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51.
Daniel B. Eckl Nicole Landgraf Anja K. Hoffmann Anja Eichner Harald Huber Wolfgang Bäumler 《Photochemistry and photobiology》2023,99(2):716-731
Many studies show that photodynamic inactivation (PDI) is a powerful tool for the fight against pathogenic, multiresistant bacteria and the closing of hygiene gaps. However, PDI studies have been frequently performed under standardized in vitro conditions comprising artificial laboratory settings. Under real-life conditions, however, PDI encounters substances like ions, proteins, amino acids and fatty acids, potentially hampering the efficacy of PDI to an unpredictable extent. Thus, we investigated PDI with the phenalene-1-one-based photosensitizer SAPYR against Escherichia coli and Staphylococcus aureus in the presence of calcium or magnesium ions, which are ubiquitous in potential fields of PDI applications like in tap water or on tissue surfaces. The addition of citrate should elucidate the potential as a chelator. The results indicate that PDI is clearly affected by such ubiquitous ions depending on its concentration and the type of bacteria. The application of citrate enhanced PDI, especially for Gram-negative bacteria at certain ionic concentrations (e.g. CaCl2 or MgCl2: 7.5 to 75 mmol L−1). Citrate also improved PDI efficacy in tap water (especially for Gram-negative bacteria) and synthetic sweat solution (especially for Gram-positive bacteria). In conclusion, the use of chelating agents like citrate may facilitate the application of PDI under real-life conditions. 相似文献
52.
Vougioukalakis GC Roubelakis MM Alberti MN Orfanopoulos M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(31):9697-9705
The influence of the solvent on the triazolinedione-alkene ene reaction mechanism has been investigated. Both inter- and intramolecular kinetic isotope effects with tetramethylethylenes and 2,2,2-(trideuterio)methyl-7-methyl-2,6-octadiene-[D3]-1,1,1 provide, for the first time, strong evidence for changes in the mechanism of the reaction on going from non-protic to polar protic solvents. In non-protic polar or apolar solvents, an aziridinium imide that equilibrates to an insignificant extent with an open intermediate (a dipolar or a polarized biradical) is formed irreversibly in the first, rate-determining step of the reaction, which is followed by fast hydrogen abstraction. On the contrary, in polar protic solvents, hydrogen abstraction is rate limiting, allowing the main dipolar intermediate to equilibrate with its open intermediate(s) as well as with the starting reagents. 相似文献
53.
Günter?GramppEmail author Anne-Marie?Kelterer Stephan?Landgraf Michael?Sacher Dominique?Niethammer Jo?o P.?Telo Rui M. B.?Dias Abel J. S. C.?Vieira 《Monatshefte für Chemie / Chemical Monthly》2005,136(4):519-536
Summary. ESR and ENDOR spectra are reported of several symmetrical substituted N,N,N,N-tetraalkyl-p-phenylenediamine radical cations in solution. Different N,N-alkyl substituted para-phenylenediamines, like the ethyl, n-propyl, and iso-propyl derivative are compared with the parent N,N,N,N-tetramethyl-p-phenylenediamine (Wursters Blue Cation). N,N,N,N-Tetrabenzyl-p-phenylenediamine, 1,4-dipyrrolidinylbenzene, and N,N-bis[4-(dimethylamino)phenyl]piperazine are additionally investigated. Experimental and calculated hyperfine coupling constants are compared. Characteristic UV-VIS data and redox potentials in acetonitrile are reported, together with the syntheses of the compounds. 相似文献
54.
55.
Landgraf RR Chalmers MJ Griffin PR 《Journal of the American Society for Mass Spectrometry》2012,23(2):301-309
Hydrogen deuterium exchange mass spectrometry (HDX-MS) is a well established method for the measurement of solution-phase
deuterium incorporation into proteins, which can provide insight into protein conformational mobility. However, most HDX measurements
are constrained to regions of the protein where pepsin proteolysis allows detection at peptide resolution. Recently, single-amide
resolution deuterium incorporation has been achieved by limiting gas-phase scrambling in the mass spectrometer. This was accomplished
by employing a combination of soft ionization and desolvation conditions coupled with the radical-driven fragmentation technique
electron transfer dissociation (ETD). Here, a hybrid LTQ-Orbitrap XL is systematically evaluated for its utility in providing
single-amide deuterium incorporation for differential HDX analysis of a nuclear receptor upon binding small molecule ligands.
