首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   264篇
  免费   28篇
  国内免费   97篇
安全科学   18篇
废物处理   20篇
环保管理   24篇
综合类   155篇
基础理论   71篇
污染及防治   68篇
评价与监测   12篇
社会与环境   11篇
灾害及防治   10篇
  2024年   1篇
  2023年   6篇
  2022年   17篇
  2021年   13篇
  2020年   10篇
  2019年   11篇
  2018年   14篇
  2017年   11篇
  2016年   23篇
  2015年   25篇
  2014年   19篇
  2013年   25篇
  2012年   24篇
  2011年   21篇
  2010年   11篇
  2009年   11篇
  2008年   18篇
  2007年   7篇
  2006年   17篇
  2005年   20篇
  2004年   5篇
  2003年   6篇
  2002年   10篇
  2001年   8篇
  2000年   6篇
  1999年   5篇
  1998年   5篇
  1997年   7篇
  1996年   6篇
  1995年   7篇
  1994年   6篇
  1993年   5篇
  1992年   1篇
  1991年   1篇
  1990年   3篇
  1988年   4篇
排序方式: 共有389条查询结果,搜索用时 311 毫秒
121.
The investigation of the photocatalytic oxidation (PCO) of multicomponent volatile organic compounds (VOCs) is very important to the application of PCO technology, because there is seldom a single VOC component in indoor air. In this paper, the characteristics of binary indoor VOCs, toluene and benzene, were experimentally studied using a mass transfer based method that we developed. The concentration ranges for toluene and benzene were 4.48-27.4 mg/m3 and 1.82-4.08 mg/m3, respectively. We found the following: (1) the PCO of each individual contaminant studied obeys the unimolecular form of the Langmuir-Hinshelwood (L-H) rate form; (2) the PCO of the binary contaminants follow the competitive adsorption L-H rate form; (3) the reaction-coefficient for PCO of individual contaminants differs from that in the competitive adsorption L-H rate form; and (4) the component impact factor of A to B, put forward in this paper, is a useful parameter describing the influence of A on the reaction coefficient of B, and it was found that the impact factor of toluene (a chemically active component) on benzene (a chemically stable component) is high, and the impact factor of benzene on toluene is low.  相似文献   
122.
倒置A2/O工艺氮平衡与脱氮效率的分析   总被引:5,自引:0,他引:5  
研究了倒置A^2/O工艺中的氮平衡和脱氮效率,并对影响脱氮效率的回流比和碳氮质量比进行分析。根据广州某城市污水处理厂水质特点,设计总回流比为3.0,其中污泥回流比为1.0,混合液回流比为2.0,理论总氮去除率为78.75%,实际运行总氮去除率达64.42%。  相似文献   
123.
2005年就业市场的运行特点 2005年三季度完成全年就业和再就业工作目标任务的90%和78% 2005年1月至9月,全国实现新增城镇就业人员810万人,达到全年目标任务(900万)的90%,下岗失业人员再就业390万人,达到全年目标任务(500万人)的78%(数据来源于劳动保障部2005年三季度新闻发布材料).其中,帮助“4050”人员再就业88万人,达到全年目标任务(100万人)的88%.三季度末,全国共有城镇登记失业人员835万人,城镇登记失业率4.2%,与上年底持平.  相似文献   
124.
环境模型方法是化学品风险评估中经常使用的方法。环境模型可提供化学品的浓度、归趋和主要迁移转化途径等信息,目前已被广泛应用于各类环境系统中。本文对该方法使用的一般步骤进行介绍,并对我国的环境模型工作提出了几点建议。  相似文献   
125.
李墨  孙瑞锋 《装备环境工程》2021,18(10):123-131
目的 研究通过加速试验在较短时间内对高可靠性、小子样电子产品的可靠性进行评估的方法.方法 分析可靠性加速试验方案的特点,梳理可靠性加速试验方案制定的基本流程,通过结合数理统计和故障物理技术,研究加速应力的确定方法和加速因子的计算模型,给出加速试验条件及试验时间的确定流程以及相应的试验结果评估方法,并进行案例应用.结果 该方法克服了常规可靠性加速试验方案设计中仅依靠经验并需要大样本量的缺点,科学有效地解决了高可靠性、小样本产品的可靠性加速试验方案设计问题,形成了电子设备基于故障物理和数理统计相结合的可靠性加速试验方案设计方法,经验证合理可行.结论 该试验方法能够满足当前可靠性要求高、进度紧、受试样品有限的武器装备研制的需求.  相似文献   
126.
