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   16303篇
  免费   1126篇
  国内免费   3468篇
安全科学   1130篇
废物处理   295篇
环保管理   4460篇
综合类   9156篇
基础理论   1837篇
环境理论   4篇
污染及防治   1180篇
评价与监测   1298篇
社会与环境   1178篇
灾害及防治   359篇
  2024年   68篇
  2023年   218篇
  2022年   382篇
  2021年   419篇
  2020年   470篇
  2019年   405篇
  2018年   410篇
  2017年   584篇
  2016年   723篇
  2015年   787篇
  2014年   756篇
  2013年   1137篇
  2012年   1158篇
  2011年   1284篇
  2010年   931篇
  2009年   927篇
  2008年   725篇
  2007年   1142篇
  2006年   1116篇
  2005年   878篇
  2004年   736篇
  2003年   748篇
  2002年   662篇
  2001年   524篇
  2000年   505篇
  1999年   423篇
  1998年   296篇
  1997年   276篇
  1996年   250篇
  1995年   220篇
  1994年   194篇
  1993年   175篇
  1992年   129篇
  1991年   103篇
  1990年   86篇
  1989年   82篇
  1988年   73篇
  1987年   72篇
  1986年   49篇
  1984年   47篇
  1983年   58篇
  1982年   58篇
  1981年   73篇
  1980年   84篇
  1979年   74篇
  1978年   53篇
  1977年   49篇
  1973年   46篇
  1972年   39篇
  1971年   59篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Warner, Richard C., Carmen T. Agouridis, Page T. Vingralek, and Alex W. Fogle, 2010. Reclaimed Mineland Curve Number Response to Temporal Distribution of Rainfall. Journal of the American Water Resources Association (JAWRA) 46(4): 724-732. DOI: 10.1111/j.1752-1688.2010.00444.x Abstract: The curve number (CN) method is a common technique to estimate runoff volume, and it is widely used in coal mining operations such as those in the Appalachian region of Kentucky. However, very little CN data are available for watersheds disturbed by surface mining and then reclaimed using traditional techniques. Furthermore, as the CN method does not readily account for variations in infiltration rates due to varying rainfall distributions, the selection of a single CN value to encompass all temporal rainfall distributions could lead engineers to substantially under- or over-size water detention structures used in mining operations or other land uses such as development. Using rainfall and runoff data from a surface coal mine located in the Cumberland Plateau of eastern Kentucky, CNs were computed for conventionally reclaimed lands. The effects of temporal rainfall distributions on CNs was also examined by classifying storms as intense, steady, multi-interval intense, or multi-interval steady. Results indicate that CNs for such reclaimed lands ranged from 62 to 94 with a mean value of 85. Temporal rainfall distributions were also shown to significantly affect CN values with intense storms having significantly higher CNs than multi-interval storms. These results indicate that a period of recovery is present between rainfall bursts of a multi-interval storm that allows depressional storage and infiltration rates to rebound.  相似文献   
992.
Kallis, Jahn, Leo Bodensteiner, and Anthony Gabriel, 2010. Hydrological Controls and Freshening in Meromictic Soap Lake, Washington, 1939-2002. Journal of the American Water Resources Association (JAWRA) 46(4): 744-756. DOI: 10.1111/j.1752-1688.2010.00446.x Abstract: The chemically stratified layer of naturally formed meromictic lakes exhibits unusual and often extreme physical and chemical conditions that have resulted in the evolution of uniquely adapted species. The Columbia Basin Irrigation Project appears to have had a marked effect on the hydrology of Soap Lake, a meromictic lake in the Grand Coulee of central Washington. The relation of hydrology to salinity was assessed by analyzing water budgets before and after the introduction of the irrigation project. Before irrigation, water gains were balanced by losses; after irrigation began groundwater gains approximately doubled. To manage lake levels and reduce groundwater influx, wells were installed to intercept groundwater. Although the hydrological cycle has been restored to pre-irrigation conditions, the meromictic character of the lake continues to change. Interception wells remove 10 to 16 Mm3 of groundwater annually, but influx continues based on change in the monimolimnion. From 1958 to 2003 the chemocline descended 1.1 m and the volume of the monimolimnion from 698,000 m3 to 114,000 m3. Annual loss of volume is occurring at a rate of 1.9% since 1958. Although groundwater interception wells are maintaining the volume of the entire lake, the recession of the chemocline indicates that conditions that have maintained meromixis at Soap Lake are currently not in equilibrium.  相似文献   
993.
