全文获取类型
收费全文 | 1479篇 |
免费 | 118篇 |
国内免费 | 148篇 |
专业分类
安全科学 | 70篇 |
废物处理 | 20篇 |
环保管理 | 452篇 |
综合类 | 560篇 |
基础理论 | 120篇 |
环境理论 | 1篇 |
污染及防治 | 31篇 |
评价与监测 | 53篇 |
社会与环境 | 382篇 |
灾害及防治 | 56篇 |
出版年
2024年 | 8篇 |
2023年 | 16篇 |
2022年 | 38篇 |
2021年 | 49篇 |
2020年 | 29篇 |
2019年 | 45篇 |
2018年 | 45篇 |
2017年 | 63篇 |
2016年 | 67篇 |
2015年 | 63篇 |
2014年 | 47篇 |
2013年 | 103篇 |
2012年 | 97篇 |
2011年 | 121篇 |
2010年 | 84篇 |
2009年 | 69篇 |
2008年 | 61篇 |
2007年 | 91篇 |
2006年 | 76篇 |
2005年 | 59篇 |
2004年 | 71篇 |
2003年 | 58篇 |
2002年 | 54篇 |
2001年 | 32篇 |
2000年 | 55篇 |
1999年 | 43篇 |
1998年 | 15篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 16篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1971年 | 2篇 |
排序方式: 共有1745条查询结果,搜索用时 703 毫秒
951.
Christiane I. Mulvihill Barry P. Baldigo 《Journal of the American Water Resources Association》2012,48(3):449-463
Mulvihill, Christiane I. and Barry P. Baldigo, 2012. Optimizing Bankfull Discharge and Hydraulic Geometry Relations for Streams in New York State. Journal of the American Water Resources Association (JAWRA) 48(3): 449-463. DOI: 10.1111/j.1752-1688.2011.00623.x Abstract: This study analyzes how various data stratification schemes can be used to optimize the accuracy and utility of regional hydraulic geometry (HG) models of bankfull discharge, width, depth, and cross-sectional area for streams in New York. Topographic surveys and discharge records from 281 cross sections at 82 gaging stations with drainage areas of 0.52-396 square miles were used to create log-log regressions of region-based relations between bankfull HG metrics and drainage area. The success with which regional models distinguished unique bankfull discharge and HG patterns was assessed by comparing each regional model to those for all other regions and a pooled statewide model. Gages were also stratified (grouped) by mean annual runoff (MAR), Rosgen stream type, and water-surface slope to test if these models were better predictors of HG to drainage area relations. Bankfull discharge models for Regions 4 and 7 were outside the 95% confidence interval bands of the statewide model, and bankfull width, depth, and cross-sectional area models for Region 3 differed significantly (p < 0.05) from those of other regions. This study found that statewide relations between drainage area and HG were strongest when data were stratified by hydrologic region, but that co-variable models could yield more accurate HG estimates in some local regional curve applications. 相似文献
952.
提出"区域开发规模扩张的资源环境响应"的概念,并构建了区域开发规模扩张的资源环境响应指数、响应度模型及评价指标体系,通过定量分析1995-2008年东北地区开发规模扩张的资源环境响应变化及影响因素,得出以下结论:1995年以来东北地区开发规模不断扩大,而资源环境水平总体呈现出"先升后降"的波动变化态势。资源环境对东北地区开发规模扩张具有由"正响应"向"负响应"转变的特征,与此相对应,区域开发规模扩张对资源环境的影响程度也呈现出由"弱促进"向"强胁迫"变化的态势,这说明近年来在东北地区开发规模加速扩展的同时,其对区域资源环境造成的压力也日益增大。1995-2008年由经济快速增长导致的资源环境压力增长是引致东北地区开发规模扩张对资源环境影响由"正向促进"向"负向胁迫"转化的重要内部因素,而区域投资的不断增长以及工业的快速发展是东北地区开发规模扩张对资源环境影响由"弱促进"向"强胁迫"变化的主要因素。 相似文献
953.
954.
基于GIS的我国农村老年人口时空发展研究 总被引:1,自引:0,他引:1
以2000年、2003年、2006年和2009年4个时间点的农村老年人口数据为基础,从农村老年人口系数、老少比和养老负担3个指标对我国大陆31个地区的农村老年人口状况做了时间和空间上的对比分析。结果表明,农村老龄化发展迅速且从东部向中西部快速递进,农村老龄化的集中程度趋于降低。 相似文献
955.
智能能源网是我国"十二五"期间完善资源开发及能源转化的重点科研攻关课题。以煤基低碳能源转化为例,提出基于智能能源网的资源开发模式。该模式可从根本上改善我国传统的对原生资源低效和掠夺式的开发方式,提高从原生资源到能源商品整个过程的资源转化效率,在极大程度上减少生产过程中对环境造成的碳排放污染。其市场匹配模式应以政府作为引导主体,按市场化所处的不同阶段积极施行经济和科技体制改革。 相似文献
956.
