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   3878篇
  免费   228篇
  国内免费   1061篇
安全科学   265篇
废物处理   222篇
环保管理   296篇
综合类   1962篇
基础理论   656篇
环境理论   1篇
污染及防治   1175篇
评价与监测   213篇
社会与环境   179篇
灾害及防治   198篇
  2024年   8篇
  2023年   54篇
  2022年   177篇
  2021年   177篇
  2020年   135篇
  2019年   136篇
  2018年   142篇
  2017年   171篇
  2016年   196篇
  2015年   205篇
  2014年   317篇
  2013年   364篇
  2012年   359篇
  2011年   334篇
  2010年   292篇
  2009年   251篇
  2008年   257篇
  2007年   218篇
  2006年   222篇
  2005年   167篇
  2004年   118篇
  2003年   130篇
  2002年   117篇
  2001年   96篇
  2000年   86篇
  1999年   77篇
  1998年   64篇
  1997年   60篇
  1996年   40篇
  1995年   39篇
  1994年   31篇
  1993年   24篇
  1992年   26篇
  1991年   14篇
  1990年   21篇
  1989年   15篇
  1988年   7篇
  1987年   5篇
  1986年   3篇
  1985年   2篇
  1984年   1篇
  1982年   4篇
  1981年   3篇
  1958年   2篇
排序方式: 共有5167条查询结果,搜索用时 328 毫秒
821.
研究磷酸铵镁(MAP)沉淀法与超声波技术相联合处理高浓度畜禽废水的最佳反应条件.结果表明,MAP沉淀法在pH值9.5、n(Mg2+):n(NH+4)∶n(PO43-)=1.2∶1∶1、反应时间10 min时脱氮除磷效果最佳,氨氮去除率为95.10%,磷酸盐去除率为97.40%.MAP沉淀与超声波辐照联合处理最佳条件下,同时增加曝气(流量为200L·h-1),6h时氨氮去除率可提高到98%.  相似文献   
822.
论开展主要环境质量指标浓度考核   总被引:1,自引:1,他引:0  
针对现行环境质量考核体系中存在问题,选取主要的环境质量考核指标,提出逐步推行浓度值考核设想,并对比分析该考核办法与现行比例考核办法的优劣。  相似文献   
823.
This study aimed to assess exposure to sound and the risk of noise-induced hearing loss (NIHL) in orchestral musicians. Sound pressure level was measured in 1 opera and 3 symphony orchestras; questionnaires were filled in. On the basis of that data, the risk of NIHL was assessed according to Standard No. ISO 1999:1990. Classical orchestral musicians are usually exposed to sound at equivalent continuous A-weighted sound pressure levels of 81?90 dB (10th?90th percentiles), for 20?45 h (10th?90th percentiles) per week. Occupational exposure to such sound levels over 40 years of employment might cause hearing loss (expressed as a mean hearing threshold level at 2, 3, 4 kHz exceeding 35 dB) of up to 26%. Playing the horn, trumpet, tuba and percussion carries the highest risk (over 20%).  相似文献   
824.
Reports on the occurrence and intake assessment of mercury for Korean seafood are currently not available. This is the first report to estimate the intake of methyl (Me-Hg) and total mercury (T-Hg) from seafood consumption in Korea. The concentrations of Me-Hg and T-Hg in seafood ranged from 1.02 to 780 (mean: 55.6) ng g(-1) wet weight and 4.89 to 1008 (mean: 100) ng g(-1) wet weight, respectively. The residue levels of Me-Hg and T-Hg in Korean seafood were moderate compared with those found in other countries. The methylation ratios of fish, cephalopods and crustaceans were similar, but shellfish had lower values compared with other species. The intakes of Me-Hg and T-Hg from seafood consumption for the general population were estimated to be 38.8 and 73.8 ng kg(-1) body weight per day, respectively. Mackerel, tuna and squid made the highest contributions to the total intake of these contaminants. Among eight age groups, 30-49 year and 3-6 year age groups had the highest exposure to Me-Hg and T-Hg. The concentrations and intakes of Me-Hg and T-Hg from Korean seafood were less than the allowable residue levels and threshold intake levels suggested by Korean and international authorities. The present study may be useful for risk management of mercury in Korean seafood.  相似文献   
825.
Prometryne is a selective herbicide of the s-triazine chemical family. Due to its weak absorption onto soil, it readily leaches down through the soil and contaminates underground water. Application of organic manure to soil has become a widespread practice as a disposal strategy to improve soil properties. In this study, we demonstrated the effect of pig manure compost (PMC) and lake-bed sludge (SL) on the sorption/desorption, mobility and bioavailability of prometryne in soil using comprehensive analysis approaches. Downward movement of prometryne was monitored in the packed soil column. Addition of PMC or SL decreased considerably the mobility and total concentration of prometryne in the soil leachate. Bioavailability analyses with wheat plants revealed that addition of the organic matter reduced accumulation of prometryne in tissues and increased plant elongation and biomass. These results indicate that the organic amendments are effective in modifying adsorption and mobility of the pesticide in soil.  相似文献   
826.
