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61.
The new organic–inorganic salt, 2,3-diaminopyridinium selenate, has been synthesized and characterized by means of single-crystal X-ray crystallography, FT-IR and FT-Raman spectroscopy. A diprotonated organic ligand, H21,3L2+, existing in the crystal structure was theoretically shown to be the most stable cationic species of 2,3-diaminopyridine. The weak non-covalent forces of N–H?O type between the hydrogen atoms of the amino and ammonio groups of 2,3-diaminopyridinium cation and oxygen atoms of tetrahedral selenate anions determine three-dimensional arrangement with complex network of intermolecular interactions of hydrogen bond type (donor–acceptor distances from 2.697(3) Å to 3.088(3) Å). Vibrational spectra have been discussed in comparison with X-ray results. Juxtaposition of spectra of the complex with the pure organic ligand and deuterated analogue of the title compound allowed to give reliable assignments of most observed vibrational bands. Presented data can be useful in elucidation of molecular mechanism of uptake of tetrahedral SeO42− anion by the living organisms. 相似文献
62.
Roman Mazurkiewicz Beata Fryczkowska Rafał Gabański Roman Luboradzki Andrzej Włochowicz Wojciech Mól 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2589-2598
A reaction of g -carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown g -( N -acylamino)vinylphosphonium salts. The same product can be obtained using the N-monosubtituted amide/Ph 3 PBr 2 /Et 3 N system instead of imidoyl halide. The key step of the reaction probably involves an intramolecular [1,3] O-to-N migration of the vinyl group, converting the primary O -imidoylation product into g -( N -acylamino)vinylphosphonium salt. 相似文献
63.
Zhiming Zhao 《Tetrahedron》2005,61(37):8888-8894
A recently developed strategy for polyhydroxylated indolizidine ring construction has been applied to the synthesis of (+)-castanospermine and possible isomers of uniflorine-A. The routes to these targets rely on the use of the earlier discovered photocyclization reaction of pyridinium perchlorate in a concise route for preparation of a key N-allylacetamidocyclopentendiol intermediate. Ring rearrangement metathesis of this substance gives an allyl-tetrahydropyridine, which is then transformed to the targets by execution of regio- and stereo-controlled hydroxylation processes followed by indolizidine ring construction. 相似文献
64.
Vladimir V. Shevchenko Natalya G. Zhegalova Andey O. Borzenko Valerij A. Nikolaev 《Helvetica chimica acta》2008,91(3):501-509
The efficiency and validity of different chemical substrates for trapping bis(methoxycarbonyl)carbene (=2‐methoxy‐1‐(methoxycarbonyl)‐2‐oxoethylidene; 1 ) is dependent on the conditions of carbene generation. On conventional photolysis of dimethyldiazomalonate (=2‐diazopropanedioic acid dimethyl ester; 2 ) by long‐wave UV light (through a Pyrex filter, λ>290 nm), the most powerful trap for carbene 1 in the series of substrates Me2S, MeOH, cyclohexane, and pyridine is Me2S (with an efficiency ratio of ca. 6 : 4 : 2 : 1, resp.). When short‐wave decomposition of diazomalonate 2 is employed (through a quartz filter, λ>210 nm), more reliable and useful chemical traps for bis(methoxycarbonyl)carbene ( 1 ) are pyridine and cyclohexane, whose adducts with 1 are rather stable under short‐wave‐irradiation conditions. Application of alcohols for the trapping of 1 proves to be preferential when simultaneous monitoring of carbene and oxoketene formation during photolysis is necessary. 相似文献
65.
M. Z. Kassaee Hassan Masrouri Farnaz Movahedi Tayyebeh Partovi 《Helvetica chimica acta》2008,91(2):227-231
A convenient one‐pot four‐component synthesis of tetrasubstituted pyrroles was carried out through the reaction of butane‐2,3‐dione with α‐aminophosphorous ylides, obtained in situ from the 1 : 1 : 1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylate, and ammonium acetate. 相似文献
66.
