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951.
The efficient total synthesis of karrikinolide (KAR1), a potent plant growth regulator discovered in smoke from burning plant material, is described. 3-Hydroxy-4-pyranone, prepared from d-xylose, was subjected to a Cu(II)-catalyzed transesterification-Wittig lactonization to afford the dihydrofuropyran in good yield. Finally, radical bromination, followed by olefin formation, provided KAR1 in acceptable yield. 相似文献
952.
953.
954.
Nam‐Ho You Tomoya Higashihara Shinji Ando Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》2010,48(3):656-662
New sulfur‐containing aromatic diamines with methyl groups at the ortho position of amino groups have been developed to prepare highly refractive and transparent aromatic polyimides (PIs) in the visible region. All aromatic PIs derived from 4,4′‐thiobis[2″‐methyl‐4″‐(p‐phenylenesulfanyl)aniline ( 2 ), 4,4′‐thiobis[2,″6″‐dimethyl‐4″‐(p‐phenylenesulfanyl)aniline ( 5 ), and aromatic dianhydride, 4,4′‐[p‐thiobis(phenylenesulfanyl)]diphthalic anhydride ( 6 ) were prepared via a two‐step polycondensation. All PIs showed good thermal properties, such as 10% weight loss temperature in the range of 497–500 °C and glass transition temperatures above 196 °C. In addition, the PIs showed good optical properties, such as optical transparency above 75% at 450 nm with a 10‐μm film thickness, high refractive indices ranging from 1.7135 to 1.7301, and small in‐plane/out‐of‐plane birefringences between 0.0066 and 0.0076. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 656–662, 2010 相似文献
955.
Yamamoto A Ueda A Brémond P Tiseni PS Kishi Y 《Journal of the American Chemical Society》2012,134(2):893-896
The first total synthesis of halichondrin C has been completed, highlighted by development of the synthetic method to construct the C8-C14 polycycle. Cr-mediated coupling reactions are used seven times to form a new C-C bond. The acid stability of halichondrin C is studied, demonstrating that the macrolactone stabilizes the C8-C14 polycycle, relative to the one present in the C1-C16 model. 相似文献
956.
The completely N(1)-selective Pd-catalyzed arylation of unsymmetric imidazoles with aryl halides and triflates is described. This study showed that imidazoles have a strong inhibitory effect on the in situ formation of the catalytically active Pd(0)-ligand complex. The efficacy of the N-arylation reaction was improved drastically by the use of a preactivated solution of Pd(2)(dba)(3) and L1. From these findings, it is clear that while imidazoles can prevent binding of L1 to Pd, once the ligand is bound to the metal, these heterocycles do not displace it. The utility of the present catalytic system was demonstrated by the regioselective synthesis of the clinically important tyrosine kinase inhibitor nilotinib. 相似文献
957.
Nomura S Arimitsu K Yamaguchi S Kosuga Y Kakimoto Y Komai T Hasegawa K Nakanishi A Miyoshi T Iwasaki H Ozeki M Kawasaki I Kurume A Ohta S Yamashita M 《Chemical & pharmaceutical bulletin》2012,60(1):94-103
(±)-8-Deisopropyladunctin B, the deisopropyl form of adunctin B, which was isolated from the leaves of Piper aduncum (Piperaceae) collected in Papua New Guinea, was synthesized in 0.77% overall yield in 17 steps from 5,7-dimethoxycoumarin-3-carboxylate. The key step was our original stereoconvergent skeleton transformation from 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-one to 1,2,4a,9b-tetrahydrodibenzofuran-4-ol with dimethylsulfoxonium methylide. 相似文献
958.
Masaki Matsui Takahiro Shiota Yasuhiro Kubota Kazumasa Funabiki Jiye Jin Tsukasa Yoshida Shinji Higashijima Hidetoshi Miura 《Tetrahedron》2012,68(22):4286-4291
The effect of N-(2-alkoxyphenyl) group in double rhodanine indoline dye on the performance of zinc oxide dye-sensitized solar cell was examined. Both Jsc and Voc were improved by introducing long alkoxy group due to prevention of H-aggregates formation and inhibition of electron recombination from zinc oxide surface to electrolyte. 相似文献
959.
Masumi Itazaki Dr. Kensuke Ueda Hiroshi Nakazawa Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(18):3313-3316
A variety of tertiary silanes , even those with functional substituents, undergo an unprecedented iron‐catalyzed dehydrogenative coupling (see scheme) in a convenient approach to disilanes, including unsymmetrical disilanes and polymers with Si? Si bonds in the backbone. Consideration of the catalytic reaction pathway revealed the intermediacy of a hydrido(disilyl)iron(IV) complex.
960.
Akinobu Naka Shinsuke Ueda Toshiko Miura Mitsuo Ishikawa 《Journal of organometallic chemistry》2010,695(23):2499-2505
The cothermolysis of benzoyl(tert-butyl)bis(trimethylsilyl)silane with 2,3-dimethylbutadiene in a sealed tube at 140 °C for 24 h afforded cis- and trans-1-tert-butyl-4,5-dimethyl-2-phenyl-2-(trimethylsiloxy)-1-(trimethylsilyl)-1-silacyclohex-4-ene (2 and 3) in a ratio of approximately 1:1 in 66% combined yield. When cis-silacyclohex-4-ene 2 was heated in a sealed tube at 250 °C for 24 h, dyotropic ring contraction took place to give 1-[(tert-butyl)(trimethylsiloxy)(trimethylsilyl)silyl]-3,4-dimethyl-1-phenylcyclopent-3-ene (4), but not trans-2-tert-butyl-4,5-dimethyl-2-phenyl-1-(trimethylsiloxy)-1-(trimethylsilyl)-1-silacyclohex-4-ene (6). The thermolysis of trans-silacyclohex-4-ene 3 under the same conditions, however, afforded two products, 1-silyl-1-phenylcyclopent-3-ene 4 and trans-1-tert-butyl-4,5-dimethyl-2-phenyl-1-(trimethylsiloxy)-2-(trimethylsilyl)-1-silacyclohex-4-ene (5). The theoretical calculations were carried out to characterize the transition states and other local minima, and to evaluate the activation energies for the dyotropic rearrangement of 2 to 4 and 6, and 3 to 4 and 5. The energy barriers between 2 and 4, between 3 and 4, and between 3 and 5 were evaluated to be 188, 191, 192 kJ mol−1, respectively. The energy barrier between 2 and 6, however, was calculated to be 201 kJ mol−1 or higher. These results are consistent with the experimental finding that the thermal isomerization of 2 affords only 4, but 3 produces both 4 and 5. 相似文献