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81.
Stereoselective analysis of flecainide enantiomers using reversed‐phase liquid chromatography for assessing CYP2D6 activity 下载免费PDF全文
Kosuke Doki Yukio Sekiguchi Keisuke Kuga Kazutaka Aonuma Yukinao Kohda Masato Homma 《Biomedical chromatography : BMC》2014,28(9):1193-1198
Stereoselective analyses of flecainide enantiomers were performed using reversed‐phase high‐performance liquid chromatography (HPLC) equipped with a polysaccharide‐based chiral column (Chiralpak AS‐RH) and fluorescence detector. Excitation and emission wavelengths were set at 300 and 370 nm, respectively. Flecainide enantiomers in serum and urine were extracted using diethyl ether. The mobile phase solution, comprising 0.1 m potassium hexafluorophosphate and acetonitrile (65:35, v/v), was pumped at a flow rate of 0.5 mL/min. The recoveries of flecainide enantiomers were greater than 94%, with the coefficients of variation (CVs) <6%. The calibration curves of flecainide enantiomers in serum and urine were linear in the concentration range 5–500 ng/mL and 0.75–15 µg/mL (r > 0.999), respectively. CVs in intra‐day and inter‐day assays were 1.8–5.8 and 3.4–7.5%, respectively. In a pharmacokinetic study, the ratios of (S)‐ to (R)‐flecainide (S/R ratio) in the area under the curve and the amount of flecainide enantiomers excreted in urine were lower in a subject carrying CYP2D6*10/*10 than in subjects carrying CYP2D6*1/*2. The S/R ratio of trough serum flecainide concentration ranged from 0.79 to 1.16 in patients receiving oral flecainide. The present HPLC method can be used to assess hepatic flecainide metabolism in a pharmacokinetic study and therapeutic drug monitoring. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
82.
Si-Young Kim Hyun-Jae Lee Seung-Hwan Park Woong Lee Mi-Na Jung Katsushi Fujii Takenari Goto Takashi Sekiguchi Jiho Chang Gyungsuk Kil Takafumi Yao 《Journal of Crystal Growth》2010,312(14):2150-2153
A new hydride vapor phase epitaxy (HVPE)-based approach for the fabrication of freestanding GaN (FS-GaN) substrates was investigated. For the direct formation of low-temperature GaN (LT-GaN) layers, the growth parameters were optimized: the polarity of ZnO, the growth temperature, and the V/III ratio. The FS-GaN layer was achieved by gas etching in an HVPE reactor. A fingerprint of Zn out-diffusion was detected in the photoluminescence measurements, especially for the thin (80 μm) FS-GaN film; however, a thicker film (400 μm) was effectively reduced by optimization of GaN growth. 相似文献
83.
A protocol for searching the most probable phase‐retrieved maps in coherent X‐ray diffraction imaging by exploiting the relationship between convergence of the retrieved phase and success of calculation 下载免费PDF全文
Yuki Sekiguchi Saki Hashimoto Amane Kobayashi Tomotaka Oroguchi Masayoshi Nakasako 《Journal of synchrotron radiation》2017,24(5):1024-1038
Coherent X‐ray diffraction imaging (CXDI) is a technique for visualizing the structures of non‐crystalline particles with size in the submicrometer to micrometer range in material sciences and biology. In the structural analysis of CXDI, the electron density map of a specimen particle projected along the direction of the incident X‐rays can be reconstructed only from the diffraction pattern by using phase‐retrieval (PR) algorithms. However, in practice, the reconstruction, relying entirely on the computational procedure, sometimes fails because diffraction patterns miss the data in small‐angle regions owing to the beam stop and saturation of the detector pixels, and are modified by Poisson noise in X‐ray detection. To date, X‐ray free‐electron lasers have allowed us to collect a large number of diffraction patterns within a short period of time. Therefore, the reconstruction of correct electron density maps is the bottleneck for efficiently conducting structure analyses of non‐crystalline particles. To automatically address the correctness of retrieved electron density maps, a data analysis protocol to extract the most probable electron density maps from a set of maps retrieved from 1000 different random seeds for a single diffraction pattern is proposed. Through monitoring the variations of the phase values during PR calculations, the tendency for the PR calculations to succeed when the retrieved phase sets converged on a certain value was found. On the other hand, if the phase set was in persistent variation, the PR calculation tended to fail to yield the correct electron density map. To quantify this tendency, here a figure of merit for the variation of the phase values during PR calculation is introduced. In addition, a PR protocol to evaluate the similarity between a map of the highest figure of merit and other independently reconstructed maps is proposed. The protocol is implemented and practically examined in the structure analyses for diffraction patterns from aggregates of gold colloidal particles. Furthermore, the feasibility of the protocol in the structure analysis of organelles from biological cells is examined. 相似文献
84.
