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31.
Steroidal glycosides from the bulbs of Camassia leichtlinii and their cytotoxic activities. 总被引:2,自引:0,他引:2
M Kuroda Y Mimaki F Hasegawa A Yokosuka Y Sashida H Sakagami 《Chemical & pharmaceutical bulletin》2001,49(6):726-731
Phytochemical analysis of the bulbs of Camassia leichtlinii (Liliaceae) resulted in the isolation of six new spirostanol saponins, a new furostanol saponin, a cholestane glucoside, and four known steroidal saponins. The structures of the new saponins were determined by detailed analysis of their spectral data, including two-dimensional NMR spectroscopy, and by the results of hydrolytic cleavage. Cytotoxic activities of the isolated compounds against human oral squamous cell carcinoma (HSC-2) cells and normal human gingival fibroblasts (HGF) are also reported. 相似文献
32.
Cao B Hasegawa M Okada K Tomiyama T Okazaki T Suenaga K Shinohara H 《Journal of the American Chemical Society》2001,123(39):9679-9680
33.
Chirality of metal complexes M(phen)3(n+) (M = Ru(II), Rh(III), Fe(II), Co(II), and Zn(II), and phen = 1,10-phenanthroline) is recognized by heptakis(6-carboxymethylthio-6-deoxy)-beta-cyclodextrin heptaanion (per-CO2(-)-beta-CD) and hexakis(2,3,6-tri-O-methyl)-alpha-cyclodextrin (TMe-alpha-CD) in D2O. The binding constant (K) for the Delta-Ru(phen)3(2+) complex of per-CO2(-)-beta-CD (K = 1250 M(-1)) in 0.067 M phosphate buffer at pD 7.0 is approximately 2 times larger than that for the Lambda-isomer (590 M(-1)). Definite effects of inorganic salts on stability of the complexes indicate a large contribution of Coulomb interactions to complexation. The fact that hydrophilic Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) does not form a complex with per-CO2(-)-beta-CD suggests the importance of inclusion of the guest molecule into the host cavity for forming a stable ion-association complex. The positive entropy change for complexation of Ru(phen)3(2+) with per-CO2(-)-beta-CD shows that dehydration from both the host and the guest occurs upon complexation. Similar results were obtained with trivalent Rh(phen)3(3+) cation. Pfeiffer effects were observed in complexation of racemic Fe(phen)3(2+), Co(phen)3(2+), and Zn(phen)3(2+) with per-CO2(-)-beta-CD with enriched Delta-isomers. Native cyclodextrins such as alpha-, beta-, and gamma-cyclodextrins as well as heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin do not interact with Ru(bpy)3(2+). However, hexakis(2,3,6-tri-O-methyl)-alpha-cyclodextrin (TMe-alpha-CD) interacts with Ru(phen)3(2+) and Ru(bpy)3(2+) and discriminates between the enantiomers of these metal complexes. The K values for the Delta- and Lambda-Ru(phen)3(2+) ions are 54 and 108 M(-1), respectively. Complexation of the Delta- and Lambda-isomers of Ru(phen)3(2+) with TMe-alpha-CD is accompanied by negative entropy changes, suggesting that cationic Ru(phen)3(2+) is shallowly included into the cavity of the neutral host through van der Waals interactions. The Delta-enantiomer, having a right-handed helix configuration, fits the primary OH group side of per-CO2(-)-beta-CD (SCH2CO2(-) side) well, while the Lambda-enantiomer, having a left-handed helix configuration, is preferably bound to the secondary OH group side of TMe-alpha-CD. The asymmetrically twisted shape of a host cavity seems to be the origin of chiral recognition by cyclodextrin. 相似文献
34.
Machiguchi T Hasegawa T Saitoh H Yamabe S Yamazaki S 《The Journal of organic chemistry》2011,76(13):5457-5460
Through variable-temperature solution-state NMR and molten- and solid-state CP/MAS (13)C NMR spectra, thiotropolone is found to exist as two rapidly equilibrated tautomeric structures, thione and enethiol, even in the solid state far below the melting point. The crystal structure shows an almost perpendicular packing, suggesting that the intramolecular hydrogen bond is dominant. 相似文献
35.
Yamamoto Y Terui N Tachiiri N Minakawa K Matsuo H Kameda T Hasegawa J Sambongi Y Uchiyama S Kobayashi Y Igarashi Y 《Journal of the American Chemical Society》2002,124(39):11574-11575
Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability. 相似文献
36.
Hasegawa E Takizawa S Iwaya K Kurokawa M Chiba N Yamamichi K 《Chemical communications (Cambridge, England)》2002,(17):1966-1967
Photoinduced electron transfer reaction of 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols. 相似文献
37.
Yoshitsugu Hasegawa Suguru Kontani Isao Tomita 《Journal of inclusion phenomena and macrocyclic chemistry》1993,16(4):329-337
Intercalation of alkylalcohols into -zirconium phosphate was investigated at 25°C and/or under reflux.n-Alcohols having two to five carbons and 2-propanol were taken up at 25°C. These alcohols, andn-hexanol and heptanol, also intercalated under reflux.n-Alcohols having eight to eighteen carbon atoms intercalated when a stepwise method was employed. 2-Butanol and tertiary amylalcohols intercalated under reflux using a butanol intercalate as a starting material. Ethanol-to-butanol intercalates were unstable at room temperature, losing alcohols and changing to -zirconium phosphate. The particle size of the -zirconium phosphate did not affect the intercalation of alcohols. 相似文献
38.
Tohru Takabatake Yumiko Hasegawa Minoru Hasegawa 《Journal of heterocyclic chemistry》1993,30(6):1477-1479
The cyclocondensations of benzofuroxan 1a with carbonyl compounds were smoothly and efficiently carried out by the adsorption of the components on the surface of silica gel or a molecular sieve to form a 2,3-disubstituted quinoxaline 1,4-dioxide. When the reactions using a molecular sieve 3A (powder) were carried out at 90°, the actual reaction times were reduced to 0.5-2 hours. Although Duerckheimer has reported the isolation of only the 7-substituted quinoxaline 1,4-dioxide when 5-methoxybenzofuroxan 1e was allowed to react with ethyl acetoacetate 2j , it produced only the 6-methoxy isomer as the reaction product by our method. 5-Carboxybenzofuroxan 1f did not react with the carbonyl compound. 相似文献
39.
Takaaki Horaguchi Eietsu Hasegawa Takahachi Shimizu Kiyoshi Tanemura Tsuneo Suzuki 《Journal of heterocyclic chemistry》1989,26(2):365-369
Cyclohepta[cd]benzofuran 2 was synthesized by heating (5-oxo-5H-benzocyclohepten-4-yloxy)acetic acid 16 with sodium acetate in acetic anhydride or by photocyclization of 16 in acetonitrile. Several reactions of cyclohepta[cd]benzofuran 2 were examined. Protonation of 2 with trifluoroacetic acid occurred at the 2-position to give a tropylium ion 17 . Catalytic hydrogenation of 2 with palladium on charcoal proceeded smoothly to give tetrahydrocyclohepta[cd]benzofuran 18 . The Diels-Alder reaction of 2 with tetracyano-ethylene produced an adduct 19 . Formylation of 2 with phosphorus oxychloride and dimethylformamide occurred easily at the 2-position to afford compound 20 . Cyclohepta[cd]benzofuran 2 has both properties of heptafulvene and benzofuran. 相似文献
40.