全文获取类型
收费全文 | 3052篇 |
免费 | 1164篇 |
国内免费 | 645篇 |
专业分类
安全科学 | 344篇 |
废物处理 | 21篇 |
环保管理 | 250篇 |
综合类 | 2705篇 |
基础理论 | 549篇 |
污染及防治 | 356篇 |
评价与监测 | 358篇 |
社会与环境 | 129篇 |
灾害及防治 | 149篇 |
出版年
2025年 | 2篇 |
2024年 | 193篇 |
2023年 | 203篇 |
2022年 | 270篇 |
2021年 | 255篇 |
2020年 | 288篇 |
2019年 | 213篇 |
2018年 | 203篇 |
2017年 | 197篇 |
2016年 | 211篇 |
2015年 | 229篇 |
2014年 | 200篇 |
2013年 | 212篇 |
2012年 | 269篇 |
2011年 | 249篇 |
2010年 | 167篇 |
2009年 | 169篇 |
2008年 | 131篇 |
2007年 | 173篇 |
2006年 | 161篇 |
2005年 | 121篇 |
2004年 | 86篇 |
2003年 | 110篇 |
2002年 | 79篇 |
2001年 | 72篇 |
2000年 | 58篇 |
1999年 | 58篇 |
1998年 | 58篇 |
1997年 | 54篇 |
1996年 | 35篇 |
1995年 | 35篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有4861条查询结果,搜索用时 15 毫秒
1.
北京市近12年空气污染变化特征及其与气象要素的相关性分析 总被引:1,自引:0,他引:1
以北京市近12年空气污染指数(API)为数据基础,首先分析了2001—2012年北京市API、污染等级、首要污染物的变化特征以及污染天数年度值、季度值、月值的变化特征;然后根据API转换得到PM10质量浓度,对其变化特征进行分析;最后采用相关系数法分析了北京市API、PM10质量浓度与气象因素的相关性。结果表明,北京市近12年空气污染天数有明显下降趋势,首要污染物主要为可吸入颗粒物;空气污染主要集中于春季,优良天气主要集中于夏季;PM10质量浓度年度最大值出现在2006年,季度最大、最小值分别出现在春、夏季,月值最大、最小值分别出现在3月和7月;气象因素与空气污染关系密切,气温、相对湿度、降雨量与污染天数和PM10质量浓度均呈显著负相关,而风速与污染天数和PM10质量浓度则呈显著正相关。 相似文献
2.
利用室内动三轴实验研究了振动频率与龄期对河道淤泥气泡混合轻质土(FMLSS)动力特性的影响。结果表明,振动频率和龄期对FMLSS的动力特性有明显影响。振动频率越小,轴向动应变和阻尼比越大,动模量越小。随着养护龄期的增长,动模量增大而阻尼比减小。动模量曲线在振动频率大、养护龄期长和水泥含量高时更加陡峭。当动应变较小时,不同龄期的FMLSS阻尼比很接近,随着动应变不断发展,阻尼比差异增大。FMLSS的动模量曲线都呈平缓衰减型,阻尼比在0.01~0.03之间,体现出FMLSS是良好的弹性材料。最后,探讨了振动频率和龄期对FMLSS动力特性的影响机理。 相似文献
3.
Pollution characteristics of 23 veterinary antibiotics in livestock manure and manure-amended soils in Jiangsu province,China 总被引:3,自引:0,他引:3
Xin Y. Guo Li J. Hao Pan Z. Qiu Rong Chen Jing Xu Xiang J. Kong 《Journal of environmental science and health. Part. B》2016,51(6):383-392
The aim of this study was to investigate the pollution characteristics of typical veterinary antibiotics in manure and soil of livestock farms in Jiangsu province. This investigation employed solid-phase extraction (SPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A total of 53 manure and 50 amended soil samples from 16 livestock farms in Jiangsu province were collected for analysis. In the manure samples, the highest detected frequencies and concentrations were those of tetracyclines (TCs, 54.1 ± 5775.6 μgkg?1), followed by fluoroquinolones (FQs, 8.4 ± 435.6 μgkg?1), sulphonamides (SAs, 3.2 ± 5.2 μgkg?1) and macrolides (MACs, 0.4 ± 110.5 μgkg?1). Statistical analysis was used to illuminate the pollution characteristics of 23 veterinary antibiotics for various animal types and different regions in Jiangsu province. The results showed that the pollution level in cow manure was relatively lower compared with pig and chicken manure due to the relative restriction of medication. Furthermore, contamination was serious in amended soil from chicken farms. The pollution level in manure among different regions was higher to the south and north compared with the centre of the region. The same outcome was found for soil. Antibiotic residues in organic fertilizer were also investigated in this study. We found that although the detected concentration was lower in organic fertilizer than in fresh manure, detection frequencies (10–90%) were high, especially for roxithromycin (90%) in MACs (30–90%). This finding suggests attention should be paid to the pollution levels in organic fertilizer. This study is the first extensive investigation of the occurrence and distribution of many kinds of typical veterinary antibiotics in manure and soil from livestock farms of Jiangsu province. This investigation systematically assesses veterinary antibiotics usage and related emissions in southeast China. 相似文献
4.
