全文获取类型
收费全文 | 5616篇 |
免费 | 448篇 |
国内免费 | 1814篇 |
专业分类
安全科学 | 599篇 |
废物处理 | 252篇 |
环保管理 | 472篇 |
综合类 | 3519篇 |
基础理论 | 825篇 |
污染及防治 | 1283篇 |
评价与监测 | 322篇 |
社会与环境 | 313篇 |
灾害及防治 | 293篇 |
出版年
2024年 | 28篇 |
2023年 | 98篇 |
2022年 | 262篇 |
2021年 | 229篇 |
2020年 | 245篇 |
2019年 | 198篇 |
2018年 | 205篇 |
2017年 | 286篇 |
2016年 | 234篇 |
2015年 | 294篇 |
2014年 | 409篇 |
2013年 | 461篇 |
2012年 | 487篇 |
2011年 | 496篇 |
2010年 | 430篇 |
2009年 | 401篇 |
2008年 | 416篇 |
2007年 | 378篇 |
2006年 | 364篇 |
2005年 | 301篇 |
2004年 | 212篇 |
2003年 | 209篇 |
2002年 | 191篇 |
2001年 | 155篇 |
2000年 | 148篇 |
1999年 | 112篇 |
1998年 | 86篇 |
1997年 | 97篇 |
1996年 | 107篇 |
1995年 | 83篇 |
1994年 | 71篇 |
1993年 | 62篇 |
1992年 | 43篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有7878条查询结果,搜索用时 15 毫秒
791.
Polychlorinated biphenyls (PCBs) levels in crucian carp were determined at 20 locations along four major river systems, several small-scale rivers and a wetland in Korea. Twenty-eight congeners, ranging from tri- to hepta-CBs were detected. A gas chromatograph with a mass selective detector was used to quantify the individual PCB congeners. The objectives of this study were to investigate the levels of contamination of PCBs in freshwater fish and to observe the pattern of their distribution. The sampling locations were chosen among 31 sampling sites that are currently used as environmental residue checkpoints by the Korean Ministry of Environment. Concentrations of individual congeners ranged from not detectable (n.d.) to 0.75 ng g(-1) on a wet weight basis. The total concentrations of PCBs at each site ranged from n.d. to 5.41 ng g(-1) of wet weight. The most heavily contaminated site was the Nakdong estuary located near the Shinpyung-Janglim factory district. The PCB 153 and 138 were the principal congeners and penta- and hexa-chlorinated biphenyls comprised the main congener groups. 相似文献
792.
793.
Monitoring of iodinated X-ray contrast media in surface water 总被引:1,自引:0,他引:1
A monitoring programme was carried out in order to determine iodinated X-ray contrast media (ICM) in the River Danube and to investigate the raw water quality for drinking water production at Langenau waterworks. The study revealed that the maximum concentrations of ICM (over 500 ng l(-1) for diatrizoic acid and iopamidol) were found in 2h-composite samples taken from the downstream of the Ulm/Neu-Ulm metropolitan area. By means of a concentration profile over one month the highest ICM concentrations were observed on weekdays. The extended data evaluation with principal component analysis shows that the upstream and downstream samples had different pattern of variations in ICM concentration and also demonstrates a clear change in ICM composition by the discharge of municipal wastewater. In addition to load profiles of ICM, time-dependent plots of principal component 1 exhibited peaks, indicating a short-term discharge of ICM between the two sampling sites. In conclusion, a point source for ICM contamination between the sampling sites in Ulm upstream and Leipheim downstream seems to be the reasonable explanation for peak ICM concentrations. Due to the observed high variations of ICM concentrations in river, the evaluation of natural waters by means of a single analysis is not representative. 相似文献
794.
Georgiadis M Cai Y Solo-Gabriele HM 《Environmental pollution (Barking, Essex : 1987)》2006,141(1):22-29
The primary objective of this study was to develop a simple method that can be used to extract the more readily mobilizable and bioavailable arsenic species from soil and sediment while at the same time minimizing the transformation between (AsIII) and (AsV), the two most commonly found arsenic species in the environment. Several extraction strategies were evaluated using phosphate as extractant in combination with either ethylenediaminetetraacetic acid (EDTA), hydroxylamine hydrochloride (NH2OH.HCl), or sodium diethyldithiocarbamate trihydrate (NaDDC). The addition of EDTA in the phosphate solution did not prevent AsIII from oxidation. While promising results were shown when 1% NH2OH.HCl was added, conversion of AsIII began to occur with extended extraction time (> 12 h). Good results were achieved using 10 mM phosphate and 0.5% NaDDC where AsIII oxidation was clearly minimized. The combined phosphate and NaDDC solution was applied to several soil and sediment samples. AsIII spiked was quantitatively recovered in all soil types tested. 相似文献
795.
通过对不同混合比率的乙醇/氢气/空气燃烧特性进行数值模拟,研究氢气添加量对点火延迟时间、层流燃烧速度、火焰厚度、化学反应滞留时间及组分分布情况的影响。研究发现一定程度上氢气添加量的增加能够缩短混合气体的点火延迟时间,并且氢气对点火延迟时间的影响随着温度的升高而逐渐减小。随着混合比率的增大,层流燃烧速度增大,并且在混合比率大于0.4时显著增大。火焰厚度及化学反应滞留时间随氢气增加而逐渐减小。此外,进一步分析组分分布情况得知氢气添加使火焰中H*、O*、OH*自由基摩尔分数峰值增大,并且H+O+OH摩尔分数峰值与层流燃烧速度存在线性关系。 相似文献
796.
797.
798.
799.
800.