全文获取类型
收费全文 | 16818篇 |
免费 | 5144篇 |
国内免费 | 27484篇 |
专业分类
安全科学 | 1973篇 |
废物处理 | 523篇 |
环保管理 | 1423篇 |
综合类 | 33167篇 |
基础理论 | 3337篇 |
环境理论 | 1篇 |
污染及防治 | 5855篇 |
评价与监测 | 1869篇 |
社会与环境 | 597篇 |
灾害及防治 | 701篇 |
出版年
2024年 | 74篇 |
2023年 | 224篇 |
2022年 | 569篇 |
2021年 | 526篇 |
2020年 | 1183篇 |
2019年 | 2131篇 |
2018年 | 2222篇 |
2017年 | 2315篇 |
2016年 | 2055篇 |
2015年 | 2559篇 |
2014年 | 3268篇 |
2013年 | 3480篇 |
2012年 | 3529篇 |
2011年 | 3000篇 |
2010年 | 2755篇 |
2009年 | 2674篇 |
2008年 | 2304篇 |
2007年 | 2344篇 |
2006年 | 1773篇 |
2005年 | 1286篇 |
2004年 | 1148篇 |
2003年 | 913篇 |
2002年 | 818篇 |
2001年 | 765篇 |
2000年 | 890篇 |
1999年 | 700篇 |
1998年 | 511篇 |
1997年 | 468篇 |
1996年 | 499篇 |
1995年 | 440篇 |
1994年 | 279篇 |
1993年 | 216篇 |
1992年 | 289篇 |
1991年 | 266篇 |
1990年 | 233篇 |
1989年 | 200篇 |
1988年 | 146篇 |
1987年 | 73篇 |
1986年 | 75篇 |
1985年 | 53篇 |
1984年 | 55篇 |
1983年 | 40篇 |
1982年 | 45篇 |
1981年 | 34篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1972年 | 5篇 |
1971年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
181.
Recent drinking water regulations have lowered the disinfection by-product standards as well as added new disinfection by-products for regulation. Natural organic matter (NOM) plays a major role in the formation of undesirable organic by-products following disinfection/oxidation of drinking water. It is suspected that most precursors to disinfection by-products are humic, although nonhumic substances are also suspected of contributing to these by-products. Many of the disinfection by-products have adverse health effects in humans (i.e., carcinogenic or mutagenic effects). The primary chlorinated disinfection by-products of concern include trihalomethanes, haloacetic acids, and haloacetonitrile. Fluorescence spectroscopy was used to study humic and fulvic acids. The two fractions of humic substances, humic and fulvic acids, were characterized by a double-peak phenomena in an overlapping fluorescing region. Disinfection by-product formation potentials of humic and fulvic acids have been correlated with total organic carbon, UV absorbance at 254 nm, specific absorbance and fluorescence. River humic and fulvic acid was found to have the highest reactivity to disinfection by-product formation as compared to soil and peat humic and fulvic acid. Fluorescence spectroscopy has shown to be a rapid and predictive tool for disinfection by-products formation potential of humic and fulvic acids. 相似文献
182.
Land use as a mitigation strategy for the water-quality impacts of global warming: a scenario analysis on two watersheds in the Ohio River Basin 总被引:4,自引:0,他引:4
This study uses an integrative approach to study the water-quality impacts of future global climate and land-use changes. In this study, changing land-use types was used as a mitigation strategy to reduce the adverse impacts of global climate change on water resources. The climate scenarios were based on projections made by the Intergovernmental Panel on Climate Change (IPCC) and the United Kingdom Hadley Centre's climate model (HadCM2). The Thornthwaite water-balance model was coupled with a land-use model (L-THIA) to investigate the hydrologic effects of future climate and land-use changes in the Ohio River Basin. The land-use model is based on the Soil Conservation Service's curve-number method. It uses the curve number, an index of land use and soil type, to calculate runoff volume and depth. The ArcView programming language, Avenue, was used to integrate the two models into a geographic information system (GIS). An output of the water-balance model, daily precipitation values adjusted for potential evapotranspiration, served as one of the inputs into the land-use model. Two watersheds were used in the present study: one containing the city of Cincinnati on the main stem of the Ohio River, and one containing the city of Columbus on a tributary of the Ohio River. These cities represent two major metropolitan areas in the Ohio River Basin with different land uses experiencing different rates of population growth. The projected hypothetical land-use changes were based on linear extrapolations of current population data. Results of the analyses indicate that conversion from agricultural land use to low-density residential land use may decrease the amount of surface runoff. The land-use practices which generate the least amount of runoff are forest, low-density residential, and agriculture; whereas high-density residential and commercial land-use types produce the highest runoff. The hydrologic soil type present was also an important factor in determining the amount of runoff and non-point-source pollution. A runoff-depth matrix and total nitrogen matrix were created for Cincinnati and Columbus to describe possible land-use mitigation measures in response to global climate change. The differences in Cincinnati and Columbus were due to differences in geographic location, air temperature, and total runoff. The results of this study may be useful to planners and policy makers for defining the possible impacts of future global climate and land-use changes on water resources. 相似文献
183.
