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91.
A new synthetic method of (+)-(1R)-acetyl-(7aR)-methyl-4-hydroinden-5-one (2) by highly enantioselective double Michael addition involving alkenylcopper-phosphine complex, 3-trimethylsilylbutenone and 2-methyl-2-cyclo-pentenone is presented. 相似文献
92.
Jiro Motoyoshiya Akira Takagi Kiyoichi Hirakawa Toshio Kakurai 《Journal of heterocyclic chemistry》1986,23(2):597-599
Several ketenimines bearing ester groups were prepared and their thermal reactions gave 2-alkoxy-3-substituted-4-quinolinols VIa-e via presumed iminoketene intermediates. Subsequent oxidation of 2-alkoxy-3-(3-methylbut-2-enyl)-4-quinolinols VIc and VId provided pyranoquinolines VIIIa and VIIIb. 相似文献
93.
This study provides conclusive proof that the thermally excited open-shell state with biradical character is contributing to the ground state of a closed-shell molecule, tF-BDPI-2Y, where four hydrogen atoms at the central phenylene ring are substituted with four fluorine atoms of 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene (BDPI-2Y). A small increase in the population of biradical species of tF-BDPI-2Y results in the formation of the dimer form by the radical recombination reaction. Controlling the equilibrium between a closed-shell diamagnetic-quinoid state and an open-shell paramagnetic-biradical state will provide significant progress in the field of pi-conjugated delocalized biradical chemistry. 相似文献
94.
Hideki Omichi Jiro Okamoto 《Journal of polymer science. Part A, Polymer chemistry》1982,20(6):1559-1568
Methyl α,β,β-trifluoroacrylate (MTFA) was grafted onto polyethylene (PE) film and fluorine-containing films to make ion-exchange membranes. In the case of PE the grafting yield was not influenced by the presence of trifluorotrichloroethane (Freon 113) in the reaction mixture, while the presence of methanol decreased the grafting yield. The transversal distribution of graft chains in the film observed by electron-probe x-ray microanalysis showed that when the grafting was carried out in the presence of Freon the amount of graft chains in the central part of PE film was much larger than that at the film surface and that the grafts obtained in the absence of Freon were located mainly at the film surface. The electric resistance of the graft PE film obtained in the presence of Freon decreased more than that of the one obtained in the absence of Freon. The weight loss of the graft films in H2O2 solution was negligibly small. 相似文献
95.
Masaaki Hirooka Hiroshi Yabuuchi Jiro Iseki Yasuto Nakai 《Journal of polymer science. Part A, Polymer chemistry》1968,6(5):1381-1396
A vinyl monomer that has the nitrile or carbonyl group conjugated to the C?C double bond, such as acrylonitrile, methyl acrylate, and methyl methacrylate, forms a complex with an alkylaluminum halide, and the complex reacts spontaneously with a hydrocarbon monomer such as styrene, propylene, or ethylene, giving a high molecular weight copolymer. The copolymers always contain the two monomer units in 1:1 ratio. Thus styrene, copolymerized with methyl acrylate or methyl methacrylate in the presence of ethylaluminum sesquichloride in homogeneous toluene solution, gives such an equimolar copolymer regardless of the initial monomer compositions. The NMR spectra of these copolymers are distinctly different from those of the equimolar copolymers obtained with azobisisobutyronitrile as initiator and have simpler and well separated patterns. The copolymers and the corresponding radical copolymers appear to be amorphous, judged by their x-ray diffraction patterns and their differential thermal analyses. Their infrared spectra resemble each other very closely. Hence, the difference in the NMR spectra may be ascribed to the matter of the sequence distribution. The infrared spectrum of ethylene–methyl acrylate copolymer shows no absorption near 720 cm.?1 due to the methylene sequence arising from ethylene–ethylene linkage. These experimental data lead to the inference that the equimolar copolymers obtained in this work may have an alternating sequence. 相似文献
96.
Yano Y Shimada K Okai J Goto K Matsumoto Y Ueoka R 《The Journal of organic chemistry》2003,68(4):1314-1318
The hydrolysis (deacylation) of enantiomeric substrates by the chemically modified enzymes decanoyl-alpha-chymotrypsin and decanoyl-trypsin was studied. Reaction activity for decanoyl-alpha-chymotrypsin was lower than that for the native enzyme, although intriguingly the enantioselectivity was markedly enhanced as compared with the native enzyme. In particular, the apparently complete enantioselective catalysis was attained for the hydrolytic cleavage of p-nitrophenyl N-dodecanoyl-D(L)-phenylalaninates. The enhancement of enantioselectivity, however, was not observed for decanoyl-trypsin. These results suggest that the chemically modified alpha-chymotrypsin by addition of hydrophobic groups has promoted enantioselectivity for the hydrolysis of hydrophobic esters. 相似文献
97.
Reduction of α-benzyloxy acetylenic ketones with zinc borohydride afforded the erythro-acetylenic vicinal diols in 95% stereoselectivity, while reduction with K-selectride gave the isomeric threo-diols in 90% stereoselectivity. 相似文献
98.
Pd(OAc)2 combined with phosphines catalyzes homolytic cleavage of the C—Cl bond of CCl4 and CCl3CO2CH3 leading to facile addition to olefins under mild conditions. BrCCl3 also reacts with olefins to give 1,1,1-trichloro-3-bromoalkanes. The reaction is accelerated under CO atmosphere, and the presence of bases such as NaOAc or K2CO3 is essential to attain high yields of the adducts. 相似文献
99.
Reaction of ethyl 2-(sulfonylmethyl)- or 2-(cyanomethyl)allyl carbonate with α,β-unsaturated esters or ketones in the presence of PD2(dba)3·.CHCl3-dppe catalyst gave highly functionalized cyclopentanes regio-selectively in good yields. 相似文献
100.
ESR and phosphorescence of phosphorescent triplet states of 4-phenylpyridine, 4,4′-bipyridine and their singly pretonated cations have been studied in methanol-water (4: 1 by volume) and in stretched poly(vinyl alcohol) films at 77 K. The stretched-film method is useful for ESR assignments of aromatic bases whose triplet states are influenced by pH. 相似文献