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   435篇
  免费   37篇
  国内免费   299篇
安全科学   10篇
废物处理   23篇
环保管理   17篇
综合类   411篇
基础理论   141篇
污染及防治   146篇
评价与监测   15篇
社会与环境   8篇
  2024年   1篇
  2023年   7篇
  2022年   25篇
  2021年   20篇
  2020年   25篇
  2019年   24篇
  2018年   19篇
  2017年   28篇
  2016年   39篇
  2015年   33篇
  2014年   46篇
  2013年   86篇
  2012年   40篇
  2011年   55篇
  2010年   39篇
  2009年   40篇
  2008年   34篇
  2007年   38篇
  2006年   33篇
  2005年   28篇
  2004年   9篇
  2003年   16篇
  2002年   13篇
  2001年   6篇
  2000年   11篇
  1999年   10篇
  1998年   4篇
  1997年   1篇
  1996年   5篇
  1995年   8篇
  1994年   9篇
  1993年   4篇
  1992年   7篇
  1991年   2篇
  1990年   4篇
  1987年   1篇
  1986年   1篇
排序方式: 共有771条查询结果,搜索用时 31 毫秒
681.
Gocza?kowice Reservoir is the biggest water reservoir in the south of Poland. For our studies bottom sediments were collected from eight different places of the reservoir at various seasons of the year.EPR spectroscopy was applied to analyse both quantitatively and qualitatively the humic acids (HA) present in the samples. EPR spectra of the extracted HA exhibited broad lines from the paramagnetic metal ions and narrow lines from free radicals. The values of the free radical concentration obtained for HA amounted to 1.14-13.6 × 1016 spin g−1 depending on the season and the place of sample collection. The values of the g factor obtained for HA were of the range 2.0027-2.0035.The EPR studies show that HA extracted from bottom sediment collected at various points of the Gocza?kowice Reservoir exhibit similar physical-chemical properties. It was also observed that the depth of the reservoir affects the content of the oxygen functional groups as well as the free radical concentration in HA.The identification of the functional groups was done by means of IR. UV/VIS spectroscopy was used to estimate the maturity of the HA.  相似文献   
682.
研究土壤、腐殖酸、粘土矿对绿草定的吸附及溶液中的光降解的结果表明:吸附强弱与土壤理化特性密切相关,Freundlich常数Kf与(3·OM%+Clay%)pH3有较好的相关性(r=0.997);腐殖酸较粘土矿的吸附容量大;绿草定在土壤中的吸附可能有离子键、氢键、配位键及偶极-偶极作用等。太阳光中小于330nm波长的光对降解有效,波长254nm的光对绿草定的降解作用是波长300nm光的3.5倍。  相似文献   
683.
对上海市老港填埋场封场6-10年矿化垃圾中的胡敏酸(HA)进行荧光光谱分析,结果表明,不同封场时间的矿化垃圾中HA的荧光光谱均为宽带峰型,pH值对HA荧光光谱的影响较小.而且随着矿化垃圾封场时间的加长,荧光特征峰波长缓慢增加.  相似文献   
684.
广州市大气气溶胶中水溶性有机物的季节变化   总被引:3,自引:0,他引:3  
采用BSTFA 衍生化预处理和GC/MS 分析技术, 于2002─2003年对广州市荔湾区大气气溶胶中的水溶性化合物进行了定量检测.结果表明,水溶性化合物呈现一定的季节变化趋势.脱水糖类在春、夏、秋、冬的质量浓度分别为132.06,160.58,301.70和244.90 ng/m3,左旋葡聚糖的秋季质量浓度达到234.9 ng/m3,表明存在大量的生物质燃烧;以葡萄糖、蔗糖为代表的糖类化合物主要来源于生长在土壤中的植物,其进入气溶胶中的主要途径是农作物的耕作和收割、风的侵蚀以及交通等,秋季质量浓度较高可能与植物落叶和秸秆燃烧有关;二酸的质量浓度在冬季达到最大值,可能与广州的气象条件有关.广州夏季盛行西南风,降雨较多,而冬季通常逆温少雨,造成二酸质量浓度升高.   相似文献   
685.
Introduction Environm ental and econom ic advantages highlight anaerobic digestion as a sustainable technology for solid w aste treatm ent (Edelm ann etal., 2000). A naerobic digestion could be described as four sequential steps: hydrolysis, acidogenesis, aceto- genesis and m ethanogenesis, am ong w hich the hydrolysis is recognized as the rate-lim iting step for particulate organic w aste (Jain et al., 1992; M ata-A lvarez, 2000). H ydrolysis occurs com m only together w ith the acidogenesi…  相似文献   
686.
