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A cheap synthesis of the so‐called ‘decalin‐1,8‐diones’ started with the conjugate (1,4‐) addition of cyclohex‐2‐en‐1‐one derivatives to the γ‐position of the dilithium derivative (buta‐1,3‐diene‐1,1‐bis(olate)) of crotonic acid. Hydrogenation of these ‘1,4‐γ’ adducts and final cyclization afforded the enol tautomers of decalin‐1,8‐diones. Nucleophilic substitutions at these 3‐oxoenols by NH3 or primary amines created only monoamino products (namely, 3‐oxoenamines) whose reactions with OPCl3 yielded dihydro(1,3,2)oxazaphosphinin‐2‐one derivatives. The two regioisomers of a trimethyl‐3‐oxoenamine served as models for the constitutional assignments of the two rapidly interconverting (hence, individually NMR‐invisible), tautomeric trimethyl‐3‐oxoenols. Such methyl substitutions served to break the ‘pretended’ symmetry of ‘decalin‐1,8‐dione’. Hydrazine and 3‐oxoenols furnished oxygen‐free indazole derivatives whose N?H bonds exchanged with t1/2=ca. 0.00035 s at ca. ?58(9) °C. 相似文献
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Industrial methods for the production of optically active intermediates 总被引:15,自引:0,他引:15
Breuer M Ditrich K Habicher T Hauer B Kesseler M Stürmer R Zelinski T 《Angewandte Chemie (International ed. in English)》2004,43(7):788-824
Enantiomerically pure amino acids, amino alcohols, amines, alcohols, and epoxides play an increasingly important role as intermediates in the pharmaceutical industry and agrochemistry, where both a high degree of purity and large quantities of the compounds are required. The chemical industry has primarily relied upon established chemical methods for the synthesis of these intermediates, but is now turning more and more to enzymatic and biotechnological fermentation processes. For the industrial implementation of many transformations alternative methods are available. The advantages of the individual methods will be discussed herein and exemplified by syntheses of relevant compounds. 相似文献
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M. Hauer D.J. Funk T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2003,77(2):297-301
Commercially available polymers often exhibit quite poor laser ablation properties for irradiation wavelengths around 248 nm.
At these wavelengths, the absorption is due to photostable aromatic groups. Photolabile triazene polymers were developed to
compare the influence of a photolabile group on the laser ablation process. The photochemically active triazene group has
a strong absorption band at 332 nm, whereas the second absorption maximum at 220 nm is due to the photostable aromatic group.
By irradiating at 308 nm and 193 nm, the influence of the photochemically active group on the ablation process can be studied.
The etching of the triazene polymer starts and ends with the laser pulse. No surface swelling, which is assigned to photothermal
ablation, is detected for fluences above the threshold of ablation. The expansion of the laser ablation induced shockwave
was measured for the photolabile triazene polymer and the photostable polyimide. The speed of the shockwave increases with
fluence and is higher for irradiation with 193 nm than with 308 nm. A shockwave with equal or higher velocity is observed
for the triazene polymer compared with polyimide.
Received: 28 August 2002 / Accepted: 20 September 2002 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +41-56/310-4412, E-mail: thomas.lippert@psi.ch 相似文献
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During experiments simulating the destruction of organic waste or the conversion of biomass with water at supercritical water conditions (SCW, T > 374 °C, p > 22.1 MPa), severe corrosion phenomena were observed. Depending on the experimental conditions applied, scale formation and precipitation of corrosion products occurred. The harsh conditions and the chemical properties of the feed solutions lead to consecutive chemical reactions with the materials involved. To study such hydrothermal reactions on simplified model systems, tubular reactors made of Ni‐based alloys were exposed to feed solutions composed of water, methanol and alkaline salts. After each experiment, the reaction tubes were cut and examined by optical microscopy. Hydrothermally formed corrosion layers were studied by field emission electron microscopy and combined energy dispersive X‐ray spectroscopy. Element line scans and mappings were performed which depicted selective dissolution of alloying elements (dealloying of Ni, Fe, Mo). The formation of the corrosion layers was accompanied by a subsequent reduction of the tube wall diameter. Atomic force microscopy gained additional morphological information; a Monte Carlo programme was applied to simulate X‐ray line scans. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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