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   404篇
  免费   15篇
  国内免费   17篇
电工技术   10篇
综合类   8篇
化学工业   102篇
金属工艺   6篇
机械仪表   26篇
建筑科学   8篇
矿业工程   1篇
能源动力   13篇
轻工业   195篇
水利工程   3篇
石油天然气   11篇
无线电   7篇
一般工业技术   29篇
冶金工业   2篇
原子能技术   1篇
自动化技术   14篇
  2023年   1篇
  2022年   5篇
  2021年   10篇
  2020年   3篇
  2019年   6篇
  2018年   6篇
  2017年   16篇
  2016年   12篇
  2015年   21篇
  2014年   26篇
  2013年   37篇
  2012年   50篇
  2011年   48篇
  2010年   20篇
  2009年   29篇
  2008年   20篇
  2007年   31篇
  2006年   28篇
  2005年   15篇
  2004年   11篇
  2003年   10篇
  2002年   7篇
  2001年   5篇
  2000年   3篇
  1999年   2篇
  1998年   3篇
  1997年   4篇
  1996年   1篇
  1994年   2篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
排序方式: 共有436条查询结果,搜索用时 15 毫秒
1.
集成项目交付(IPD)模式主要有 3 种类型:过渡型 IPD 模式、多方合同型 IPD 模式和单一实体型(SPE)IPD 模式。目前适用于 SPE 型 IPD 模式的合同范本是美国建筑师协会颁布的 AIA C195 系列合同。通过文献阅读和翻译,归纳出SPE 型 IPD 模式主要参与方的合同结构;对 C195 系列合同下的两层次组织结构——治理委员会和项目管理团队进行分析,并介绍了 C195 系列合同决策方式的 3 个特点。将项目全周期划分为 8 个阶段,对各个阶段的集成项目交付服务范围进行阐述。旨在完善国内 IPD 模式合同文本的理论研究,为行业实践提供理论支持。  相似文献   
2.
This study investigated the use of tailings from apatite ore beneficiation in the remediation of a heavily contaminated shooting range soil. The tailings originating in Siilinjärvi carbonatite complex, Finland, consist of apatite residues accompanied by phlogopite and calcite. In a pot experiment, organic top layer of a boreal forest soil predisposed to pellet-derived lead (Pb) was amended with tailings of various particle-sizes (Ø > 0.2 mm, Ø < 0.2 mm and unsieved material) differing in their mineralogical composition. After 9-, 10-, 14- and 21-month incubation, the samples were monitored for tailings-induced changes in the different Pb pools by means of sequential fractionation. Following the incubation, the samples were extracted with water and the extracts were analyzed for Pb species distribution by means of a cation exchange resin. The results revealed that Pb was continuously released from the shotgun pellet fragments due to weathering. However, the apatite and calcite compartments in the tailings counteracted the mobility of the released Pb through the formation of sparingly soluble fluorpyromorphite and cerussite. Furthermore, the tailings efficiently reduced the bioavailability of Pb by transferring it from the water-soluble and exchangeable pools into the organic one. The material also increased the proportion of the less toxic non-cationic Pb to the total dissolved Pb from the initial level of 5% to 9-12%. The results suggest that the tailings-induced stabilization of Pb may be an environmentally sound remediation technique at polluted sites.  相似文献   
3.
Tricaine mesylate (MS-222) is one of the most used anesthetics in fish. It can be absorbed by the human body via food consumption, with related detriments to human health. In this study, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed for the determination of MS-222 in carp muscle and water samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). For cleanup procedure, multiplug filtration cleanup (m-PFC) method with n-Hexane delipidation was adopted. The extraction solvent, cleanup methods and sorbents were optimized. All method validation parameters were in the acceptable range. The dissipation behavior study was followed by the method development. Firstly, the anesthesia dose and time were optimized in application study. Secondly, carps were revived for different period of time with (experimental group) and without (control group) the oxygenation aeration treatment to compare the dissipation rate of MS-222. After being anesthetized for 6 h at 50 mg/L and 12 h of elimination, the concentrations of MS-222 in crap muscle and water of experimental group was lower than those of control group. After 36 h of elimination under oxygenation aeration, over 90% of MS-222 was dissipated in carp muscle. The results showed that the half-life of MS-222 in carp muscle was 6.2 h. The findings suggested that the commonly-used oxygenation aeration treatment in aquaculture production had potential effects in accelerating the dissipation of MS-222 in carp and water. In this study, three days of withdrawal period was recommended in carps after MS-222 administration under oxygenation aeration.  相似文献   
4.
A simple and rapid magnetic solid-phase extraction (M-SPE) procedure using multi-walled carbon nanotube-magnetic nanoparticles (MWCNT-MNPs) as sorbents was established for purification of zearalenone (ZEA), α-zearalenol (α-ZOL), β-zearalenol (β-ZOL), zearalanone (ZAN), α-zearalanol (α-ZAL) and β-zearalanol (β-ZAL) in maize. The main parameters affecting the clean-up efficiency were thoroughly investigated, and high purification efficiencies for all analytes were obtained. The resulting MWCNT-MNP-ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was validated for maize samples. The matrix effects were greatly minimized using the M-SPE approach, with signal suppression/enhancement values decreased from 69.9–127.6% to 92.1–103.8%. Consequently, complex matrix-matched calibration curves were not necessary and the calibrations constructed in acetonitrile could be applied for accurate quantification of the targeted mycotoxins in real samples. The average recoveries ranged from 75.8 to 104.1% and the inter- and intra-day precision values expressed as RSDs, were all lower than 14%. Limits of detection and quantification were in the range of 0.03–0.04 and 0.07–0.10 μg/kg, respectively. The analytical performance of the developed method was also successfully evaluated with maize samples, and this method was proved to be a powerful tool for monitoring ZEA and its derivatives in maize.  相似文献   
5.
