全文获取类型
收费全文 | 731篇 |
免费 | 55篇 |
国内免费 | 181篇 |
专业分类
安全科学 | 41篇 |
废物处理 | 61篇 |
环保管理 | 76篇 |
综合类 | 402篇 |
基础理论 | 98篇 |
污染及防治 | 200篇 |
评价与监测 | 34篇 |
社会与环境 | 24篇 |
灾害及防治 | 31篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 52篇 |
2021年 | 38篇 |
2020年 | 34篇 |
2019年 | 21篇 |
2018年 | 28篇 |
2017年 | 29篇 |
2016年 | 29篇 |
2015年 | 36篇 |
2014年 | 54篇 |
2013年 | 57篇 |
2012年 | 61篇 |
2011年 | 58篇 |
2010年 | 54篇 |
2009年 | 45篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 26篇 |
2005年 | 27篇 |
2004年 | 18篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 24篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 21篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有967条查询结果,搜索用时 390 毫秒
861.
862.
为深入研究菏泽市秋冬季PM2.5中水溶性离子污染特征,于2017年10月15日-2018年1月31日对菏泽市3个监测点同步进行PM2.5的采集和分析,分析探讨了不同污染程度下ρ(PM2.5)及水溶性离子化学特征.结果表明:①菏泽市秋冬季PM2.5呈区域污染特征.②整个观测期间,ρ(PM2.5)范围为26.72~284.10 μg/m3,平均值为103.27 μg/m3,其中水溶性离子对ρ(PM2.5)贡献率较大,为44.65%~49.87%;SNA(NO3-、NH4+、SO42-的统称)的占比较高,SNA占总水溶性离子质量浓度的86.88%,说明二次气溶胶为菏泽市大气PM2.5中的重要组成部分.③SNA三角图解和水溶性离子相关性结果表明,采样期间大气中NO3-、SO42-可能以NH4NO3、(NH4)2SO4形式存在;ρ(Cl-)与ρ(K+)相关性较高(清洁天和污染天的相关系数分别为0.79和0.81),由此推测Cl-与K+具有同源性,二者主要源于生物质燃烧.④重度及以上污染天的SOR(硫氧化率)和NOR(氮氧化率)分别为0.54和0.37,分别是清洁天的2.08和2.06倍;轻/中污染天的SOR和NOR分别为0.37和0.29,分别是清洁天的1.42和1.61倍.随着污染程度的加重,SO2和NO2向SO42-和NO3-的二次转化增强.重污染日SOR、NOR和相对湿度均大于清洁天和轻/中度污染天,而温度则未表现出相似的变化趋势,说明非均相反应是菏泽市秋冬季SO42-和NO3-形成的重要原因.研究显示,菏泽市污染呈区域性污染特征,二次气溶胶是菏泽市大气PM2.5的重要组成部分,污染天ρ(NO3-)、ρ(SO42-)、ρ(NH4+)均与相对湿度呈显著正相关(P < 0.05),均与温度呈负相关,表明在污染天高湿低温对SO2、NO2转化为SO42-、NO3-有推动作用. 相似文献
863.
本研究开展单组分和多组分DNAPL加热实验,旨在建立热处理过程中温度与DNAPL去除之间的联系.结果表明,单组分DNAPL实验中可以观察到明显的共沸温度平台,而多组分DNAPL实验则是一段温度逐渐上升的共沸区域,两组实验中共沸时间均与初始DNAPL饱和度呈正相关.仅根据局部温度数据判断热修复进程可能会导致错误的结论,当温度结果显示共沸结束后,体系内仍残留有饱和度0.94%~1.60%的DNAPL.温度数据会受到DNAPL组成和温度监测点位置影响,它通常仅能反映局部加热情况,修复时可结合气体和土壤样品中污染物组分变化情况辅助判断修复进程. 相似文献
864.
