نتایج جستجو برای: simple condition
تعداد نتایج: 754253 فیلتر نتایج به سال:
the silica boron sulfuric acid nanoparticles (sbsans) as an efficient heterogeneous solid acid catalyst with both brønsted and lewis acidic sites catalyzed the preparation of bis-4-hydroxycoumarin derivatives using reaction of aldehydes and 4-hydroxycoumarin under mild and solvent-free condition at room temperature. this new and efficient methodology has advantages in comparison with currently ...
a water soluble, bronsted acid, 5-sulfosalicylic acid as an efficient organocatalyst was used for the synthesis of physiologically active 2-substituted benzimidazole derivatives from o-phenylenediamine and aromatic aldehydes in ethanol at reflux condition. cost-effectiveness, use of non-hazardous solvents, metal free and commercially available catalyst, single-step, environmentally friendly gre...
abstract the first purpose of this study was to investigate the effect of consciousness-raising (c-r) activities on learning grammatical structures (simple present tense in this case) by iranian guidance school efl learners. the second one was to investigate the effect of gender on learning the simple present tense through c-r activities and tasks. finally, this study aimed to investigate the ...
the rationale behind the present study is that particular learning strategies produce more effective results when applied together. the present study tried to investigate the efficiency of the semantic-context strategy alone with a technique called, keyword method. to clarify the point, the current study seeked to find answer to the following question: are the keyword and semantic-context metho...
A simple, green synthesis of N-alkyl-3-acetyl-2-methylpyrrole derivatives using ZnO nanoparticles from the three component reaction of aliphatic amines, acetylacetone (as a 1,3-dicarbonyl compound) and α-haloketones under solvent-free condition is described.
We de ne a sound and complete proof system for aÆne -retractions in simple types (built over many atoms), and we state a necessary condition for arbitrary -retractions in simple types. We also show a simple necessary condition for polymorphic -retractability and we disprove an earlier conjecture about a stronger necessary condition.
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