Zardari, Noor ul Hassan, Ian Cordery, and Ashish Sharma, 2010. An Objective Multiattribute Analysis Approach for Allocation of Scarce Irrigation Water Resources. Journal of the American Water Resources Association (JAWRA) 46(2):412-428. DOI: 10.1111/j.1752-1688.2009.00410.x Abstract: In this study, end user (farmer) and decision maker (water allocator) opinions were surveyed and a conjoint analysis (CA) based method was applied to the quantitative and qualitative data to assess the utility associated with each attribute that plays a role in forming the final thinking of the water users. The application of CA for estimating the utility for each attribute level is a novel approach, which helps provide a formal, objective basis for assigning relative scales for each attribute interval within a multiattribute decision-making model. The utilities (part-worths) obtained from the CA have a cardinal scale and were found to be comparable within and across the attributes. A farmers’ survey on five water allocation attributes was completed from 62 farmers and their opinions on the relative importance of attributes were elicited for a subarea of the Indus River Basin. The CA method was then applied to the survey data and the utilities for each attribute level were determined. This allowed, for instance, decisions to be made, which take account of the perceived value of the water and of the availability of local labor to work on the farm. Finally, these interval scales were used within the specification of the ELECTRE multiattribute decision-making method to provide a complete and objective ranking of nine irrigation districts so that the best decisions on water allocation could be made.  相似文献   
994.
Smith, Monica Lipscomb, Weiqi Zhou, Mary Cadenasso, Morgan Grove, and Lawrence E. Band, 2010. Evaluation of the National Land Cover Database for Hydrologic Applications in Urban and Suburban Baltimore, Maryland. Journal of the American Water Resources Association (JAWRA) 46(2):429-442. DOI: 10.1111/j.1752-1688.2009.00412.x Abstract: We compared the National Land Cover Database (NLCD) 2001 land cover, impervious, and canopy data products to land cover data derived from 0.6-m resolution three-band digital imagery and ancillary data. We conducted this comparison at the 1 km2, 9 km2, and gauged watershed scales within the Baltimore Ecosystem Study to determine the usefulness and limitations of the NLCD in heterogeneous urban to exurban environments for the determination of land-cover information for hydrological applications. Although the NLCD canopy and impervious data are significantly correlated with the high-resolution land-cover dataset, both layers exhibit bias at <10 and >70% cover. The ratio of total impervious area and connected impervious area differs along the range of percent imperviousness – at low percent imperviousness, the NLCD is a better predictor of pavement alone, whereas at higher percent imperviousness, buildings and pavement together more resemble NLCD impervious estimates. The land-cover composition and range for each NLCD urban land category (developed open space, low-intensity, medium-intensity, and high-intensity developed) is more variable in areas of low-intensity development. Fine-vegetation land-cover/lawn area is incorporated in a large number of land use categories with no ability to extract this land cover from the NLCD. These findings reveal that the NLCD may yield important biases in urban, suburban, and exurban hydrologic analyses where land cover is characterized by fine-scale spatial heterogeneity.  相似文献   
995.
Southard, Gregory M., Loraine T. Fries, and Aaron Barkoh, 2010. Prymnesium parvum: The Texas Experience. Journal of the American Water Resources Association (JAWRA) 46(1):14-23. DOI: 10.1111/j.1752-1688.2009.00387.x Abstract: Golden alga Prymnesium parvum was first identified in Texas during a fish kill investigation on the Pecos River in 1985. Since then golden alga kills occurred sporadically in a variety of waters in the western part of the state until 2001 when the alga became endemic in the Brazos, Canadian, Colorado, Red, and Rio Grande river systems, including the water supplies of two public fish hatcheries, the Possum Kingdom and Dundee state fish hatcheries. The increasing area adversely affected by the alga and frequent massive fish kills heightened public and political awareness and concerns regarding the ecological and economic impacts of P. parvum blooms. The Texas Parks and Wildlife Department (TPWD), the wildlife conservation agency of the state, responded to these concerns with a program to assess the ecological and economic impacts and to develop management options. To date 33 water bodies have been affected and losses are conservatively estimated at 34 million fish valued at US$13 million. Several sport fisheries, including smallmouth bass Micropterus dolomieu, striped bass Morone saxatilis, channel catfish Ictalurus punctatus, and blue catfish Ictalurus furcatus, have been severely affected. Additionally, 26 imperiled fish species occur in the affected water basins and some have been adversely affected. Economic losses associated with reduced fishing and other water-based recreational activities appear considerable. The combined economic losses to three counties (Palo Pinto, Stephens, and Young) surrounding Possum Kingdom reservoir for 2001 and 2003 were estimated at US$2.8 million and US$1.1 million, respectively. This paper describes how the TPWD responded to public and political concerns relative to the emergence of golden alga, its harmful effects to fisheries, and its historic and current statewide distribution.  相似文献   
996.
基于分形理论的江苏沿江城镇体系研究   总被引:7,自引:0,他引:7  
开放条件下,“全球 地方”作用深刻影响着区域城镇体系,沿江发达地区表现尤其典型。基于分形的相关理论和方法,以2006年为时空断面,对江苏沿江地区城镇体系的空间分布进行实证研究。结果表明:(1)区域城镇规模等级结构服从Zipf定律,首位城市南京在区域城市体系中的垄断性相对较强,但并非处于绝对垄断地位;(2)空间关联维数显示,沿江地区城镇体系的交通网络通达性优良,各城镇间联系紧密;(3)根据分维数和无标度区分析,三大城市群中,宁镇扬城市群分形发育最好,苏锡常次之,通泰城市群分形发育最差;(4)扬州、镇江、南京和苏州的城镇集聚程度较高,分形发育较为成熟;南通、泰州、无锡和常州的集聚程度均较低,分形结构不佳。扬州在区域城镇体系中分形发育最为完善,中心性最好,历史上形成的这种空间格局至今没有变化.  相似文献   
997.
