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131.
By the reaction of α-methylaldehydes with trimethylsilylethylidenetriarylphosphoranes the introduction of vinyl group is effected in highly Cram-selective manner. 相似文献
132.
Yoichi Habata Sachiko Yamada 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):17-20
The structure of the silver(I) triflate complex with N,N′,N″,N?-tetrakis-(3′,5′-difluorobenzyl)-1,4,8,11-tetraazacyclotetradecane is reported. The Ag+–π interaction between the Ag+ ion incorporated in the cyclam moiety and the aromatic side-arm was observed in solid and solution by X-ray crystallography and UV–VIS titration experiments, respectively. It is also revealed that the Ag+ complex is stable in gas phase from the FAB-MS. The energy of the Ag+–π interaction was estimated as about 30 kJ/mol by Hartree–Fock/3-21G(*) and DFT (B3LYP/3-21G(*)) calculations. The NBO analysis indicated that s donation is the main contribution to the Ag+–aromatic ring interaction. 相似文献
133.
Kitamura M Tsukamoto M Bessho Y Yoshimura M Kobs U Widhalm M Noyori R 《Journal of the American Chemical Society》2002,124(23):6649-6667
The mechanism of asymmetric hydrogenation of alpha-(acylamino)acrylic esters with Ru(CH(3)COO)(2)[(S)-binap] (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), giving the S saturated products in >90% ee, has been investigated by means of a kinetic study, deuterium labeling experiments, isotope effect measurements, and NMR and X-ray analysis of certain Ru complexes. The hydrogenation in methanol under a low H2 pressure proceeds via a monohydride-unsaturate mechanism that involves the initial RuH formation followed by a reaction with an olefinic substrate. The migratory insertion in the enamide-RuH chelate complex occurs reversibly and endergonically in an exo manner, giving a five-membered metallacycle intermediate. The cleavage of the Ru-C bond is achieved with either H2 (major) or CH3OH (minor). Both of the pathways result in overall cis hydrogenation products. The hydrogen at C3 is mainly from an H2 molecule, and the C2 hydrogen is from another H2 or protic CH3OH. The major S and minor R enantiomers are produced via the same mechanism involving diastereomeric intermediates. The turnover rate is limited by the step of hydrogenolysis of a half-hydrogenated metallacyclic intermediate. The participation of two different hydrogen donor molecules is in contrast to the pairwise dihydrogenation using a single H2 molecule in the RhI-catalyzed reaction which occurs via a dihydride mechanism. In addition, the sense of asymmetric induction is opposite to that observed with S-BINAP-RhI catalysts. The origin of this phenomenon is interpreted in terms of stereocomplementary models of the enamide/metal chelate complexes. A series of model stoichiometric reactions mimicking the catalytic steps has indicated that most NMR-observable Ru complexes are not directly involved in the catalytic hydrogenation but are reservoirs of real catalytic complexes or even side products that retard the reaction. 相似文献
134.
Dr. Masahito Yoshida Dr. Koya Saito Dr. Hikaru Kato Prof. Dr. Sachiko Tsukamoto Prof. Dr. Takayuki Doi 《Angewandte Chemie (International ed. in English)》2018,57(18):5147-5150
The total synthesis of siladenoserinol A, an inhibitor of the p53–Hdm2 interaction, has been achieved. AuCl3‐catalyzed hydroalkoxylation of an alkynoate derivative smoothly and regioselectively proceeded to afford a bicycloketal in excellent yield. A glycerophosphocholine moiety was successfully introduced through the Horner–Wadsworth–Emmons reaction using an originally developed phosphonoacetate derivative. Finally, removal of the acid‐labile protecting groups, followed by regioselective sulfamate formation of the serinol moiety afforded the desired siladenoserinol A, and benzoyl and desulfamated analogues were also successfully synthesized. Biological evaluation showed that the sulfamate is essential for biological activity, and modification of the acyl group on the bicycloketal can improve the inhibitory activity against the p53–Hdm2 interaction. 相似文献
135.
136.
Oseki Y Fujitsuka M Cho DW Sugimoto A Tojo S Majima T 《The journal of physical chemistry. B》2005,109(41):19257-19262
Photoinduced intramolecular charge separation (CS) and recombination (CR) processes of the tetrathiophene-substituted benzene dyads with an amide spacer (4T-PhR, R = 4-H (1), 4-CN (2), 3,4-(CN)2 (3), 4-NO2 (4), 3,5-(NO2)2 (5)) in solvents of different polarities were investigated using various fast spectroscopies. It was revealed that the CS rates depend on the ability of the acceptor and solvent polarity. Ultrafast CS with the rate of 5 x 10(12) s(-1) was revealed for 5 in PhCN and MeCN. The ultrafast CS can be attributed to the large electronic coupling matrix element between the donor and the acceptor despite the relative long donor-acceptor distance. The existence of the state with large electron density on the spacer between 14T*-PhR and LUMO should facilitate the CS process in the present dyad system. It was also revealed that the CR rates in these dyads were rather fast because of the enhanced superexchange interaction through the amide spacer. 相似文献
137.
Uenishi J Hamada M Aburatani S Matsui K Yonemitsu O Tsukube H 《The Journal of organic chemistry》2004,69(20):6781-6789
Stereospecific substitutions of optically pure 1-(pyridinyl)ethyl methanesulfonates with various amines are described. The reaction of (R)- or (S)-1-(2-pyridinyl)ethyl methanesulfonate with primary amines, including amino acid esters, gives N-substituted (S)- or (R)-1-(2-pyridinyl)ethylamines (4) with inversion of the configuration. Secondary cyclic amines are also reacted with (R)-2 to give the corresponding substituted amines (5) in excellent yields. Optically pure and meso triamine ligands having two pyridine rings, (S,S)-4f and meso-4f, (S,S)-9e, (S,R)-9e, and (S,S)-9f, have been prepared in stereochemically pure form by this method. Not only the substitution reaction of optically active 2 but also that of 1-(4-pyridinyl)ethyl and 1-(3-pyridinyl)ethyl methanesulfonates 11 and 14 take place stereospecifcally with inversion of the chiral center. 相似文献
138.
139.
Masayuki Ohmori Sachiko Yamada Hiroaki Takayama Kiyoshige Ochi 《Tetrahedron letters》1982,23(45):4709-4712
Novel stereoselective method to introduce side chain onto 17-oxosteroids has been deviced, and using the method cholesterol and 25-hydroxycholesterol are synthesized. 相似文献
140.
Summary A manual method for predicting the detection ranges of fluorescent compounds for the HPLC-peroxyoxalate chemiluminescence
detection system is presented utilizing bis(4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl) oxalate (TDPO) as a chemilumigenic
reagent. The generated chemiluminescence decay curves were measured on a photomultiplier and extrapolated to zero time based
on the first part of the decay curve. Dipyridamole, perylene, DNS-Ser, Rose Bengal, DNS-Asp, Trp-P-1, pyrencarboxylic acid
methyl ester, perfenazine, alimemazine, oxypertine, Glu-P-2, benzydamine and doxorubicin gave chemiluminescence intensity
(Icl) values of 3.2 × 106, 2.8 × 106, 2.3 × 105, 2.1 × 105, 1.9 × 105, 1.4 × 105, 9.4 × 103, 6.2 × 103, 4.2 × 103, 3.3 × 103, 2.3 × 103, 9.7 × 102 and 3.1 × 102, respectively. The reaction conditions for the HPLC-CL detection system were investigated and optimum conditions obtained. 相似文献