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   82篇
  免费   2篇
安全科学   1篇
环保管理   12篇
综合类   4篇
基础理论   37篇
污染及防治   28篇
评价与监测   1篇
灾害及防治   1篇
  2015年   2篇
  2014年   2篇
  2013年   28篇
  2012年   1篇
  2011年   1篇
  2007年   1篇
  2006年   4篇
  2005年   5篇
  2004年   3篇
  2003年   4篇
  2002年   1篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1995年   3篇
  1992年   1篇
  1991年   2篇
  1990年   4篇
  1989年   1篇
  1988年   2篇
  1986年   2篇
  1985年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1970年   1篇
排序方式: 共有84条查询结果,搜索用时 31 毫秒
61.
Abstract:  The rainforests of the Amazon basin are being cut by humans at a rate >20,000 km2/year, leading to smaller and more isolated patches of forest, with remaining fragments often in the range of 1–100 ha. We analyzed samples of understory birds collected over 20 years from a standardized mist-netting program in 1– to 100-ha rainforest fragments in a dynamic Amazonian landscape near Manaus, Brazil. Across bird guilds, the condition of second growth immediately surrounding fragments was often as important as fragment size or local forest cover in explaining variation in abundance. Some fragments surrounded by 100 m of open pasture showed reductions in insectivorous bird abundance of over 95%, even in landscapes dominated by continuous forest and old second growth. These extreme reductions may be typical throughout Amazonia in small (≤10 ha), isolated fragments of rainforest. Abundance for some guilds returned to preisolation levels in 10- and 100-ha fragments connected to continuous forest by 20-year-old second growth. Our results show that the consequences of Amazonian forest loss cannot be accurately described without explicit consideration of vegetation dynamics in matrix habitat. Any dichotomous classification of the landscape into "forest" and "nonforest" misses essential information about the matrix.  相似文献   
62.
63.
A 27-year-old gravida 4, para 3 was found to have anhydramnios at 14 weeks' gestation following a size/date discrepancy noted at her routine prenatal visit. A detailed ultrasound revealed multiple fetal anomalies including congenital heart defect, chest hypoplasia, and bilateral dysplastic kidneys. Karyotype revealed trisomy 16 in 15/15 cells from a tissue specimen obtained from the fetal cord insertion site following elective pregnancy termination.  相似文献   
64.
Why Economics Matters for Endangered Species Protection   总被引:3,自引:0,他引:3  
Abstract: We offer three reasons why economics matters more to species protection than many people think and what this implies for the ongoing debate over the reauthorization of the Endangered Species Act of 1973. Economics matters because (1) human behavior generally, and economic parameters in particular, help determine the degree of risk to a species; (2) in a world of scarce resources, the opportunity cost of species protection—the costs of reduced resources for other worthwhile causes—must be taken into account in decision making; and (3) economic incentives are critical in shaping human behavior, and consequently the recovery of species. Endangered species protection that explicitly addresses these basic principles can avoid wasting valuable resources that yield no gain in species protection.  相似文献   
65.
66.
The air pollution potential of any area is directly related to its population and economic development. In New York State, this pollution potential ranges from that existing in the sparsely inhabited recreational zones to that prevailing in the densely populated and/or heavily industrialized areas. No one set of air quality standards or objectives can be developed which can reasonably be applied on a statewide basis. A classifications-air quality objectives system has been adopted by the State Air Pollution Control Board for application in New York State. In accordance with this system, specific areas can be classified in one of 16 categories. Air quality objectives, in keeping with each classification, are designed to protect health and to promote the maximum comfort and enjoyment and use of property consistent with the needs of the area concerned. The system was developed by the staff with the assistance of a council of technical advisors. Units of measurement related to the most important effect of specific contaminants are utilized. Methods of sampling and analysis are specified. The details of the classifications-objectives system, the place of the system in the state’s air resource management plan, the manner in which each segment of the state after study will be classified, and how attainment will be evaluated are described.  相似文献   
67.
This paper briefly reviews the historical development of air pollution training activities in the U. S. It describes the various types of training programs currently available, such as short courses, specialized programs, and university training at the graduate level. The level of financial support and the number of individuals enrolled in these programs are discussed. The paper concludes with an outline of future needs in terms of changes in existing training programs, extension into new areas, and the critical problem of recruitment of qualified candidates for training.  相似文献   
68.
69.
This paper examines various health effects of photochemical air pollution in Japan, primarily through the review of epidemiological studies. Health effects discussed include subjective respiratory symptoms, respiratory function testing, ocular effects, and hospital diagnostic tests. The downward trend in oxidant cautions and paralleled health effects, as reported by the Japanese Environmental Agency, are discussed. The methods determined by Japanese ordinance for measurement of oxidants, SO2, NO x , and CO are described.  相似文献   
70.
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