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排序方式: 共有120条查询结果,搜索用时 15 毫秒
111.
The reactions between [M(NO){HB(3,5-Me2C3HN2)3}X2] (M = Mo, X = Cl, Br, I; M = W, X = Cl) and the monosaccharides 2,3:4,5-di-O-iso-propylidene-β-
-fructopyranose, 2,3:5,6-di-O-isopropylidene--
-mannofuranose, methyl--
-glucopyranoside and
-(+)-mannofuranose have been investigated and the complexes [M(NO){HB(3,5- Me2C3HN2)3}X(OR)] (M = Mo, X = Cl, Br, I; M = W, X = Cl; ROH = 2,3:4,5-di-O- isopropylidene-β-
-fructopyranose) have been isolated as mixtures of diastereoisomers. 相似文献
112.
Noncoordinating solvents permit the halogen-metal exchange-induced formation of benzyne (aryne) from di- and trihalobenzene precursors in the presence of cyclopentadiene to give 1,4-dihydro-1,4-methano-naphthalenes. Studies with mixed halide precursors and nonacidic Diels-Alder diene traps reveal that ethereal and hydrocarbon solvents influence the halide leaving group facility, resulting in a reversal of 3-halobenzyne regioselectivity. 相似文献
113.
Badyal JP Cameron AM Cameron NR Coe DM Cox R Davis BG Oates LJ Oye G Spanos C Steel PG 《Chemical communications (Cambridge, England)》2004,(12):1402-1403
Plasmachemical surface modification of porous polystyrene beads with allylamine or diaminopropane provides reactive amine functionality exclusively at accessible surface sites, allowing faster reactions than classically prepared materials. 相似文献
114.
Anthony I. Day Rodney J. Blanch Andrew Coe Alan P. Arnold 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(3-4):247-250
The synthesis of new cryptands containing 1-methyl or 1-hexadecyl-pyrazole is described in high yield using metal templated [3+2] tripodal condensation. 相似文献
115.
116.
Coe JW 《Organic letters》2000,2(26):4205-4208
[reaction:see text] A synthesis of racemic cytisine 1 has been developed utilizing an intramolecular Heck cyclization to prepare the bridged tricyclic intermediate 2. The cyclization employs activated glutarimide-derived ketene aminals 3 (X = P(O)OEt(2) or SO(2)CF(3)) and represents the first use of such intermediates in metal-catalyzed processes. 相似文献
117.
Boubekeur-Lecaque L Coe BJ Harris JA Helliwell M Asselberghs I Clays K Foerier S Verbiest T 《Inorganic chemistry》2011,50(24):12886-12899
Nine nonlinear optical (NLO) chromophores with pyridinium electron acceptors have been synthesized by complexing new proligands with {Ru(II)(NH(3))(5)}(2+) electron-donor centers. The presence of long alkyl/fluoroalkyl chain substituents imparts amphiphilic properties, and these cationic complexes have been characterized as their PF(6)(-) salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Each complex shows three reversible/quasireversible redox processes; a Ru(III/II) oxidation and two ligand-based reductions. The energies of the intense visible d → π* metal-to-ligand charge-transfer (MLCT) absorptions correlate to some extent with the ligand reduction potentials. (1)H NMR spectroscopy also provides insights into the relative electron-withdrawing strengths of the new ligands. Single crystal X-ray structures have been determined for two of the proligand salts and one complex salt, [Ru(II)(NH(3))(5)(4-C(16)H(33)PhQ(+))]Cl(3)·3.25H(2)O (PhQ(+) = N-phenyl-4,4'-bipyridinium), showing centrosymmetric packing structures in each case. The PF(6)(-) analogue of the latter complex has been used to deposit reproducibly high-quality, multilayered Langmuir-Blodgett (LB) thin films. These films show a strong second harmonic generation (SHG) response from a 1064 nm laser; their MLCT absorbance increases linearly with the number of layers (N) and I(2ω)/I(ω)(2) (I(2ω) = intensity at 532 nm; I(ω) = intensity at 1064 nm) scales quadratically with N, consistent with homogeneous deposition. LB films on indium tin oxide (ITO)-coated glass show electrochemically induced switching of the SHG response, with a decrease in activity of about 50% on Ru(II) → Ru(III) oxidation. This effect is reversible, but reproducible over only a few cycles before the signal from the Ru(II) species diminishes. This work extrapolates our original solution studies (Coe, B. J. et al. Angew. Chem., Int. Ed.1999, 38, 366) to the first demonstration of redox-switching of NLO activity in a molecular material. 相似文献
118.
EI Balmond DM Coe MC Galan EM McGarrigle 《Angewandte Chemie (International ed. in English)》2012,51(36):9152-9155
Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety. The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism. 相似文献
119.
The photoelectron spectra of (H2O)(n = 2-69) - and (D2O)(n = 2-23) - are presented, and their spectral line shapes are analyzed in detail. This analysis revealed the presence of three different groupings of species, each of which are seen over the range, n = 11-16. These three groups are designated as dipole boundlike states, seen from n = 2-16, intermediate states, found from n = 6-16, and bulk embryonts, starting at n = 11 and continuing up through the largest sizes studied. Almost two decades ago [J. V. Coe et al., J. Chem. Phys. 92, 3980 (1990)], before the present comprehensive analysis, we concluded that the latter category of species were embryonic hydrated electrons with internalizing excess electrons (thus the term embryonts). Recent experiments with colder expansion (high stagnation chamber pressures) conditions by Neumark and coworkers [J. R. R. Verlet et al., Science 307, 93 (2005)] have also found three groups of isomers including the long-sought-after surface states of large water cluster anions. This work confirms that the species here designated as embryonts are in the process of internalizing the excess electron states as the cluster size increases (for n > or = 11). 相似文献
120.
Daniel Lin Matthew Coe Vinayak Krishnamurti Xanath Ispizua-Rodriguez G. K. Surya Prakash 《Chemical record (New York, N.Y.)》2023,23(9):e202300104
In the last few years, many reagents and protocols have been developed to allow for the efficient fluorofunctionalization of a diverse set of scaffolds ranging from alkanes, alkenes, alkynes, and (hetero)arenes. The concomitant rise of organofluorine chemistry and visible light-mediated synthesis have synergistically expanded the fields and have mutually benefitted from developments in both fields. In this context, visible light driven formations of radicals containing fluorine have been a major focus for the discovery of new bioactive compounds. This review details the recent advances and progress made in visible light-mediated fluoroalkylation and heteroatom centered radical generation. 相似文献