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   659篇
  免费   33篇
  国内免费   57篇
化学   615篇
晶体学   5篇
力学   6篇
综合类   44篇
数学   19篇
物理学   60篇
  2024年   13篇
  2023年   19篇
  2022年   57篇
  2021年   70篇
  2020年   40篇
  2019年   32篇
  2018年   19篇
  2017年   35篇
  2016年   20篇
  2015年   22篇
  2014年   20篇
  2013年   44篇
  2012年   39篇
  2011年   35篇
  2010年   24篇
  2009年   27篇
  2008年   34篇
  2007年   27篇
  2006年   32篇
  2005年   21篇
  2004年   24篇
  2003年   26篇
  2002年   19篇
  2001年   5篇
  2000年   10篇
  1999年   11篇
  1998年   6篇
  1997年   4篇
  1996年   1篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1986年   1篇
  1983年   1篇
排序方式: 共有749条查询结果,搜索用时 15 毫秒
21.
Wet air oxidation(WAO), a liquid phase reaction between organic materials in water and oxygen, is one of the most economical and technologically viable advanced oxidation processes for wastewater treatment, particularly toxic and high organic content wastewater. WAO is the liquid phase oxidation of organics or oxidizable inorganic components at elevated temperatures(125–320 °C) and pressures(0.5–20 MPa) using gaseous oxygen(or air) as oxidant. In the past two decades, the WAO process was widely studied and applied in the treatment of dye wastewater. Compared to conventional WAO, catalytic WAO processes have higher efficiency and use moderate reaction conditions. The catalysts included homogenous and heterogeneous types. The key points that need to be solved are recycling of homogenous catalysts and better stability of heterogeneous catalysts. In the present review, the technological processes are first introduced, then some research history and hotspots of WAO research are presented, and finally, its application in the treatment of dye wastewater in the past two decades is summarized to reveal the impressive changes in modes, trends, and conditions used. The application includes model pollutant studies and wastewater tests.  相似文献   
22.
采用光催化法对造纸废水的处理进行了研究.探讨了光催化反应机理,比较了光催化剂的活性顺序,讨论了复相光催化剂的组成、用量、试液pH值、光照时间与COD、色度去除率的关系.实验结果表明:采用WO3/α-Fe2O3/W为复相光催化剂,其组成为WO3:α-Fe2O3:W=75:24:1,当其用量为0.500g、pH=6.5、光照22h,造纸废水的COD和色度去除率分别达到68.3%和71.2%.  相似文献   
23.
This work presents the selective and simultaneous separation of nickel (Ni2+) and gold ([Au(CN)2]) ions, in trace amounts, from alkaline solution via hollow fiber supported liquid membrane (HFSLM) technique. HFSLM is challengingly carried out in real rinse wastewater generated by the ENIG plating process. The influence of various chemical parameters, including the type of extractant and their concentrations, molar ratios of mixed extractant as well as type of strippant, are also studied. The organophosphorus extractant mixtures of D2EHPA and TBP provide a synergistic effect for target Ni2+ ions but has an antagonistic effect as regards the extraction of non-target [Au(CN)2] ions. Compared to other inorganic acids, HCl is seen to be the most suitable strippant for the selective stripping. Results demonstrate that percentages of extraction and stripping of Ni2+ ions achieved 85.7 and 83.2%, respectively. In contrast, percentages of extraction and stripping of non-target [Au(CN)2] ions attained 15.6 and 1.94%.  相似文献   
24.
The rapid source identification and environmental risk assessment (ERA) of hundreds of chemicals of emerging concern (CECs) in river water represent a significant analytical challenge. Herein, a potential solution involving a rapid direct-injection liquid chromatography–tandem mass spectrometry method for the quantitative determination of 102 CECs (151 qualitatively) in river water is presented and applied across six rivers in Germany and Switzerland at high spatial resolution. The method required an injection volume of only 10 µL of filtered sample, with a runtime of 5.5 min including re-equilibration with >10 datapoints per peak per transition (mostly 2 per compound), and 36 stable isotope-labelled standards. Performance was excellent from the low ng/L to µg/L concentration level, with 260 injections possible in any 24 h period. The method was applied in three separate campaigns focusing on the ERA of rivers impacted by wastewater effluent discharges (1 urban area in the Basel city region with 4 rivers, as well as 1 semi-rural and 1 rural area, each focusing on 1 river). Between 25 and 40 compounds were quantified directly in each campaign, and in all cases small tributary rivers showed higher CEC concentrations (e.g., up to ~4000 ng/L in total in the R. Schwarzach, Bavaria, Germany). The source of selected CECs could also be identified and differentiated from other sources at pre- and post- wastewater treatment plant effluent discharge points, as well as the effect of dilution downstream, which occurred over very short distances in all cases. Lastly, ERA for 41 CECs was performed at specific impacted sites, with risk quotients (RQs) at 1 or more sites estimated as high risk (RQ > 10) for 1 pharmaceutical (diclofenac), medium risk (RQ of 1–10) for 3 CECs (carbamazepine, venlafaxine, and sulfamethoxazole), and low risk (RQ = 0.1–1.0) for 7 CECs (i.e., RQ > 0.1 for 11 CECs in total). The application of high-throughput methods like this could enable a better understanding of the risks of CECs, especially in low flow/volume tributary rivers at scale and with high resolution.  相似文献   
25.
