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排序方式: 共有119条查询结果,搜索用时 15 毫秒
1.
Armstrong A Ahmed G Dominguez-Fernandez B Hayter BR Wailes JS 《The Journal of organic chemistry》2002,67(24):8610-8617
Several alpha-substituted N-carbethoxytropinones have been evaluated as catalysts for asymmetric epoxidation of alkenes with Oxone, via a dioxirane intermediate. alpha-Fluoro-N-carbethoxytropinone (2) has been studied in detail and is an efficient catalyst which does not suffer from Baeyer-Villiger decomposition and can be used in relatively low loadings. This ketone was prepared in enantiomerically pure form using chiral base desymmetrization of N-carbethoxytropinone. Asymmetric epoxidation catalyzed by 2 affords epoxides with up to 83% ee. Among other derivatives tested, the alpha-acetoxy derivative 7 affords the highest enantioselectivities. 相似文献
2.
L. I. Belen’kii A. V. Kolotaev V. Z. Shirinyan M. M. Krayushkin Yu. P. Strokach T. M. Valova Z. O. Golotyuk V. A. Barachevskii 《Chemistry of Heterocyclic Compounds》2005,41(1):86-92
The polar [4+2] cycloaddition reaction of 1,2-bis(2,5-dimethyl-3-thienyl)acetylene with thiobenzamide and certain aldehydes of the thiophene and furan series catalyzed by boron trifluoride etherate gives the corresponding 4-hetaryl-5,6-di(2,5-dimethyl-3-thienyl)-2-phenyl-4H-1,3-thiazines. The photochromic properties of the products have been studied.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 100–106, January, 2005. 相似文献
3.
Paired electrosynthesis of cyanoacetic acid 总被引:1,自引:0,他引:1
Batanero B Barba F Sánchez-Sánchez CM Aldaz A 《The Journal of organic chemistry》2004,69(7):2423-2426
Cyanoacetic acid is formed by cathodic reduction of CO(2) and anodic oxidation of the tetraalkylammonium salt anion; the process is conduced in acetonitrile using a divided cell with a medium porosity glass-frit diaphragm. A mechanism for this paired electrochemical reaction is proposed. 相似文献
4.
Cathodic reduction of phenacyl bromides N-acyl hydrazones lead to dimeric 1,4-diaryl-1,4-butanedione di-N-acylhydrazones, which give the corresponding 1-N-acylamino-2,5-diarylpyrroles in good yields. 相似文献
5.
Najwa Sbei Belen Batanero Fructuoso Barba Beya Haouas Mohamed Lamine Benkhoud Isidoro Barba 《Tetrahedron》2018,74(16):2068-2072
A new series of 3,4-disubstituted quinazolin-2-ones, with potential T-type calcium channel antagonist activity, and new 4-methylene-quinazolin-2-ones, promising catalysts as N-heterocyclic olefins, have been prepared in good yield by a simple reaction between 2-aminobenzophenone, or 2-aminoacetophenone, and cyanomethyl anion electrogenerated by acetonitrile reduction at a graphite electrode, followed by the addition of different organic isocyanates and subsequent heterocyclization. 相似文献
6.
Covalent Grafting of Coordination Polymers on Surfaces: The Case of Hybrid Valence Tautomeric Interphases 下载免费PDF全文
Pablo González‐Monje Dr. Fernando Novio Dr. Daniel Ruiz‐Molina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10094-10099
We have developed a novel approach for grafting coordination polymers, structured as nanoparticles bearing surface reactive carboxylic groups, to amino‐functionalized surfaces through a simple carbodiimide‐mediated coupling reaction. As a proof‐of‐concept to validate our approach, and on the quest for novel hybrid interphases with potential technological applications, we have used valence tautomeric nanoparticles exhibiting spin transition at or around room temperature. SEM and AFM characterization reveal that the nanoparticles were organized chiefly into a single monolayer while X‐ray photoelectron spectroscopy (XPS) measurements confirm that the nanoparticles retain a temperature‐induced electronic redistribution upon surface anchorage. Our results represent an effective approach towards the challenging manufacture of coordination polymers. 相似文献
7.
