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51.
Shi X Nishimura Y Akashi S Takamizawa A Hiraoka K 《Journal of the American Society for Mass Spectrometry》2006,17(4):611-620
We have applied laser spray mass spectrometry developed by Hiraoka et al. to investigate the binding affinity of protein-mutant DNA complexes. The results were compared with our previous data of collision-induced dissociation (CID) experiments using electrospray ionization mass spectrometry (ESI-MS). Systematic experiments were carried out on the complexes of the c-Myb DNA binding domain (c-Myb DBD) bound to eight kinds of 16- or 22-mer point mutant double-stranded DNA (dsDNA), whose solution K(d) values are different in the range from 10(-9) M to 10(-7) M. The dissociation curve as a function of laser power was plotted for each complex, and the laser power where 50% of complex was dissociated (E(50%)) in population was obtained. The correlation coefficient between E(50%) and the relative binding free-energy change (DeltaDeltaG) of each complex formation in solutions was 0.9808, which is much better than the coefficient obtained by the previous ESI-CID experiments that was 0.859. In addition, complexes of the c-Myb DBD with five other mutant dsDNA were also examined to confirm that laser spray can be used to estimate the K(d) values of a DNA-protein complex in solutions if an appropriate calibration curve is available. In the process of laser spray, dissociations of these noncovalent complexes occur in solutions, but not in the gas phase. This differs greatly from ESI-CID. Laser spray mass spectrometry has been found to be better than ESI-CID in evaluating binding affinity of a protein to various mutant DNA. 相似文献
52.
Fujitsuka M Cho DW Tojo S Yamashiro S Shinmyozu T Majima T 《The journal of physical chemistry. A》2006,110(17):5735-5739
The intramolecular dimer radical cation and charge-transfer complex of various cyclophanes were investigated by using pulse radiolysis measurements. The charge resonance band due to the dimer radical cation of cyclophanes appeared in the near-IR region, which showed a blue-shift as the distance between the two benzene rings of cyclophane decreased. The stabilization energy of the dimer radical cation, which was estimated from the peak position of the charge resonance band, was explained by the exchange interaction, while the substituent effect was small. The absorption peak of the charge-transfer complex with chlorine atom also showed the shift in accordance with the oxidation potential of cyclophanes. 相似文献
53.
Three metabolites of 1-nitropyrene, i.e., 3-hydoxy-1-nitropyrene (3-OHNP), 6-hydoxy-1-nitropyrene (6-OHNP) and 8-hydoxy-1-nitropyrene (8-OHNP), were sensitively and selectively detected by HPLC with peroxyoxalate chemiluminescence (CL) detection. In the system, the three OHNPs were reduced to their corresponding amino derivatives through a reduction column packed with Pt/Rh-coated alumina and then concentrated on a concentrator column. By rotating a switching valve, the analytes were eluted into a separator column (ODS), separated and then detected by the bis(2,4,6-trichlorphenyl)oxalate-H(2)O(2) CL system. The detection limits (signal-to-noise ratio=3) were in the range from 5fmol (6-OHNP and 8-OHNP) to 12fmol (3-OHNP) per injection. To demonstrate the proposed method, it was used to determine three compounds in the incubation mixture of 1-nitropyrene and rat S9 mix. 相似文献
54.
55.
Tamamura H Tsutsumi H Masuno H Mizokami S Hiramatsu K Wang Z Trent JO Nakashima H Yamamoto N Peiper SC Fujii N 《Organic & biomolecular chemistry》2006,4(12):2354-2357
A linear type of several low molecular weight CXCR4 antagonists were developed based on T140 analogs, which were previously found to be strong CXCR4 antagonists that block X4-HIV-1 entry and have inhibitory activities against cancer metastasis/progression and rheumatoid arthritis. 相似文献
56.
