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91.
The synthesis of linear and crosslinked polymers starting with 4-(diisopropyl-phosphinyl) styrene is described. Treatment
with triphosgene yields the corresponding phosphine dichloride group in the polymers. Using these reactive polymers benzyl
alcohol was converted to benzyl chloride at room temperature. The regeneration of the reactive polymers using triphosgene
was achieved. The yields of benzyl chloride were in general lower than those previously reported using triphenylphosphine
dichloride groups in the polymers. The difference in reactivity between triphenylphosphine dichloride- and diisopropylphenylphosphine
dichloride substituted-polymers are discussed with the aid of semi-empirical computer calculations.
Received: 17 June 1997/Revised: 4 September 1997/Accepted: 9 September 1997 相似文献
92.
María del Carmen García‐Martínez Luis M. Rodríguez‐Alcalá Susana Marmesat Leocadio Alonso Javier Fontecha Gloria Márquez‐Ruiz 《International Journal of Food Science & Technology》2010,45(11):2337-2344
Lipid stability of standard infant formula was evaluated at ambient temperatures, namely 25, 30 and 37 °C, during 3 months. Lipids were thoroughly analysed to evaluate changes in fatty acid composition and trans fatty acid isomers, non‐volatile oxidation compounds including oxidised, dimeric and polymeric triacylglycerols, and tocopherol. No significant changes in either of the parameters examined were found in total lipids extracted from infant formula along the storage period. However, the minor free oil fractions (about 7.5% of total lipids) showed a significant increase in oxidation compounds and marked decrease in tocopherol levels during storage at all temperatures. Samples stored at 37 °C for 3 months were rancid and, accordingly, contained the highest oxidation level in the free oil fraction, whereas total lipids extracted were apparently not oxidised. Results showed the necessity of analysing separately the free oil fraction in infant formulae to obtain a clear picture of the oxidation status. 相似文献
93.
Probiotic potential and sensory properties of coconut flan supplemented with Lactobacillus paracasei and Bifidobacterium lactis 总被引:1,自引:1,他引:0
Sabrina B. M. Corrêa Inar A. Castro & Susana M. I. Saad 《International Journal of Food Science & Technology》2008,43(9):1560-1568
The effect of probiotic cultures on sensory performance of coconut flan during storage at 5 °C and the viability of these micro organisms for up to 28 days were investigated. Sensory analyses of the product were performed after 7, 14 and 21 days of storage. Coconut flans were produced with no addition of cultures (T1, control), or supplemented with Bifidobacterium lactis (T2), Lactobacillus paracasei (T3) and B. lactis + L. paracasei (T4). Populations of L. paracasei and B. lactis as single or in co-culture remained above 7 log CFU g−1 during the entire storage period. Viability of L. paracasei was higher for T3. All products were well accepted and no significant differences ( P > 0.05) were detected between the coconut flans studied. The addition of L. paracasei and B. lactis to coconut flan resulted in its having great potential as a functional food, which has high sensory acceptability. 相似文献
94.
Analysis of ultrasonic-assisted drilling of Ti6Al4V 总被引:1,自引:0,他引:1
J. Pujana A. Rivero A. Celaya L.N. López de Lacalle 《International Journal of Machine Tools and Manufacture》2009,49(6):500-508
In this study ultrasonic vibration was applied on the drilling of Ti6Al4V workpiece samples. Several parameters of ultrasonic-assisted drilling were monitored, including feed force, chip formation by means of high-speed imaging, and temperature measurement on the drill tip by means of infrared radiation thermometry. Ultrasonic assistance offered lower feed force and higher process temperatures as compared to conventional drilling. It has also shown higher force reductions and higher temperature increments when vibration amplitude was increased. 相似文献
95.
