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891.
Nazar Dovhaniuk Dr. Oleksandr P. Blahun Bohdan Sosunovych Mykhailo O. Redka Bohdan V. Vashchenko Prof. Dr. Oleksandr O. Grygorenko 《European journal of organic chemistry》2023,26(3):e202201226
A novel efficient method for the synthesis of licochalcone C in good yield on up to 30 g scale was developed. The reaction sequence included relied on the directed ortho-metalation (DOM) of bis-O-MOM-protected resorcinol for the regioselective C-prenylation, followed by metalation-formylation, selective O-deprotection of a hydroxyl group located between the formyl and prenyl groups, its methylation, and aldol reaction with p-hydroxyacetophenone. Synthesis of structurally related retrochalcones, i.e., licoagrochalcones B, C, and D, was also proposed. 相似文献
892.
Javier E. Alfonso-Ramos Ruben Van Lommel David Hernández-Castillo Prof. Frank De Proft Roy González-Alemán Prof. Erik V. Van der Eycken Gerardo M. Ojeda-Carralero 《European journal of organic chemistry》2023,26(3):e202201028
1,3-Dipolar cycloadditions are the preferred method to generate five-membered heterocyclic rings. Surprisingly, cycloadditions based on acyl-isocyanide ylides have remained underexplored by the chemical community. Acyl-isocyanide ylides readily react with dipolarophiles, such as substituted alkenes, to yield Δ1-pyrroline derivatives. As an explanation for the observed reactivity of this reaction is lacking, extensive density functional theory calculations were performed to scrutinize the mechanistic features of the transformation. Herein we explain the experimental outcome of the reaction using a variety of reactivity theories and predict opposed regioselectivity for electron-poor and electron-rich dipolarophiles. With the insights obtained, we hope to incentivize the design of new cycloaddition reactions based on the acyl-isocyanide ylides motif. 相似文献
893.
We developed a highly regioselective synthesis of multi-substituted alkenylboronates via a heterogeneous ligand-free nano-copper catalyst that was highly dispersed and supported on the porous polyvinyl chloride. In this catalytic system, substituents on the terminal alkynes could affect the configuration of products. Terminal alkynes and general internal alkynes gave β-selective borylation products, whereas heteroatom-substituted alkynes like alkynamides, thioacetylenes, and ynol ethers gave α-selective borylation products in good chemical yields with exclusive regioselectivity. 相似文献
894.
Dr. Gang Liu Dr. Xianfeng Mu Dr. Miao Tian Dr. Weili Wang Dr. Chunhui Zou Dr. Yiwen Chen Prof. Mingwu Yu 《European journal of organic chemistry》2023,26(13):e202201491
Herein, we report the development of a radical deoxy-functionalization strategy for the direct C−H alkylation of purines and purine nucleosides with alcohols (1°, 2°, 3°) intervened by oxalates under 12 W blue LED irradiation. The reaction shows high regioselectivity at C6−H position of purine and is suitable for N9-, N7-substitued purines. The process accommodates purines and alcohols to deliver a wide range of products (31 examples) in 41–91 % yields, which avoids transition metal catalysts and organometallic reagents, and is not sensitive to moisture and air. Besides, the mild protocol displays broad functional groups tolerance and is easily up scalable to gram scale and can be used for late-stage C−H alkylation of purine to synthesize pharmaceutical 6-cyclopentyl nebularine with anti-CEM activity or natural d -menthol modification. 相似文献
895.
Chiral Brønsted base (BB) catalyzed asymmetric transformations constitute an important tool for synthesis. A meaningful fraction of these transformations proceeds through transiently generated enolate intermediates, which display quite versatile reactivity against a variety of electrophiles. Some years ago, our group became interested in developing BB-catalyzed asymmetric reactions of enolizable carbonyl substrates that involve π-extended enolates in which, besides control of reaction diastereo and enantioselectivity, the site-selectivity control is an additional issue in most cases. In the examples covered in this account the opportunities deployed, and the challenges posed, by these methods are illustrated, with a focus on the generation of quaternary carbon stereocenters. In the way, new bifunctional BB catalysts as well as achiral templates were developed that may find further applications. 相似文献
896.
Franck Schillinger Uwe Hahn Sebastiano Guerra Thi Minh Nguyet Trinh David Sigwalt Michel Holler Iwona Nierengarten Jean-François Nierengarten 《Helvetica chimica acta》2023,106(6):e202300026
Bis- and tris-malonates constructed around a silicon atom have been prepared by reaction of malonate derivatives bearing an alcohol function with di-tert-butylsilyl bis(trifluoromethanesulfonate) and tert-butyl(trichloro)silane, respectively. These compounds have been used for the regioselective bis- and tris-functionalization of C60 under Bingel conditions. By changing the nature of the linker between the central Si atom and the reactive malonate groups, the malonate precursors have been optimized to produce specific bis- and tris-adducts with excellent regioselectivity. A complete understanding of the electronic and stereochemical factors governing the regioselectivity has been obtained by combining computational studies with a complete analysis of the by-products formed during the reactions of the Si-tethered tris-malonates with C60. Finally, desilylation reactions of the resulting fullerene bis- and tris-adducts have been carried out to generate the corresponding acyclic fullerene bis- and tris-adducts bearing alcohol functions. 相似文献