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排序方式: 共有1310条查询结果,搜索用时 15 毫秒
991.
Tetsuya Aono Jost H. Bieri Manfred Hesse Kalina Kostova Annalaura Lorenzi-Riatsch Yoshihiko Nakashita Roland Prewo 《Helvetica chimica acta》1985,68(4):1033-1053
Crystal structures have been determined of methyl trans-1-hydroxy-6-nitro-3-oxobicyclo[4.4.0]decane-2-carboxylate ( 19 ), cis-3-methyl-6-nitro-2-oxabicyclo[4.4.0]decan-1-ol ( 2 ), cis-7-hydroxy-1-nitrobicyclo[5.4.0]undecan-9-one ( 13 ), and the medium-ring compounds 2-acetyl-4-nitrocyclooctanone ( 9 ), methyl 5-nitro-2-oxocyclooctane-carboxylate ( 4 ), 2-acetyl-4-nitrocyclononanone ( 11 ), 2-acetyl-4-nitrocyclodecanone ( 15 ), benzyl 5-nitro-2,11-dioxocycloundecanecarboxylate ( 24 ), methyl 5-nitro-2,12-dioxocyclododecanecarboxylate ( 21 ), and 8-nitro-11-oxo-13-tridecanolide ( 7 ), which are intermediates, side products, or end products of the ‘Zip’ ring-enlargement reaction. The conformations of most of the medium-ring compounds are very similar to equal-sized ring compounds previously determine by other authors. 相似文献
992.
Terao Y Wakui H Nomoto M Satoh T Miura M Nomura M 《The Journal of organic chemistry》2003,68(13):5236-5243
The palladium-catalyzed arylation of alpha,alpha-disubstituted arylmethanols with aryl halides proceeds not only via C-H bond cleavage at the ortho-position, but also via cleavage of the sp(2)-sp(3) C-C bond with the liberation of ketones (beta-carbon elimination) to give the corresponding biaryls. Both reactions appear to occur through common arylpalladium(II) alcoholate intermediates. The results of systematic studies with respect to which C-C or C-H bond is preferentially cleaved in the arylation are reported. Among the important findings is the selective elimination of ortho-substituted aryl groups even from aryl(diphenyl)methanols due to steric reasons. Thus, various biaryls having ortho-substituents can be produced efficiently by treatment of the corresponding aryl(diphenyl or dimethyl)methanols with aryl bromides and chlorides. 相似文献
993.
Zhiwei Tong Tetsuya Shichi Guozhen Zhang Katsuhiko Takagi 《Research on Chemical Intermediates》2003,29(3):335-341
Investigations to elucidate the structures of the cobalt(III) and manganese(III) complexes of tetra(p-sulfonatophenyl)porphinate anions (M(III)TSPP; M = Co and Mn), intercalated in Mg-Fe/Cl and Mg-Al/Cl layered double hydroxides (LDHs) have been carried out. Powder X-ray diffraction analysis, IR and UV-vis diffuse reflectance spectroscopy of Co(III)TSPP and Mn(III)TSPP intercalated into the interlayer spaces of LDH resulted in their perpendicular alignment against the host layers in the plane of the hybrid. 相似文献
994.
Oxidative stress-induced cellular damage caused by UV and methyl viologen in Euglena gracilis and its suppression with rutin 总被引:1,自引:0,他引:1
Palmer H Ohta M Watanabe M Suzuki T 《Journal of photochemistry and photobiology. B, Biology》2002,67(2):116-129
The effects of ultraviolet radiation (UV-A: 320-400 nm and UV-B: 280-320 nm) and methyl viologen (MV) single or combined exposure, on the cell growth, viability and morphology of two strains of the unicellular flagellate Euglena gracilis, using the Z strain as a plant model and the achlorophyllous mutant SMZ strain as an animal model were investigated. Cell growth was not affected by MV only, whereas UV-A or UV-B single and combined exposure with MV inhibited the cell growth or decreased the viability. The SMZ strain had a higher number of abnormal cells than the Z strain after the third dose of UV-B was delivered simultaneously with MV. The abnormal cell number decreased when E. gracilis SMZ cells were preincubated with 100 microM rutin prior to the UV-B and MV exposure. There were higher abnormal cell numbers with groups exposed to UV rather than MV single exposure. Combined exposure to UV-B and 200 microM MV induced the highest levels of TBARS in both strains, and with the supplementation of rutin these high levels were suppressed. These results suggest that UV-A or UV-B irradiation alone or combined with MV cause considerable oxidative damage in E. gracilis cells, and rutin supplementation may suppress their adverse effects. 相似文献
995.
Shin-Ichi Takahashi Tetsuya Fujimoto Takeaki Miyamoto Hiroshi Inagaki 《Journal of polymer science. Part A, Polymer chemistry》1987,25(4):987-994
The solubility behavior of O-methyl cellulose (MC) in water was investigated in terms of the distribution of substituents along the cellulose chain as well as in the anhydroglucose (AHG) units. For this purpose, three different types of MC samples were prepared by respective homogeneous reaction, i.e.. (i) methylation of cellulose acetate (CA) prepared from cellulose triacetate (CTA), followed by deacetylation, (ii) methylation of CA prepared by direct acetylation of cellulose in a 10% LiCl–dimethylacetamide (DMAc) solution, followed by deacetylation, and (iii) methylation of cellulose with dimethyl sulfate in a 10% LiCl–DMAc solution. Their water solubility was compared with that of MC samples prepared by the alkali cellulose process, i.e., by the heterogeneous reaction, including commercial products. It was found that water-soluble MC samples prepared by the alkali cellulose process exhibit a thermally-reversible sol-gel transition in aqueous solution, but all of the MC samples preapred homogeneous reactions show a normal phase separation in aqueous solution. This result gives a direct support for the consideration that the highly substituted glucose sequences present in the commercial MC act as “crosslinking loci” on warming. The distribution of substituents in the AHG units was estimated by 13C-NMR method. The results on the water solubility of MC were also discussed in terms of the distribution of substituents in the AHG units. 相似文献
996.
