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121.
A.S. Aricò A.K. Shukla K.M. El-Khatib P. Cretì V. Antonucci 《Journal of Applied Electrochemistry》1999,29(6):673-678
The structure, chemistry and morphology of commercially available carbon-supported and unsupported Pt–Ru catalysts are investigated by X-ray diffraction, energy-dispersive analysis by X-rays and electron microscopy. The catalytic activities of these materials towards electrooxidation of methanol in solid-polymer-electrolyte direct methanol fuel cells have been investigated at 90C and 130C with varying amounts of Nafion ionomer in the catalytic layer. The unsupported Pt–Ru catalyst exhibits higher performance with lower activation-control and mass-polarization losses in relation to the carbon-supported catalyst.On leave from the 相似文献
122.
固相萃取-气相色谱测定地下水中多环芳烃的质量控制研究 总被引:10,自引:0,他引:10
以USEPA及国家标准为基础研究了利用固相萃取——气相色谱测定地下水中16种多环芳烃的分析方法.探讨了几种空白用水的效果,得出市售纯净水是最简单且效果最好的空白溶剂,同时研究表明.该分析方法的检出限可以达到0.004~0.010μg/L.标准偏差在2.6%~12.4%范围内。基质加标回收率达到71.5%~99.7%。本研究方法不仅适用于地表水中多环芳烃的分析测定.同时也可以用于地下水及各种淋滤水样中多环芳烃的分析测定。为国内尽快建立利用固相萃取技术处理环境样品中多环芳烃的标准方法提供必要的数据依据。 相似文献
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An optimised off-line SPE–GC–FID method based on the use of silver-silica gel was developed for the determination of mineral oil saturated hydrocarbons (MOSH) in vegetable oils, including olive pomace oil. The method is specific in not including the aromatic hydrocarbons. The performance of different silica gels (untreated, activated and treated with silver nitrate) was compared in terms of capacity to retain fat and retention of interfering olefins present in particularly large amounts in refined olive oils. A coefficient of variation of 9% was obtained performing six replicate analyses of an extra virgin olive oil fortified with an amount of MOSH near the estimated LOQ (15 mg/kg). Recoveries were close to 100%. The use of activated aluminium oxide as an additional tool to eliminate interference by endogenous long-chain n-alkanes, is discussed. 相似文献
127.
《Carbon》2015
The structural and chemical transformations occurring in alumina–carbon composites upon heat treatment were investigated by using a combination of X-ray diffraction (XRD) and solid-state 27Al nuclear magnetic resonance (NMR) spectroscopy. Two different carbon precursors were employed: a commercial activated carbon and a char obtained by carbonization of the endocarp of babassu coconut at 700 °C. The alumina–carbon composites were prepared by aqueous impregnation of the carbon supports with aluminum nitrate and, after filtering and drying, the as-synthesized powders were heat-treated under argon flow at temperatures up to 1000 °C. The Al compounds present in the as-synthesized samples were identified by XRD and solid-state 27Al NMR as nanocrystalline aluminum oxyhydroxides or hydroxides, depending on the synthesis conditions. All Al-containing phases were XRD-amorphous in the char-derived nanocomposites, with the presence of a distribution of AlO6 (octahedral Al site), AlO5 (pentacoordinated Al) and AlO4 (tetrahedral Al site) units revealed by solid-state 27Al NMR spectroscopy. The heat treatments caused the formation of transition aluminas dispersed over the carbon supports, with the occurrence of different amounts of AlO6, AlO5 and AlO4 units depending on the heat treatment temperature and on the type of carbon precursor used for the preparation of the composites. 相似文献
128.
以苹果、梨、葡萄、橘子、白菜、西兰花、菠菜、胡萝卜、番茄和黄瓜共10种植物性食品为研究对象,建立了植物性食品中氟吗啉残留量的QuEChERS-HPLC检测方法。样品经0.1%冰醋酸乙腈提取,醋酸钠和无水硫酸镁盐析后,取上清液,加入伯仲胺粉分散固相萃取净化,用配有二极管阵列检测器的高效液相色谱测定,外标法定量。氟吗啉在0.1~2mg/L的范围内具有较好的线性关系,氟吗啉在0.1、0.2、0.5mg/kg三个添加水平平均回收率81%~116%,RSD2.3%~12.1%,定量限为0.05mg/kg。本方法前处理简单、快速,适用于多种植物性食品中氟吗啉残留量测定。 相似文献
129.
Isoflavones from cotyledons of soybean sprouts were extracted with aqueous ethanol and further concentrated to obtain a product with a high concentration of isoflavone. The ethanol concentration, extraction time and reaction temperature were optimized by using response surface methodology (RSM). Isoflavones in aqueous ethanol were concentrated by a three-step procedure comprised of solid phase extraction (SPE) with Diaion HP-20 and Amberlite-XAD-2 adsorption columns, acid hydrolysis, and liquid–liquid extraction. The maximum amount of isoflavone in aqueous ethanol extracts (11.6 mg/g solid) was obtained when isoflavones in cotyledons (2.18 mg/ g solid) were extracted with 80–90% (v/v) aqueous ethanol above 90 °C for more than 100 min. The isoflavone extracts, obtained by SPE with a Diaion HP-20 column contained 100 mg/g solid. The liquid–liquid extraction (LLE) with ethyl ether further concentrated the extracts up to 229 mg/g solid, retaining 63% of the initial isoflavones. 相似文献
130.