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71.
72.
[reaction: see text] The facile modular assembly of polyarylpyridine fluorophores provides two important advantages in the development of fluorescent chemosensors: it allows rapid dissection of the structural requirements for fluorescent chemosensing and it allows dramatic tuning of emission wavelength by changes in a substituent remote from the binding site. 相似文献
73.
Tris(bipyridyl)ruthenium(II) complexes modified such that one of the bipyridines is appended with a crown ether display luminescence that is responsive to complexation with metal ions. The parent species, Ru(bpy)3(2+), is moderately luminescent, with an emission lifetime of about 1 micros in fluid solution at room temperature. The modified complexes are much less emissive, with lifetimes near 1 ns. Conformational flexibility and distortion in the crown-ether complexes enhance nonradiative decay. Noncovalent binding of metal ions, however, restores luminescence intensity by reducing nonradiative decay and increasing the lifetime 10- to 100-fold. Reported here are the syntheses and steady-state and time-resolved luminescence measurements in addition to other supporting spectroscopic characterization. Seven metals were investigated; significant luminescence enhancements occur in the presence of Mg2+, Ca2+, and Pb2+. Effective concentrations of metal ions range from tens of microM to hundreds of mM. The steady-state enhancements are readily measured, but they are less than would be expected from the lifetime changes, partly because only a portion (not more than 50%) of the fast (1 ns) decay in Ru(bpy)2(bpy-crown) is capable of converting to the conformation possessing the longer lifetime. A photophysical model is proposed to explain these and other observations. 相似文献
74.
We report here a new approach to the discovery of fluorescent chemosensors in which a new signaling mechanism allows a core fluorophore to be used in a combinatorial search for new binding events, thus reversing the reigning discovery paradigm. 相似文献
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77.
The first visual fluorescence-based assay for the peroxide explosive triacetone triperoxide (TATP) is described. The assay is based on a conceptually new fluorescence signaling mechanism, in which nonemissive pyrenyl sulfoxide profluorophores are oxidized to visibly emissive pyrenyl sulfones. Although not without limitations, these first-generation fluorescent probes can provide a visual response to ca. 100 nmol of TATP. In addition, the success of this assay suggests the potential for broader application of aryl sulfoxides in fluorescent chemosensing. 相似文献
78.
Blomgren P Palacios A Zhu B Daw S Finney C Halow J Pannala S 《Chaos (Woodbury, N.Y.)》2007,17(1):013120
We use a low-dimensional, agent-based bubble model to study the changes in the global dynamics of fluidized beds in response to changes in the frequency of the rising bubbles. The computationally based bifurcation analysis shows that at low frequencies, the global dynamics is attracted towards a fixed point since the bubbles interact very little with one another. As the frequency of injection increases, however, the global dynamics undergoes a series of bifurcations to new behaviors that include highly periodic orbits, chaotic attractors, and intermittent behavior between periodic orbits and chaotic sets. Using methods from time-series analysis, we are able to approximate nonlinear models that allow for long-term predictions and the possibility of developing control algorithms. 相似文献
79.
Salzmann CG Hallbrucker A Finney JL Mayer E 《Physical chemistry chemical physics : PCCP》2006,8(26):3088-3093
Raman spectra of recovered ordered H(2)O (D(2)O) ice XIII doped with 0.01 M HCl (DCl) recorded in vacuo at 80 K are reported in the range 3600-200 cm(-1). The bands are assigned to the various types of modes on the basis of isotope ratios. On thermal cycling between 80 and 120 K, the reversible phase transition to disordered ice V is observed. The remarkable effect of HCl (DCl) on orientational ordering in ice V and its phase transition to ordered ice XIII, first reported in a powder neutron diffraction study of DCl doped D(2)O ice V (C. G. Salzmann, P. G. Radaelli, A. Hallbrucker, E. Mayer, J. L. Finney, Science, 2006, 311, 1758), is demonstrated by Raman spectroscopy and discussed. The dopants KOH and HF have only a minor effect on hydrogen ordering in ice V, as shown by the Raman spectra. 相似文献
80.
Bowron DT Finney JL Hallbrucker A Kohl I Loerting T Mayer E Soper AK 《The Journal of chemical physics》2006,125(19):194502
Using isotope substitution neutron scattering data, we present a detailed structural analysis of the short and intermediate range structures of the five known forms of amorphous ice. Two of the lower density forms--amorphous solid water and hyperquenched glassy water--have a structure very similar to each other and to low density amorphous ice, a structure which closely resembles a disordered, tetrahedrally coordinated, fully hydrogen bonded network. High density and very high density amorphous ices retain this tetrahedral organization at short range, but show significant differences beyond about 3.1 A from a typical water oxygen. The first diffraction peak in all structures is seen to be solely a function of the intermolecular organization. The short range connectivity in the two higher density forms is more homogeneous, while the hydrogen site disorder in these forms is greater. The low Q behavior of the structure factors indicates no significant density or concentration fluctuations over the length scale probed. We conclude that these three latter forms of ice are structurally distinct. Finally, the x-ray structure factors for all five amorphous systems are calculated for comparison with other studies. 相似文献