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111.
Takeshi Hanamoto Yuhko Iwamoto Kenji Yamada Ryoko Anno 《Journal of fluorine chemistry》2007,128(10):1126-1130
The 1,3-dipolar cycloaddition reaction of fluoro(trimethylsilyl)acetylene prepared in situ with an excess of diazomethane smoothly proceeded to give the corresponding 4-fluoro-5-trimethylsilyl-1H-pyrazole in 84% yield. The copper iodide-catalyzed N-arylation of the fluorinated pyrazole with a variety of aryl iodides afforded N-aryl-4-fluoropyrazoles as desilylation products in good to excellent yields. 相似文献
112.
113.
The natural stereoisomer of serricornin was synthesized stereoselectively from levoglucosenone. This firmly established the absolute stereochemistry of serricornin to be 4S,6S,7S. A short synthesis of (?)-δ-multistriatin was also reported. 相似文献
114.
Photochemie von tricyclischen β, γ-γ′, δ′-ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen
Photochemistry of tricyclic β, γ-γ′, δ′-unsaturated ketones The easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3-acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4 . However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa-di-π-methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6 . The conversion 5 → 6 represents a novel photochemical 1,4-acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4-acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2 , respectively, underwent a 1,3-acyl shift upon irradiation followed by decarbonylation, and the oxa-di-π-methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ-unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6). 相似文献
115.
Stereoselective synthesis of cruciferous indole phytoalexin (R)-(+)-1-methoxyspirobrassinin and its unnatural (S)-(−)-enantiomer was achieved by spirocyclization of 1-methoxybrassinin in the presence of (+)- and (−)-menthol and subsequent oxidation of the obtained menthyl ethers. Methanolysis of menthyl ethers in the presence of TFA afforded (2R,3R)-(−)-1-methoxyspirobrassinol methyl ether as well its unnatural (2S,3S)-, (2R,3S)-, and (2S,3R)-isomers. 相似文献
116.
Tomohisa Nagamatsu Yoshiji Hantani Minoru Yamada Kenji Sasaki Hiromi Ohtomo Taiji Nakayama Takashi Hirota 《Journal of heterocyclic chemistry》1993,30(1):193-202
As a series of polyheterocyclic compounds for exploitation as anti-platelet agents, tricyclic heterocyclic compounds, 4-substituted 6,7-dihydro-5H-pyrimido[5,4-d][1]benzazepines 3–6, 9, 12–14 , and 16–26 , having nitrogen, oxygen, or sulfur containing functional groups at the 4-position, were prepared. In addition, tetra-cyclic heterocyclic compounds, 3-methyl-1,2,5,6-tetrahydro-4H-imidazo[1′,2′:1,6]pyrimido[5,4-d][1]benzaze-pinium chloride ( 7 ), 1,2,5,6-tetrahydro-4H-imidazo[1′,2′:1,6]pyrimido[5,4-d][1]benzazepines 10a-e , 2,3,6,7-tetrahydro-1H 5H-pyrimido[1′,2′:1,6]pyrimido[5,4-d][1]benzazepine ( 11 ), and 1,2,5,6-tetrahydro-4H-thiazolo-[3′,2′:1,6]pyrimido[5,4-d][1]benzazepinium chloride ( 15 ) via ring closure of 4-(hydroxyalkylamino)- 6, 9a-e , and 3c , and 4-(2-hydroxyethylthio)-6,7-dihydro-5H-pyrimido[5,4-d][1]benzazepine ( 14 ) with phosphoryl chloride or thionyl chloride, respectively, were also prepared. Their inhibitory activities against collagen-induced aggregation of rabbit blood platelets in vitro were investigated. Among them, compound 5 having a morpholino group at the 4-position on the tricyclic nucleus, which enhanced the activity more than 14-fold as compared with aspirin, was found to have the most satisfactory in inhibitory activity. 相似文献
117.
Polypeptides with two histidines and an iron porphyrin (1H40-7H46) were synthesized with a variety of positions of a histidine. In 4H43, histidine (H43) was in the hydrophobic region of an α-helix. The other polypeptides were of slightly or substantially distorted conformation. In the pH 7.2 buffer solution, two histidines of the polypeptide coordinated the iron porphyrin regardless of their positions. Some polypeptides (1H40, 3H42, and 5H44) showed an enhanced catalytic activity in the peroxidase reaction using cumene hydroperoxide compared to that of 4H43, whereas some polypeptides (2H41 and 6H45) were ineffective catalysts. The distortion of the peptide conformation by the addition of MeOH was also effective for the peroxidase reaction. 相似文献
118.
A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.04,7] nonane, ) was achieved. The stereochemistry of (+)-lineatin was established as 1, 4, 5, 7 by an X-ray crystallographic analysis of an intermediate . 相似文献
119.
Shin-ichi NayaHisashi Miyama Kenji YasuTohru Takayasu Makoto Nitta 《Tetrahedron》2003,59(10):1811-1821
Three-step reactions starting from 2-chlorotropone with barbituric acid afforded novel 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (9·BF4−), which is the isoelectronic compound of the 5-ethyl-3-methyllumiflavinium ion. The stability of cation 9 is expressed by the pKR+ value, which was determined spectrophotometrically, as ca. 6.0. The electrochemical reduction of 9 exhibited low reduction potential at −0.58 (V vs Ag/AgNO3), upon cyclic voltammetry (CV). In a search for the reactivity, reactions of 9·BF4− with some nucleophiles, hydroxide, hydride, amines, thiols, and methanol, were carried out to exhibit that the introduction of nucleophiles is dependent on the nucleophile itself. The photo-induced oxidation reactions of some alcohols catalyzed by 9·BF4− under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compound 9·BF4−], suggesting the oxidizing function of 9·BF4− toward alcohols in the autorecycling process. The UV-vis and fluorescence spectra of 9 were studied to suggest the electron transfer from alcohols to the excited 9. 相似文献
120.
Investigation of the Interactions of β‐Peptides with DNA Duplexes by Circular Dichroism Spectroscopy
Kenji Namoto James Gardiner Thierry Kimmerlin Dieter Seebach 《Helvetica chimica acta》2006,89(12):3087-3103
The interaction of β‐peptides with the DNA duplexes of dA20dT20 and a GCN4‐binding CRE sequence was examined. To gauge the factors that govern these interactions, two β‐pentadecapeptides, 1 and 2 , a β‐dodecapeptide, 3 , three β‐decapeptides, 4 – 6 , three β‐heptapeptides, 7 – 9 , and β‐octaarginine 10 were designed and synthesized. The β‐peptides were conceived to adopt a β‐peptide 314 helix, in which the side chains at position i and i + 3 are aligned vertically along one side of the helix. The side chains of Lys, Asn, and Arg were positioned such that potential H‐bonding sites were created for a helical conformation to interact with the base pairs of DNA. CD Analysis showed that β‐peptides 1, 2 , and 10 interacted with dA20dT20. In addition, β‐peptides 1 and 2 showed significant interaction with a DNA‐duplex 20mer containing the ATF/CREB recognition sequence for the regulatory protein GCN4. It is impossible, at this stage of the investigation, to make a safe proposal about the actual nature of the interaction of the structures(s) of the complexes, the formation of which is suggested by the CD spectra reported herein. 相似文献