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输水管材的选择及设计施工中应注意的问题 总被引:1,自引:0,他引:1
结合工程实例对城市输水工程管材的选择进行了论述,介绍了各种管材的优缺点,简述了输水工程经济流速与经济管径的选择,探讨了在设计施工中注意的问题并提出了相应的改进措施,以适应国民经济的发展,缓解城市的工业用水与生活用水困难的问题。 相似文献
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采用变密度法和折衷规划法建立了结构的多目标拓扑优化模型,并利用分析层级法确定了子目标权重。以"U"型结构为对象进行了多目标拓扑优化设计,得到了结构质量较轻的新结构形式。该方法可应用于结构的优化设计。 相似文献
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《Food Control》2015
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
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Robert Sevenich Elke Kleinstueck Colin Crews Warwick Anderson Celine Pye Katerina Riddellova Jaromir Hradecky Eliska Moravcova Kai Reineke Dietrich Knorr 《Journal of food science》2014,79(2):M230-M237
The benefits that high‐pressure thermal sterilization offers as an emerging technology could be used to produce a better overall food quality. Due to shorter dwell times and lower thermal load applied to the product in comparison to the thermal retorting, lower numbers and quantities of unwanted food processing contaminants (FPCs), for example, furan, acrylamide, HMF, and MCPD‐esters could be formed. Two spore strains were used to test the technique; Geobacillus stearothermophilus and Bacillus amyloliquefaciens, over the temperature range 90 to 121 °C at 600 MPa. The treatments were carried out in baby food puree and ACES‐buffer. The treatments at 90 and 105 °C showed that G. stearothermophilus is more pressure‐sensitive than B. amyloliquefaciens. The formation of FPCs was monitored during the sterilization process and compared to the amounts found in retorted samples of the same food. The amounts of furan could be reduced between 81% to 96% in comparison to retorting for the tested temperature pressure combination even at sterilization conditions of F0‐value in 7 min. 相似文献
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A simple and rapid multiresidue method for the determination of different veterinary drug residues in meat-based baby food (MBF) and powdered milk-based infant formulae (PMIF) has been developed. The method involves an extraction procedure based on buffered QuEChERS (quick, easy, cheap, effective, rugged and safe) methodology, without any further clean-up step, followed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The method has been validated in two baby food matrices (MBF and PMIF) at three different concentration levels, obtaining suitable recoveries and precision (inter and intra-day precision) values. Quantification was carried out using matrix-matched standard calibration. Furthermore, the decision limit (CCα) and the decision capability (CCβ) were evaluated, ranging from 0.5 to 16.2 μg/kg and from 1.2 to 22.4 μg/kg, respectively. Finally, the method was applied to the analysis of several kinds of baby food samples and traces of some veterinary drugs were detected. 相似文献
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《Ergonomics》2012,55(7):784-789
The purpose of this study was to determine the effect of load position in an internal frame backpack on physiological and perceptual variables. Ten female participants walked on a level treadmill for 10?min carrying 25% of their body weight in a high, central, or low position. The variables measured included oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (R), respiratory rate (RR), minute ventilation (VE), and rating of perceived exertion (RPE). VO2, VE, and RPE were significantly lower in the high position (18.6?±?2.3?ml/kg/min, 31.7?±?5.0?l/min, 2.8?±?0.8, respectively) compared to the low position (22.2?±?3.0?ml/kg/min, 38.6?±?7.5?l/min, 3.7?±?1.0, respectively). HR, R, and RR did not change significantly as the load was moved from the high (129.8?±?16.8, 0.89?±?0.06, 30.3?±?4.2, respectively) to the low position (136.0?±?25.3, 0.92?±?0.04, 33.8?±?5.2, respectively). The results of this study suggest that load placement is an important factor in the physiological and perceptual responses to load carriage, and that packing heavy items high in the backpack may be the most energy efficient method of carrying a load on the back. 相似文献