从处理采油废水的活性污泥中分离出4株产生物表面活性剂的正十六烷高效降解菌。菌株A14和B45为非脱羧勒克菌(Leclercia adecarboxylata),菌株C28和A27为肠杆菌(Enterobacter sp.)。在NaCl质量浓度15~25 g/L、pH 6.0~7.0、接种量10%(φ),培养温度37 ℃,摇床转速160 r/min、正十六烷体积分数0.30%的条件下降解16 d后,菌株A14、B45、C28和A27的正十六烷降解率分别为93.7%,87.8%,73.3%,65.7%。4株菌所产生的生物表面活性剂均为磷脂类表面活性剂。菌体生长满足逻辑斯蒂模型,正十六烷的降解满足一级反应动力学模型。菌株C28、A27的生长速率快于菌株A14、B45,菌株A14、B45的正十六烷降解速率快于菌株C28、A27。  相似文献   
687.
In this study, the effect of operational parameters, such as solids retention time (SRT), pH, and substrate total solids (TS) concentration, on acid fermentation efficiency was investigated. From batch tests, it was shown that the appropriate pH range for thermophilic acidogens was around 6–7 and that the optimum pH condition was 6. From the continuous experiment, pH and SRT were shown to be the most important operational parameters for solubilization and organic acid production. In contrast, TS concentration did not show any obvious effect on chromium chemical oxygen demand (CODcr) solubilization when TS was in the range 3.5%–10%. The optimum operational conditions for thermophilic acid fermentation were an SRT of 2 days and a pH of 6. This research was carried as a part of the CREST project of Japan Science and Technology Agency.  相似文献   
688.
A nanofiltration strategy for tailing pond waters (TPWs) that utilizes cyclodextrin (CD)-based polymeric materials as supramolecular sorbents is proposed. Naphthenic acids (NAs) from the Athabasca TPWs are investigated as the target sorbate molecules.The sorption properties of several supramolecular porous materials were characterized using equilibrium sorption isotherms in aqueous solution wherein electrospray ionization mass spectrometry was used to monitor the concentration of NAs in aqueous solution. The characterization of the supramolecular sorbents was performed using 13C NMR and IR spectroscopy, while nitrogen porosimetry was used to estimate their surface area and pore structure properties. Independent estimates of surface area were obtained using a chromophore dye adsorption method in aqueous solution.The sorption results for NAs in solution were compared between a commercially available standard; granular activated carbon (GAC) and three types of synthetic materials. The sorption capacities for GAC ranged from 100 to 160 mg NAs/g of material whereas the polymeric materials ranged from 20 to 30 mg NAs/g of material over the experimental conditions investigated. In general, differences in the sorption properties between GAC and the CD-based sorbents were observed and related to differences in the surface areas of the materials and the chemical nature of the sorbents. The CD-based supramolecular materials displayed sorption capacities ranging from 36.2 to 657 m2/g as compared to that for GAC (795 m2/g).  相似文献   
689.
Formation of bound residues of pollutants in soils and sediments is an important process to control the fate of pollutants in the environment. The most of bound residue is not solvent extractable. In this paper, we measured both extractable and non-extractable polycyclic aromatic hydrocarbons (PAHs) in different organic matter fractions of samples from the Pearl River Delta, China. Non-extractable PAHs concentration was 234.45-1424.57 μg/kg and accounted for 33.78-57.44% of total PAHs. 2-3 Ring PAHs were the dominant species and differed in concentration substantially between the samples. The atomic ratio of PAHs over organic-C in the fractions ordered as solvent soluble organic matter > humin > humic acids, matching the content of aliphatic moieties in the fractions of organic matter. The ratio of extractable and non-extractable PAHs may relate to the aging process of PAHs in soil and sediment.  相似文献   
690.
近代分析技术研究农药与土壤活性组份作用机理   总被引:12,自引:1,他引:11       下载免费PDF全文
土壤中的粘土矿物和腐植酸是对农药吸附的最主要两类活性组份。作者从基于红外光谱(IR)、电子自旋共振谱(ESR)、X-衍射等近代分析技术,对农药在土壤活性组份上吸附机理的研究方法和主要结论进行了综述。  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