全文获取类型
收费全文 | 1300篇 |
免费 | 116篇 |
国内免费 | 215篇 |
专业分类
安全科学 | 190篇 |
废物处理 | 7篇 |
环保管理 | 171篇 |
综合类 | 699篇 |
基础理论 | 230篇 |
污染及防治 | 54篇 |
评价与监测 | 85篇 |
社会与环境 | 131篇 |
灾害及防治 | 64篇 |
出版年
2024年 | 6篇 |
2023年 | 30篇 |
2022年 | 54篇 |
2021年 | 61篇 |
2020年 | 55篇 |
2019年 | 45篇 |
2018年 | 46篇 |
2017年 | 57篇 |
2016年 | 47篇 |
2015年 | 57篇 |
2014年 | 60篇 |
2013年 | 68篇 |
2012年 | 82篇 |
2011年 | 118篇 |
2010年 | 77篇 |
2009年 | 102篇 |
2008年 | 59篇 |
2007年 | 86篇 |
2006年 | 75篇 |
2005年 | 56篇 |
2004年 | 57篇 |
2003年 | 44篇 |
2002年 | 36篇 |
2001年 | 43篇 |
2000年 | 38篇 |
1999年 | 32篇 |
1998年 | 22篇 |
1997年 | 23篇 |
1996年 | 12篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1631条查询结果,搜索用时 31 毫秒
441.
Rajan K. Sampath Edward W. Sparling Robert A. Young Kenneth C. Nobe 《Journal of the American Water Resources Association》1986,22(2):191-204
ABSTRACT: During the last three decades, developing countries have invested enormous amounts of resources (running into billions of dollars) in the development of large surface irrigation systems. Investment funds were largely spent on the development of the main systems such as dams, canals and distributaries. Very little attention and resources have been spent on the development of below-the-outlet subsystems, in spite of very low levels of water use efficiency due to lack of proper land leveling, high water losses in field channels, and skewed distribution of available water among farmers served by individual water courses. This state of affairs has resulted in a lack of confidence on the part of most farmers in the reliability of surface irrigation systems to deliver water on time and in adequate quantities which, in turn, has resulted in farmers using below optimum levels of all other complementary inputs except labor. Realizing the importance of improving water use efficiency, both the domestic governments and donor agencies are increasingly paying serious attention to these problems. On-Farm Water Management (OFWM) as a strategy to improve water use efficiency and consequently agricultural production in many developing countries has been currently receiving very wide and vigorous consideration among economists, water management experts, policymakers, and donor agencies. A judicious use of the newly allocated funds of OFWM projects obviously needs proper evaluation procedures so that money could be allocated for the most deserving purposes and projects. In particular, recently, private profitability calculations due to public investments in OFWM activities have received attention from economists and decision makers in developing countries’governments and in donor agencies are very much interested in knowing the impacts of their investments in OFWM activities on farmers’income and welfare. However, the evaluation procedures commonly used in empirical studies, using a production function approach, seem to be at variance and sometimes inconsistent with proper comparative-static procedures. Thus, the primary objective of this paper is to develop consistent procedures for evaluating the impacts created by OFWM investments on farmers’income and resource use. In this context, the paper examines the critical relationship between the market price of the agricultural output and production function parameters which are affected by the OFWM investments. 相似文献
442.
Vijetha Ponnam Naresh Kumar Katari Ramesh Naidu Mandapati Satyasree Nannapaneni Subbaiah Tondepu 《Journal of environmental science and health. Part. B》2020,55(4):396-405
AbstractBentazone is one of the toxic insecticides used to control forest tent caterpillar moths, boll weevils, gypsy moths, and other types of moths in various field crops. We report the efficacy of biochar prepared from the Azardirachta Indica waste biomass as adsorbent for removal of Bentazone. Biochar material was prepared by pyrolysis process under limited oxygen conditions. Biochar material was characterized by proximate and ultimate analysis, SEM analysis, FTIR analysis and TG/DTA analyses. The Bentazone adsorption capacity by biochar from aqueous solutions was assessed. Effect of time, adsorbent dosage, insecticide concentration and pH on the adsorption characteristics of the biochar were evaluated. Adsorption parameters were obtained at equilibrium contact time of 150?min, with biochar dosage of 0.5?g at pH 8. From the optimization studies, desirability of 0.952 was obtained with response (adsorption uptake) of 79.40?mg/g, for initial concentration of insecticide (50?mg/L), adsorbent dosage (0.448?g), time 30.0?min and pH 2. The adsorption isotherm data for the removal of Bentazone fitted well with the Freundlich isotherm. This study indicates that the biochar produced from the bark of Azardirachta Indica biomass could be employed as a potential adsorbent for removal of synthetic organic pollutants from the water streams. 相似文献
443.