The mycotoxin patulin is known to be the predominant natural contaminant of apples, apple-based products and a variety of other fruits. Because of its high incidence and harmful health effects, patulin is included with mycotoxins, which are strictly monitored. In this study, a sensitive and reliable ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) method was developed and validated for determination of patulin in a variety of fruit matrices. A combination of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure along with a solid phase extraction (SPE) clean-up strategy enabled an effective removal of sample matrix and pre-concentration of patulin. This resulted in low limits of quantification ranging from 1 to 2.5 μg/kg, depending on fruit type. In our study, quantification of patulin was based on a stable isotope dilution assay (SIDA) using 13C7-patulin as the internal standard. Data showed that the procedure described, in combination with neat solvent internal calibration, can be used for accurate quantification of patulin regardless the type of fruit. Although the SIDA method allowed omission of matrix-matched calibration, matrix-effects were estimated in order to assess suppression of the patulin signal caused by a variety of fruit samples. The method was fully validated for apples, apple baby food, apple juice, peaches, strawberries and blueberries. The recovery values were in the range from 92 to 109%. Repeatability of the method was below 10% for all tested matrices. The method was applied to the monitoring of patulin in 135 samples of fresh fruits and fruit products and can also be used as an efficient tool for routine monitoring of this contaminant in a variety of fruit-based foods.  相似文献   
6.
Modular ligation strategies for the functionalization of polymeric microspheres provide new perspectives for their applications in material science. In the current trend article we highlight variable synthetic procedures for generating functional microspheres via orthogonal modular conjugation chemistries. An overview of the different surface chemistries available is provided, followed by surface-sensitive characterization techniques relevant for the microparticles. Finally, we explore future trends in modular orthogonal modification approaches on microparticles and provide an outlook on the perspectives that the field of surface-modification of polymeric microparticles holds.  相似文献   
7.
This study describes the development of a validated method for the quantification of rotenone in yam bean. The milled seeds were submitted to a Soxhlet dichloromethane extraction which allowed extracting 90% of the seeds rotenone. Elimination of the lipids was obtained via solid phase extraction. Rotenone was eluted with dichloromethane/methanol and the solution dried under vacuum and solubilised directly in methanol before injection in HPLC. The whole process was realised as much as possible protected from light and at temperatures lower than 40 °C which allowed high recovery rates of spiked rotenone. Total error was used as criterion for the validation process and accuracy profiles drawn. The method allows the quantification of rotenone in yam bean seeds from 0.07% up to 1.25% (w/w). This method was applied to the quantification of rotenone in the seeds of several accessions of Pachyrhizus erosus and Pachyrhizus ahipa. The results range from 1.13 to 2.76 mg/g dry material.  相似文献   
8.
采用固相萃取-气相色谱质谱法分析了水中24种致癌芳香胺的含量,结果表明,该方法的检出限低于0.36 μg/L。固相萃取的优化条件为:选用Envi-chromp固相萃取小柱,水样pH 8~10,二氯甲烷洗脱2次。绝大多数芳香胺的空白水样加标回收率在88.8%~111.8%之间,标准偏差为6.8%~9.9%。对浙江省13个饮用水源地的地表水进行检测,均未检出24种致癌芳香胺。降解实验表明,大多数芳香胺化合物在水中能稳定存在14 d以上。  相似文献   
9.
固相萃取-气相色谱质谱法测定食用油中邻苯二甲酸酯   总被引:2,自引:0,他引:2  
建立了固相萃取-气相色谱质谱法测定食用油中邻苯二甲酸酯的分析方法。以正己烷为提取剂萃取试样中的邻苯二甲酸酯,样液经中性氧化铝自组装固相萃取柱净化后进行GC/MS测定分析。采用选择离子扫描方式,用外标法进行定量分析。方法的检出限(S/N=3)为1~6μg/kg。在加标水平为50μg/kg时,平均回收率为67.3~107%,相对标准偏差(RSD)为3.6~6.1%;在加标水平为100μg/kg时,平均回收率为67.5~103%,相对标准偏差(RSD)为3.2~6.2%。本方法简便、快速地实现了食用油中邻苯二甲酸酯的检测。  相似文献   
10.
高效液相色谱法同时测定饮料中的7种人工合成色素   总被引:1,自引:0,他引:1  
样品经自制聚酰胺粉固相萃取柱富集和净化后进行HPLC分析。采用Agilent Eclipse XDB-C18(4.6mm×150mm×4.6μm)色谱柱,以甲醇/乙腈(1∶2,体积比)和乙酸铵(0.02mol/L)为流动相进行梯度洗脱,流速1.0mL/min,检测波长为254nm和627nm,分析时间15min左右。7种人工合成色素在1.00~20.0mg/L质量浓度范围内线性关系良好(r均大于0.9999),加标回收率在89.0%~101%之间,相对标准偏差0.4%~3.4%。该方法操作简便,结果准确可靠,重复性好,适用于饮料中多种人工合成色素的同时检测。  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