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441.
Menacher F Stepanenko V Würthner F Wagenknecht HA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(24):6683-6688
Perylene bisimides (PBI) have been synthetically incorporated as caps onto a Y-shaped DNA triple strand. These PBI caps serve as "sticky" ends in the spontaneous assembly of larger DNA ensembles, linking the triangular DNA through stacking interactions. This, in turn, yields a hypsochromic shift in the absorption and a red shift in the fluorescence as characteristic optical readouts. This assembly occurs spontaneously without any enzymatic ligation process and without the use of overhanging DNA as sticky ends. Instead, dimerizations of the PBI chromophores in the assembly are controlled by the DNA as a structural scaffold. Thereby, the PBI-driven assembly is fully reversible. Due to the fact that PBI dimerization does not occur in the single strand, the aggregates can be destroyed by thermal dehybridization of the DNA scaffold and reassembled by reannealing of the DNA construct. In view of the fact that PBI forms stable radical anions, the presented DNA architectures are not only interesting optical biomaterials, but are also promising materials for molecular electronics with DNA. 相似文献
442.
Green fluorescent protein (GFP) is an unusually stable autofluorescent protein that is increasingly being exploited for many
applications. In this report, we have used fluorescence spectroscopy to study the effect of pH on the denaturation of GFP
with sodium dodecyl sulfate (SDS), urea, and heat. Surprisingly, SDS (up to 0.5%) did not have any significant effect on the
fluorescence of GFP at pH 7.5 or 8.5 buffers; however, at pH 6.5, the protein lost all fluorescence within 1 min of incubation.
Similarly, incubation of GFP with 8 M urea at 50°C resulted in time dependent denaturation of GFP, but only in pH 6.5 buffer. At higher pH values (pH 7.5 and pH
8.5), the GFP was quite stable in 8 M urea at 50°C, showing only a slight decrease in fluorescence. Heat denaturation of GFP was found to be pH dependent as well,
with the denaturation being fastest at pH 6.5 as compared to pH 7.5 or pH 8.5. Like the denaturation studies, renaturation
of heat-denatured GFP was most efficient at pH 8.5, followed by pH 7.5, and then pH 6.5. These results suggests that GFP undergoes
a structural/stability shift between pH 6.5 and pH 7.5, with the GFP structure at pH 6.5 being very sensitive to denaturation
by SDS, urea, and heat. 相似文献
443.
Joakim Andréasson Prof. Dr. Stephen D. Straight Dr. Thomas A. Moore Prof. Dr. Ana L. Moore Prof. Dr. Devens Gust Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(16):3936-3939
Off and on : A molecular triad, consisting of a porphyrin linked to two different, independently addressable photochromic moieties, functions as a molecular keypad lock with all‐photonic inputs and output. The porphyrin correlates the responses of the two inputs to light of different wavelengths and provides an appropriate output as fluorescence, which results only when one of eight possible input combinations has been applied (see figure).
444.
Elizaveta A. Savicheva Guyzel Yu. Mitronova Laura Thomas Marvin J. Bhm Jan Seikowski Vladimir N. Belov Stefan W. Hell 《Angewandte Chemie (International ed. in English)》2020,59(14):5505-5509
1‐Aminopyrenes with three ω‐hydroxylated N‐alkylsulfonamido or alkylsulfonyl residues in positions 3, 6, and 8 were prepared, O‐phosphorylated, and applied for reductive amination of oligosaccharides. The dyes (?≈20 000 m ?1 cm?1) with six negative charges (pH≥8) and low m/z ratios enable labeling and fluorescence detection of reducing sugars (glycans) related to the most structurally and functionally diverse class of natural products. Under excitation with a 488 nm laser, the new glycoconjugates emit yellow light of about 560 nm, outperforming (with respect to brightness and faster electrophoretic mobilities) the corresponding APTS derivatives (benchmark dye with green emission in conjugates). 相似文献
445.
Prof. Dr. Masaki Shimizu Dr. Youhei Takeda Masahiro Higashi Prof. Dr. Tamejiro Hiyama 《化学:亚洲杂志》2011,6(9):2536-2544
Dimethoxybis(3,3,3‐trifluo‐ropropen‐1‐yl)benzenes were prepared through palladium‐catalyzed double cross‐coupling reactions of diiododimethoxybenzenes with CF3C≡CZnCl, followed by reduction of CF3C≡C groups with LiAlH4 or H2 in the presence of the Lindlar catalyst. The edges of the absorption spectra of 1,2‐(MeO)2‐4,5‐(CF3CHC=CH)2benzenes 1 and 1,3‐(MeO)2‐4,6‐(CF3CH=CH)2benzenes 2 in cyclohexane ranged from 348 to 360 nm, whereas the absorption spectra of 1,4‐(MeO)2‐2,5‐[(E)‐CF3CH=CH]2 benzene ((E)‐ 3 ) ended at 406 nm. These findings indicate that the effective conjugation length of (E)‐ 3 was significantly larger than those of 1 and 2 . Consistently, 1 and 2 in cyclohexane exhibited fluorescence with emission maxima in the UV region, whereas (E)‐ 3 in cyclohexane emitted violet light with an emission maximum at 407 nm. All the fluorescence spectra of 1 – 3 in various solvents redshifted as the solvent polarity increased. The photoluminescence of 1 , E‐1 , Z‐1 , 2 , E‐2 , E‐2H , Z‐2 , E‐3 , E‐3H , Z‐3 in the solid states was also observed with emission maxima in the violet region. It is important to note that the quantum yields of (E)‐ 3 in a neat thin film and in a doped polymer film were 0.37 and 0.49, respectively. Density functional theory calculations suggested that the fluorine atoms contribute to a slight extension of both the HOMOs and the LUMOs, as well as narrowing of the HOMO–LUMO gaps when compared with the corresponding fluorine‐free analogues. In the case of (E)‐ 3 , it is suggested that the HOMO–LUMO transition includes charge transfer from the ethereal oxygen atoms to the C(sp2) CF3 moieties. 相似文献
446.
