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431.
Kamal A. R. Salib Salah B. El-Maraghy Samy M. Abu El-Wafa Saied M. El-Sayed 《Transition Metal Chemistry》1989,14(4):306-308
Summary Normal sulphites of metals were prepared by the reaction of metal salts with sodium metabisulphite, in aqueous acid solutions, to prevent the formation of basic sulphites. Visible spectra and magnetic moments show that the transition metal sulphites have distorted octahedral structures. The i.r. spectra showed that the sulphite groups act as O-bonded bridging ligands linking the metal atoms in polymeric chains. 相似文献
432.
In a recent article by Devi et al. [Eur. Phys. J. B 87, 268 (2014)], thestructural, electronic, elastic and some thermal properties of B2 type RHg(R = Ce, Pr, Eu and Gd)intermetallic compounds have been studied by ab initio calculations. After the study oftheir article I found that there are some mistakes in predicted crystal density,longitudinal, transverse and average elastic wave velocities, and Debye temperature data.The crystal density has been found multiplied per 4. Also the longitudinal, transverse andaverage elastic wave velocities and Debye temperature are different from my reexaminedvalues (all results represented by Devi et al. have been found divided per 2). Althoughthese small mistakes do not influence their conclusion, it is better to correct them. Inthe present work, I reexamined all data again by using the right formulas, based on thelattice parameters and the elastic constants obtained in the work of Devi et al. 相似文献
433.
Ben Salah H Jarraya R Martin MT Veitch NC Grayer RJ Simmonds MS Damak M 《Chemical & pharmaceutical bulletin》2002,50(9):1268-1270
A new flavonol triglycoside, isorhamnetin 3-O-beta-D-xylopyranosyl-(1"-->3)-alpha-L-rhamnopyranosyl-(1'-->6")-beta-D-galactopyranoside, has been isolated from the leaves of Hammada scoparia together with two known compounds, isorhamnetin 3-O-beta-D-apiofuranosyl-(1'-->2")[alpha-L-rhamnopyranosyl-(1"-->6")]-beta-D-galactopyranoside and isorhamnetin 3-O-alpha-L-rhamnopyranosyl-(1'-->2")[alpha-L-rhamnopyranosyl-(1"-->6")]-beta-D-galactopyranoside. The structures were determined by spectroscopic methods. 相似文献
434.
A simple and rapid differential electrolytic potentiometric titration method for the determination of ciprofloxacin was developed. The work is based on the fast complexation reaction between iron(III) and ciprofloxacin in a ratio of 1:3, respectively, in sulfuric acid media of 0.09 mol dm−3. Among the electrodes tested silver amalgam electrodes were found to be a suitable indicating system. By applying a current density of 0.5 μA cm−2 to these electrodes and using iron(III) solution of 0.097 mol dm−3 as a titrant, normal titration curves were obtained. The method was successfully applied for the determination of ciprofloxacin in drug formulations as low as 4.0 ppm. 相似文献
435.
The acid-catalysed hydrolysis of [Co(trpn)(CO3)]+ and [Co(trpn)(HCO3)]2+ ions (trpn = 3,3,3-triaminotripropylamine) have been studied spectrophotometrically in aqueous 1.0m HClO4/NaClO4. For the carbonato complex, [HClO4] = 0.02–0.25m and T = 20–35°C; for the bicarbonato complex, [HClO4] = 0.025–0.30m and T = 25°C. Both complexes hydrolyse to form the same cis-diaqua species. The rate law for the hydrolysis is d(ln[CoIII])/dt = k0+k1[H3O+]. The values of the rate constants (25°C), H (kJmol–1) and S (Jmol–1K–1)are:[Co(trpn)(CO3)]+,k0 = (1.7±0.6)× 10–4s–1, H 0 = 57±21, S 0 = –126±75; k1 = (1.0 ±0.1)×10–2m–1s–1, HDagger;1 = 62±8, S1 = –75 ±21, and for [Co(trpn)(HCO3)]2+, k0 = (2.9±0.7)× 10–4s–1, and k1 = (7.8±1.0)×10–2m–1s–1. The carbonato complex exhibits a deuterium isotope effect with k1D/k1H = 1.9, consistent with a rapid pre-equilibrium protonation, followed by rate-controlling ring-opening. The rate constants k0 and k1 (25°C and = 1.0m) for the ring-opening decarboxylation of the two systems studied lie within the experimental error. The results are compared with o ther related systems and the factors which influence the ring-opening decarboxylation (steric hindrance, ring strain, electron-donor ability of the amines) are discussed. The k1 path is interpreted in terms of concerted ring-opening and bond-making in the highly unstable aquabicarbonato intermediate. 相似文献
436.
