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   1348篇
  免费   31篇
  国内免费   9篇
安全科学   54篇
废物处理   50篇
环保管理   341篇
综合类   135篇
基础理论   412篇
污染及防治   220篇
评价与监测   113篇
社会与环境   48篇
灾害及防治   15篇
  2023年   7篇
  2022年   14篇
  2021年   23篇
  2020年   15篇
  2019年   17篇
  2018年   27篇
  2017年   28篇
  2016年   45篇
  2015年   35篇
  2014年   32篇
  2013年   86篇
  2012年   73篇
  2011年   75篇
  2010年   54篇
  2009年   46篇
  2008年   62篇
  2007年   73篇
  2006年   81篇
  2005年   55篇
  2004年   54篇
  2003年   59篇
  2002年   39篇
  2001年   24篇
  2000年   31篇
  1999年   19篇
  1998年   24篇
  1997年   25篇
  1996年   23篇
  1995年   19篇
  1994年   13篇
  1993年   16篇
  1992年   18篇
  1991年   8篇
  1990年   15篇
  1989年   10篇
  1988年   11篇
  1987年   10篇
  1986年   11篇
  1985年   7篇
  1984年   14篇
  1983年   10篇
  1982年   12篇
  1981年   19篇
  1980年   6篇
  1979年   13篇
  1978年   7篇
  1977年   6篇
  1976年   4篇
  1974年   3篇
  1973年   2篇
排序方式: 共有1388条查询结果,搜索用时 500 毫秒
71.
72.
73.
ABSTRACT: Interbasin water transfer is one of the most controversial water-resources-planning topics. Local communities, particularly those from which the water is to be taken (donor regions), generate enough opposition to doom many projects to failure. The opposition often arises because planners have traditionally considered excess water a free commodity rather than a marketable resource. To make transfer schemes mutually acceptable to donor and recipient regions, visible benefits must be offered. Agreement must be made on an acceptable purchase price and/or on other benefits such as a substantial amount of low flow augmentation or possibly some degree of flood control on the donor source stream. The hydrologic and economic feasibility of water transfer from the East Susquehanna River basin to the Delaware Reservoir System for supplemental supply to the New York City area was investigated. Nine alternative schemes for diversions up to 400 cfs and compensations in the form of low flow augmentation and/or flood control were considered resulting in unit costs to the recipient region between $90 and $380/mg. If only the minimum state-mandated flow is released to the Susquehanna River, the savings to the water recipients would be sufficient to pay a purchase price of about $21/mg, which would be equivalent to a total amount of $420,000/year for an average export of 100 cfs.  相似文献   
74.
ABSTRACT: Concern over the pollution of our lakes and streams has become a major issue in the United States. Sedimentation from sigricultural lands has been identified as a significant factor in water pollution. Some citizens suggest that government should force compliance with soil loss standards, while others suggest that we ask farmers to voluntarily comply. Related questions are “DO farmers think government should be involved in controlling erosion and protecting water quality?”“To what extent should government be involved?” What level of government should be involved? Federal? State? Local?“Why should pay for water quality projects?” Farmers from a small watershed in northeastern Indiana were interviewed before and after a major demonstration project. Their responses suggest that farmers feel that individual landowners should be responsible for controlling erosion and agricultural nonpoint source water pollution. However, over 60 percent of the study fanners indicated that the federal government should play an important role, in terms of both technical and financial assistance.  相似文献   
75.
This study investigates the production of organic fertilizer using Anaerobic Digestate (as a nutrient source) and limestone powder as the raw materials. A two-level factorial experimental design was used to determine the influence of process variables on the nutrient homogeneity within the granules. Increasing the liquid-to-solid ratio during granulation resulted in increased granule nutrient homogeneity. Increasing the processing time and the impeller speed were also found to increase the nutrient homogeneity. In terms of nutrients release into deionized water, the granules effectively released both potassium and phosphate into solution.  相似文献   
76.
77.
78.
79.
Liquid hazardous waste disposal in landfills is usually allowed only after solidification/stabilization. Although various procedures are commonly practiced, little is known about the mechanism(s) of the processes. A particular problem is the interference of organics. Small amounts of organics can interfere with the reaction between inorganic sludges and cementitous matrices. The present communication reports studies of the interaction between selected organic hazardous wastes and Type I Portland cement. Microscopic studies of the structural differences between cements set with water and those set with water plus organic liquids are discussed. In these studies the scanning electron microscope is used to observe samples fractured at 78K. The results provide technical background data on the ultimate stability of critical waste constituents solidified by various binding agents.  相似文献   
80.
Summary. We investigated the hypothesis that aggregation signals produced by male webbing clothes moths (WCM), Tineola bisselliella (Hum.) (Lepidoptera: Tineidae), and close-range male attractant signals produced by females have a pheromonal basis, at least in part. Gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses of bioactive methanolic extracts of male WCM disclosed three candidate pheromone components: hexadecanoic acid methyl ester (16:Ester), (Z)-9-hexadecenoic acid methyl ester (Z9—16:Ester), and octadecanoic acid methyl ester (18:Ester). In bioassay experiments in a large Plexiglas™ arena, a blend of synthetic 16:Ester plus Z9—16:Ester was attractive to male and virgin (but not mated) female WCM; the 18:Ester was inactive. GC-EAD analyses of pheromone gland extracts from female WCM revealed (E,Z)-2,13-octadecadienal (E2Z13—18:Ald) and (E,Z)-2,13-octadecadienol (E2Z13—18:OH) as candidate sex pheromone components. In arena bioassay experiments, 1—5 female equivalents of synthetic E2Z13—18:Ald (0.2 ng) and E2Z13—18:OH (0.1 ng) were more attractive to male WCM than were two virgin female WCM. We anticipate that the combination of aggregation and sex pheromones, male-produced sonic aggregation signals, and habitat-derived semiochemicals will be highly effective in attracting male and female WCM to commercial traps. Received 12 January 2001; accepted 8 June 2001.  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