收费全文 | 2608篇 |
免费 | 231篇 |
国内免费 | 935篇 |
安全科学 | 308篇 |
废物处理 | 117篇 |
环保管理 | 187篇 |
综合类 | 1657篇 |
基础理论 | 424篇 |
环境理论 | 1篇 |
污染及防治 | 694篇 |
评价与监测 | 134篇 |
社会与环境 | 139篇 |
灾害及防治 | 113篇 |
2024年 | 16篇 |
2023年 | 62篇 |
2022年 | 151篇 |
2021年 | 148篇 |
2020年 | 150篇 |
2019年 | 128篇 |
2018年 | 127篇 |
2017年 | 122篇 |
2016年 | 135篇 |
2015年 | 184篇 |
2014年 | 215篇 |
2013年 | 286篇 |
2012年 | 259篇 |
2011年 | 234篇 |
2010年 | 206篇 |
2009年 | 188篇 |
2008年 | 161篇 |
2007年 | 159篇 |
2006年 | 129篇 |
2005年 | 91篇 |
2004年 | 64篇 |
2003年 | 71篇 |
2002年 | 65篇 |
2001年 | 64篇 |
2000年 | 67篇 |
1999年 | 50篇 |
1998年 | 57篇 |
1997年 | 41篇 |
1996年 | 29篇 |
1995年 | 35篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
The present study aimed to improve the performance of microbial fuel cells (MFCs) by using an intermittent connection period without power output. Connecting two MFCs in parallel improved the voltage output of both MFCs until the voltage stabilized. Electric energy was accumulated in two MFCs containing heavy metal ions copper, zinc, and cadmium as electron acceptors by connection in parallel for several hours. The system was then switched to discharge mode with single MFCs with a 1000-Ω resistor connected between anode and cathode. This method successfully achieved highly efficient removal of heavy metal ions. Even when the anolyte was run in sequencing batch mode, the insufficient voltage and power needed to recover heavy metals from the cathode of MFCs can be complemented by the developed method. The average removal ratio of heavy metal ions in sequencing batch mode was 67 % after 10 h. When the discharge time was 20 h, the removal ratios of zinc, copper, and cadmium were 91.5, 86.7, and 83.57 %, respectively; the average removal ratio of these ions after 20 h was only 52.1 % for the control group. Therefore, the average removal efficiency of heavy metal ions increased by 1.75 times using the electrons stored from the bacteria under the open-circuit conditions in parallel mode. Electrochemical impedance data showed that the anode had lower solution resistance and polarization resistance in the parallel stage than as a single MFC, and capacitance increased with the length of time in parallel.
相似文献Wastewater treatment plants (WWTPs) have been recognized as important sources for anthropogenic greenhouse gas (GHG) emission. The objective of the study was to thoroughly investigate a typical industrial WWTP in southern Taiwan in winter and summer which possesses the emission factors close to those reported values, with the analyses of emission factors, mass fluxes, fugacity, lab-scale in situ experiments, and impact assessment. The activated sludge was the important source in winter and summer, and nitrous oxide (N2O) was the main contributor (e.g., 57 to 91 % of total GHG emission in a unit of kg carbon dioxide-equivalent/kg chemical oxygen demand). Albeit important for the GHGs in the atmosphere, the fractional contribution of the GHG emission to the carbon or nitrogen removal in wastewater treatment was negligible (e.g., less than 1.5 %). In comparison with the sludge concentration or retention time, adjusting the aeration rate was more effective to diminish the GHG emission in the activated sludge without significantly affecting the treated water quality. When the aeration rate in the activated sludge simulation was reduced by 75 %, the mass flux of N2O could be diminished by up to 53 % (from 9.6 to 4.5 mg/m2-day). The total emission in the WWTP (including carbon dioxide, methane, and N2O) would decrease by 46 % (from 0.67 to 0.36 kg CO2-equiv/kg COD). However, the more important benefit of changing the aeration rate was lowering the energy consumption in operation of the WWTP, as the fractional contribution of pumping to the total emission from the WWTP ranged from 46 to 93 % within the range of the aeration rate tested. Under the circumstance in which reducing the burden of climate change is a global campaign, the findings provide insight regarding the GHG emission from treatment of industrial wastewater and the associated impact on the treatment performance and possible mitigation strategies by operational modifications.
相似文献Implications: In China, one of the major environmental problems caused by confined feeding is odor pollution, which brings a major threat to the sustainability, profitability, and growth of the livestock industry. To couple the LiP with the electron acceptors, a low–cost, simple, and feasible method for odor removal was established in this study. Based on the study results, a practical treatment method was provided for odor pollution and supply the farm operators a more flexible time to dispose treated manure. 相似文献