Mohamed Salah K. Youssef Ahmed A. Omar 《Monatshefte für Chemie / Chemical Monthly》2007,138(10):989-995
Summary. 5-Amino-3-(3-methyl-5-oxo-1-phenyl-2-pyrazolin-4-yl)-7-phenyl-7H-thiazolo[3,2-a]pyrimidine-6-carbonitrile was synthesized via the reaction of 4-(2-aminothiazol-4-yl)-3-methyl-1-phenyl-2-pyrazolin-5-one with benzylidene malononitrile and was then transformed
to related fused heterocyclic systems. The antifungal and antibacterial studies revealed in some cases excellent biocidal
properties. 相似文献
437.
Fluxional poly(pyrazolyl)borate complexes of copper and silver, including the carbonyl Cu(CO)B(pz)4, contain coordinated and free pyrazolyl groups, which interchange rapidly on the NMR time scale at room temperature; low temperature limiting spectra can be obtained for some copper complexes at ?100°. 相似文献
438.
Atef A. T. Ramadan Salah B. El-Maraghy Mohammed S. Aabdel-Moez Ali M. Taha 《中国化学会会志》1986,33(3):201-213
Complex equilibria of DCPHD with proton and Ni2+, Sm3+, and Yb3+ ions has been measured in various mixed aqueous solvents, viz: isopropanol-water, acetone-water, ethanol-water, and methanol-water. Based on potentiometric equilibrium measurements of hydrogen ion concentration at 30°C, ionic strenght 0.10 M (KNO3) and in the above various mixed aqueous solvents, the values of the protonation constants of DCPHD and the stability constants of DCPHD with Ni2+, Sm3+, and Yb3+ have been evaluated. The variation of protonation and stability constants with the inverse of dielectric constant or mole fraction of the solvent was studied. Application of Fuoss expression and consideration of electrosatic and non-electrostatic effects are made to explain the values of the constants. 相似文献
439.
Small amounts of cobalt (0.1–0.25 mg in 15 ml solution) were determined heterometrically in the presence of potassium thiocyanate by titration with nitron acetate solution. A strong electrolyte (Na2SO4) must be added to obtain a clear end point. The titration can be carried out in the presence of a number of diverse ions e.g., Cd2+, Ni2+, Pb2+, Mn2+, Cr3+, MoO42?, WO42, CrO42?, NO3?, Au3+, Pt4+ without interference; Fe3+ can be masked with NaF. Copper and zinc interfere and must be absent. The titration takes about 2–3 min. and the maximum error was 1.5%. 相似文献
440.
El Fallah MS Escuer A Vicente R Badyine F Solans X Font-Bardia M 《Inorganic chemistry》2004,43(22):7218-7226
The syntheses, structural characterization, and magnetic behavior of the three new polynuclear copper(II) complexes with formulas [Cu(4)(eta(2):mu-CH(3)COO)(2)(mu-OH)(2)(mu-OH(2))(mu-bdmap)(2)](ClO(4))(2).H(2)O (1), [Cu(8)(NCO)(2)(eta(1):mu-NCO)(4)(mu-OH)(2)(mu(3)-OH)(2)(mu-OH(2))(3)(mu-bdmap)(4)](ClO(4))(2)x2H(2)O (2), and [Cu(9)(eta(1):mu-NCO)(8)(mu(3)-OH)(4)(OH(2))(2)(mu-bdmap)(4)](ClO(4))(2).4H(2)O (3), in which bdmapH is 1,3-bis(dimethylamino)-2-propanol, are reported. Tetranuclear complex 1 crystallizes in the triclinic system, space group P, with unit cell parameters a = 12.160(1) A, b = 13.051(1) A, c = 13.235(1) A, alpha = 110.745(1) degrees , beta = 109.683(1) degrees , gamma = 97.014(1), and Z = 2. Octanuclear complex 2 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 26.609(1) A, b = 14.496(1) A, c = 16.652(1) A, beta = 97.814(1) degrees , and Z = 4, and nonanuclear complex 3 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 24.104(1) A, b = 13.542(1) A, c = 24.355(1) A, beta = 109.98(1) degrees , and Z = 4. The magnetic behavior of the three complexes has been checked showing strong antiferromagnetic coupling in all the cases. 相似文献