85.
D. Cerizza W. Sekiguchi T. Tsukahara T. A. Zaki Y. Hasegawa 《Flow, Turbulence and Combustion》2016,97(4):1211-1233
We consider a turbulent channel flow, where a scalar point source with a time-harmonic intensity releases a substance that can be modeled as a passive scalar. With the source location known, our objective is to estimate the time history of the source intensity based on sensor measurements at different locations downstream of the source by adopting an adjoint approach. It is shown that the proposed algorithm reproduces the original coherent sinusoidal wave of the scalar source accurately from the chaotic scalar signals measured by our sensors. By systematically changing the source-sensor distance and the pulsation frequency of the source, we clarify how these two factors affect the estimation accuracy. The proposed scheme is also applicable to estimation with multiple sensors. We demonstrate that increasing the number of sensors improves the estimation greatly when the scalar is released from a source away from the wall, where large-scale eddies dominate the scalar dispersion. In contrast, the estimation performance remains poor even with multiple sensors when the scalar source is located near the wall, where the source information is quickly lost due to the strong turbulence activity and the scalar diffusion in the near-wall region. 相似文献
86.
Akhtar W Filidou V Sekiguchi T Kawakami E Itahashi T Vlasenko L Morton JJ Itoh KM 《Physical review letters》2012,108(9):097601
Pulsed electron paramagnetic resonance spectroscopy of the photoexcited, metastable triplet state of the oxygen-vacancy center in silicon reveals that the lifetime of the m(s)=±1 sublevels differs significantly from that of the m(s)=0 state. We exploit this significant difference in decay rates to the ground singlet state to achieve nearly ~100% electron-spin polarization within the triplet. We further demonstrate the transfer of a coherent state of the triplet electron spin to, and from, a hyperfine-coupled, nearest-neighbor (29)Si nuclear spin. We measure the coherence time of the (29)Si nuclear spin employed in this operation and find it to be unaffected by the presence of the triplet electron spin and equal to the bulk value measured by nuclear magnetic resonance. 相似文献
87.
Takahiro Yamada Hisanori Yamane Takenari Goto Takafumi Yao Yongzhao Yao Takashi Sekiguchi 《Crystal Research and Technology》2007,42(7):713-717
Colorless transparent prismatic crystals (0.5‐2.0 mm long) and hopper crystals (1.0‐2.5 mm long) of GaN were prepared by heating a Ga melt at 800°C in Na vapor under N2 pressures of 7.0 MPa for 300 h. The photoluminescence (PL) spectrum of a prismatic crystal at 4 K showed the emission peaks of neutral donor‐bound exciton (D0‐X) and free exciton (XA) at 3.472 eV and 3.478 eV, respectively, in the near band edge region. The full‐width at half‐maximum (FWHM) of (D0‐X) peak was 1.9 meV. The emission peaks of a donor–acceptor pair transition (D0‐A0) and its phonon replicas were observed in a lower energy range (2.9‐3.3 eV). The emission peaks of the D0‐A0 and phonon replicas were also observed in the cathodoluminescence (CL) spectrum at 20 K. The (D0‐X) PL peak of a hopper crystal at 4 K was at 3.474 eV (2.1 meV higher), having a FWHM of 6.1 meV which was over 3 times larger than that of the prismatic crystal. A strong broad band with a maximum intensity around 1.96 eV was observed for the hopper crystals in the CL spectrum at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
88.
The spectroscopic properties of metal-ion complexes of several imidazopyrazinone derivatives with Li+, Mg2+, Ca2+, Ba2+, Sc3+, and La3+ ions were studied. The spectral characteristics and the formation constants of the complexes changed continuously depending on the Lewis acidity of the metal ion, suggesting that the imidazopyrazinones can find application as indicators of Lewis acidity. In the case of bis-imidazopyrazinone derivatives, the complexation abilities were enhanced by chelate effects. 相似文献
89.
90.
We have investigated the photon-stimulated ion-desorption from deuterated formic acid (DCOOD) monolayer chemisorbed on Si(100) crystal by applying a photoion-photoion-coincidence technique. The true-coincidence yields of an ion pair C+---D+ are given in the photon energy range (275–400 eV) above the C 1s absorption edge. The partial ion yields and Auger electron yields re presented for comparison. It was found that the multielectron (shake-off) excitation promotes the multiple bond-breaking of the adsorbate and the ion pair C+–D+ desorption events. 相似文献