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391.
The synthesis of 4-(N-methylpyridinium) t-butyl nitrone (4-MePyBN) and its use as a spin trap for superoxide radicals produced in aqueous solutions is reported (aN= 13.78 G, aHß= 1.65 G, and g = 2.0091). The half-life of the spin adduct as a function of pH (83 s at pH 5.5, 78 s at pH 7.0, and 65 s at pH 8.0) the effects of iron salts, diethylenetriaminepentacetic acid (DETAPAC), and superoxide dismutase were examined, and comparisons made between 4-MePyBN and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as spin trapping agents for the superoxide radical. 相似文献
392.
A. Paul Krapcho Cynthia E. Gallagher Abdelhakim Hammach Miles P. Hacker Ernesto Menta Ambrogio Oliva Roberto Di Domenico Giovanni Da Re Andrea Lotto Silvano Spinelli 《Journal of heterocyclic chemistry》1998,35(4):895-906
Synthetic routes have been developed which lead to ring-hydroxylated aza-analogues of antitumor anthrapyrazoles, namely, 2,5-bis[(aminoalkyI)amino] substituted 10-hydroxymdazolo[3,4-fg]isoquinolin-6(2H)-ones 1 and 7-hydroxyindazolo[4,3-gh]isoquinolin-6(2H)-ones 2 . The regiospecific synthesis of 6,9-dihalo-4-hydroxybenz[g]isoquinolines 3 and 4 has been accomplished. Intermediate 3 was constructed in a multistep process involving Diels-Alder chemistry of benzoylacrylates whereas 4 was assembled using Ni(II) mediated coupling of methyl 3-chloro-5-methoxyisonicotinate ( 15b ) with the organic zinc reagent 18 derived from 2-fluoro-5-chlorobenzyl bromide ( 17 ). After protection of the hydroxy group with a p-methoxybenzyl moiety, the different nucleofugacities of the leaving groups present in 10 and 20 allowed sequential displacements by substituted hydrazines and amines, respectively, to lead to the desired p-methoxybenzyl protected analogues 12 and 22 . Deprotection led to the side arm modified compounds 1 and 2 . The displacements of 21a and 21b with N,N-dimethylethylenediamine also led to the tri[(aminoalkyl)amino]substituted analogues 23a and 23b , respectively, which arose from further SNAr substitutions of the p-methoxybenzyloxy group. 相似文献
393.
Davies SG Garner AC Long MJ Morrison RM Roberts PM Savory ED Smith AD Sweet MJ Withey JM 《Organic & biomolecular chemistry》2005,3(15):2762-2775
Conjugate addition of lithium dibenzylamide to methyl 5-isopropyl, 5-phenyl- and 5-tert-butyl-cyclopentene-1-carboxylates occurs with high levels of substrate control (>88% de), with preferential addition to the face of the cyclic alpha,beta-unsaturated acceptor anti- to the stereodirecting 5-alkyl substituent. Treatment of a range of methyl (+/-)-5-alkyl-cyclopentene-1-carboxylates with both lithium (+/-)-N-benzyl-N-alpha-methylbenzylamide and lithium (+/-)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide indicates significant enantiorecognition in their mutual kinetic resolutions, with preferential addition anti- to the 5-alkyl substituent, giving the 1,2-syn-1,5-anti-arrangement (E >16) after enolate protonation anti- to the amino functionality. The kinetic resolution of a range of methyl (+/-)-5-alkyl-cyclopentene-1-carboxylates with lithium (S)-N-benzyl-N-alpha-methylbenzylamide, and their efficient parallel kinetic resolution with a pseudoenantiomeric mixture of lithium (S)-N-benzyl-N-alpha-methylbenzylamide and lithium (R)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide are also demonstrated, giving a range of 5-alkyl-cispentacin derivatives in >98% de and high ee after N-deprotection. 相似文献
394.
Thomas J. Schwan Nelson J. Miles James L. Butterfield 《Journal of heterocyclic chemistry》1976,13(5):973-976
2,4-Diphenyl-5-pyrimidinyl methyl ketone ( 8 ) and 2-phenyl-4-methyl-5-pyrimidinyl phenyl ketone ( 12 ) were prepared by condensation of benzamidine with 2-ethoxymethyl-1-phenyl-1,3-butanedione ( 10 ). Their structures were elucidated by the nmr spectra of their derivative alcohols 13 and 14 , respectively. The ketone 8 was converted by way of the bromoketone 15 to 2-[1-methylethylamino]-1-[2,4-diphenyl-5-pyrimidinyl]ethanol hydrochloride ( 17 ) and 2-amino-1-[2,4-diphenyl-5-pyrimidinyl]ethanol hydrochloride ( 20 ). Pharmacologic testing indicated that 17 and 20 did not possess either antihypertensive or beta adrenergic blocking activities. 相似文献
395.
396.
George C. Wright Thomas J. Schwan Nelson J. Miles 《Journal of heterocyclic chemistry》1974,11(6):849-851
The compound 5,6-dihydro-8-hydroxy-9-methoxy-1H,7H-benzo[ij]quinolizine-1,7-dione ( 4a ) was synthesized from 3-(1,4-dihydro-6,7-dimethoxy-4-oxo-1-quinolyl)propionic acid ( 3a , free base), involving spontaneous demethylation with ring closure. The structural assignment of 4a was based on an analogous, unequivocal synthesis of 5,6-dihydro-9-ethoxy-8-hydroxy-1H,7H-benzo[ij]quinolizine-1,7-dione hydrochloride ( 4b ). 相似文献
397.
Pratt LM Newman A Cyr JS Johnson H Miles B Lattier A Austin E Henderson S Hershey B Lin M Balamraju Y Sammonds L Cheramie J Karnes J Hymel E Woodford B Carter C 《The Journal of organic chemistry》2003,68(16):6387-6391
The effects of lithium dialkylamide structure, mixed aggregate formation, and solvation on the stereoselectivity of ketone enolization were examined. Of the lithium dialkylamides examined, lithium tetramethylpiperidide (LiTMP) in THF resulted in the best enolization selectivity. The stereoselectivity was further improved in the presence of a LiTMP-butyllithium mixed aggregate. The use of less polar solvents reduced the enolization stereoselectivity. Ab initio calculations predict LDA and LiTMP to form mixed cyclic dimers in ethereal solvents. The calculations also predict LiTMP-alkyllithium mixed aggregates to competitively inhibit the formation of less stereoselective LiTMP-lithium enolate mixed aggregates. 相似文献
398.
K. K. Luk M. L. Miles L. H. Bowen 《Journal of Radioanalytical and Nuclear Chemistry》1984,82(2):255-262
Precipitate formation between phosphotungstic acid and crown ethers is a general phenomenon, producing solids with selective ion exchange behavior for the alkali metal ions. Distribution coefficients for Li+, Na+, K+, and Cs+ were measured for a series of these precipitates with different crown ethers. The sorption data are more complicated than for the corresponding phosphomolybdates and indicate a variability in the number of exchangeable sites with H+ and M+ concentration. The crown ether used markedly affects the cation selectivity of the phosphotungstate precipitates. 相似文献
399.
400.