全文获取类型
收费全文 | 2272篇 |
免费 | 203篇 |
国内免费 | 751篇 |
专业分类
安全科学 | 226篇 |
废物处理 | 116篇 |
环保管理 | 204篇 |
综合类 | 1368篇 |
基础理论 | 367篇 |
污染及防治 | 598篇 |
评价与监测 | 131篇 |
社会与环境 | 135篇 |
灾害及防治 | 81篇 |
出版年
2024年 | 9篇 |
2023年 | 39篇 |
2022年 | 141篇 |
2021年 | 127篇 |
2020年 | 115篇 |
2019年 | 79篇 |
2018年 | 92篇 |
2017年 | 111篇 |
2016年 | 101篇 |
2015年 | 118篇 |
2014年 | 168篇 |
2013年 | 219篇 |
2012年 | 200篇 |
2011年 | 199篇 |
2010年 | 174篇 |
2009年 | 184篇 |
2008年 | 174篇 |
2007年 | 175篇 |
2006年 | 157篇 |
2005年 | 110篇 |
2004年 | 66篇 |
2003年 | 78篇 |
2002年 | 54篇 |
2001年 | 53篇 |
2000年 | 43篇 |
1999年 | 37篇 |
1998年 | 32篇 |
1997年 | 36篇 |
1996年 | 28篇 |
1995年 | 29篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有3226条查询结果,搜索用时 941 毫秒
731.
通过在杭州、衢州和温州三个城市开展PM2.5手工法和自动法比对试验,分析PM2.5手工法和自动法的比对差异及其与气象条件的影响关系,以期为PM2.5自动监测的现场手工比对工作积累一定的经验,确保PM2.5自动监测数据的准确性。 相似文献
732.
733.
Shortage in phosphorus (P) resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar (Ca-Mg/biochar) application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360 min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63 mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600 > Ca-Mg/B450 > Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment. 相似文献
734.
735.
NOx emissions from biogenic sources in soils play a significant role in the gaseous loss of soil nitrogen and consequent changes in tropospheric chemistry. In order to investigate the characteristics of NOx fluxes and factors influencing these fluxes in degraded sandy grasslands in northern China, diurnal and spatial variations of NOx fluxes were measured in situ. A dynamic flux chamber method was used at eight sites with various vegetation coverages and soil types in the northern steppe of China in the summer season of 2010. Fluxes of NOx from soils with plant covers were generally higher than those in the corresponding bare vegetation-free soils, indicating that the canopy plays an important role in the exchange of NOx between soil and air. The fluxes of NOx increased in the daytime, and decreased during the nighttime, with peak emissions occurring between 12:00 and 14:00. The results of multiple linear regression analysis indicated that the diurnal variation of NOx fluxes was positively correlated with soil temperature (P < 0.05) and negatively with soil moisture content (P < 0.05). Based on measurement over a season, the overall variation in NOx flux was lower than that of soil nitrogen contents, suggesting that the gaseous loss of N from the grasslands of northern China was not a significant contributor to the high C/N in the northern steppe of China. The concentration of NOx emitted from soils in the region did not exceed the 1-hr National Ambient Air Quality Standard (0.25 mg/m3). 相似文献
736.
Qian Zhao Hongjun Han Baolin Hou Haifeng Zhuang Shengyong Ji Fang Fang 《环境科学学报(英文版)》2014,26(11):2231-2239
A system combining granular activated carbon and powdered activated carbon technologies along with shortcut biological nitrogen removal (GAC-PACT-SBNR) was developed to enhance total nitrogen (TN) removal for anaerobically treated coal gasification wastewater with less need for external carbon resources. The TN removal efficiency in SBNR was significantly improved by introducing the effluent from the GAC process into SBNR during the anoxic stage, with removal percentage increasing from 43.8%49.6% to 68.8%-75.8%. However, the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge to the GAG compartment, the granular carbon had a longer service-life and the demand for external carbon resources became lower. Eventually, the TN removal rate in SBNR was almost constant at approx. 43.3%, as compared to approx. 20.0% before seeding with sludge. In addition, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory chemical oxygen demand (COD) degradation by autotrophic bacteria in SBNR under oxic conditions. PACT showed excellent resilience to increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with the three compartments were in good agreement with the removal of typical pollutants. The study demonstrated that pre-adsorption by the GAC-sludge process could be a technically and economically feasible method to enhance TN removal in coal gasification wastewater (CGW). 相似文献
737.
738.
采用职业卫生调查、职业卫生检测、检查表分析法等方法对某铝厂熔铸项目存在的职业病危害进行了识别、分析,提出了职业病危害防护措施方面的建议。 相似文献
739.
通过对机械制造业中某一电镀企业重金属离子铬的产排污情况分析,评价了该企业的清洁生产水平,制定了清洁生产的中高费方案,即将镀铬工序产生的含铬废水蒸发浓缩后,浓缩液进入镀铬槽内进行回用,蒸馏水则回用于水洗槽用作清洗用水。并从技术、环境和经济3个方面进行了评估,环境评估从7个方面进行,如资源与能源、废弃物排放量变化、回收利用情况等,证明该方案实施是可行的,为我国机械制造业中镀铬工序的清洁生产提供了参考依据。 相似文献
740.
从新疆煤炭产业布局看我国主体功能区规划实施 总被引:1,自引:0,他引:1
新疆经济发展对煤炭资源依赖程度愈发强烈,在限制开发区大力发展煤炭矿区及煤电化,不可避免地使资源环境承载压力加剧,使主体功能区规划实施效果大打折扣。在这一背景下,为了促进主体功能区规划在我国经济发展中发挥更有效的作用,本文从新疆煤炭产业布局入手,分析主体功能区规划实施中的问题,并提出改进建议。 相似文献