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81.
Carboxymethyl cellulose-silver nanoparticle (AgNp)-silica hybrids have been synthesized in a modified Stöber process. The hybrid synthesis was optimized to obtain an efficient immobilization matrix for diastase alpha amylase, a multimeric enzyme of high technological significance. The synthesized hybrids were characterized using FTIR, XRD, SEM, TGA and BET studies. The enzyme immobilization was done by adsorption and using the immobilized enzyme, the hydrolysis of soluble starch has been optimized in comparison to free enzyme. The optimum usable pH for the immobilized enzyme ranged from pH 4 to 5, while pH 5 was optimum pH for the free enzyme activity. The kinetic parameters for the immobilized, (K M = 3.4610 mg ml?1; V max = 6.3540 mg ml?1 min?1) and free enzyme (K M = 4.1664 mg ml?1; V max = 4.291 mg ml?1 min?1) hydrolysis indicated that the immobilization at the nanohybrid has significantly improved the catalytic property of the enzyme. In the immobilized state, the enzyme remained usable for many repeated cycles like our previous material, gum acacia-gelatin-AgNp-silica. Storage experiments indicated that the immobilization has increased the stability of the enzyme and also that AgNps play a role in stabilizing the immobilized enzyme. 相似文献
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83.
Kumar M Bhalla V Dhir A Babu JN 《Dalton transactions (Cambridge, England : 2003)》2010,39(42):10116-10121
Synthetic strategies are described to synthesize the calix[4]arene diamine 4 of partial cone (paco) conformation, which on condensation with 9-anthracene carbaldehyde forms the chemosensor 5 in paco conformation. The chemosensor 5 undergoes fluorescence enhancement in the presence of Ni(2+) ions. 相似文献
84.
New thiacalix[4]crown derivatives 4 and 5 of 1,3-alternate conformation possessing anthracene and quinoline moieties respectively were synthesised and examined for their cation recognition abilities toward different cations by fluorescence spectroscopy. Selective optical recognition with fluorescence amplification was observed for Fe(3+)/K(+) and Hg(2+)/K(+) in chemosensors 4 and 5 respectively. Further it was observed that the formation of 4·Fe(3+) complex triggers the decomplexation of K(+) ion. Similar allosteric behaviour between Hg(2+) and K(+) was observed in chemosensor 5. 相似文献
85.
A new terphenyl based chemosensor 3 has been designed and synthesized. The binding behavior of 3 and its chemosensing ensemble 3-Hg toward various anions (F(-), Cl(-), Br(-), I(-), HSO(4)(-), H(2)PO(4)(-), CH(3)COO(-), NO(3)(-), N(3)(-), SO(4)(2-), SO(3)(2-), and Cr(2)O(7)(2-)) has been investigated by UV-Vis, fluorescence and NMR spectroscopy. Compound 3 shows a sensitivity for both F(-) and CH(3)COO(-) ions among various anions tested, whereas the ensemble 3-Hg shows a better selectivity for CH(3)COO(-) ions. The ensemble is utilized for CH(3)COO(-) recognition in a blood plasma like system. 相似文献
86.
Zinc ensemble of hexaphenylbenzene derivative 3 exhibits sensitive response toward adenosine monophosphate (AMP) and H(2)PO(4)(-) ions. Further, the application of derivative 3 as a multichannel molecular keypad could be realized in the presence of inputs of Zn(2+) ions, H(2)PO(4)(-) ions, and AMP. 相似文献
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A series of novel bisthiacalix[4]arenes with diimine linkages of different aromatic or heteroaromatic dialdehydes have been synthesized. The structure of one of the bisthiacalixarene has been analyzed by X-ray crystallography. These molecules quantitatively extract silver ion from aqueous into organic phase under neutral conditions. 相似文献
90.
Semiempirical SCF-MO studies of tautomerism in alloxan preclude the possibility of direct proton transfer in the gas phase
due to the strain in the four-centred transition state, in which the proton being transferred is forced to come close to the
positively charged carbon atom at the opposite corner of the four-membered ring. However, in aqueous solution, the activation
barrier reduces appreciably, not only due to reduction in strain, but also due to charge separation in the transition state,
which is stabilized due to ionic resonance. The N-H bond is almost broken, while the O-H bond is only partially formed in
the transition state. The other stabilizing effect in aqueous solution is due to bulk solvent dielectric effects, which stabilize
the transition state to a greater extent due to its higher dipole moment. Although the transition states for proton transfer
to the neighbouring oxygen atoms on either side have comparable energies, as the mechanisms of proton transfer leading to
the formation of the 2-hydroxy and 4-hydroxy tautomers are similar, bulk solvent effects are larger in the latter due to the
higher dipole moment of the transition state. The reason is the almost complete separation of the two entities, i.e. the alloxan
anion and the hydronium ion in the latter case, indicating that in this case a dissociative mechanism of the kind encountered
in acid-base equilibria is operating. 相似文献