Mary C. Freeman Catherine M. Pringle C. Rhett Jackson 《Journal of the American Water Resources Association》2007,43(1):5-14
Abstract: Cumulatively, headwater streams contribute to maintaining hydrologic connectivity and ecosystem integrity at regional scales. Hydrologic connectivity is the water‐mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. Headwater streams compose over two‐thirds of total stream length in a typical river drainage and directly connect the upland and riparian landscape to the rest of the stream ecosystem. Altering headwater streams, e.g., by channelization, diversion through pipes, impoundment and burial, modifies fluxes between uplands and downstream river segments and eliminates distinctive habitats. The large‐scale ecological effects of altering headwaters are amplified by land uses that alter runoff and nutrient loads to streams, and by widespread dam construction on larger rivers (which frequently leaves free‐flowing upstream portions of river systems essential to sustaining aquatic biodiversity). We discuss three examples of large‐scale consequences of cumulative headwater alteration. Downstream eutrophication and coastal hypoxia result, in part, from agricultural practices that alter headwaters and wetlands while increasing nutrient runoff. Extensive headwater alteration is also expected to lower secondary productivity of river systems by reducing stream‐system length and trophic subsidies to downstream river segments, affecting aquatic communities and terrestrial wildlife that utilize aquatic resources. Reduced viability of freshwater biota may occur with cumulative headwater alteration, including for species that occupy a range of stream sizes but for which headwater streams diversify the network of interconnected populations or enhance survival for particular life stages. Developing a more predictive understanding of ecological patterns that may emerge on regional scales as a result of headwater alterations will require studies focused on components and pathways that connect headwaters to river, coastal and terrestrial ecosystems. Linkages between headwaters and downstream ecosystems cannot be discounted when addressing large‐scale issues such as hypoxia in the Gulf of Mexico and global losses of biodiversity. 相似文献
444.
河北省海洋灾害遥感动态监测系统简介 总被引:2,自引:0,他引:2
为及时获取海洋灾害发生及其影响的监测信息,并为当地政府和有关部门提供决策服务,根据渤海湾海洋灾害发生的特点,从风暴潮、赤潮、海冰、海域污染等海洋灾害的遥感监测技术方法研究入手,介绍了河北省海洋灾害遥感动态监测系统的功能。应用服务情况表明,该系统对渤海的风暴潮、赤潮、海冰、海域污染的遥感监测效果良好。重点对利用NOAA/AVHRR数据开展的1998—2006年春季渤海海域污染遥感监测情况进行了客观的分析,结果表明,渤海湾近海水域从1999年开始出现大范围污染,其中,2002年最为严重,2003年以后有所好转,但是近两年的污染状况又趋严重。 相似文献
445.
城镇建设用地需求预测与配置研究 总被引:11,自引:0,他引:11
针对我国现行城镇建设用地预测方法存在的问题,对城镇建设用地预测方法进行了探索性研究;通过构建科学的建设用地需求预测方法,为土地利用规划提供科学依据。在C—D生产函数的基础上,提出了土地、资本与产出GDP的要素关系模型、恩格尔系数与人均建设用地面积关系模型和时间序列的ARIMA建设用地模型。对成都市城镇建设用地总量进行了实证分析,对4种预测方法的结果进行了定量评价,并据此提出成都市建设用地的配置方案。 相似文献
446.
厌氧生物处理技术在抗生素废水处理中的应用 总被引:1,自引:0,他引:1
抗生素废水是一类成分复杂、硫酸盐浓度高、含有多种抑制性物质的高浓度难降解有机废水,主要来源于抗生素生产废水、洗涤废水和冷却水等。分析了抗生素废水的来源和水质特征,介绍了国内外抗生素废水治理的各种厌氧生物处理技术方法及其应用,最后对厌氧生物法应用于抗生素废水处理的前景进行了展望。 相似文献
447.
矿井通风系统抗灾变能力的确定和提高对于矿山减灾救灾具有重要意义。在通风系统抗灾变能力评价中,指标体系的选取至关重要。根据矿井火灾、救灾、防灾的具体情况及相关文献,从防火措施、防火管理、指挥救灾和井下工人救火素质4方面选取了22个指标,确定了矿井通风系统抗灾变能力的模糊综合评价指标体系,给出了矿井通风系统抗灾变能力指标分级界定值,并采用层次分析法对各个指标的重要性进行排序,提出了通风系统抗灾变能力层次分析结构模型。 相似文献
448.
阜新市产业结构调整与可持续发展战略研究 总被引:14,自引:3,他引:11
阜新市产业结构调整及发展战略规划课题组 《中国人口.资源与环境》2000,10(3):71-75
本文系统总结了国内外资源型衰退地区产业结构调整的经验及模式,并从区域竞争和创新思想出发,在分析阜新市产业结构调整与区域发展面临的核心问题,竞争优势的基础上,提出了阜新市区域发展战略模式及相关行动计划。 相似文献
449.
矿井通风系统抗灾变能力分析 总被引:3,自引:2,他引:3
通风系统的抗灾变能力对于救灾和通风系统评价具有重要意义,通风系统抗灾变能力涉及通风系统结构、人员素质、管理水平等诸多因素,笔者根据矿井火灾的救灾、防灾具体情况及相关文献,选取了4类共22个指标建立了矿井通风系统抗灾变能力的模糊综合评价数学模型,给出了矿井通风系统抗灾变能力指标体系及分级界定值,采用模糊综合评价法对矿井通风系统抗灾变能力进行了分析。 相似文献
450.
康东伟 《中国环境管理干部学院学报》2006,16(4):43-45
昌黎黄金海岸自然保护区存在着土地权属、资源保护与开发矛盾、经费不足和管理执法力量薄弱等诸多现实问题.因此,结合保护区概况,提出发展生态旅游,解决土地权属、协调资源保护与开发关系和实施社区共管等方式等可行性对策与措施. 相似文献