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51.
Matsumoto M Suzuki H Watanabe N Ijuin HK Tanaka J Tanaka C 《The Journal of organic chemistry》2011,76(12):5006-5017
Thermally stable rotamers of bicyclic dioxetanes bearing 6-hydroxynaphthalen-1-yl (anti-5a and syn-5a), 3-hydroxynaphthalen-1-yl (anti-5b and syn-5b), and 5-hydroxy-2-methylphenyl groups (anti-5c and syn-5c) were synthesized. These dioxetanes underwent TBAF (tetrabutylammonium fluoride)-induced decomposition accompanied by the emission of light in DMSO and in acetonitrile at 25 °C. For all three pairs of rotamers, the chemiluminescence efficiency Φ(CL) for anti-5 was 8-19 times higher than that for syn-5, and the rate of CTID (charge-transfer-induced decomposition) for anti-5 was faster than that for syn-5. The chemiluminescence spectra of the rotamers for 5a and 5c, respectively, were different. This discrepancy in the chemiluminescence spectra between rotamers can presumably be attributed to the difference in the structures of de novo keto imide anti-14 and syn-14 in an excited state, which inherit the structures of the corresponding intermediary anionic dioxetanes anti-13 and syn-13. The important difference in chemiluminescence efficiency between anti-5 and syn-5 is discussed from the viewpoint of a chemiexcitation mechanism for CTID of oxidophenyl-substituted dioxetane. 相似文献
52.
Hashimoto H Suzuki K Setaka W Kabuto C Kira M 《Journal of the American Chemical Society》2004,126(42):13628-13629
Novel disilene-iron complexes [(E)- (1E) and (Z)-(eta2-R3SiClSi=SiClSiR3)Fe(CO)4 (1Z), SiR3 = tBu2MeSi] were synthesized by the reaction of the corresponding tetrachlorodisilane with an excess amount of K2Fe(CO)4, and the structures of 1E and 1Z were determined by X-ray crystallography. These complexes constitute not only the first transition-metal complexes with E,Z-isomerism but also the first complexes with halogen-substituted disilene ligands. The initial formation of 1Z during the synthetic reaction and the slow one-way isomerization of 1Z to 1E are rationalized by the intervention of the corresponding silylene complex (R3SiCl2Si)(R3Si)Si=Fe(CO)4. 相似文献
53.
Enantiomeric purities of axially chiral biaryls with hydroxyl, amino, and carboxyl groups can be easily determined by pmr spectra using MTPA derivatives and shift reagent. 相似文献
54.
Absolute configurations of axially chiral biaryls with hydroxyl, amino, and carboxyl groups can be easily determined by pmr spectra using MTPA derivatives and shift reagents. 相似文献
55.
X-ray analysis of 9,10-diphenylbicyclo[6.2.0]decapentaene has revealed good planarity of the decapentaene nucleus, remarkably long bond length of the central bond, and appreciably small alternation of the peripheral bonds. It is thus concluded that is a pericyclic 10 π aromatic compound. 相似文献
56.
Sakaba H Yoshida M Kabuto C Kabuto K 《Journal of the American Chemical Society》2005,127(20):7276-7277
Reactions of (eta5-C5Me4R)(CO)2(MeCN)WMe (R = Me, Et) with HPh2SiCCtBu gave the novel alkynyl-bridged W-Si complexes, (eta5-C5Me4R)(CO)2W(mu-eta1:eta2-CCtBu)(SiPh2) (R = Me, Et), whose alkynyl ligands bridge the tungsten and silicon atoms in an eta1:eta2-coordination mode. The structures of these complexes were fully characterized, including X-ray crystallography. Treatment of (eta5-C5Me5)(CO)2W(mu-eta1:eta2-CCtBu)(SiPh2) with acetone resulted in acetone insertion into the silicon-alkynyl linkage followed by intramolecular C-H activation of the tBu group to give the chelate-type alkyl-alkene complex, (eta5-C5Me5)(CO)2W(eta1:eta2-CH2CMe2C=CHSiPh2OCMe2). 相似文献
57.
