收费全文 | 2908篇 |
免费 | 273篇 |
国内免费 | 994篇 |
安全科学 | 275篇 |
废物处理 | 147篇 |
环保管理 | 249篇 |
综合类 | 1754篇 |
基础理论 | 486篇 |
污染及防治 | 793篇 |
评价与监测 | 171篇 |
社会与环境 | 192篇 |
灾害及防治 | 108篇 |
2024年 | 16篇 |
2023年 | 61篇 |
2022年 | 180篇 |
2021年 | 173篇 |
2020年 | 155篇 |
2019年 | 103篇 |
2018年 | 113篇 |
2017年 | 146篇 |
2016年 | 154篇 |
2015年 | 158篇 |
2014年 | 207篇 |
2013年 | 266篇 |
2012年 | 246篇 |
2011年 | 238篇 |
2010年 | 227篇 |
2009年 | 226篇 |
2008年 | 204篇 |
2007年 | 217篇 |
2006年 | 193篇 |
2005年 | 129篇 |
2004年 | 101篇 |
2003年 | 114篇 |
2002年 | 91篇 |
2001年 | 94篇 |
2000年 | 59篇 |
1999年 | 47篇 |
1998年 | 42篇 |
1997年 | 48篇 |
1996年 | 37篇 |
1995年 | 39篇 |
1994年 | 16篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1977年 | 1篇 |
During the excavation of high gas mine, gas and dust often exist at the same time. In order to ensure that the gas concentration remains within a safe range and minimize the risk of workers’ pneumoconiosis, we simulated the interaction mechanism of airflow, gas, and dust, explored the pollution law of gas and dust, and obtained the optimal purification distance (Lp) by the CFD method. The reliability of the numerical simulation was verified by field measurements. Firstly, the properties of the gas and dust affected the structure of the airflow field. At the same time, the change in the airflow field affected the concentration distributions of the gas and dust. During the diffusion process, some high-risk regions in which the gas or dust concentrations exceeded 0.80% or 200 mg/m3, respectively, were discovered. Moreover, we have found that the airflow velocity in the top region of the tunnel and at the intersection corner between the cutting face and tunnel wall was the main factor affecting the purification effects. When Lp = 5–8 m, the gas concentration remained below 0.50%. When Lp = 6 m, the dust concentration reached a minimum of 287.5 mg/m3. Therefore, the optimal purification distance was determined to be 6 m; in which case, the gas and dust concentrations decreased by 32.84% and 47.02%, respectively.
相似文献Schemes to protect the geological environment and reclaim land are core requirements for an application for mining rights and complying with mining regulations. Mining enterprises must be supervised to ensure they fulfill their obligations. To guide oversight of such schemes and to provide references for their compilation and review, this study evaluates land reclamation schemes in mining areas using a multi-attribute group decision-making method. First, linguistic intuitionistic fuzzy numbers are used to describe the evaluation information. Considering the authority and preferences of experts, methods for determining expert weights in four cases are established. Max–min deviation then determines the attribute weights, and a method for linguistic intuitionistic fuzzy group decision-making is proposed. Finally, the practicability of this method is verified through a comparative analysis of land reclamation schemes for four mining areas in Sichuan Province, China. The results show the proposed method to give simple and effective evaluation, making it reasonably applicable to the compilation and review of land reclamation schemes.
相似文献The levels of metals in sediments of urban river ecosystems are crucial for aquatic environmental health and pollution assessment. Yet little is known about the interaction of nutrients with metals for environmental risks under contamination accumulation. Here, we combined hierarchical cluster, correlation, and principal component analysis with structural equation model (SEM) to investigate the pollution level, source, toxicity risk, and interaction associated with metals and nutrients in the sediments of a river network in a city area of East China. The results showed that the pollution associated with metals in sediments was rated as moderate degree of contamination load and medium-high toxicity risk in the middle and downstream of urban rivers based on contamination factor, pollution load index, and environmental toxicity quotient. The concentration of mercury (Hg) and zinc (Zn) showed a significant correlation with toxic risks, which had more contribution to toxicity than other metals in the study area. Organic nitrogen and organic pollution index showed heavily polluted sediments in south of the study area. Though correlation analysis indicated that nutrients and metals had different input zones from anthropogenic sources in the urban river network, SEM suggested that nutrient accumulation indirectly intensified toxicity risk of metals by 13.6% in sediments. Therefore, we suggested the combined consideration of metal toxicity risk with nutrient accumulation, which may provide a comprehensive understanding to identify sediment pollution.
相似文献