滇池水污染总量控制中污染源系统特征研究 总被引:6,自引:0,他引:6
湖泊流域同入湖水系的流域单元组成,本文以滇池流域单元为基础,进行了污染源总量控制片区划分,并对各片区进行了污染源系统特征研究,从而为滇池主要污染物总量控制提出了工作重点和具体对象。 相似文献
184.
政和—大埔断裂带经历多期复杂的构造变形变质作用,不同地段的时空演化特征有所差异,总体上可划分为四个演化阶段。即:①前加里东期(?)—加里东期韧性剪切变形变质作用(D_1),发生于中、下地壳,是顺层剪切(固态流变)的结果,为纯韧性变形,②印支期韧性剪切变形变质作用(D_2)——政和—大埔断裂的形成,以平移型剪切为主,形成S——C糜棱岩,为半韧性变形环境;③印支末期—燕山早期逆冲—推覆作用(D_3),为多层次逆冲推覆,东部所谓的“天窗”部分为这一时期逆冲岩片的残留体,随着早燕山期花岗岩的侵入逐渐过渡到伸展拆离环境,同时西部推覆体后缘出现拉张,形成有限的火山岩盆地,为半脆性—脆性变形环境;④燕山期(—喜山期)伸展—拆离作用(D_4),在相对年轻的拆离断层之下出露变质核杂岩(如稻香组和熊山岩体),并形成裂陷盆地堆积(梨山组),东部部分“天窗”属这类成因,形成环境跨度大,为半韧性→半脆性→脆性。 相似文献
185.
186.
REMIS is one of key research projects sponsored by the central government. It is recommended to regional EPAs as a main tool of the environmental management. REMIS simulates the functions of the regional EPAs and aimed to improve their management level. The national environmental management information system will base on REMIS.Functional analysis is the kernel of the REMIS system analysis. Data and data flow analysis are used to support the functional analysis.Investigations on the functions of the local EPAs of eight provinces and 12 cities have been taken. The functions were carefully sorted. Modular design method was used in system analysis and system design.The system analysis included functional analysis, data analysis and data flow analysis. The system design is based on the system analysis. HIPO diagram of each modular, data base structure, menu design, selection of hardware and software environment were the main items of the system design. 相似文献
187.
对呼吸计量法应用于校准ASM1作了简明的阐述。在呼吸速率与模型组分关系的基础上,介绍了ASM1中废水与污泥各组分浓度的测定方法,并指出模型组分细化的意义。 相似文献
188.
项目环境影响评价与战略环境评价比较 总被引:6,自引:0,他引:6
结合国内外战略环境评价研究状况,对战略环境评价和项目环境影响评价的关系进行了较为全面地比较.通过分析项目环境影响评价的不足和战略环境评价的优点, 指出开展战略环境评价,可完善环境影响评价体系,促进可持续发展战略实施.并就战略环境评价与项目环境评价在研究对象、管理体系、技术特点、方法体系和技术手段等方面的区别作了明确阐述.最后分析了二者的联系,明确了二者的层次关系及可供借鉴之处. 相似文献
189.
SO2 和氟化物对农作物的危害可通过症状、镜检和受害叶片的化学分析来鉴别 ,并从风向、与污染源距离、障碍物和叶片成熟程度几方面与作物病虫等影响因素相区别。排放浓度、接触时和作物本身抗性是影响危害程度的主要因素。应从治理污染、选种抗性强树木、避开作物敏感生育期、合理种植、加强施肥等方面采取措施加以防治 相似文献
190.