Cycloaddition reactions between 2-vinylthiophen and the dienophiles maleic anhydride, dimethyl acetylenedicarboxylate,' methyl propiolate, and methyl acrylate, are reported. Products include simple benzo[b]thiophen carboxylates (6, 13, 17) and reduced derivatives (3, 4, 18). The acetylenic dienophiles also gave a dihydrobenzthienyl-acrylate (16) or -fumarate (11), and the dithienylcyclohexene esters (7) and (14). 相似文献
8.
In terms of the density functional theory (DFT) using B3LYP/6-31G(d) method with full geometry optimization, gas-phase quantum chemical calculations were performed for ??-complexes formed upon the attack of electrophiles E (E = H+, Me+, Me3Si+, Br+, NO2 +, MeCO+, SO3) on ??- and ??-positions of furan, thiophene, selenophene, pyrrole, and N-substituted pyrroles (NR-pyrroles, R = Me, But, SiMe3, SiPri 3, C6H4NO2-p, SO2Ph, CHO, COOMe) and for respective ??- and ??-substituted electrophilic substitution products. The energy differences between the ??- and ??-isomers of the ??-complexes characterize the preferred direction of the electrophilic attack, while the energy differences between the isomeric products make it possible to estimate the energy preference of a particular product. An analysis of the results obtained demonstrates the effect of the structure of heterocycle, the nature of electrophile, and thermodynamic and steric factors on the positional selectivity (??/?? ratio) in electrophilic substitution reactions of ??-electron rich five-membered heteroaromatics. 相似文献
9.
Krayushkin M. M. Shirinian V. Z. Belen"kii L. I. Shadronov A. Yu. Vorontsova L. G. Starikova Z. A. 《Russian Chemical Bulletin》2002,51(8):1510-1514
The conditions for acylation of 2,5-dimethylthiophene with squaric acid dichloride were optimized, and 3,4-bis(2,5-dimethylthiophen-3-yl)cyclobut-3-ene-1,2-dione was obtained in good yield. X-ray diffraction analysis demonstrated that the by-product has the structure of 1a,1b-dichloro-5-(2,5-dimethylthiophen-3-yl)-3-hydroxy-4,5a-dimethyl-1b,4a,5,5a-tetrahydro-1aH-1-thiacyclopropa[a]pentalen-2-one. 相似文献
10.
Lamoureux M Patard L Hernandez B Couesnon T Santini GP Cognet JA Gouyette C Cordier C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(1):84-94
Successive investigations over the last decade have revealed and confirmed a stable loop closure in a family of d-[GTAC-5Pur6N7N-GTAC] hairpins, where 5Pur6N7N is a AAA, GAG and AXC loop (X being any nucleotide). The trinucleotide loop is characterized by a well defined 5Pur-7N mispairing mode, and by upfield chemical shifts for three sugar protons of the apical nucleotide 6N. The GTTC-ACA-GAAC DNA hairpin, of interest for its likely involvement in Vibrio cholerae genome mutations, has now been investigated. The GTAC-ACA-GTAC DNA hairpin has also been studied because it is intermediate between the other structures, as it contains the loop of the hairpin under consideration and the stem of the above family. The two hairpins with the ACA loop are stable. They show the same mispairing mode and similar upfield shifts as the previous family, but GTTC-ACA-GAAC seems to be slightly less compact than any other. GTTC-ACA-GAAC is remarkable in that it exhibits a B(II) character for the phosphate-ester conformation at 8Gp9A, together with a swing of the upper hairpin into the major groove that, in particular, brings 6CH1' roughly as close to 7AH2 as to 6CH6. These unexpected structural features are qualitatively deduced from (1)H and (31)P NMR spectra, and confirmed by Raman spectroscopy. This comparative study shows that not only the loop sequence but also the stem sequence may control hairpin structures. 相似文献