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51.
Krishnamoorthy G Webb SP Nguyen T Chowdhury PK Halder M Wills NJ Carpenter S Kraus GA Gordon MS Petrich JW 《Photochemistry and photobiology》2005,81(4):924-933
Hydroxy and methoxy perylene quinones are synthesized in an attempt to isolate the essential spectroscopic and biological features of light-induced antiviral agents such as hypericin and hypocrellin. Unlike their naturally occurring counterparts, these synthetic quinones bear the carbonyl, hydroxyl, and methoxy groups in the "bay region." The hydroxy and methoxy compounds have rich absorption spectra with broad features in the visible (approximately 450-800 nm) and relatively more intense and narrow features at wavelengths < or = 350 nm. High-level ab initio quantum mechanical calculations assign the features in the absorption spectra to electronic transitions from S0 to S2 and to higher-lying electronic states. The calculations indicate that in the ground state the trans dihydroxy isomer is 12.5 kcal/mol lower in energy than the cis dihydroxy isomer and is thus the only species present. The lowest-energy trans methoxy ground state isomer and the lowest-energy cis methoxy ground state isomer are found to be degenerate. An additional cis methoxy isomer 6.3 kcal/mol higher in energy than the global minimum is assumed to contribute to the spectrum and is also considered. Finally, the synthetic compounds exhibit similar light-induced antiviral activity to each other, but significantly less than that of hypericin. 相似文献
52.
Prithankar Pramanik Debdatta Halder Siddhartha Sankar Jana Suhrit Ghosh 《Macromolecular rapid communications》2016,37(18):1499-1506
The synthesis, micellar aggregation, and pH‐triggered intracellular drug delivery ability of an amphiphilic statistical copolymer (P2) are studied. Two methacrylate derivatives, one containing a hydrophilic pendant and the other containing a hydrophobic pendant chain, are copolymerized to produce P2. The hydrophobic pendant chain is linked to the polymer backbone by a β‐thiopropionate linkage, known to undergo slow hydrolysis at mild acidic pH. P2 forms a multimicellar cluster in water with a critical aggregation concentration of 0.02 mg mL−1 and encapsulates a hydrophobic guest such as pyrene, Nile red, or the anti‐cancer drug doxorubicin (Dox). Sustained release of the entrapped Dox (80% after 100 h) is noticed at pH 5.2, while release is significantly slower (35% after 100 h) at pH 7.4. Acidic hydrolysis of the β‐thiopropionate linkage leading to the reduction of the hydrophobicity is established as the cause for micellar disassembly and triggered drug release. Cell‐culture studies with the human breast cancer cell line, MCF‐7, reveal biocompatibility of P2 (below 150 μg mL−1). It is further tested for intracellular delivery of Dox. MCF‐7 cells remain healthy at pH 7.4 but become unhealthy at pH 5.2 when treated with a Dox‐loaded P2 micelles.
53.
Amal Halder Sandip K. Nayak Subrata Chattopadhyay Sumanta Bhattacharya 《Journal of Molecular Liquids》2010,151(2-3):125-129
Ground state non-covalent interactions between a macro cyclic calixarene receptor, namely, 4-tert-butylcalix[6]arene (1), and fullerenes (C60 and C70) were studied in toluene medium by absorption spectrophotometric method. Absorption band due to the charge transfer (CT) transition have been observed in the visible region between fullerenes and 1. Utilizing the CT absorption bands, various important physicochemical parameters like oscillator strength, resonance energy, transition dipole strength of the fullerene-1 complexes and ionization potential of 1 is determined in present investigations. From Jobs method of continuous variation, it is observed that both C60 and C70 form stable 1:1 complexes with 1. The most fascinating feature of the present study is that 1 binds selectively C70 compared to C60 as obtained from binding constant (K) data of C60–1 (KC60–1) and C70–1 (KC70–1) complexes, i.e., KC60–1 = 32,400 dm3·mol? 1 and KC70–1 = 110,000 dm3.mol? 1 and selectivity (KC70–1/KC60–1) = 3.4. 1H NMR analysis provides very good support in favor of strong binding between C70 and 1. 相似文献
54.
