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61.
62.
Stereoselective total synthesis of the C(40)-diacetylenic carotenoid alloxanthin (1) and the C(31)-acetylenic apocarotenoid triophaxanthin (2) was accomplished by Wittig condensation of C(10)-dialdehyde 20 or C(16)-keto aldehyde 19, respectively, with C(15)-acetylenic tri-n-butylphosphonium salt 12. 相似文献
63.
Localization of carboxyl groups at surface layer of carboxylated polymer emulsion particles by alkali treatment 总被引:1,自引:0,他引:1
For the purpose of localizing carboxyl groups from inside to particle surface, styrene — butyl acrylate — methacrylic acid (74.3/17.0/8.7, mol ratio) terpolymer emulsion was kept under pH 9 at different temperatures. The amount of carboxyl groups at the particle surface, As, was remarkably increased by the alkali-treatment above 35 °C. On the other hand, As value of the alkalitreated emulsion was decreased by keeping under ph 3 above 45 °C, although in the case of the original emulsion without the alkalitreatment, it was not changed by the acid-treatment. These results suggest that a part of polymer segments which have ionized carboxyl groups is dragged out at the surface by an increase in the affinity of the groups against water, and the dragged segments turn back into the inside again when the carboxyl groups are deionized.Part 97 of the series Studies on Suspension and Emulsion. 相似文献
64.
Srinivas Kantevari Mahankhali Venu Chary Srinivasu V.N. Vuppalapati 《Tetrahedron》2007,63(52):13024-13031
A systematic investigation into the regioselective one-pot, three-component condensation of enaminones 1a–g, β-dicarbonyl compounds 2a–c, and ammonium acetate in the presence of a catalytic amount of K5CoW12O40·3H2O (0.01 equiv or 1.0 mol %) under solvent free conditions, as well as in refluxing isopropanol, has been reported. The reaction was highly efficient to produce 2,3,6-trisubstituted pyridines 3a–g, 4a–g, and novel 2,7,7-trisubstituted-5,6,7,8-tetrahydroquinoline-5-ones 5a–g in excellent yields. The present procedure offers advantages of short reaction time, simple work-up, and the catalyst exhibited remarkable reusable activity. 相似文献
65.
J.S. Yadav B.V. Subba Reddy G. Madhusudhan Reddy D. Narasimha Chary 《Tetrahedron letters》2007,48(49):8773-8776
2-Azidoalcohols derived in situ from epoxides and sodium azide undergo smooth coupling with alkynes under neutral conditions by means of ‘click reactions’ to furnish β-hydroxytriazoles in excellent yields and with high regioselectivity. This reaction proceeds smoothly in water at room temperature without the need for acid catalysis. 相似文献
66.
J.S. Yadav B.V.S. Reddy Gakul Baishya S.J. Harshavardhan Ch. Janardhana Chary Manoj Kumar Gupta 《Tetrahedron letters》2005,46(20):3569-3572
Alkenes undergo smooth bromo- and iodohydroxylation with N-bromo- and N-iodosuccinimides/water, respectively, using the air and moisture stable ionic liquid [bmim]BF4 as a novel recyclable reaction medium in high to quantitative yields. N-Halosuccinimides show enhanced reactivity in ionic liquids thereby reducing the reaction times and improving the yields considerably. 相似文献
67.
N. K. Nag B. Mahipal Reddy K. V. R. Chary V. S. Subrahmanyam 《Reaction Kinetics and Catalysis Letters》1985,27(1):125-128
Kinetics of hydrogenation of cyclohexene on a sulfided Ni–W/Al2O3 catalyst has been studied with a flow microreactor under normal atmospheric pressure. The reaction rate is found to be zero and first order with respect to cyclohexene and hydrogen partial pressures, respectively, in the temperature range 250–350°C.
Ni–W/Al2O3 . , , 250–350°C.相似文献
68.
Sateesh Kumar Beepala Harisekhar Mitta Hussain Sk Putrakumar Balla V.R Chary Komandur 《印度化学会志》2022,99(6):100451
Amination of cyclohexanol was investigated in vapour phase over copper catalysts supported on mesoporous SBA-15. The different products identified during reductive amination of cyclohexanol reaction were cyclohexanone, cyclohexylamine, along with small amounts of N-Cyclohexylidinecyclohexylamine and dicyclohexylamine. Among several catalysts tested for the reductive amination, 5% Cu supported on SBA-15 exhibited better catalytic performance than other catalysts with 36% selectivity towards cylclohexylamine at 80% cyclohexanol conversion. The optimum reaction conditions employed to achieve the best catalyst performance were at 250 °C, 0.1 MPa of H2/NH3, TOS-10h. The active Cu sites, acidity of the catalyst, and effect of reaction parameters play a pivotal role in the reductive amination reaction. The prepared catalysts were characterized by XRD, BET, SEM, H2-TPR and NH3-TPD. The dispersion of Cu, particle size, and metal surface area (m2/g) calculated from pulse N2O decomposition method. TPR findings reveal the presence of substantially dispersed copper oxide species at lower loadings which is easily reducible than the bulk copper oxide species found at higher Cu loadings. The acidity measurements by NH3-TPD analysis suggest that the maximum acidic strength was obtained at 5 wt% copper on porous SBA-15, and decreased with Cu loadings. The catalytic properties are well in agreement with the findings of catalysts characterization. 相似文献
69.
70.
Characterization and catalytic functionalities of copper oxide catalysts supported on zirconia 总被引:1,自引:0,他引:1
A series of zirconia supported copper oxide catalysts with varying copper loadings (1.2-19.1 wt %) were prepared by impregnation method. The catalysts were characterized by X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and temperature-programmed desorption of CO2. Copper dispersion and metal area were determined by N2O decomposition method. X-ray diffraction patterns indicate the presence of crystalline CuO phase beyond 2.7 wt % of Cu on zirconia. UV-visible diffuse reflectance spectra suggest the presence of two types of copper species on the ZrO2 support. XPS peaks intensity ratio of Cu 2p3/2 and Zr 3d5/2 was compared with Cu dispersion calculated from N2O decomposition. TPR patterns reveal the presence of highly dispersed copper oxide at lower temperatures and bulk CuO at higher temperatures. The basicity of the catalysts was found to increase with Cu loading, and the activity of the catalysts was also found to increase with the increase in Cu loading up to 2.7 wt % Cu loading. The catalytic properties were evaluated for the dehydrogenation of cyclohexanol to cyclohexanone and were related to surface properties of the copper species supported on zirconia. 相似文献