利用可持续发展指数(SDI)对湖北“两圈”各市州发展现状进行了评价,而后利用9年的人均生物资源生态承载量年平均增长率、人口年平均增长率和足迹承载量比值年平均增长率及2006年相关数据对未来44年进行了预测。结果表明,截至2006年底,湖北省有一半以上国土面积的生物资源开采超过当地土地负荷,人均生物资源生态承载量持续下降,资源日益紧张,呈不可持续发展;武汉城市圈2006年生物资源生态足迹超出生物资源生态承载量的32%;鄂西生态文化旅游圈(简称:鄂西生态圈)除襄樊、荆州、荆门因人口多,生物资源生态足迹较大等原因导致SDI值较高外,其他市州的SDI值均较低;神农架的SDI最小;武汉城市圈人均生物资源生态承载量呈负增长,人口控制较好,足迹承载量比值增长较快;鄂西生态圈人均生物资源生态承载量呈负增长,增长速率大于武汉城市圈和湖北省,人口控制较差,足迹承载量比值增长较慢;按照现有发展模式,无论是武汉城市圈还是鄂西生态圈,无论其当前发展是可持续性还是不可持续的,未来他们都将进入不可持续的发展状态。因此,对“两圈”进行规划时要根据各自发展现状制定长期、科学的发展规划.  相似文献   
998.
基于事故树的三峡库区水体污染公共安全事件诱因分析   总被引:1,自引:0,他引:1  
三峡库区蓄水后对长江水体自净能力的极大削弱,沿江聚集的各类生产、生活活动对长江水质的多渠道污染极易引发库区各类水体污染公共安全事件。结合对库区水体污染公共安全事件多维度诱发因素的调研结果,运用事故树的分析方法对三峡库区水体污染公共安全事件的逐级诱发过程进行分析。研究表明:存在13条诱发库区水体污染公共安全事件的路径以及3条防治水体污染公共安全事件的路径;在不考虑诱因发生概率的情况下,排污因素是诱发库区水体污染公共安全事件最重要、最根本的因素,促成库区水体自净能力下降的回水区变长,水流紊动减弱和水位抬升三方面因素是次重要的诱发因素。只有对不同的诱因施行不同的监测和控制策略,才能对库区水体污染公共安全事件开展有效预警、预控.  相似文献   
999.
近年来,随着我国经济的飞速发展、社会经济的转型,以及人们环境意识的提高,滨水区开发已成为我国城市开发建设的热点。城市滨水区景观规划设计研究对于合理、充分利用城市滨水区景观资源,塑造特色鲜明的城市形象,提高城市生态环境质量,促进城市滨水区开发有着重要意义。从复合生态系统理论的角度,在湘江滨水区景观资源调查、景观资源分类的基础上,运用灰色聚类法对湘江滨水区景观资源进行定量评价,提出景观资源优化思路,探讨滨水区景观规划设计的途径。认为现代城市大规模滨水区更新改造和开发大背景下的城市滨水区景观规划设计,应尊重城市地域性特点、文化内涵和风土人情,并与传统的滨水活动有机结合,保护和突出城市历史格局和风貌特色。  相似文献   
1000.
River Nile is one of the longest transboundery rivers and it is shared and used by Burundi,Democratic Republic of Congo,Egypt,Ethiopia,Eritrea,Kenya,Rwanda,Sudan,Tanzania and Uganda.As of today,the Nile is a crucial resource for the economic development of the Nile Basin countries and a vital source of livelihood for 160 million inhabitants as well as 300 million people living in the 10 riparian countries.The Nile Basin Initiative(NBI) is one of the international cooperative river basin management program and regional partnership where all the Nile Basin countries except Eritrea unite to pursue long-term sustainable development,improved land use practices and management.This review therefore focused on the challenges not faced on NBI in terms of integrated use of the river and conducted analysis of strengths,weaknesses,opportunities and threats(SWOT) based on secondary data.The result of the review revealed that for decades,the Nile Basin people have been facing many complex environmental,social,economic and political challenges that have made it difficult for the proper management and sustainability of Nile water.The initiative provides training to develop skills in government ministries,non-governmental organizations and local communities in each country.It is also working to raise awareness of critical environmental issues by strengthening networks of environmental education practitioners;developing curriculum in the education sector.The challenges of NBI include the involvement and funding of World Bank,lack of sufficient staff,procedural and policies conflicts,lack of coordination and linkage with other regional institutions and lack of recognition as river basin organization.Considering the complex nature of the project,it is recommended that the NBI should come up with a strong multi-disciplinary monitoring and evaluation team to follow up all implemented projects.The NBI should carry out participatory land use planning in communities along the river basin.Moreover,livelihood analysis should be carried out especially in communities along the Nile to come up with poverty eradication projects which are socially acceptable,applicable,economically viable and affordable.  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