Murakami Y Kenji E Nosaka AY Nosaka Y 《The journal of physical chemistry. B》2006,110(34):16808-16811
The important roles of OH radicals for remote oxidation using TiO(2) photocatalysts were evidenced by the in situ detection of OH radicals in the gas phase using the laser-induced fluorescence (LIF) technique. The appearance of OD-LIF intensities after the exposure of D(2)O vapors over TiO(2) powders and the decrease of the time-resolved signals of OH-LIF intensities with increasing calcined temperatures of TiO(2) powders suggested that the exchangeable water at the TiO(2) surface is the origin of the diffused OH radicals. 相似文献
57.
Electron spin resonance studies on the oxidation mechanism of sterically hindered cyclic amines in TiO2 photocatalytic systems 总被引:1,自引:0,他引:1
Nosaka Y Natsui H Sasagawa M Nosaka AY 《The journal of physical chemistry. B》2006,110(26):12993-12999
A sterically hindered cyclic amine, 4-hydroxy-2,2,6,6-tetramethylpiperidine (HTMP), is converted to the corresponding aminoxyl radical (nitroxide radical), 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (TEMPOL radical) as a result of a photocatalytic reaction in TiO2 aqueous suspension. The time profile of the radical formation and the effect of additives, such as SCN-, I-, methanol, and H2O2, on the initial formation rate were measured in order to elucidate the reaction mechanism. The experimental observations indicated that the direct photocatalytic oxidation of HTMP followed by reaction with O2 is the dominant process in the formation of TEMPOL radicals. Electrochemical measurements showed that HTMP is oxidized at 0.7 V (vs NHE), which is consistent with the proposed mechanism. The possibility of other processes, involving reactions with singlet molecular oxygen, superoxide radical, and hydroxyl radical, were excluded from the reaction mechanism. 相似文献
58.
59.
N(G)-Monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), and N(G),N(G)'-dimethyl-L-arginine (SDMA) are emerging cardiovascular risk factors. A high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of L-NMMA, ADMA and SDMA is described. The assay employed 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorescent derivatization reagent. After solid phase extraction with cation-exchange column, the methylated arginines were converted to fluorescent derivatives with NBD-F, and the derivatives were separated within 32 min on a reversed-phase column. Nomega-Propyl-L-arginine was Used as an internal standard. Extrapolated detection limits were 12 nM (12 fmol per injection) for L-NMMA and 20 nM (20 fmol per injection) for ADMA and SDMA, respectively, with a signal-to-noise ratio of 3. The calibration curves for L-NMMA, ADMA and SDMA were linear within the range of 50-5000 fmol. The method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in 200 microl of rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.03, 0.80 +/- 0.25 and 0.40 +/- 0.21 microM, respectively (n = 5). 相似文献
60.
Satoko?OkubayashiEmail author Ulrich?J.?Griesser Thomas?Bechtold 《Cellulose (London, England)》2005,12(4):403-410
The dynamic vapor water sorption and desorption experiments were performed on cellulosic fibers with different characteristics.
The hysteresis between moisture sorption and desorption cycle at 10% relative humidity (RH) was independent on the total moisture
regain and approximately 45% for all materials except for viscose fibers. Brunauer–Emmett–Teller surface volume (Vm) for moisture sorption and retention capacity of liquid water (WRV) were also measured. The Vm and WRV increase in proportion to the total amount of moisture sorption (Minf(total)) in all specimen except in poplar fiber. The coefficients of parallel exponential kinetics (PEK) were estimated by the curve-fitting
of experimental data of the moisture regain, and the influences of the fiber characteristics on the PEK coefficients, the
moisture regain, the hysteresis, Vm and WRV are discussed. The total equilibrium moisture content in the viscose fibers was higher but the moisture uptake and
release rate was slower than the lyocell and poplar fibers. The cationization and the modification of shape of cross section
accelerated the total equilibrium moisture content in the viscose fiber. A drying process at low temperature enhanced both
the equilibrium moisture content and the moisture uptake and release rate in lyocell fibers while a spin finish retarded them.
The total equilibrium moisture content was heightened by the crosslinking of the fiber, however, no obvious effect of the
crosslinking on the moisture uptake and release rate was found. Effects of the type of the specimen and linear density on
the moisture accessibilities are also discussed. 相似文献