Headley LS Mukherjee P Anderson JL Ding R Halder M Armstrong DW Song X Petrich JW 《The journal of physical chemistry. A》2006,110(31):9549-9554
Steady-state and time-resolved Stokes shift data for the probe coumarin 153 in two imidazoles, six imidazolium-based ionic liquids, and several other solvents are presented. These results are consistent with our original suggestion (J. Phys. Chem. B 2004, 108, 10245-10255) that initial solvation is dominated by the organic moiety of the ionic liquid, and they show that for the imidazole-based liquids initial solvation is in all cases very rapid. Solvation by methylimidazole and butylimidazole is complete in 100 ps, and all of the imidazolium ionic liquids demonstrate similarly rapid initial solvation. Owing to the importance of determining the amount of initial solvation that is missed in a given experiment with finite time resolution, we discuss a method of estimating the intramolecular contribution to the reorganization energy. This method yields 2068 cm(-1) and is compared with an alternative method. 相似文献
55.
Amal Halder Dulal C. Mukherjee Sumanta Bhattacharya 《Journal of solution chemistry》2010,39(9):1327-1340
Ground state non-covalent interactions between a macrocyclic receptor, C-methylcalix[4]resorcinarene (1) and fullerenes (C60 and C70) have been studied in benzonitrile by an absorption spectrophotometric method. Absorption bands are located in the visible
region due to the charge transfer (CT) transition between 1 and various electron acceptors (including fullerenes), namely, 2,3-dichloro-5,6-dicyano-p-benzoquinone, tetracyanoquinodimethane and p-chloranil. Utilizing the CT absorption bands, various important physicochemical parameters, including oscillator strength,
resonance energy, transition dipole strength of all the acceptor-1 complexes and vertical ionization potential of 1 are determined. Job’s method of continuous variation reveals 1:1 stoichiometry between fullerenes and 1. The most fascinating feature of the present study is that 1 binds selectively to C70 compared to C60 as obtained from binding constant (K) data of C60-1 (KC60-1K_{\mathrm{C}60\mbox{-}\mathbf{1}}) and C70-1 (KC70-1K_{\mathrm{C}70\mbox{-}\mathbf{1}}) complexes, i.e., KC60-1=190K_{\mathrm{C}60\mbox{-}\mathbf{1}}=190 dm3⋅mol−1 and KC70-1=5,800K_{\mathrm{C}70\mbox{-}\mathbf{1}}=5{,}800 dm3⋅mol−1 and selectivity (KC70-1
/KC60-1
) ∼30. Quantum chemical calculations based on hybrid density functional theory estimate the enthalpies of formation of the
fullerene-1 complexes in vacuo and provide very good support for selectivity in the K values of the C70 and C60 complexes of 1. The exchange and correlation energies have been calculated using a hybrid DFT functional method. We have opted to use the
hybrid DFT functional over the Hartree-Fock method, as it can account for correlation effects also. Molecular electrostatic
potential map calculations give a clear picture on the electronic structures of the fullerene-1 complexes. 相似文献
56.
57.
S. Halder T. Schneller R. Waser 《Applied Physics A: Materials Science & Processing》2007,87(4):705-708
Almost all platinized substrates manufactured presently use an TiO2 adhesion layer to improve the adhesion between the SiO2 and the Pt. These substrates however are stable till only 800 °C. We show that simply by replacing the TiO2 with Al2O3, the stability of the electrodes can be increased to 1000 °C and more. These substrates can be used for high temperature
depositions which standard platinized substrates cannot withstand. Further we show that dielectric thin films of BaTiO3 and (Ba,Sr)TiO3 crystallized at higher temperatures show almost a threefold increase in permittivity on these high temperature stable platinized
silicon substrates.The large increase in permittivity is attributed to an increase in grain size at high temperatures.
PACS 61.82.Fk; 68.35.Np; 68.60.Dv; 77.55.+f; 81.20.Fw 相似文献
58.
59.
The reaction of GaMe3 and InMe3 (Me = CH3) with equimolar amounts of α-tropolone forms dimethylgallium tropolonate and dimethylindium tropolonate, respectively, in high yields. Both compounds are monomeric in solution, almost planar 7-/5-ring bicyclic structures of C2v symmetry can be discussed. According to the X-ray structure determination of Me2GaTrop (Trop = C7H5O2) this compound is dimeric in the solid state and crystallizes in the monoclinic space group P21/c with 4 formula units (2 dimers) per unit cell. Me2SnTrop2 is formed by the interaction of Me2SnCl2 with LiTrop in a molar ratio. This ditropolonate is monomeric not only in solution but also in the solid state. The compound crystallizes in the triclinic space group P (Z = 4), and the molecules have a cis-structure of approximate C2-symmetry. The vibrational and NMR spectra of all compounds were measured and are partly assigned. 相似文献
60.