We are able to show that instrumental parameters can be optimized to minimize scrambling and can be incorporated into an established
and fully automated HDX platform making differential single-amide HDX possible for bottom-up analysis of complex systems.
We have applied this system to determine differential single amide resolution HDX data for the peroxizome proliferator activated
receptor bound with two ligands of interest. 相似文献
56.
Schnell M Sävert A Landgraf B Reuter M Nicolai M Jäckel O Peth C Thiele T Jansen O Pukhov A Willi O Kaluza MC Spielmann C 《Physical review letters》2012,108(7):075001
We investigate the properties of a laser-plasma electron accelerator as a bright source of keV x-ray radiation. During the interaction, the electrons undergo betatron oscillations and from the carefully measured x-ray spectrum the oscillation amplitude of the electrons can be deduced which decreases with increasing electron energies. From the oscillation amplitude and the independently measured x-ray source size of (1.8±0.3) μm we are able to estimate the electron bunch diameter to be (1.6±0.3) μm. 相似文献
57.
Summary. Since the first application of laser diodes (LD) for the determination of fluorescence lifetimes in our group in 1995, great
technical improvements have been made to increase the time resolution of the apparatus. Using the phase fluorometric method,
measurements down to 100 ps are now possible. Values can be measured in steps of 10 ps with good reproducibility using a high-frequency
signal generator and a GHz digital storage oscilloscope. No additional optical equipment is necessary for this new method.
Following an easy calibration procedure, results are available within one minute without any adjustments. The components of
the new apparatus including light source, sample chamber for standard fluorescence cuvettes, and detection unit are situated
in a 12 × 13 × 9 cm setup. The apparatus was tested with different fluorophores, and the results correlate very well with
known values in the range of 0.1 to 1000 ns.
Received February 16, 2000. Accepted March 13, 2000 相似文献
58.
V. B. Avakov V. A. Bogdanovskaya B. A. Ivanitskii A. V. Kapustin A. V. Kuzov I. K. Landgraf A. D. Modestov M. V. Radina M. M. Stankevich M. R. Tarasevich O. V. Tripachev 《Russian Journal of Electrochemistry》2014,50(7):656-668
A cathodic catalyst, which can replace monoplatinum commercial catalyst, is developed and investigated. New catalyst combines a smaller consumption of platinum with a higher mass activity and corrosion resistance. A method of fabrication of ternary (PtCoCr/C) catalyst is improved in order to obtain the catalytic system containing 45–50 wt % platinum. This is necessary to form thinner active layers of cathodes of membrane-electrode assemblies of hydrogen-air fuel cells. The activity of the synthesized PtCoCr/C catalyst is by 1.2–1.5 times higher than that of the monoplatinum catalyst containing 60–70 wt % Pt. According to the accelerated-test data, the corrosion resistance of PtCoCr/C catalyst is also higher than that of Pt/C system. 相似文献
59.
Mariza N. AlbertiGeorgios C. Vougioukalakis Michael Orfanopoulos 《Tetrahedron letters》2003,44(5):903-905
The regioselectivity of the ene pathway in the photooxidation of several 1-aryl-2-methylpropenes, as probed by stereoselective deuterium-labeling, depends on the electronic nature of the para phenyl-substituents. The reaction of the same array of alkenylarenes with 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) gives ene products with an impressive >97% allylic hydrogen abstraction from the more substituted side of the alkene. 相似文献
60.
An example of Floquet operator with purely point spectrum and energy instability is presented. In the unperturbed energy eigenbasis
its eigenfunctions are exponentially localized.
CRdeO was partially supported by CNPq (Brazil).
MSS was supported by CAPES (Brazil).
Submitted: September 21, 2006. Accepted: December 12, 2006. 相似文献