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161.
162.
1,4‐Polymyrcene was synthesized by anionic polymerization of β‐myrcene and was subjected to photochemical functionalization with various thiols (i.e. methyl thioglycolate, methyl 3‐mercaptopropionate, butyl 3‐mercaptopropionate, ethyl 2‐mercaptopropionate and 2‐methyl‐2‐propanethiol) using benzophenone/UV light as the radical source. The yield of thiol addition to the trisubstituted double bonds of 1,4‐polymyrcene decreased in the order 1° thiol (ca 95%) > 2° thiol (ca 80%) > 3° thiol (<5%), due to the reversibility of the thiol‐ene reaction. Remarkably, thiol addition to the side‐chain double bonds was 8 ? 10 times (1° thiol) or 24 times (2° thiol) faster than to the main‐chain double bonds, which can be explained by the different accessibility of the double bonds and steric hindrance. Despite the use of a 10‐fold excess of thiol with respect to myrcene units, the thiol‐ene addition was accompanied by chain coupling reactions, which in the extreme case of 3° thiol (or in the absence of thiol) resulted in the formation of insoluble crosslinked material. As an example, a methyl‐thioglycolate‐functionalized 1,4‐polymyrcene was saponified/crosslinked to give submicron polyelectrolyte particles in dilute alkaline solution. © 2018 Society of Chemical Industry 相似文献
163.
Pyrene functionalized side chain alanine and histidine containing copolyacrylates prepared by free radical copolymerization
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An optically active copolyacrylate, poly(N‐acryloyl‐L‐alanine‐co‐N‐acryloyl‐L‐histidine), is prepared by classical radical copolymerization of N‐acryloyl‐L‐alanine and N‐acryloyl‐L‐histidine, and further chemically modified with 1‐pyrene‐methanol. The structures of the synthesized compounds are confirmed by spectral analysis (FTIR, 1H/13C‐NMR, UV, fluorescence spectroscopy), thermal methods, and molecular weight measurements. Also, their optical activity is studied using circular dichroism (CD) spectroscopy and optical rotation measurements. The specific rotation values reveal that the direction of rotation of the parent copolymer is dictated by the monomer containing L‐alanine. CD data suggest negative and positive Cotton effects regarding the monomers with amino acids. In the case of the unmodified copolymer it is noted the changes of ellipticity values with increasing pH while the random‐coil conformation is preserved, which makes it suitable as a pH‐responsive system. Photochemical and photophysical investigations reveal that the pyrene‐functionalized chiroptical copolyacrylate can be used as a fluorescent chemosensor for the detection of nitro‐derivatives in organic media. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44457. 相似文献
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Ikeda S Kubota T Wang DO Yanagisawa H Umemoto T Okamoto A 《Chembiochem : a European journal of chemical biology》2011,12(18):2871-2880
A binary photocontrolled nucleic acid probe that contains a nucleotide modified with one photolabile nitrobenzyl unit and two hybridization-sensitive thiazole orange units has been designed for area-specific fluorescence imaging of RNA in a cell. The synthesized probe emitted very weak fluorescence regardless of the presence of the complementary RNA, whereas it showed hybridization-sensitive fluorescence emission at 532 nm after photoirradiation at 360 or 405 nm for uncaging. Fluorescence suppression of the caged probe was attributed to a decrease in the duplex-formation ability. Caged fluorescent nucleotides with other emission wavelengths (622 and 724 nm) were also synthesized in this study; they were uncaged by 360 nm irradiation, and emitted fluorescence in the presence of the complementary RNA. Such probes were applied to area-specific RNA imaging in a cell. Only probes in the defined irradiation area were activated by uncaging irradiation, and subnuclear mRNA diffusion in a living cell was monitored. 相似文献
166.
含CL-20改性双基推进剂激光点火特性 总被引:5,自引:0,他引:5
采用CO2激光点火方法,研究了含六硝基六氮杂异戊兹烷(CL-20)改性双基(CMDB)推进剂在不同功率密度作用下的点火特性,探讨了Al粉含量和燃烧催化剂对该类推进剂激光点火性能的影响。实验结果表明,在激光功率密度25.5~127.0 W/cm2范围内,不含催化剂的CL-20-CMDB推进剂点火延迟时间随功率密度增加而递减,且点火延迟时间变化逐渐减缓,点火均首先在推进剂表面产生;而含有催化剂推进剂试样的点火延迟时间和点火过程则与功率密度密切相关:在高激光功率密度时,含催化剂的推进剂点火没有发生在推进剂表面,而是在试样表面的气相中,且点火延迟时间增加。Al粉含量对其点火延迟的影响在低激光功率密度时较大,随着功率密度增加影响减弱。 相似文献
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170.
Fabrication and Spatially Resolved Functionalization of 3D Microstructures via Multiphoton‐Induced Diels–Alder Chemistry
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Alexander S. Quick Hannah Rothfuss Alexander Welle Benjamin Richter Joachim Fischer Martin Wegener Christopher Barner‐Kowollik 《Advanced functional materials》2014,24(23):3571-3580
Three‐dimensional microstructures are fabricated utilizing direct laser writing combined with a non‐radical step polymerization based on multiphoton‐induced Diels–Alder chemistry of o‐quinodimethanes and maleimides. Woodpile photonic crystals with a total of five axial periods and a rod spacing of down to 500 nm are fabricated. The structures are characterized via scanning electron microscopy and focused ion beam milling. In addition, corresponding photonic stop bands are investigated via light microscopy as well as transmission and reflection spectroscopy. The Diels–Alder based network formation during direct laser writing is verified via infrared spectroscopy. Spatially resolved surface patterning of covalently bonded functional molecules on fabricated structures is demonstrated by employing the direct laser writing setup and a bromine containing maleimide. The successful surface modification is verified via time‐of‐flight secondary ion mass spectrometry. 相似文献