Wolfgang Pfleiderer 《Helvetica chimica acta》2008,91(2):338-353
A variety of pyrimidine precursors 12 – 25 were converted into a series of new 7‐hydroxylumazines (=7‐hydroxypteridine‐2,4(1H,3H)‐diones) 26 – 35 which functioned as starting materials for the transformation into the corresponding 7‐chlorolumazines 36 – 45 . Subsequent reaction with hydrazine led to the 7‐hydrazinolumazines 46 – 55 which gave on nitrosation the 7‐azidolumazines 1 and 56 – 64 . These compounds were subjected to short heating in xylene whereby 1 and 56 – 61 showed a new pteridine–purine interconversion in forming a new type of 1,3‐disubstituted or 3‐substituted xanthin‐8‐amine‐derived nitrilium ylides (2,3,6,7‐tetrahydro‐N‐methylidyne‐2,6‐dioxo‐1H‐purin‐8‐aminium ylides) 11 and 65 – 70 . The presence of an additional 6‐alkyl substituent in the 7‐azidolumazines 63 and 64 or of an unsubstituted N(3) position in 62 caused further rearrangement to xanthine‐9‐carbonitriles 71 – 73 . Prolonged heating of 7‐azido‐1,3‐dimethyllumazine ( 1 ) also afforded theophylline‐9‐carbonitrile (=1,2,3,6‐tetrahydro‐1,3‐dimethyl‐2,6‐dioxo‐9H‐purine‐9‐carbonitrile; 5 ). The nitrilium ylide function was established by NMR and UV spectra as well as by elemental analyses. Confirmation of the nitrilium ylide structures was suggested by the result of the heating of 1,3‐dimethyl‐N‐methylidynexanthin‐8‐aminium ylide 11 in EtOH or of 1 in pentan‐1‐ol leading to 8‐aminotheophylline (=8‐amino‐3,7‐dihydro‐1,3‐dimethyl‐1H‐purin‐2,6‐dione; 74 ). 相似文献
67.
The RhII‐catalyzed cycloaddition cascade of an indolyl‐substituted α‐diazo imide was used for the total synthesis of the complex pentacyclic alkaloid (±)‐aspidophytine. Treatment of the resulting dipolar cycloadduct with BF3?OEt2 induces a domino fragmentation cascade. The reaction proceeds by an initial cleavage of the oxabicyclic ring and formation of a transient N‐acyl iminium ion which reacts further with the adjacent tert‐butyl ester and sets the required lactone ring present in aspidophytine. A three‐step sequence was then used to remove both the ester and OH groups. Subsequent functional group manipulations allowed for the high‐yielding conversion to (±)‐aspidophytine. 相似文献
68.
Dmytro Poliakov 《Tetrahedron letters》2007,48(38):6798-6800
Carbene-nitrile ylide 2 undergoes an unusual non-symmetrical dimerization catalyzed by stable bis(diisopropylamino)carbene. 相似文献
69.
Liviu Birzan Mihaela Cristea Constantin C. Draghici Victorita Tecuceanu Anamaria Hanganu Eleonora-Mihaela Ungureanu Alexandru C. Razus 《Tetrahedron》2017,73(17):2488-2500
The synthesis of pyrylium and pyridinium salts and pyridines with azulene-1-yl moieties in position 4 and two 2-heteroarylvinyl groups in positions 2 and 6 was accomplished. The pyrylium salts were obtained starting from pyranones and pyridines could be prepared from these salts by treating them with ammonium acetate. The general procedures for the synthesis of pyridinium salts, which occur with good results in less delocalized electronic systems, do not take place when applied to the above obtained pyrylium salts. Therefore, as starting material 4-(azulen-1-yl)-1-(n-butyl)-2,6-dimethylpyridinium perchlorate was used, which was condensed with heteroarylcarboxaldehydes. These compounds were completely characterized and some of their spectra were discussed. Their interaction with some metal ions was revealed, observing an affinity better than in the case of simple azulenepyridines. In the last part of the paper are presented redox potentials for several pyrylium salts and pyridines in comparison with those of the nonvinylogated derivatives. 相似文献
70.
Dihetaryl thioketones react with thiocarbonyl ylides to give 1,3‐dithiolanes in high yields. No competitive side reactions of the thiocarbonyl ylides were observed, evidencing the ‘superdipolarophilic’ character of this less‐known group of thioketones. Depending on the type of substituents present in both the thiocarbonyl ylide and the thioketone, formal [3+2] cycloadditions occur with complete regioselectivity or with formation of a mixture of both regioisomers. Regioselective formation of the sterically more crowded 1,3‐dithiolanes is explained via a mechanism involving stabilized 1,5‐biradicals. In systems with less‐efficient radical stabilization, e.g., in the case of adamantanethione S‐methanide, substantial violation of the regioselectivity was observed as a result of steric hindrance. 相似文献