Time-resolved single-particle measurements were conducted during Chinese New Year in Nanning, China. Firework displays resulted in a burst of SO_2, coarse mode, and accumulation mode(100–500 nm) particles. Through single particle mass spectrometry analysis, five different types of particles(fireworks-metal, ash, dust, organic carbon-sulfate(OC-sulfate), biomass burning) with different size distributions were identified as primary emissions from firework displays. The fireworks-related particles accounted for more than70% of the total analyzed particles during severe firework detonations. The formation of secondary particulate sulfate and nitrate during firework events was investigated on single particle level. An increase of sulfite peak(80SO_3~-) followed by an increase of sulfate peaks(97HSO_4~-+ 96SO_4~-) in the mass spectra during firework displays indicated the aqueous uptake and oxidation of SO_2 on particles. High concentration of gaseous SO_2, high relative humidity and high particle loading likely promoted SO_2 oxidation. Secondary nitrate formed through gas-phase oxidation of NO_2 to nitric acid, followed by the condensation into particles as ammonium nitrate. This study shows that under worm, humid conditions, both primary and secondary aerosols contribute to the particulate air pollution during firework displays.  相似文献   
127.
Methane/coal dust/air explosions under strong ignition conditions have been studied in a 199 mm inner diameter and 30.8 m long horizontal tube. A fuel gas/air manifold assembly was used to introduce methane and air into the experimental tube, and an array of 44 equally spaced dust dispersion units was used to disperse coal dust particles into the tube. The methane/coal dust/air mixture was ignited by a 7 m long epoxypropane mist cloud explosion. A deflagration-to-detonation transition (DDT) was observed, and a self-sustained detonation wave characterized by the existence of a transverse wave was propagated in the methane/coal dust/air mixtures.The suppressing effects on methane/coal dust/air mixture explosions of three solid particle suppressing agents have been studied. Coal dust and the suppressing agent were injected into the experimental tube by the dust dispersion units. The length of the suppression was 14 m. The suppression agents examined in this study comprised ABC powder, SiO2 powder, and rock dust powder (CaCO3). Methane/coal dust/air explosions can be efficiently suppressed by the suppression agents characterized by the rapid decrease in overpressure and propagating velocity of the explosion waves.  相似文献   
128.
The Chinese government initiated a massive conservation program called “Grain-for-Green” in 1999 to reduce soil erosion and improve ecosystem function. Implementing practical sustainable development in the loess plateau still remains problematic, particularly in its eco-fragile areas. Here we discussed an approach for sustainable development at the watershed scale by integrating land use suitability, ecosystem services and public participation in the loess hilly area. We linked land use scenario analysis and economic modeling to compare the outcomes of three scenarios, CLU (Current Land Use), GOLU (Grain-production Oriented Land Use) and PSLU (Potential Sustainable Land Use). The results indicated that compared to PSLU, GOLU may provide a higher economic productivity in the short-term, but not in the long-term. CLU ranked lowest in terms of economic benefits and did not meet the daily needs of the local farmers. To reconcile the land use adjustments with farmers’ basic needs, a labor-saving land use strategy is necessary. Since the PSLU scenario assumes that slope cropland should be converted to pastures or orchards, more time may be available for off-farm work and for more public participation in integrated ecosystem management. Financial support to the local farmers for environmental conservation should be modulated in function of their positive contribution to ecosystem management.  相似文献   
129.
南通龙王桥河沉积物中酸挥发性硫化物的研究   总被引:1,自引:0,他引:1  
本研究对南通通甲河支流龙王桥河的表层沉积物中酸挥发性硫化物(AVS)随时间的变化情况,AVS与同步浸提重金属(SEM)的关系,以及AVS与有机质(OM)的关系进行了一个月的监测。结果表明:①龙王桥河表层沉积物中AVS的平均含量为1700mg/kg,远高于其他河段,上覆水中AVS的含量达到1.0mg/L,污染严重;②归一法算得SEM/AVS1,沉积物中重金属主要以硫化物形式存在;③沉积物中OM含量与AVS有相关性,OM较高时AVS的含量也较高。  相似文献   
130.
摘要:根据生命周期评价,对燃料乙醇的节能和减排效果进行分析,依据发展规划,得出广西南宁发展燃料乙醇对节能减排的影响。结果表明,发展燃料乙醇将在节能和减排方面均产生积极作用,应加大在南宁乃至广西发展非粮燃料乙醇产业的力度。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号