收费全文 | 4142篇 |
免费 | 48篇 |
国内免费 | 26篇 |
安全科学 | 76篇 |
废物处理 | 284篇 |
环保管理 | 331篇 |
综合类 | 449篇 |
基础理论 | 846篇 |
环境理论 | 6篇 |
污染及防治 | 1563篇 |
评价与监测 | 383篇 |
社会与环境 | 264篇 |
灾害及防治 | 14篇 |
2023年 | 49篇 |
2022年 | 131篇 |
2021年 | 170篇 |
2020年 | 68篇 |
2019年 | 71篇 |
2018年 | 157篇 |
2017年 | 163篇 |
2016年 | 237篇 |
2015年 | 129篇 |
2014年 | 253篇 |
2013年 | 384篇 |
2012年 | 291篇 |
2011年 | 308篇 |
2010年 | 224篇 |
2009年 | 163篇 |
2008年 | 241篇 |
2007年 | 251篇 |
2006年 | 194篇 |
2005年 | 152篇 |
2004年 | 113篇 |
2003年 | 95篇 |
2002年 | 93篇 |
2001年 | 52篇 |
2000年 | 38篇 |
1999年 | 28篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1988年 | 2篇 |
1985年 | 4篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1970年 | 2篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1964年 | 5篇 |
1962年 | 3篇 |
1959年 | 4篇 |
1958年 | 15篇 |
1957年 | 6篇 |
1956年 | 2篇 |
1955年 | 2篇 |
The presence of potentially hazardous elements (PHEs) in playground soils is generally associated with anthropogenic sources such as vehicle traffic, industries, construction sites, and biomass burning. Studies indicate that PHEs are harmful to human health and may even be carcinogenic. Therefore, the aim of this study was to evaluate the physicochemical, morphological, and mineralogical properties of soil samples from three public playgrounds located in the cities of Bogota, Medellin, and Barranquilla. Besides, the possible impacts caused by the aerodynamics of particles in Colombian cities were verified. The morphology, composition, and structure of the nanoparticles (NPs) (< 100 nm) present in these soils were evaluated by field emission scanning electron microscopy (FE-SEM) equipped with high-precision field emission (FE) and high-resolution transmission electron microscopy (HR-TEM). Soil samples were predominantly feldspar, quartz, and, to a lesser extent, clay minerals, carbonates, and hematites. The average content of PHEs was anthropogenically enriched in relation to the upper continental crust. As and Sn showed a large spatial variation, indicating the influence of local sources, such as vehicle traffic and industries. There is an inverse relationship between the total concentrations of some elements and their leachable fractions. The accumulation of traffic-derived PHEs has a negative impact on human health and the environment, which is alarming, especially for elements such as Pb, Sb, or As. Therefore, the presence of PHEs should receive greater attention from public health professionals, and limits should be set and exposures controlled. This study includes the construction of a baseline that provides basic information on pollution, its sources, and exposure routes for humans in the vicinity of Colombia’s major cities, characterized by their increasing urbanization and industrialization.
相似文献Natural products may be applied in a wide range of domains, from agriculture to food and pharmaceutical industries. In this study, the antioxidant properties and the capacity to inhibit some enzymatic activities of Euphorbia resinifera and Euphorbia officinarum aqueous extracts and honeys were assessed. The physicochemical characteristics were also evaluated. Higher amounts of iron, copper and aluminium were detected in E. officinarum honey, which may indicate environmental pollution around the beehives or inadequate storage of honey samples. This honey sample showed higher amounts of total phenols and better capacity for scavenging superoxide anion free radicals and DPPH free radicals as compared with E. resinifera honey, but poorer capacity for inhibiting lipoxygenase, acetylcholinesterase, tyrosinase and xanthine oxidase. The ratio plant mass:solvent volume (1:100) and extraction time (1 - 2 h) were associated with higher total phenols and better antioxidant activities and lipoxygenase, acetylcholinesterase and tyrosinase inhibitory activities, regardless of the plant species. The aqueous extracts had systematically higher in vitro activities than the respective honey samples.
相似文献Among the most frequent targets for toxic effects of modern pesticides, namely organophosphates and carbamates, one may find cholinesterases (ChEs). ChEs exist in a wide variety of animals and have been used actively to discriminate among the environmental effects of different pollutant groups, including the aforementioned pesticides. This study had three purposes, namely (i) identifying the ChE forms present in tissues (eyes and walking legs muscle) of two crab species, Carcinus maenas and Pachygrapsus marmoratus; to (ii) determine the in vitro toxicological effects, and (iii) compare the sensitivity of such enzymatic forms towards commonly used anti-ChE pesticides, namely the organophosphate chlorpyrifos and the carbamate carbofuran. Our results showed that there was not a clear preference for any of the tested substrates in any of the tissues from both species. Furthermore, the ChE activity was almost completely suppressed following incubation with eserine and with the specific inhibitor BW284C51 in all tissues from both species. In vitro exposure to chlorpyrifos promoted a significant decrease in ChE activity in both species. Furthermore, the ChE activity was completely suppressed following incubation with carbofuran and chlorpyrifos. These results suggest that the major ChE forms present in tissues of both crab species show intermediate structural properties and activity patterns, halfway between classic acetylcholinesterase and pseudocholinesterases. However, the sensitivity of the found forms towards ChE inhibitors was established, and the responsiveness of such forms towards common anti-ChE chemicals was established. Both tested species seem to be promising test organisms to be used in marine and coastal scenarios of putative contaminations by anti-ChE chemicals, considering the here reported patterns of response.
相似文献