Andrea C Galvis‐Snchez Susana C Fonseca ngel Gil‐Izquierdo María I Gil F Xavier Malcata 《Journal of the science of food and agriculture》2006,86(4):509-517
Pears (Pyrus communis L. cv. ‘Rocha’) were exposed to air or controlled atmosphere (CA) containing various concentrations of CO2: 0, 0.5 and 5 kPa, all with 2 kPa O2. After 4 months of storage at 2 °C, the fruits were transferred to air at room temperature, and assessed in terms of soluble solids, titratable acidity, pH, incidence of brown heart and flesh browning, phenolic content, vitamin C content and polyphenol oxidase activity. By 4 months of storage, soluble solids and pH increased, and acidity decreased relative to harvest, but no differences were detected between pears stored under air or any of the CA tested. Higher contents of hydroxycinnamic derivatives and flavan‐3‐ols in the peel than in the flesh were recorded. However, the content of arbutin was higher in the flesh than in the peel, whereas flavonols were only detected in the peel. In general, hydroxycinnamic derivatives and flavonols were stable throughout storage, but flavan‐3‐ols decreased in concentration under air or CA. Arbutin was the only phenolic compound that increased in concentration as time elapsed. No clear relation was found between the storage conditions tested and the phenolic concentration in pears. Regarding ascorbic acid (AA) and dehydroascorbic acid (DHA), their concentrations were higher in the peel than in the flesh. Furthermore, AA and DHA were strongly affected by storage: the former decreased, whereas the latter increased in content. A decrease in PPO activity was apparent after harvest and during storage, particularly under higher levels of CO2. The combination 2 kPa O2 + 5 kPa CO2 increased the incidence of internal disorders (viz. brown heart and flesh browning) after storage. Copyright © 2005 Society of Chemical Industry 相似文献
96.
Malheiro R de Pinho PG Casal S Bento A Pereira JA 《Journal of the science of food and agriculture》2011,91(9):1693-1701
BACKGROUND: The volatile composition of alcaparras stoned table olives produced from five of the most representative olive cultivars (cv. Cobrançosa, Madural, Negrinha de Freixo, Santulhana and Verdeal Transmontana) from the Trás‐os‐Montes region (north‐east of Portugal) was analytically characterised using headspace–solid phase microextraction/gas chromatography–ion trap–mass spectrometry. RESULTS: Overall, 42 volatile compounds were identified, belonging to distinct chemical classes: 15 aldehydes, seven esters, five alcohols, five sesquiterpenes, four norisoprenoids derivates, three monoterpenes, o ne ketone and two alkenes. Aldehydes were the major chemical class identified in all olive cultivars studied (more than 74% of all the volatile compounds identified). Hexanal, phenylacetaldehyde and (E,E)‐2,4‐heptadienal were the major volatile compounds identified. CONCLUSIONS: It was possible to discriminate the results obtained from the volatile profile of the five olive cultivars by using principal component analysis. Both qualitative and quantitative fractions of alcaparras table olives were influenced by olive cultivar, which confers a single aroma. This fact certainly influences consumer preference and acceptability towards a specific olive cultivar. Copyright © 2011 Society of Chemical Industry 相似文献
97.
98.
Mauricio Osorio Marcela Carvajal Alejandra Vergara Estefania Butassi Susana Zacchino Carolina Mascayano Margarita Montoya Sophia Mejías Marcelo Cortez-San Martín Yesseny Vsquez-Martínez 《International journal of molecular sciences》2021,22(11)
Prenylated flavonoids are an important class of naturally occurring flavonoids with important biological activity, but their low abundance in nature limits their application in medicines. Here, we showed the hemisynthesis and the determination of various biological activities of seven prenylated flavonoids, named 7–13, with an emphasis on antimicrobial ones. Compounds 9, 11, and 12 showed inhibitory activity against human pathogenic fungi. Compounds 11, 12 (flavanones) and 13 (isoflavone) were the most active against clinical isolated Staphylococcus aureus MRSA, showing that structural requirements as prenylation at position C-6 or C-8 and OH at positions C-5, 7, and 4′ are key to the antibacterial activity. The combination of 11 or 12 with commercial antibiotics synergistically enhanced the antibacterial activity of vancomycin, ciprofloxacin, and methicillin in a factor of 10 to 100 times against drug-resistant bacteria. Compound 11 combined with ciprofloxacin was able to decrease the levels of ROS generated by ciprofloxacin. According to docking results of S enantiomer of 11 with ATP-binding cassette transporter showed the most favorable binding energy; however, more studies are needed to support this result. 相似文献
99.
Romero Yesa Susana Aláez-Martínez Marian Ferran Zubillaga Ane García-Olalla Ana 《Universal Access in the Information Society》2021,20(3):573-593
Universal Access in the Information Society - This study focuses on a case study developed at a higher education institution, which comprises developing a new virtual teaching unit (VTU) aimed at... 相似文献
100.