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   1228篇
  免费   49篇
  国内免费   13篇
安全科学   65篇
废物处理   136篇
环保管理   248篇
综合类   171篇
基础理论   251篇
环境理论   4篇
污染及防治   279篇
评价与监测   55篇
社会与环境   63篇
灾害及防治   18篇
  2023年   10篇
  2022年   13篇
  2021年   22篇
  2020年   17篇
  2019年   26篇
  2018年   41篇
  2017年   40篇
  2016年   54篇
  2015年   47篇
  2014年   29篇
  2013年   126篇
  2012年   45篇
  2011年   71篇
  2010年   59篇
  2009年   65篇
  2008年   63篇
  2007年   78篇
  2006年   67篇
  2005年   35篇
  2004年   38篇
  2003年   27篇
  2002年   35篇
  2001年   20篇
  2000年   17篇
  1999年   22篇
  1998年   14篇
  1997年   13篇
  1996年   10篇
  1995年   9篇
  1994年   13篇
  1993年   9篇
  1992年   11篇
  1991年   15篇
  1990年   10篇
  1989年   8篇
  1988年   10篇
  1987年   6篇
  1986年   9篇
  1985年   5篇
  1984年   3篇
  1983年   3篇
  1982年   6篇
  1981年   5篇
  1980年   3篇
  1977年   5篇
  1972年   4篇
  1971年   3篇
  1961年   3篇
  1957年   5篇
  1955年   5篇
排序方式: 共有1290条查询结果,搜索用时 11 毫秒
11.
Arachnoid cysts are an uncommon central nervous system malformation, representing only 1 per cent of all intracranial masses. We report the second-trimester prenatal diagnosis of a posterior fossa arachnoid cyst, associated with an unbalanced X;9 translocation.  相似文献   
12.
13.
Accurate carrier testing and prenatal diagnosis in Duchenne muscular dystrophy (DMD) families is facilitated when an Xp21 deletion is found to be segregating within a family. We discuss the results of the DNA testing in two families, one in which DNA from affected males was available for study and the other in which no DNA from an affected male was available. Factors complicating the counselling of DMD deletion families are outlined.  相似文献   
14.
To test the effectiveness of the 404 permit program in preventing a net loss of wetland resources, 75 Section 404 projects permitted in the years 1987–1989 and located in a portion of southern California were evaluated. From this group of projects, 80.47 ha of wetlands were affected by Section 404 permits and the Army Corps of Engineers required 111.62 ha of wetland mitigation. To verify the successful completion of each mitigation project, all 75 project sites were visited and evaluated based on the amount of dead vegetation, growth and coverage, and the number of invasive species. Based on the field verification results, the actual amount of completed mitigation area was 77.33 ha, resulting in a net loss of 3.14 ha of wetland resources in the years 1987–1989. By comparing the types of wetlands lost to the types of wetlands mitigated, it is apparent that, in particular, freshwater wetlands are experiencing a disproportionately greater loss of area and that riparian woodland wetlands are most often used in mitigation efforts. The net result of these accumulated actions is an overall substitution of wetland types throughout the region. Results also indicate that, typically, large-scale mitigation projects are more successful compared to smaller projects and that successful compliance efforts are not evenly distributed throughout the region. We recommend that better monitoring, mitigation in-kind, mitigation banking, and planning on a regional or watershed scale could greatly improve the effectiveness of the Section 404 permitting program.  相似文献   
15.
Results from a survey of power utility biologists indicate that terrestrial biodiversity is considered a major issue by only a few utilities; however, a majority believe it may be a future issue. Over half of the respondents indicated that their company is involved in some management for biodiversity, and nearly all feel that it should be a goal for resource management. Only a few utilities are funding biodiversity research, but a majority felt more research was needed. Generally, larger utilities with extensive land holdings had greater opportunities and resources for biodiversity management. Biodiversity will most likely be a concern with transmission rights-of-way construction and maintenance, endangered species issues and general land resource management, including mining reclamation and hydro relicensing commitments. Over half of the companies surveyed have established voluntary partnerships with management groups, and biodiversity is a goal in nearly all the joint projects. Endangered species management and protection, prevention of forest fragmentation, wetland protection, and habitat creation and protection are the most common partnerships involving utility companies. Common management practices and unique approaches are presented, along with details of the survey.  相似文献   
16.
Although the reaction mechanics are somewhat mysterious, the use of iron for in situ groundwater treatment has recently gained considerable attention and respect in the remediation industry. The basic scientific principles of both applications of iron have been known for over a century; however, both were nearly unheard of as remediation technologies five years ago. Both technologies have a strong potential for widespread use. They are commercially available, have been proven in field studies, are less expensive than traditional pump and treat technologies, and, in many types of groundwater systems, may be able to meet difficult-to-achieve groundwater treatment standards. As these technologies continue to undergo development, there could be considerably more aggressive applications used to treat ground-water containing high concentrations of chlorinated organics and DNAPLs.  相似文献   
17.
18.
19.
20.
A promising new pathway for research on environmental justice is understanding public perceptions of justice or equity around a range of issues. Here we focus on policies intended to reduce air pollution from road traffic. We ask different urban communities, distinguished by the quality of local air and by socio-economic status, to judge the equitability of policies intended to reduce traffic emissions, both in terms of the environmental benefits of the policies and allocating the financial burden of paying for improvements. In the latter case, we are interested not only in the popular principles of equity that emerge, but also in whether a trade-off might exist between such principles of equity and the overall effectiveness and cost of the policy.  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