Arinobu T Hattori H Seno H Ishii A Suzuki O 《Journal of the American Society for Mass Spectrometry》2002,13(3):204-208
Sonic spray ionization (SSI) was compared with atmospheric pressure chemical ionization (APCI) as an interface of high-performance liquid chromatography (HPLC)-mass spectrometry (MS) for sensitive analyses of a neuroleptic drug, haloperidol and its two metabolites, such as reduced haloperidol and 4-(4-chlorophenyl)-4-hydroxypiperidine (CPHP), in biological samples. For both SSI and APCI interfaces, HPLC-MS-MS gave higher sensitivity than HPLC-MS. The sensitivities by HPLC-SSI-MS-MS for haloperidol and reduced haloperidol were 100 and 30 times higher, respectively, than those by HPLC-APCI-MS-MS; no spectrum with recognizable peaks was obtained for CPHP with the APCI interface. Therefore, detection limits and regression equations were examined by the HPLC-SSI-MS-MS for human plasma and urine samples spiked with the above drug and its metabolites. Haloperidol, reduced haloperidol, and CPHP showed good linearity in the ranges of 5-800, 10-800, and 100-800 ng/mL, respectively, for both human plasma and urine; their detection limits were 2.5, 5, and 75 ng/mL, respectively, using a new polymer HPLC column which enabled direct application of biological samples. 相似文献
997.
An efficient and practical method for the large-scale synthesis of an anti-inflammatory glycocluster having seven sialyl Lewis X (SLeX) residues was established on the basis of chemical and enzymatic strategy from β-cyclodextrin (β-CD) as a key starting scaffold material. A key intermediate, β-CD derivative having seven N-acetyl-d-glucosamine (GlcNAc) residues [(GlcNAc)7CD], was prepared by a coupling reaction with heptakis 6-deoxy-6-iodo-β-cyclodextrin and sodium thiolate containing a GlcNAc residue. Subsequent sugar elongation reactions of (GlcNAc)7CD proceeded smoothly by means of β-1,4-galactosyltransferase, α-2,3-sialyltransferase, and α-1,3-fucosyltransferase V in the presence of the corresponding sugar nucleotides (UDP-Gal, CMP-Neu5Ac, and GDP-Fuc) and allowed to give a mono-dispersed glycodendrimer (Mw=7924.5, calcd for C301H490N21O196S7Na7; MALDI-TOF MS, m/z 7946 [M+Na]+) that completely substituted with seven SLeX branches at C-6 positions in excellent overall yield (74%, 3 steps). Hyper-branched glycodendrimer, (SLeX)7CD, exhibited highly amplified inhibitory effect on the interaction of E-selectin with SLeXn-BSA immobilized on the sensor chip by means of surface plasmon resonance method. 相似文献
998.
Kunishima M Nakata D Sakuma T Kono K Sato S Tani S 《Chemical & pharmaceutical bulletin》2001,49(1):97-100
Transformation of acetals into ethers by partial reduction using a samarium diiodide-Lewis acids-acetonitrile system is described. The reaction with aromatic acetals occurred in good yields in the presence of aluminum chloride (2 eq) whereas the corresponding aliphatic, vinylic, and alkynyl derivatives did not afford ethers under the same conditions. Beta-elimination to give an enol ether becomes predominant when aliphatic acetals that possess a hydrogen at the 2-position are treated with iodotrimethylsilane in the presence of SmI2 or SmI3. 相似文献
999.
Masaru Senuma Katsuhiko Nakamichi Koichi Nabe Shigeru Nishimoto Tetsuya Tosa 《Applied biochemistry and biotechnology》1989,22(2):141-150
An industrial production method of L-2-amino-4-phenylbutyric acid from 2-oxo-4-phenylbutyric acid by microbial cells containing
aminotransferase activity was investigated. By usingParacoccus denitrificans pFPr-1, 0.19M L-2-amino-4-phenylbutyric acid was produced with a 95% conversion yield. Accumulated L-2-amino-4-phenylbutyric acid was readily
isolated in pure form. Overall yield from 2-oxo-4-phenylbutyric acid was 83.7%. 相似文献
1000.
An apparatus for measurements of equilibrium ligand vapor pressure has been applied in order to determine the stoichiometry of benzene and cyclohexene complexes of silver(I) trifluoroacetate (AgCF3CO2) and silver(I) trifluoromethanesulfonate (silver(I) triflate, AgCF3SO3) in the solid state. It has been found that the equilibrium leads the formation of such complexes as: (AgCF3CO2)2(C6H6), (AgCF3CO2)2(C6H10), (AgCF3CO2)2(C6H10)3, (AgCF3SO3)2(C6H6), (AgCF3SO3)(C6H6), (AgCF3SO3)(C6H10) and (AgCF3SO3)(C6H10)2. The temperature dependence of the gas-solid equilibrium ligand pressure has also been examined for these complexes, and the enthalpy and entropy changes according to the following complex dissociation reactions were estimated: (AgCF3CO2)Lm (s) AgCF3CO2 (s)+mL (g): and (AgCF3SO3)Ln (s) AgCF3SO3 (s)+nL (g), where L's are benzene and cyclohexene. On the basis of the thermodynamic data obtained, the effects of the counter anion as well as the ligand on the complex stability are discussed. 相似文献