The present study focuses on predicting the concentration of intracellular storage polymers in enhanced biological phosphorus removal (EBPR) systems. For that purpose, quantitative image analysis techniques were developed for determining the intracellular concentrations of PHA (PHB and PHV) with Nile blue and glycogen with aniline blue staining. Partial least squares (PLS) were used to predict the standard analytical values of these polymers by the proposed methodology. Identification of the aerobic and anaerobic stages proved to be crucial for improving the assessment of PHA, PHB and PHV intracellular concentrations. Current Nile blue based methodology can be seen as a feasible starting point for further enhancement. Glycogen detection based on the developed aniline blue staining methodology combined with the image analysis data proved to be a promising technique, toward the elimination of the need for analytical off-line measurements.  相似文献   
26.
Five cassava flour wastewater (manipueira) preparations were tested as culture media for biosurfactant production by a wild-type Bacillus sp. isolate. No-solids (F), no-solids diluted (F/2), natural (I), natural diluted (I/2), and decanted (IPS) were the tested manipueira media. The microorganism was able to grow and to produce biosurfactant on all manipueira preparations. The media whose solids were removed (F and F/2) showed better results than preparations with the presence of solids (I, I/2, and IPS). No-solids medium (F) showed a surface tension of 26,59 mN/m and reciprocal of critical micelle concentration of over 100 and was selected as a potential substrate for biosurfactant production.  相似文献   
27.
采用超声波辐照、臭氧氧化以及超声波辐照-臭氧氧化降解废水中的结晶紫;考察了废水初始pH、超声波功率和频率、氧气流量、反应温度等因素对降解效率的影响.结果表明:超声波和臭氧对结晶紫的降解具有协同作用;当废水溶液初始质量浓度为200mg.L-1、pH为10.0时,控制超声波功率和频率分别为100 W和30kHz,氧气流量为0.4L.min-1,反应温度为25℃,反应时间为90 min,则总有机碳(TOC)的去除率可达89.2%,相应的一级反应速率常数为2.38×10-2min-1.  相似文献   
28.
Recent developments in wastewater treatment have led to a renewed interest to obtain elemental sulphur (S°) as a by-product from bioreactors. However, practical studies are limited by the gap of adequate analytical techniques for its determination. This paper provides a statistical study and matrix effect evaluation of an adapted spectrophotometric method for routine S° analyses in aqueous samples, based on a methodology previously described by Hart (1961). Four complex matrices were tested: domestic sewage and effluent samples from three different bioreactors. Tested performance criteria included linearity, matrix effect, limit of detection and quantification and S° recovery. Results were linear (R2 = 0.99994) in the studied range (5 to 100 mg S° L?1) and no matrix effect was observed. The accuracy was based on recovery values that varied from 100% to 106%. The colloidal S° separation and extraction protocol was also considered suitable for aqueous samples, reaching more than 99.0% of S° recovery.  相似文献   
29.
The monitoring of the heavy metal pollution in wastewater is increasingly becoming a crucial global issue since they tend to accumulate in food chains and can cause many biological abnormalities. In this work, it was developed a novel lead ion-imprinted polymer (IIP) using sodium dodecyl sulphate (SDS) as a second template to be used as adsorbent in solid phase extraction (SPE) for determination of lead from wastewater samples by UV–vis spectrophotometry. The polymer called IIP–SDS was synthesised by a double-imprinting process with lead (template) and SDS (template). IIP–SDS was characterised by infrared spectroscopy Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. IIP–SDS showed good recovery for lead (around 82.0%), while the IIP (only lead as template) was 72.2% and non-IIP was 44.9%. Thus, the double-imprinting process for the preconcentration of Pb2+ proved to be a more adequate methodology than IIP with a single template. The optimised parameters of sample preparation were washing solvent (2.0 mL of tetrahydrofuran), type and volume of eluent (5 mL of 1 mol L?1 hydrochloric acid), sample amount (30 mL of water spiked with 10.0 µg mL?1), amount of IIP–SDS (400 mg) and sample pH (pH = 4.5). Linearity ranged from 10 to 125 µg L?1 with r > 0.992. The limit of detection and quantification were 6.3 and 10 µg L?1, respectively. The precision (relative standard deviation, %) and accuracy (relative error, %) were lower than 15%. Finally, IIP–SDS may be an alternative and effective adsorbent for SPE procedures in monitoring of wastewater samples.  相似文献   
30.
化学需氧量(CODCr)与总有机碳(TOC)指标均可用来表征废水的有机物污染程度.不过,以CODCr表征有机物污染程度一般只能反映水中部分有机物的量,而TOC能更全面地反映废水中有机物的含量.以丙烯酸生产外排废水为研究对象,分析结果表明:在一定范围内,废水中CODCr与TOC满足关系式y=1.147 4x+74.75(R2=0.955 26),回收率范围98%~115%,TOC测定结果的精密度高、可靠、准确,在一定条件下,可使用TOC来间接换算CODCr.  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