in some tropical uplands. These changing circumstances, we believe, suggest two new and differing strategies for biodiversity conservation in the tropics, one focused on conserving uplands and the other on promoting environmental stewardship in lowlands and other areas conducive to industrial agriculture.  相似文献   
173.
在活动流场模型的基础上建立了新的溶质运移控制方程,研究了流场分形特征参数的计算方法;采用4组染色示踪试验资料,分析了活动流场模型模拟土壤水流运动和溶质运移宏观非均匀特征的适用性.模拟分析表明,活动流场模型能较准确地捕捉到土壤中的优先流特别是不稳定流的宏观运动特征;土壤存在大孔隙结构的情况下,水流和溶质将更快的迁移到深层土壤,活动流场模型模拟计算的入渗深度偏小,但大于连续性模型的模拟计算结果;当土壤中的大孔隙结构较少时,活动流场模型模拟预测的土壤含水率分布和溶质浓度分布与实测结果比较一致.  相似文献   
174.
175.
176.
177.
178.
In recent years, many electronic manufacturing firms have looked upon Cleaner Production (CP) as the means by which they could maintain environmental practice and competitive advantages. CP has been adopted by companies as an important factor in enhancing industrial productivity. Sustainable projects that deal appropriately with environmental and social factors are also more likely to be the most profitable.This paper investigated the criteria and attributes that determine a successful adoption and implementation of CP in reference to PWB manufacture in Taiwan. Fuzzy Analytic Hierarchy Process (FAHP) methodology is used to discuss the different decision criteria that include Organizing, Systems and Technologies, Measurement and Feedback, Working environment and Worker's Culture which are all vital factors in an effective CP implementation. AHP is an efficient tool in controlling the fuzziness of the data involved in choosing the most preferred decision variables. The linguistic level of comparisons produced by the manufacturers and experts are tapped and constructed in a form of triangular fuzzy numbers in order to construct fuzzy pairwise comparison matrices. The implementation of the system is demonstrated by a problem involving three stages of hierarchy which contains different criteria and attributes at a wider perspective within an environmental uncertainty. The findings advocate that these enterprises would need to setup the priorities of the CP implementation. The results suggest a generic hierarchical model of organizations of which the highest level is to be prioritized among the CP implementation factors.  相似文献   
179.
As part of the tier 2 of a site-specific risk assessment, this study was the first reporting an intensive in situ application of the bait-lamina assay; two exposure periods (7 and 14 days) were tested during four seasons in ten different sites, within a uranium mine area and at two different depths. The most contaminated sites (by deposition of sludge from the effluent treatment pond) were discriminated after 14 days of exposure because extremely low percentages of feeding activity were recorded. Previous sub-lethal ecotoxicological assays, already had demonstrated that the habitat function of these soils is compromised. Nevertheless, seasonality has proved to have a significant influence on responses. Thus to strength conclusions about the impact of contaminants, the in situ bait-lamina assay should be performed on different annual seasons, at least for temperate regions. It was also found that some environmental parameters (e.g. soil moisture and litter) can act as confounding factors in the bait-lamina assay.  相似文献   
180.
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