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41.
Nowicka AM Zabost E Donten M Mazerska Z Stojek Z 《Analytical and bioanalytical chemistry》2007,389(6):1931-1940
A method is presented for the electroanalytical characterization of interactions of dsDNA with a drug, under conditions that
both agents are dissolved in the phosphate buffer solution and both are electroactive. Normal pulse, square wave, differential
pulse, and cyclic voltammetries were employed in the measurements of the drug and dsDNA oxidation signals at carbon electrodes.
UV–Vis spectroscopy was used as a non-electrochemical method to support the electroanalytical data. An anticancer drug, C-1311
(5-diethylaminoethyl-amino-8-hydroxyimidazoacridinone), has been selected for the examination. Normal pulse voltammetry was
particularly useful in showing that under the conditions employed neither dsDNA nor the drug were adsorbed at the electrode
surface. Necessary conditions for the appearance of the well-defined dsDNA voltammetric signal (guanine peak) are: rigorous
chemical and biological purity in the cell and appropriate purity of DNA. An analysis of the obtained results confirmed that
there were two modes of interaction between C-1311 and dsDNA: by intercalation and electrostatically. In the presence of excess
NaCl the electrostatic interactions deteriorate. The binding constants (K
1 and K
2, respectively) and the number (n) of nucleic base pairs (bp) and the number (m) of phosphate groups (pg) interacting with one molecule of drug have been determined. For strong interactions (intercalation)
the values of the binding constant, K
1, and the binding-site size, n, equal 3.7 × 104 M−1 and 2.1, respectively. For the weak electrostatic interactions the K
2 and m parameters equal 0.28 × 104 M−1 and 4.7. The intercalation process is rather slow and its rate (the conditions of pseudo-first-order reaction) was estimated
to equal 7 × 10−4 s−1. The possibility of independent determination of both interacting agents was very useful in the study.
Figure Intercalation of C-1311 into a dsDNA fragment 相似文献
42.
The complexes of glyoxal (Gly), methylglyoxal (MGly), and diacetyl (DAc) with water have been studied using Fourier transform infrared (FTIR) matrix isolation spectroscopy and MP2 calculations with 6-311++G(2d,2p) basis set. The analysis of the experimental spectra of the Gly(MGly,DAc)/H2O/Ar matrixes indicates formation of one Gly...H2O complex, three MGly...H2O complexes, and two DAc...H2O ones. All the complexes are stabilized by the O-H...O(C) hydrogen bond between the water molecule and carbonyl oxygen as evidenced by the strong perturbation of the O-H, C=O stretching vibrations. The blue shift of the CH stretching vibration in the Gly...H2O complex and in two MGly...H2O ones suggests that these complexes are additionally stabilized by the improper C-H...O(H2) hydrogen bonding. The theoretical calculations confirm the experimental findings. They evidence the stability of three hydrogen-bonded Gly...H2O and DAc...H2O complexes and six MGly...H2O ones stabilized by the O-H...O(C) hydrogen bond. The calculated vibrational frequencies and geometrical parameters indicate that one DAc..H2O complexes, two Gly...H2O, and three MGly...H2O ones are additionally stabilized by the improper hydrogen bonding between the C-H group and water oxygen. The comparison of the theoretical frequencies with the experimental ones allowed us to attribute the calculated structures to the complexes present in the matrixes. 相似文献
43.
Krzysztof Staliński Zofia Urbańczyk-Lipkowska Leszek Rupnicki 《Journal of organometallic chemistry》2006,691(11):2394-2402
A series of tri- and tetraorganotin compounds containing the optically active 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand and tert-butyl, methyl and/or phenyl groups on the tin has been synthesized. All the novel compounds have been characterized, especially by means of the multinuclear NMR investigation, the results of which are discussed. The tin halides, as pairs of diastereoisomers in solution, crystallize in the form of one diastereoisomer. The single-crystal X-ray analysis of tin iodide 10a revealed pseudo-equatorial position of the tert-butyl group opposite to the isopropyl group. In the corresponding diastereomeric tin hydrides values of 1J(1H-117/119Sn) differ significantly, suggesting a different pseudo-axial/equatorial position of the hydrogen atom. 相似文献
44.
