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81.
In this work, the development of two solid-phase extraction procedures (off-line and on-line formats) for the identification and quantification of several (fluoro)quinolones in hospital sewage water by HPLC-UV is described. Both procedures are based on the use of C18 and anion exchange (SAX) sorbents for the preconcentration and clean-up steps, respectively, and all variables influencing both steps were optimised. In the off-line format, after its pH was adjusted to 2.5, sample was preconcentrated on a C18 cartridge and eluted with 4 mL of methanol/ammonia (94/6). The methanolic extract must be diluted up to 10 mL with water to allow quantitative retention of the analytes on the SAX cartridge. In the on-line format, the addition of 2.5% of NH4Cl to the sewage water sample (pH = 2.5) was necessary to increase the breakthrough volumes of the analytes in the C18 precolumn. Quantitative transfer of the (fluoro)quinolones from the C18 precolumn to the SAX precolumn was accomplished by pumping 2 mL of a mixture methanol/water (40/60, pH = 9.2) at 2 mL min(-1). Elution of the analytes from the SAX precolumn by means of the chromatographic mobile phase required the inclusion of an additional isocratic step at the beginning of the gradient program. Both off-line and on-line solid phase extraction procedures coupled to HPLC-UV were applied to the analysis of a sewage water sample collected in the sewer system at the output of the St Dimphna Hospital (Geel, Belgium). The fluoroquinolone ciprofloxacin was found in this sample and quantified at 5.8 +/- 0.4 microg L(-1) (off-line method) and 5.6 +/- 0.5 microg L(-1) (on-line method). The analysis of spiked samples containing the seven (fluoro)quinolones studied provided quantitative recoveries in all cases with low RSD values (from 6 to 12%), and all the analytes could be identified by means of their UV spectra with match factors varying from 950 to 985 depending on the (fluoro)quinolone. 相似文献
82.
83.
Manuel Soriano-García Rubén Toscano René Villena Adela Rodríguez Antonio Campero-Celis 《Journal of chemical crystallography》1988,18(6):671-678
The title compound is C3H3O4Cs, CsHM, monoclinic,P21/c,a=8.393 (3),b=7.960(2),c=9.023(2) Å,=92.11(2)°. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.023 for 760 observed reflections. The CsHM has no internal symmetry and one carboxy group, but not the other, is twisted almost at right angles (96°) to the plane of the three central carbon atoms. The hydrogen malonate anions are linked together by two short and symmetrical O-HO hydrogen bonds [2.468(4) and 2.482(4) Å]. The structure consists of hydrogen malonate chains cross-linked by the Cs+ ion. The IR spectrum of CsHM has been analyzed. 相似文献
84.
Gaussian analysis of bands between 500 cm−1 and 600 cm−1 attributed to the
as (Cu4O) stretching vibration of the tetrahedral Cu4O core in Cu4OBr
n
Cl(6−n)(4-Mepy)4 (n = 0–6) complexes showed two bands, symmetry reduction of the T
2 mode of vibration towards the A
1 and E modes and vibrational coupling with an R-sensitive in-plane pyridine ring bending. The Cu-O bond is considered as vibrationally
coupled with the Cu-N bond and the pyridine ring through the donor-acceptor vibrational coupling and the corresponding equilibrium
charge distribution. The linear correlation between
as(Cu4O) and the number of bromides in Cu4OBr
n
Cl(6−n)(4-Mepy)4 complexes was used for the estimation of partial charges on the 4-Mepy ligands which were positive for the prevailing donors
and negative for the prevailing acceptors thus evoking a π-back bonding between the Cu(II) atoms and the 4-Mepy ligands. Correlations involving selected bond lengths and bond angles
in the molecular structure of the Cu4OCl6(4-Mepy)4 complex with four symmetrically independent molecules present in the unit cell indicate a symmetry reduction of the T
2 mode of vibration and the π-back bonding between the Cu(II) atoms and the 4-Mepy ligands. 相似文献
85.
86.
87.
Pilar Bermejo-Barrera Luisa María Fernndez-Snchez Manuel Aboal-Somoza Rosa María Anllo-Sendín Adela Bermejo-Barrera 《Microchemical Journal》2001,69(3)
A method to determine iodide in infant formula samples by indirect atomic absorption spectrometry (IAAS) was developed. The iodide in solution resulting from an alkaline digestion (Na2CO3–NaOH) of the sample is precipitated with silver; the precipitate is redissolved by adding cyanide solution, and this solution is subjected to GF-AAS. Temperatures of 1000 and 2100°C were selected for the ashing and atomization steps, respectively, using a mixture of Pd and Mg(NO3)2 as a matrix modifier (at concentrations of 36 and 16 μg ml−1, respectively). The sensitivity, LOD, LOQ and characteristic mass obtained were, respectively, 1.12×10−2 l μg−1, 3.1 μg g−1 and 10.4 μg g−1 and 7.3 pg, referred to sample. The linear interval of concentrations extends up to 10 μg l−1 of iodide, with no need to use the standard addition method; the mean R.S.D. of data within this range is 3.4%, with 2.9% over the whole procedure. No interfering effects were observed among the foreign ions studied, and 100.0% was the mean analytical recovery achieved within the linear range of concentrations. The application of the method to seven real samples gave a mean content of 12.8 μg g−1 of iodide, as well as less than 3.1 μg g−1 in eight other samples. 相似文献
88.
89.
Finite element methods for problems given in complex domains are often based on tetrahedral meshes. This paper demonstrates that the so-called rational Large Eddy Simulation model and a projection-based Variational Multiscale method can be extended in a straightforward way to tetrahedral meshes. Numerical studies are performed with an inf-sup stable second order pair of finite elements with discontinuous pressure approximation. 相似文献
90.
Julián García José S. Torrecilla Adela Fernández Mercedes Oliet Francisco Rodríguez 《The Journal of chemical thermodynamics》2010,42(1):144-150
(Liquid + liquid) equilibria of 14 binary systems composed of n-hexane, n-heptane, benzene, toluene, o-xylene, m-xylene, or p-xylene and 1-ethyl-3-methylimidazolium ethylsulfate, [emim]EtSO4, or 1-butyl-3-methylimidazolium methylsulfate, [bmim]MeSO4, ionic liquids have been done in the temperature range from (293.2 to 333.2) K. The solubility of aliphatic is less than those of the aromatic hydrocarbons. In particular, the solubility of hydrocarbons in both ionic liquids increases with the temperature in the order n-heptane < n-hexane < m-xylene < p-xylene < o-xylene < toluene < benzene. Considering the high solubility of aromatics and the low solubility of aliphatic hydrocarbons as well as totally immiscibility of the ionic liquids in all hydrocarbons, these new green solvents may be used as potentials extracting solvents for the separation of aromatic and aliphatic hydrocarbons. 相似文献