Wei Fang Xuedong Zhang Panyue Zhang Jijun Wan Hongxiao Guo Dara S.M. Ghasimi Xavier Carol Morer Tao Zhang 《环境科学学报(英文版)》2020,32(1):93-111
In recent years, volatile fatty acid (VFA) production through anaerobic fermentation of sewage sludge, instead of methane production, has been regarded as a high-value and promising roadmap for sludge stabilization and resource recovery. This review first presents the effects of some essential factors that influence VFA production and composition. In the second part, we present an extensive analysis of conventional pretreatment and co-fermentation strategies ultimately addressed to improving VFA production and composition. Also, the effectiveness of these approaches is summarized in terms of sludge degradation, hydrolysis rate, and VFA production and composition. According to published studies, it is concluded that some pretreatments such as alkaline and thermal pretreatment are the most effective ways to enhance VFA production from sewage sludge. The possible reasons for the improvement of VFA production by different methods are also discussed. Finally, this review also highlights several current technical challenges and opportunities in VFA production with spectrum control, and further related research is proposed. 相似文献
865.
Highland catchments in tropical regions are frequently subjected to soil erosion and the transport of chemicals downstream.
Any drastic changes in land use will increase the severity of these processes of land degradation. A simulation study using
GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) was conducted at a catchment presently under tea farming
in Cameron Highlands, Malaysia. Soil, water and nutrient transport associated with several alternative land uses was studied.
In addition, the effect of a disruptive form of land clearing on soil, water and nutrient losses was also investigated. Modelling
with GLEAMS required information from field measurements and observations, laboratory analyses, guide tables, industry records,
maps and reports published by soil survey and meteorological departments.
The most critical step in simulating soil and water movement using GLEAMS is the identification of a representative flow sequence.
In the catchment under study, the representative flow sequence was overland flow–channel 1–channel 2. Input data on soil erodibility,
porosity and surface roughness were manipulated to represent various degrees and forms of disturbance to the surface soil
layer. For all land uses studied, the highest soil loss was predicted for the overland flow area where slope gradient is high
and the soil friable. The variations in soil loss, runoff and nutrient loss between landscape elements and between land uses
were consistent with soil erosion features observed in the field. Soil and nutrient losses were substantial for crops such
as cabbage that required land shaping activities and frequent ploughing of the soil. Predicted data on enrichment ratio of
specific surface (ERSS) are consistent with nutrient enrichment processes in the field and could prove to be useful in studies
on chemical transport in highland catchments. 相似文献
866.
Gregory A. Graves Yongshan Wan Dana L. Fike 《Journal of the American Water Resources Association》2004,40(6):1405-1419
ABSTRACT: Starting in 1998, a study was conducted to characterize storm water quality from predominant land use types in a coastal watershed along the south central coast of Florida, namely citrus, pasture, urban, natural wetland, row crop, dairy, and golf courses. Sixty‐three sampling sites were located at strategic points on drainage conveyances for each of seven specific land use areas. Runoff samples were collected following storm events that met defined rainfall criteria for a period of 30 months. Nitrogen (N), phosphorus (P), heavy metals, pesticides, and other water quality parameters were determined, and the results were analyzed to compare and characterize land uses as relative sources for these constituents in runoff. Results showed that runoff from most land use types had low dissolved oxygen concentration and that sediment and nutrient concentrations were closely related to land use, particularly to the amount of fertilizer applied in each land use. Among the eight heavy metals tested, copper was the most frequently detected and was mostly associated with runoff from citrus and golf course land uses. High levels of arsenic were also detected in golf course runoff. The most frequently detected pesticide was simazine from citrus. The information and methodologies presented may facilitate pollution source characterization and ecological restoration efforts. 相似文献
867.
868.
目前 ,我国工伤保险加快了改革的步伐 ,工伤保险必将对安全生产起到很大的促进作用。讲座从工伤保险的意义与作用、现状与发展、基本原则和特点、工伤保险补偿待遇、工伤保险费率水平与调节作用及工伤保险基金管理等方面讲述了工伤保险及其相关知识 相似文献
869.
对于现代企业来说,如何激励经营者,充分发挥其潜能,为企业和股东创造出最大经济价值,成了债权人、股东、经营者等利益集团十分关心的问题。国家应建立和完善经营者的激励机制,企业应结合自身发展战略,重新设计经营者的薪酬计划,有效地推动经营者个人的行为表现,带领企业朝着整体战略目标迈进。 相似文献
870.