45.
Anna Michnik Aleksandra Kłos Zofia Drzazga 《Journal of Thermal Analysis and Calorimetry》2004,77(1):269-277
Protein unfolding events were studied by differential scanning calorimetry (DSC) for bovine serum albumin (BSA) aqueous solutions
exposed to radio-frequency radiation. No immediate effect of this radiation on thermal unfolding of BSA was observed. The
differences between irradiated and control samples have appeared during the storage of BSA solution. The irradiated samples
changed faster than non-irradiated. Our results indicated that the age-related changes were stronger for 3.5 and 5 MHz than
for 247 MHz frequency and dependent on energy power of radiation. Deconvolution of DSC traces allowed to study the effect
of radio-frequency radiation on each component transition.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
46.
47.
Zusammenfassung Eine polarographische Methode zur direkten Bestimmung von Diazepam in Leichenblut ohne vorherige Extraktion wird beschrieben. Als Grundelektrolyt wird Britton-Robinson-Puffer (pH 2,8) und Methanol (41v/v) empfohlen. Die untere Bestimmungsgrenze liegt bei 20 g Diazepam/ml Blut.
Polarographic determination of diazepam in cadaver blood without prior extraction
Summary A polarographic method is described for the direct determination of diazepam in cadaver blood without previous extraction. The fundamental electrolyte recommended is Britton-Robinson buffer solution (pH=2.8) and methanol (41v/v). The lower determination limit is situated at 20g diazepam/ml blood.相似文献
48.
The effect of ethanol on human serum albumin stability in aqueous solution
was studied by use of differential scanning calorimetry. A deconvolution of
DSC traces in 2-state model with ΔC
p=0
and ΔC
p≠0
was performed and analysed to obtain information on the interaction of ethanol
with different parts of albumin molecule both fatty acid containing and fatty
acid free. The differences in ethanol binding affinity for both kinds of albumin
were found. At very low concentrations ethanol was observed to be a stabilizer
of the folded state of albumin contrary to the higher concentration where
its binding to the unfolded protein predominates. 相似文献
49.
Alan R. Katritzky Clifford H. Watson Zofia Dega-Szafran John R. Eyler 《Journal of mass spectrometry : JMS》1989,24(11):1017-1021
Three novel collisionally induced dissociation pathways, additional to the usual formation of pyridine or pyridinium cation, are described for laser-desorbed N-substituted pyridinium cations. Particularly prevalent is the formation of an ion of m/z 94, corresponding to [PyCH3]+. Doubly charged pyridiniums tend to lose H+, and one example of the apparent formation of the neutral radical C5H6N˙ is reported. 相似文献
50.
Krzysztof Bujnowski Ludwik SynoradzkiEckhard Dinjus Thomas ZevacoEwa Augustynowicz-Kope? Zofia Zwolska 《Tetrahedron》2003,59(11):1885-1893
Within the study covering the search for new methods of synthesis of rifamycin antibiotics, the reactions of 3-formylrifamycin SV (2) with primary amines or ammonia were studied. In the reaction of 2 with methylamine, unstable 3-methyliminomethylrifamycin SV (8) was formed, which was further oxidised to stable 3-methyliminomethylrifamycin S (9). In the reaction of 2 with ammonia, N,15-didehydro-15-deoxo-pyrimido-(4,5-b)rifamycin SV (10), a new compound with a chromophore system enlarged by a pyrimidine ring, was obtained. The product of its reduction with sodium borohydride—(11)—was also isolated. The structures of the compounds and an explanation of the synthesis mechanism have been proposed on the basis of mass spectrometry results as well as (1D) and (2D) 1H- and 13C NMR analysis. In vitro antituberculous activity of the new compounds have been investigated. 相似文献