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91.
Asaumi T Matsuo T Fukuyama T Ie Y Kakiuchi F Chatani N 《The Journal of organic chemistry》2004,69(13):4433-4440
The direct carbonylation of C-H bonds in the benzene ring of N-phenylpyrazoles via catalysis by ruthenium or rhodium complexes is described. The reaction of N-phenylpyrazoles with carbon monoxide and ethylene in the presence of Ru(3)(CO)(12) or Rh(4)(CO)(12) resulted in the site-selective carbonylation of the ortho C-H bonds in the benzene ring to give the corresponding ethyl ketones. A variety of functional groups on the benzene ring can be tolerated. N-Phenylpyrazoles have higher reactivities than would be expected, based on the pK(a) values of the conjugate acid of pyrazole. The choice of solvent for this reaction is significant, and N, N-dimethylacetamide (DMA) gives the best result. 相似文献
92.
Tojino M Otsuka N Fukuyama T Matsubara H Schiesser CH Kuriyama H Miyazato H Minakata S Komatsu M Ryu I 《Organic & biomolecular chemistry》2003,1(23):4262-4267
Free-radical mediated cyclizative carbonylations of azaenynes were carried out using TTMSS as a radical mediator to compare the efficiency and the stereochemistry with those using tributyltin hydride. Using a substrate concentration of 0.1 M, the reactions gave good yields of alpha-silylmethylene lactams having four to seven-membered rings. The observed E-diastereoselectivity of the resulting vinylsilane moiety is in sharp contrast to the Z-selectivity observed during the analogous carbonylation using tributyltin hydride. When hexanethiol was used as the radical mediator, alpha-thiomethylene lactams were formed with E-favoring stereoselectivity again. Ab initio and DFT molecular orbital calculations on the stability of E and Z products were carried out for a set of five-membered methylene lactams bearing SnH3, SiH3, and SMe groups. The distinct thermodynamic preference for the Z-isomer was only predicted for the Sn-bearing lactam. A steric effect due to the bulky (TMS)3Si group is proposed for the E-selectivity observed in the TTMSS-mediated reaction. 相似文献
93.
Omura S Fukuyama T Horiguchi J Murakami Y Ryu I 《Journal of the American Chemical Society》2008,130(43):14094-14095
An efficient cross-addition reaction of dienes with aldehydes was developed by using RuHCl(CO)(PPh3)3 as a catalyst to give a wide variety of beta,gamma-unsaturated ketones, where a pi-allylruthenium species, derived from hydroruthenation of diene, may be involved as a key intermediate. 相似文献
94.
Rahman AF Bhattacharya S Peng X Kimura T Komatsu N 《Chemical communications (Cambridge, England)》2008,(10):1196-1198
In spite of having small pi-conjugation systems, azulenes show large binding constants (10(4)-10(5)) to C(60) and C(70), which are larger than those of monoporphyrins and alternant aromatic hydrocarbons. 相似文献
95.
Takahide Kimura Takashi Ando Tetsushi Maruyama Takashi Sugiyama Atsuyoshi Ohno Mutsuo Okamura 《Heteroatom Chemistry》1995,6(1):57-62
Complexation of lanthanoid metal ions with 1,2-bis(o-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid and its two derivatives, in which the distance between the chelating functions is changed, has been studied by potentiometric pH titration. There are two complexation modes depending on the size of the metal ion. Structural flexibility of the chelator accounts for the change in the complexation mode. 相似文献
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Coupling‐Reagent‐Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids
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Dr. Shinya Furukawa Prof. Takahide Fukuyama Akihiro Matsui Mai Kuratsu Ryotaro Nakaya Takashi Ineyama Hiroshi Ueda Prof. Ilhyong Ryu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):11980-11983
A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl‐glycyl‐glycine, present in IMREG‐1, also. 相似文献
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