2014年7月-2015年5月典型季节期间在重庆城区选择典型站点开展PM2.5样品采集,并测量质量浓度,分析样品中水溶性离子、无机元素、OC和EC等组分,在此基础上对组分化学组成进行了质量重构。结果表明:观测期间PM2.5年均值为76.4 μg·m-3,浓度季节变化为冬季 > 秋季 > 春季 > 夏季;组分方面,以二次转化为主的SO42-、NH4+、NO3-和OC是PM2.5组分中最主要成分,OC/EC比值4个季度均大于2,表明城区二次有机碳生成显著;硫氧化率(SOR)分析,气态污染物SO2的二次转化效率较高,大气存在明显的二次转化过程。PM2.5质量重构后主要组成为有机气溶胶(OM)、二次无机离子(SNA)和矿物尘,重庆城区应协同控制一次排放的颗粒物和气态污染物SO2和NOx,从而控制二次组分浓度。 相似文献
5.
6.
Randall J. Schaetzl L. Keith Hendrie Scott W. Kirsch 《Journal of the American Water Resources Association》1989,25(5):1023-1030
ABSTRACT: Soil water was monitored by neutron scattering in six soils, three each within two drainage catenas in east-central Illinois, over a 15-month time span. The prairie soils have formed in: (1) 76–152 cm of silt loam, eolian sediments (bess) over glacial till (Catlin-Flanagan-Drummer catena), and (2) bess greater than 152 cm in thickness (Tama-Ipava-Sable catena). We characterized the water content of these soils over the total time span and for wet and dry climatic subsets, as an aid to potential irrigation decisions. Soils of the thin bess, C-F-D catena dried out to lower water contents and had greater soil water variability than did the thick bess soils. Under wet conditions, soil water contents in the two catenas were quite similar. Alleviation of surface and subsurface drying via irrigation would thus be more advantageous to yields on the C-F-D soils than on the T-I-S soils. 相似文献
7.
广东省耕地资源的动态变化特征 总被引:3,自引:0,他引:3
耕地资源问题已成为制约广东省农业以至社会经济发展的主要因素之一。本文通过分析该省耕地资源数量、质量变化特征及各地区耕地资源的流失、净增减情况,得出耕地资源动态变化特征,并简要地阐述了产生这些变化的机制和原因,最后提出了保护耕地资源的基本对策 相似文献
8.
中国湿地现状综述 总被引:9,自引:0,他引:9
刘军 《中国环境管理干部学院学报》2004,14(2):64-67
湿地是重要的自然资源,对人类生存起着重要作用。本文综述了湿地的含义、功能与 价值、中国湿地的特点与现状,以促进中国湿地的可持续发展与利用。 相似文献
9.
10.
Laura Jean Wilcox Robert S. Bowman Nabil G. Shafike 《Journal of the American Water Resources Association》2007,43(6):1595-1603
Abstract: Previous investigations observed significant seepage losses from the Rio Grande to the shallow aquifer between Socorro and San Antonio, New Mexico. High‐resolution telescopic modeling was used along a 10‐km reach of the Rio Grande and associated drains and canals to evaluate several management alternatives aimed at improving river conveyance efficiency. Observed data consisted of ground‐water and surface‐water elevations, seepage rates along the Rio Grande and associated canals and drains, and borehole geology. Model calibration was achieved by adjusting hydraulic conductivity and specific storage until the output matched observed data. Sensitivity analyses indicated that the system was responsive to changes in hydrogeologic properties, especially when such alterations increased vertical connectivity between layers. The calibrated model predicted that removal of the low flow conveyance channel, a major channel draining the valley, would not only decrease river seepage by 67%, but also decrease total flow through the reach by 75%. The decreased flow through the reach would result in increased water logging and an average increase in ground‐water elevations of 1.21 meter. Simulations of the system with reduced riparian evapotranspiration rates or a relocated river channel also predicted decreased river seepage, but to a much lesser degree. 相似文献