水稻光合碳在植株-土壤系统中分配与稳定对施磷的响应   总被引:4,自引:1,他引:3  
为探究稻田土壤光合碳的输入及分配对施磷的响应特征,本研究选用籼性常规水稻品种(中早39),在两个施磷(0 mg·kg-1和80 mg·kg-1;分别记为P0和P80)条件下进行盆栽试验,同时采用13CO2连续标记技术量化光合碳在水稻-土壤系统中的分配.结果表明,施磷显著增加光合碳在水稻地上部的分配,降低其在根际土的分配(P<0.05);施磷使拔节期水稻的光合碳含量增加了70%,根系干重降低了31%.与不施磷相比,施磷显著提高了水稻地上部全碳含量0.31 g·pot-1P<0.05),显著降低了水稻根冠比;施磷使进入非根际土壤微生物量的光合碳(13C-MBC)显著增加了0.03 mg·kg-1,但降低其在根际土壤的分配;光合碳在非根际土壤颗粒态有机碳(POC)和矿物结合态有机碳(MOC)的分配对施磷的响应不显著,但在根际土壤施磷处理显著降低了其在POC中的含量.因此,施磷增加了光合碳在水稻-土壤系统的分配,但降低了光合碳在土壤中的积累.本研究探讨施磷对水稻光合碳在水稻-土壤系统的分配及其稳定的影响,为缺磷土壤的合理施用磷肥及其对土壤有机碳积累的影响提供理论基础和数据支撑;对理解稻田土壤光合碳的传输与分配特征及其固碳潜力具有重要意义.  相似文献   
827.
采用不同工艺制备V2O5-WO3-MoOx/TiO2堇青石整体式催化剂,以甲苯和NO为探针分子,考察了Mo的负载量、涂覆方法、粘结剂的种类等制备工艺对整体式催化剂性能的影响,用XRD、SEM-EDS、FT-IR、BET等技术对催化剂进行了表征分析.结果表明,采用涂敷法,以添加量为1%的甲基纤维素为粘结剂所制备的V1W6Mo3/TiO2堇青石蜂窝陶瓷整体式催化剂具有最优活性和稳定性(T90为307℃,负载率为28.26%,脱落率为6.81%),在燃煤烟气中具有优异的同步去除VOCs与NO性能,甲苯去除率可达99%,NO去除率为100%,N2选择性为99%.XRD、SEM-EDS表明V、W、Mo活性组分分布均匀且高度分散.FT-IR证明添加甲基纤维素的整体式催化剂具有优异的抗硫性能.  相似文献   
828.
针对石化企业用火作业背后隐藏的高风险,分析了目前石化企业用火管理方面存在的问题,提出了"两减一提"硬核管控用火,细化用火职责,建立过程管控责任清单,现场用火过程动态监督检查,多种方式提升安全技能等具体管控措施。  相似文献   
829.
针对低温干式接头密封失效造成甲烷泄漏的情况,采用CFD软件FLACS对LNG气化后的泄漏扩散过程进行数值模拟,对甲烷扩散过程的浓度分布及云团扩散速度进行研究,并分析了泄漏过程中可燃气体云团量的变化情况。结果表明:LNG泄漏后迅速气化扩散,40 s后各监测浓度维持稳定;最远扩散距离约40 m,气体扩散总范围最长直径约70 m,扩散最高处大约1.5 m; 120 s内LNG泄漏量为30 kg,气化后天然气体积为42.3 m~3,可燃气体云团量为140 m~3;LNG泄漏吸收空气中的热量,在地面形成流动层,贴近地面浓度高,远离地面浓度低,随着高度上升气体的可燃爆炸危险区域逐步缩小。  相似文献   
830.
Volatile organic compounds (VOCs) with high toxicity and carcinogenicity are emitted from kinds of industries, which endanger human health and the environment. Adsorption is a promising method for the treatment of VOCs due to its low cost and high efficiency. In recent years, activated carbons, zeolites, and mesoporous materials are widely used to remove VOCs because of their high specific surface area and abundant porosity. However, the hydrophilic nature and low desorption rate of those materials limit their commercial application. Furthermore, the adsorption capacities of VOCs still need to be improved. Porous organic polymers (POPs) with extremely high porosity, structural diversity, and hydrophobic have been considered as one of the most promising candidates for VOCs adsorption. This review generalized the superiority of POPs for VOCs adsorption compared to other porous materials and summarized the studies of VOCs adsorption on different types of POPs. Moreover, the mechanism of competitive adsorption between water and VOCs on the POPs was discussed. Finally, a concise outlook for utilizing POPs for VOCs adsorption was discussed, noting areas in which further work is needed to develop the next-generation POPs for practical applications.  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