全文获取类型
收费全文 | 147篇 |
免费 | 15篇 |
国内免费 | 48篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 5篇 |
环保管理 | 24篇 |
综合类 | 104篇 |
基础理论 | 27篇 |
污染及防治 | 21篇 |
评价与监测 | 1篇 |
社会与环境 | 4篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 23篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 19篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1980年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有210条查询结果,搜索用时 62 毫秒
61.
62.
摘要本文采用逐步回归等方法处理了山东相公庄水准 EW、SN 向1989年1月1日至1990年9月30日的五日均值观测资料。回归分析结果表明:苍山4.4(M_L)级地震前相公庄水准 EW、SN 向均有10天左右的短临前兆异常,异常最大幅值分别为0.84mm和0.42mm,地震发生在异常达最大值的前一天,回归剩余标准差分别为±0.17mm和±0.12mm。据动态灰箱法处理的结果说明:短临异常在月均值上也有一定显示,只是幅度小些。作者认为:距震中50km左右的定点形变台,在一定条件下有可能监测到4级以上地震的短临前兆异常。 相似文献
63.
李仙江流域梯级电站开发建设即有单个电站对生态环境的影响特征,又有影响的累积性、群体性、系统性、波及性和潜在性。分析了流域梯级电站开发建设对植被、生物多样性、鱼类、水文、水质等产生的影响,提出了相应的防治措施。 相似文献
64.
Six ponds of age 3 were selected 45 km north from Suzhou in the Tailake region, and research conducted on nitrogen and phosphorus cycling in P. vannanmei(Penaeus vannanme) ponds and M. nipponense(Macrobrachium nipponense) hatchery ponds under normal management. Two treatments each had three replications. The results confirmed that feed was the major path of nitrogen and phosphorus input, each accounted for 61.24%(193.81 kg ha–1) and 81.08%(45.20 kg ha–1) of the total nitrogen and phosphorus input for P. vannanme ponds; the values for M. nipponense ponds were 43.93%(86.31 kg ha–1) and 57.67%(14.61 kg ha–1), respectively. Water pumped into ponds contributed on average 83.57 kg ha–1 nitrogen and 8.48 kg ha–1 phosphorus for P. vannanmei ponds, and 87.48 kg ha–1 nitrogen and 7.00 kg ha–1 phosphorus for M. nipponense hatchery ponds. Shrimp harvest recovered 102.81 kg ha–1 nitrogen (32.94% of the total nitrogen input) and 7.94 kg ha–1phosphorus (14.23% of the total phosphorus input) for P. vannanme ponds; and 43.94 kg ha–1 nitrogen and 4.46 kg ha–1phosphorus for M. nipponense hatchery ponds. The sum of nitrogen losses through volatilization, denitrification and sedimentation was 173.62 and 122.39 kg ha–1, 54.86% and 62.29% of the total nitrogen input for P. vannanme ponds and M. nipponense hatchery ponds, respectively. Sediment accumulated 41.46 and 14.63 kg ha–1 phosphorus, 74.37% and 64.85% of the total phosphorus input for P. vannanm ponds and M. nipponense hatchery ponds. Draining and seeping caused 40.06 kg ha–1 nitrogen (12.66% of total nitrogen input) and 6.36 kg ha–1 phosphorus (11.40% of total phosphorus input) loss to the surrounding water from P. vannanme ponds in 114 days; 30.14 kg ha–1nitrogen (15.34% of the total input) and 4.45 kg ha–1 phosphorus (17.57% of the total input) to channel water from M. nipponense hatchery ponds in 87 days, respectively. Countermeasures for sustainable pond management include improving feeds and feeding, sediment treatments, machine aerating, chemicals with no pollution, and integrated fish-shrimp cultivation. Management of water resources for pond and methods to reduce nitrogen and phosphorus loading into surrounding water from drainage are elucidated. 相似文献
65.
66.
67.
阿司匹林生产过程中会产生大量的粉末状废弃活性炭,对环境造成了较大的影响。提出了不外加活化气体的微波加热一步再生法再生废弃活性炭,使之循环利用。通过试验考察了再生温度、再生时间和物料厚度等因素对再生活性炭吸附性能和得率的影响。在再生温度700℃、再生时间10 min和物料厚度20 mm的优化条件下,亚甲基蓝吸附量为180 mg/g,再生活性炭的得率为40.875%,与常规方法再生药用活性炭相比,降低了再生温度,再生时间缩短了50%左右。此时再生活性炭的比表面积为1 296 m~2/g,平均孔径为3.016nm,适合于吸附亚甲基蓝,总孔体积为0.977 4 m L/g,其中微孔占47.81%,表明微孔和中孔都较为发达。扫描电镜和傅里叶变换红外光谱图分析表明,活性炭孔隙和表面性质得到了有效的再生恢复。微波一步再生法避免了通入活化气体而导致大量粉末活性炭被带走的问题,并且该方法具有速度快、效率高等优势。 相似文献
68.
The size and complexity of industrial plants, along with the characteristics of the products used, require a study, analysis and control of the existing risks in every industrial process.In this paper, a methodology for risk assessment in industrial plants, based on the combination of risks identification through the Hazard and Operability (HAZOP) analysis and the risks evaluation through linguistic variables and fuzzy numbers is applied to a case study consisting on a compound feed plant located in the town of Silla (Valencia, Spain).The results from this study show that the main risk in the compound feed production process is the formation of explosive atmospheres (ATEX). Therefore, the corrective measures will focus on reducing the concentration of dust in the atmosphere and eliminating the possible sources of ignition, such as electrostatic discharges or sparks during the different phases of the process (the grinding, the transport of the raw materials, etc.) 相似文献
69.
荣誉 《中国环境管理干部学院学报》2000,(2)
针对以往空气环境质量的模糊综合评价方法存在的不足提出了采用综合指数和模糊综合评价方法相结合的方法评价空气环境质量的新方法。 相似文献
70.
Burchard H. Heede 《Journal of the American Water Resources Association》1972,8(3):523-530
ABSTRACT The influence of a forest on the formation of steps in two small streams of the Colorado Rocky Mountains was studied. Steps provided by logs fallen across the channel added to flow energy reduction. The streams required additional gravel bars to adjust to slope. Average step length between logs and gravel bars was strongly related to channel gradient and median bed material size. Based on the average number of log steps per 50 feet of channel, an average of 116 percent of gravel bars were added at Fool Creek and 60 percent at Deadhorse Creek. The latter had 52 percent more logs in the channel and therefore required less bed material movement than the former. Although these are “rushing mountain streams,” most flow velocities ranged between 0.5 and 2.5 f.p.s. Exponents of a function relating rate of change of depth or velocity to discharge indicated that dynamic stream equilibrium was attained. Implications for forest management are that sanitation cuts (removal of dead and dying trees) would not be permissible where a stream is in dynamic equilibrium and bed material movement should be minimized. 相似文献