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   454篇
  免费   32篇
  国内免费   94篇
安全科学   8篇
废物处理   4篇
环保管理   89篇
综合类   243篇
基础理论   68篇
污染及防治   27篇
评价与监测   30篇
社会与环境   88篇
灾害及防治   23篇
  2024年   3篇
  2023年   7篇
  2022年   15篇
  2021年   22篇
  2020年   19篇
  2019年   17篇
  2018年   10篇
  2017年   17篇
  2016年   24篇
  2015年   21篇
  2014年   14篇
  2013年   43篇
  2012年   35篇
  2011年   34篇
  2010年   23篇
  2009年   27篇
  2008年   23篇
  2007年   39篇
  2006年   27篇
  2005年   27篇
  2004年   16篇
  2003年   18篇
  2002年   14篇
  2001年   14篇
  2000年   7篇
  1999年   14篇
  1998年   9篇
  1997年   8篇
  1996年   3篇
  1994年   6篇
  1993年   4篇
  1992年   3篇
  1991年   4篇
  1990年   3篇
  1987年   2篇
  1985年   2篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1975年   1篇
  1973年   1篇
排序方式: 共有580条查询结果,搜索用时 93 毫秒
291.
How integrated is river basin management?   总被引:2,自引:0,他引:2  
Land and water management is increasingly focused upon the drainage basin. Thirty-six terms recently used for schemes of “integrated basin management” include reference to the subject or area and to the aims of integrated river basin management, often without allusion to the multiobjective nature. Diversity in usage of terms has occurred because of the involvement of different disciplines, of the increasing coherence of the drainage basin approach, and the problems posed in particular parts of the world. The components included in 21 different approaches are analyzed, and, in addition to showing that components related broadly to water supply, river channel, land, and leisure aspects, it is concluded that there are essentially five interrelated facets of integrated basin management that involved water, channel, land, ecology, and human activity. Two aspects not fully included in many previous schemes concern river channel changes and the dynamic integrity of the fluvial system. To clarify the terminology used, it is suggested that the termcomprehensive river basin management should be used where a wide range of components is involved, whereasintegrated basin management can signify the interactions of components and the dominance of certain components in the particular area.Holistic river basin management is advocated as a term representing an approach that is both fully comprehensive and integrated but also embraces the energetics of the river system and consideration of changes of river channels and of human impacts throughout the river system. The paradigm of working with the river can be extended to one of working with the river in the holistic basin context.  相似文献   
292.
293.
ABSTRACT: This article offers a procedure for identifying the primary effects of financing and cost sharing rates on four basic levels: program, technical, incidence, and comprehensive impacts. A process is developed for identifying these effects based upon two alternative approaches. One method would follow the effects of rate changes through the four levels of impact, another would look in depth at the consequences of rate changes on a particular impact. For this study the information and suggested changes found in the Section 80(c) Study were used to illustrate possible impacts. The process suggested herein could be used in anticipating impacts of any major policy change.  相似文献   
294.
Stable isotope (18O–H2O, 2H–H2O 34S–SO4 2-) andhydrochemical data (SO4 2-, Fe-concentrations) have beenused to estimate the annual groundwater inflow and outflow of mining lake ML 111 and to calculate the total amount of dissolvedsulfate and iron that is carried into the lake by groundwater. The hydrological balance suggests an annual groundwater inflow of 23 700 m3 and an annual groundwater outflow of 15 700 m3. The calculation of the sulfur and iron balances yielded an annual sulfate input of 37 800 kg and an annual iron input of 7000 kg with the groundwater inflow. Furthermore it was shown that significant fluxes of these elements go into the lake sediments which results in continuous release of acidity in the lake water.  相似文献   
295.
ABSTRACT: A mathematical model of agricultural water use and a hydrological and economic simulation model were linked to quantify the economic and hydrological impact of deficit irrigation, increased water application efficiency, and farm storage dams when maintaining an IFR (instream flow requirement) under stochastic water supply conditions. The main finding was that a water conservation policy aimed at reducing the amount of water withdrawn from the river could bring more pressure to bear on stream flow. Water can only be saved if consumptive use is reduced. Increased water application efficiency is detrimental to other users as a result of reduced return flow. The economic cost of maintaining a specific IFR increases with the use of all three strategies as the probability of maintaining the IFR increases. Because of the control that can be exercised over the supply of water, a farm storage dam is the best strategy for minimizing the costs for irrigators. The interaction between water legislation, water policy administration, technology, hydrology, and human value systems necessitates an integrated approach to facilitate water management at catchment level and to formulate policies that will be in the interest of society.  相似文献   
296.
经济发展与耕地变化的关系--以江苏省为例   总被引:5,自引:0,他引:5  
一直以来,对于经济发展与耕地变化间的关系问题,许多学者都认为两者是负相关的关系.辨证地分析了经济发展与耕地变化之间的关系,并结合对江苏省的实证研究,对这一问题有了更深的认识:即经济发展对耕地变化不仅有负面作用,还在一定程度上存在着正向作用.从总体来看,经济发展所消耗的耕地数量将先上升后下降,呈现明显的倒"U"型曲线状.  相似文献   
297.
洞庭湖区水文气象灾害及其对渔业生产的影响   总被引:1,自引:0,他引:1  
方至 《灾害学》1993,8(4):46-50
本文通过大量而系统的资料,阐述了越来越严重的水文气象灾害,导致洞庭湖湖面萎缩、湖容减小、洪涝频仍、气温年差增大,湖泊效应衰退,使鱼类生态系统受到破坏。并针对上述情况提出了防治对策。  相似文献   
298.
Utilization of amniocentesis for prenatal diagnosis because of the indication of advanced maternal age (≥ 35 years at delivery) was examined in the population of B.C. over an 8-year period (1976–1983). As of 1983, approximately one out of three eligible women (≥ 35 years at delivery) is having the test. In the older group (≥ 38 years at delivery) approximately one out of two eligible women is having the test. The data do not indicate that the proportion of eligible women having amniocentesis has reached a plateau; utilization is continuing to increase. It appears that prenatal diagnosis is an ethically acceptable alternative for a large proportion of the population.  相似文献   
299.
根据“十五”、“十一五”期间“创模”指标体系,分析了各阶段指标体系差异和变化,而最新的指标体系能更全面地反映环境质量。同时,“创模”指标的变化趋势分析表明,“创模”指标的发展必然是反映当时的环保工作重点,“创模”的基本条件门槛会不断提升,“创模”指标的内涵会不断丰富,以确保国家环境保护模范城市的先进性和示范性。  相似文献   
300.
中国耕地变化的空间格局与重心曲线动态分析   总被引:10,自引:0,他引:10  
采用罗伦兹曲线、重心模型等G IS技术,利用1980 s和2000年两期覆盖全国跨度10多年的土地利用数据,构造耕地指数、耕地变化指数对中国耕地空间分布及其空间变化格局进行分析。主要结论:①中国耕地主要分布在黑、川、蒙、豫、鲁等北部和中部省份,其中苏、粤、冀、鲁、浙等19个省份的耕地有所减少,黑、蒙、吉、新等13个省份的耕地有所增加;②胡焕庸线之东南40%的国土面积分布着全国88%的耕地;西北60%的国土面积分布着全国12%的耕地,中国耕地空间分布可划分为高度稀疏区、低度稀疏区、一般过渡区、低度集聚、高度集聚区等5种类型;③中国耕地变化区域类型可适度划分为高度增长区、中度增长区、低度增长区、基本不变区、低度减少区、中度减少区、高度减少区等7大类型。顾及耕地质量背景下的中国耕地空间分布格局及变化特征等应进一步研究。  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