The substituent effect on the thermal denitrogenation mechanism of 7,7-disubstituted 2,3-diazabicyclo[2.2.1]hept-2-enes, concerted versus stepwise, has been investigated in detail. Unrestricted DFT calculations at the B3LYP/6-31G(d) level of theory suggest that azoalkanes that possess electron-withdrawing substituents at C(7) prefer to expel the nitrogen molecule in a stepwise manner. The activation energy is calculated to be ca. 36 kcal/mol for the dihydroxy-substituted azoalkane. In contrast, the preferred mechanism of the concerted denitrogenation is predicted for azoalkanes that possess electron-donating substituents at C(7). The activation energy is computed to be ca. 28 kcal/mol for the silyl-substituted azoalkane. The theoretical prediction of the substituent effects on the mechanistic change is supported by analyzing the activation parameters of the azoalkane decompositions. The activation enthalpy for the decomposition of the 7,7-diethoxy-substituted azoalkane is determined to be 39.1 kcal/mol, which is 13.1 kcal/mol higher in energy for the denitrogenation of the 7-silyl-substituted azoalkane. These dramatic substituent effects can be reasonably explained by the preferred electronic configuration of the lowest singlet state of the cyclopentane-1,3-diyls produced during the denitrogenation of the azoalkanes. 相似文献
58.
Sakaba H Watanabe S Kabuto C Kabuto K 《Journal of the American Chemical Society》2003,125(10):2842-2843
Reactions of cis-Cp*(CO)2W(MeCN)Me (1) with HSiMe2(CH=CR2) (R = H, Me) afford the novel eta3-1-silaallyl complexes Cp*(CO)2W(eta3-Me2SiCHCR2) [R = H (2), Me (3)] accompanied by liberation of MeCN and CH4 via thermal Si-H bond activation. eta3-Coordination and exo conformation of the 1-silaallyl ligand in 3 are shown by X-ray crystal analysis, which reveals the partial double bond character of the Si-C bond (1.800(4) A) in the silaallyl moiety. Complexes 2 and 3 show extremely high reactivity toward MeOH to give the hydrido-(methoxysilyl)alkene complex trans-Cp*(CO)2WH(eta2-MeOMe2SiCH=CH2) (4) and the four-membered metallacycle Cp*(CO)2WCH(CHMe2)SiMe2OMe (6), respectively. 相似文献
59.
Omata K Fujioka M Kabuto K Sasaki Y 《Chemical communications (Cambridge, England)》2008,(40):4903-4905
(1)H NMR analyses of individual alpha-amino acids in their mixture were simultaneously conducted in the presence of Sm-(pdta-d(8)) in water: high regularity, promising for direct simultaneous determination of absolute configurations of each alpha-amino acids in peptide hydrolysate mixtures, was observed between absolute configuration and the induced shifts. 相似文献
60.
Akio Kabuto Yuko Sakai Toru Yahata Eisuke Okazaki Mitsuru Satoh 《Colloid and polymer science》2008,286(5):535-543
A salt-induced physical gelation was found for the aqueous solution of poly(carboxylate)s having three kinds of hydroxyl groups,
i.e., primary, tertiary and one on a hemiacetal ring. The gelation point (critical salt concentration) was positively correlated
with the content of the hemiacetal component, while the previously confirmed hydrogen bond between the hemiacetal OH and –COO− group does not seem to essentially contribute to the physical gelation. Above a critical polymer concentration, the solution
viscosity was first decreased and then increased with increasing NaCl concentration, leading to gelation. However, below the
critical polymer concentration, the viscosity decreased. These different behaviors of the solution viscosity depending on
the polymer concentration were ascribed to a preferential promotion of intermolecular or intramolecular hydrogen bonds among
the hemiacetal OH groups above and below the critical polymer concentration, respectively. 相似文献