447.
448.
Rmulo A. Ando Antonio C. Borin Paulo S. Santos 《Journal of Raman spectroscopy : JRS》2009,40(9):1158-1161
The dideprotonation of 4‐(4‐nitrophenylazo)resorcinol generates an anionic species with substantial electronic π delocalization. As compared to the parent neutral species, the anionic first excited electronic transition, characterized as an intramolecular charge transfer (ICT) from the CO− groups to the NO2 moiety, shows a drastic red shift of ca. 200 nm in the λmax in the UV‐vis spectrum, leading to one of the lowest ICT energies observed (λmax = 630 nm in dimethyl sulfoxide (DMSO)) in this class of push‐pull molecular systems. Concomitantly, a threefold increase in the molar absorptivity (εmax) in comparison to the neutral species is observed. The resonance Raman enhancement profiles reveal that in the neutral species the chromophore involves several modes, as ν(C N), ν(NN), ν(CC) and νs(NO2), whereas in the dianion, there is a selective enhancement of the NO2 vibrational modes. The quantum chemical calculations of the electronic transitions and vibrational wavenumbers led to a consistent analysis of the enhancement patterns observed in the resonance Raman spectra. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
449.
Tom E. Stennett Philipp Bissinger Stefanie Griesbeck Stefan Ullrich Ivo Krummenacher Michael Auth Andreas Sperlich Matthias Stolte Krzysztof Radacki Chang‐Jiang Yao Frank Würthner Andreas Steffen Todd B. Marder Holger Braunschweig 《Angewandte Chemie (International ed. in English)》2019,58(19):6449-6454
Herein, two new quadrupolar acceptor‐π‐donor‐π‐acceptor (A‐π‐D‐π‐A) chromophores have been prepared featuring a strongly electron‐donating diborene core and strongly electron‐accepting dimesitylboryl (BMes2) and bis(2,4,6‐tris(trifluoromethyl)phenyl)boryl (BFMes2) end groups. Analysis of the compounds by NMR spectroscopy, X‐ray crystallography, cyclic voltammetry, and UV/Vis‐NIR absorption and emission spectroscopy indicated that the compounds have extended conjugated π‐systems spanning their B4C8 cores. The combination of exceptionally potent π‐donor (diborene) and π‐acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO–LUMO gaps, resulting in strong absorption in the near‐IR region with maxima in THF at 840 and 1092 nm and very high extinction coefficients of ca. 120 000 m ?1 cm?1. Both molecules also display weak near‐IR fluorescence with small Stokes shifts. 相似文献
450.
Marcelo H. Kravicz Debora T. Balogh Mrityunjoy Kar Stefanie Wedepohl Maria Vitoria L. B. Bentley Marcelo Caldern 《Macromolecular bioscience》2019,19(10)
The development of polymers with low toxicity and efficient gene delivery remains a significant barrier of nonviral gene therapy. Modification and tuning of chemical structures of carriers is an attractive strategy for efficient nucleic acid delivery. Here, polyplexes consisting of plasmid DNA (pDNA) and dodecylated or non‐dodecylated polysuccinimide (PSI)‐based polycations are designed, and their transfection ability into HeLa cells is investigated by green fluorescent protein (GFP) expressing cells quantification. All cationic polymers show lower cytotoxicity than those of branched polyethyleneimine (bPEI). PSI and bPEI‐based polyplexes have comparable physicochemical properties such as size and charge. Interestingly, a strong interaction between dodecylated polycations and pDNA caused by the hydrophobic moiety is observed in dodecylated PSI derivatives. Moreover, the decrease of GFP expression is associated with lower dissociation of pDNA from polyplexes according to the heparin displacement assay. Besides, a hydrophobization of PSI cationic derivatives with dodecyl side chains can modulate the integrity of polyplexes by hydrophobic interactions, increasing the binding between the polymer and the DNA. These results provide useful information for designing polyplexes with lower toxicity and greater stability and transfection performance. 相似文献