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51.
New host molecules for anions, adamantane, and alkyl urea derivatives substituted by naphthalene chromophores, were synthesized. Their binding with F−, Cl−, Br−, OAc−, HSO4−, NO3−, and H2PO4− was investigated by UV-vis, fluorescence and NMR spectroscopy. The anion binding ability of adamantyl bisurea derivatives was compared with the analogous host molecules, wherein the urea moieties are separated by flexible alkyl linkers of the same length, and adamantane monourea derivative. The host molecules show the highest selectivity toward F− and H2PO4−. The binding stoichiometry and the values of the association constants depend on the basicity of anions, availability of H-bonding sites, preorganization, and rigidity of the hosts, as well as solvent polarity and H-bonding availability. Rigid adamantane receptors, compared to flexible analogues show increased selectivity for H2PO4−, whereas binding of OAc− is better with flexible receptors. The binding of OAc− and H2PO4− was investigated by microcalorimetry. The stoichiometries and the stability constants of the corresponding complexes obtained by this method were in good agreement compared to those determined by UV-vis titrations. In both cases the enthalpic contribution to the overall complex stability was predominant. 相似文献
52.
Zora Popović Draginja Mrvoš-Sermek Željka Soldin Vesna Tralić-Kulenović 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):20-21
The reaction of 2-methyl-1,3-benzothiazole (mebta) with mercury(II) chloride in methanol in a 1:1 molar ratio resulted in the formation of single crystals of the title compound, [HgCl2(C8H7NS)]n. The molecules exist as continuous chlorine-bridged chains in which Hg atoms lie in distorted trigonal bipyramidal environments. The equatorial positions are occupied by an N atom from the ligand [2.236 (8) Å] and two Cl atoms [2.428 (3) and 2.459 (3) Å]. The two axial Hg—Cl contacts to two neighbouring molecules [2.874 (3) and 2.964 (3) Å] are significantly shorter than the sum of the respective van der Waals radii, and form close to linear Cl—Hg—Cl sequences [177.80 (7)°]. 相似文献
53.
In this paper, using the context of complete partial metric spaces, some common fixed point results of maps that satisfy the generalized(φ, ψ)-weak contractive conditions are obtained. Our results generalize, extend, unify, enrich and complement many existing results in the literature. Example are given showing the validaty of our results. 相似文献
54.
55.
Miloš R. Filipović Dr. Alaric C. W. Koh Dr. Stéphane Arbault Dr. Vesna Niketić Dr. Andrea Debus Ulrike Schleicher Dr. Christian Bogdan Dr. Manon Guille Dr. Fréderic Lemaître Dr. Christian Amatore Dr. Ivana Ivanović‐Burmazović Dr. 《Angewandte Chemie (International ed. in English)》2010,49(25):4228-4232
56.
57.
Marković Gordana Marinović-Cincović Milena Vodnik Vesna Radovanović Blaga Budinski-Simendić Jaroslava Veljković Olivera 《Journal of Thermal Analysis and Calorimetry》2009,97(3):999-1006
The properties of chlorosulphonated polyethylene (CSM) rubber, acrylonitrile rubber (NBR) and their blend (50/50 w/w) were
studied. Fourier transform infrared (FTIR) studies supported that CSM/NBR rubber blend is self curable, when cross-linking
takes place between acrylonitrile groups of NBR and –SO2Cl groups or in situ generated allyl chloride moieties of CSM. The thermal stability of vulcanizates was analyzed in nitrogen
by thermogravimetry. It was found that the initial degradation temperature of elastomer based on CSM rubber is lower than
of pure NBR rubber. By adding NBR to CSM rubbers, the degradation temperature of crosslinked material increased, indicating
higher thermal stability. The activation energy for the degradation are determined using the Arrhenius equation The activation
energies for the rubber blends are higher than for elastomers based on pure rubbers. It was found that the mass loss of the
blends at any temperature was between those of the pure rubbers. The differential scanning calorimetry (DSC) was used for
the glass transition temperature determination. It is estimated thermodynamic immiscibility of NBR/CSM blend based on noticed
two different glass transition temperatures, corresponding to CSM and NBR rubbers. 相似文献
58.
Enantiodivergent formal synthesis of (+)- and (−)-muricatacins from d-xylose has been accomplished through utilization of the latent plane of symmetry present in the starting monosaccharide. This approach was extended to the preparation of two novel (+)- and (−)-muricatacin 7-oxa analogs (2 and ent-2, respectively), which showed in vitro antitumor activity toward some human malignant cells. The analog ent-2 showed a powerful antiproliferative activity against the K562 cell line, being 36-fold more potent than the standard cytotoxic agent, doxorubicin. Compound 2, however, showed a powerful cytotoxic activity against HL-60 cells, being more than 17-fold more potent with respect to the reference compound. 相似文献
59.
Cerkvenik-Flajs V 《Biomedical chromatography : BMC》2006,20(10):985-992
Validation of an analytical method for determining chloramphenicol residues in muscle tissue by gas chromatography-electron capture detection (GC-ECD) was performed according to the latest European Union criteria for the analysis of veterinary drugs in food, laid down by Commission Decision 2002/657/EC. The method using the meta isomer of chloramphenicol as an internal standard proved to be very selective, specific to other related phenicols and accurate to within +3.6% at a concentration level of 8.9 microg/kg, as present in the certified reference material available. The correlation coefficient of the calibration curve was 0.9991. At all three fortification levels studied (0.3, 0.45 and 0.6 microg/kg), repeatability and intra-laboratory reproducibility were <8 and < or =9%, respectively. The decision limit (CCalpha) and detection capability (CCbeta) were 0.07 and 0.12 microg/kg, respectively. The validation results and the results of participation in an international inter-laboratory proficiency test indicate that the method presented is completely suited for regulatory control to screen and quantify chloramphenicol residues in various muscle tissues on a routine basis. 相似文献
60.
CH/pi interactions between the coordinated acetylacetonato ligand and phenyl rings were analyzed in the crystal structures from the Cambridge Structural Database and by quantum chemical calculations. The acetylacetonato ligand may engage in two types of interactions: it can be hydrogen atom donor or acceptor. The analysis of crystal structures and calculations show that interactions with the acetylacetonato ligand acting as hydrogen atom donor depend on the metal in an acetylacetonato chelate ring; the chelate rings with soft metals make stronger interactions. The same trend was not observed in the interactions where the acetylacetonato chelate ring acts as the hydrogen atom acceptor. 相似文献