Xiao-Song He Bei-Dou Xi Xiang Li Hong-Wei Pan Da An Shuo-Guo Bai Dan Li Dong-Yu Cui 《Chemosphere》2013
The present several humification indexes cannot provide the whole fluorescence information on organic matter composition and the evaluation results from them are inconsistent sometimes. In this study, fluorescence excitation–emission matrix spectra coupled with parallel factor analysis and fluorescence regional integration analysis were utilized to investigate organic matter humification, and the projection pursuit cluster (PPC) model was applied to form a suitable index for overcoming the difficulties in multi-index evaluation. The result showed that the ratio between the volume of humic- and fulvic-like fluorescence region and the volume of protein-like fluorescence region not only revealed the heterogeneity of organic matter, but also provided more accurate information on organic matter humification. In addition, the results showed that the PPC model could be used to characterize integrally the humification, and the projected characteristic value calculated from the PPC model could be used as the integrated humification evaluation index. 相似文献
957.
S. A. Clay R.H. Dowdy J.A. Lamb J.L. Anderson B. Lowery R.E. Knighton 《Journal of environmental science and health. Part. B》2013,48(3):259-278
Abstract This study was conducted to evaluate atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl‐1, 3, 5‐triazine) and alachlor (2‐chIoro‐N‐(methoxymethyl)acetamide) dissipation and movement to shallow aquifers across the Northern Sand Plains region of the United States. Sites were located at Minnesota on a Zimmerman fine sand, North Dakota on Hecla sandy loam, South Dakota on a Brandt silty clay loam, and Wisconsin on a Sparta sand. Herbicide concentrations were determined in soil samples taken to 90 cm four times during the growing season and water samples taken from the top one m of aquifer at least once every three months. Herbicides were detected to a depth of 30 cm in Sparta sand and 90 cm in all other soils. Some aquifer samples from each site contained atrazine with the highest concentration in the aquifer beneath the Sparta sand (1.28 μg L‐1). Alachlor was detected only once in the aquifer at the SD site. The time to 50% atrazine dissipation (DT50) in the top 15 cm of soil averaged about 21 d in Sparta and Zimmerman sands and more than 45 d for Brandt and Hecla soils. Atrazine DT50 was correlated positively with % clay and organic carbon (OC), and negatively with % fine sand. Alachlor DT50 ranged from 12 to 32 d for Zimmerman and Brandt soils, respectively, and was correlated negatively with % clay and OC and positively with % sand. 相似文献
958.
在中试规模下,研究青岛市餐厨垃圾与菜市场垃圾混合(质量比1∶1)高温厌氧消化实验,通过监测厌氧消化过程中产气量、气体组成等产气情况和消化液中pH值、SCOD、NH3-H、VFAs含量和组分等化学指标变化,确定混合厌氧消化的最大有机负荷,并分析混合高温厌氧消化技术的可行性,结果表明,(1)青岛市餐厨垃圾与菜市场垃圾混合高温厌氧消化产甲烷具有技术可行性;(2)混合厌氧消化的最大有机负荷可达4.069 kg VS/(m3.d);(3)当系统最大有机负荷时,每天每千克VS最高可产生甲烷量0.346 m3;(4)混合厌氧消化可削减氨氮对餐厨垃圾单独厌氧消化产沼气的影响。 相似文献
959.
郝淑丽 《再生资源与循环经济》2013,(11):10-12
在世界气候变暖的大背景下,发达国家作为温室气体的主要排放责任国,负有义不容辞的减排义务.各国采取了各种政策工具进行减排,较普遍也较重要的政策工具是碳税政策和碳排放交易权政策.选取美国、欧盟、日本、英国几个代表性的发达国家,对其碳税和碳交易权政策工具的实施情况进行了系统分析. 相似文献
960.
Marie Briguglio Liam Delaney Alex Wood 《Journal of Environmental Planning and Management》2016,59(10):1751-1774
This paper assesses the determinants of take-up of a voluntary waste separation scheme, in a scenario where residents sorted, stored and paid for collection of recycling waste even though mixed waste was collected at the kerbside more conveniently, free of charge and without any quantity limits. Uptake of the scheme was positive, persistent and diverse across localities, offering an opportunity to assess the factors determining voluntary participation in the presence of disincentives. We employ a unique panel data-set (n = 4,644) from Malta, including data on recyclable waste kilogrammes collected over the first 86 weeks of the scheme's operation. Drawing on insights from environmental economics and psychology, a model is empirically estimated. Results indicate that uptake is suppressed by the initial constraints households may face and stimulated by collection frequency. Political vote is an important determinant of participation and this interacts with scheme promotion to create diverse uptake rates. 相似文献