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41.
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Nanoparticles were prepared by utilizing the thermosensitive aggregation of alpha-elastin and gamma ray crosslinking. Three different heating process, “Slow heating”, “Fast heating”, and “Heat shock”, were applied for the aggregation of the alpha-elastin and examined to yield nanoparticles by gamma rays crosslinking. As a result, only “Slow heating” process yielded nanoparticles with diameters of about ca. 300 nm above cloud point (CP) and about ca. 100 nm below CP, and a narrow size distribution above 1.0 mg/ml concentration (exclude 1.0 mg/ml). 相似文献
43.
44.
Coherent convergent beam electron diffraction is for the first time applied to the analysis of lattice fitting between vacuum-deposited PbTe and MgO thin crystals in the plan-view mode. The possibility of determination of the rigid-body shift is discussed on the basis of simulated diffraction patterns from the bi-crystals as well as the preliminary experimental results obtained by a 200 kV transmission electron microscope with a field emission electron gun. In the analysis, the importance of the position of interference fringes at overlaps of PbTe 200 and MgO 200 diffraction disks and that of the corresponding mirror symmetry in the whole pattern are emphasized in order to determine the rigid-body shift and the probe-position. 相似文献
45.
Yutaka Nagai Nakahara Kouji Yoneyama Yoshifumi Kawano Katsuyasu Tanaka Katsumi Nakata Ryouhei 《Journal of Physics and Chemistry of Solids》2004,65(11):1861-1870
The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF2 doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na+-FV dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na+-FV dipole band was observed in 3 nominal mole% NaF-doped CaF2, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands. 相似文献
46.
Yasuda M Chiba K Ohigashi N Katoh Y Baba A 《Journal of the American Chemical Society》2003,125(24):7291-7300
Michael addition of stannyl ketone enolates to alpha,beta-unsaturated esters was accomplished in the presence of a catalytic amount of tetrabutylammonium bromide (Bu(4)NBr). Other typical systems using lithium enolate or silyl enolate with catalysts (TiCl(4) or Bu(4)NF) failed to give the desired products. The bromide anion from Bu(4)NBr coordinates to the tin center in enolate to accelerate the conjugate addition where a five-coordinated tin species was generated. The coordination of the bromide anion significantly raises the HOMO level of tin enolate and enhances its nucleophilicity. The conjugate addition provides the intermediate Michael adduct, which has an ester enolate moiety, and the adduct immediately transforms to alpha-stannyl gamma-ketoester by keto-enol tautomerization. This step contributes to the stabilization of the product system and leads to a thermodynamically favorable reaction course. An ab initio calculation reveals that the activation energy in the reaction using the bromide anion is lower than that of the reaction without using it. The transition state in either reaction course has a linear structure, not a cyclic one. This system can be applied to a variety of tin enolates and alpha,beta-unsaturated carbonyls involving enoates, enones, and unsaturated amides. 相似文献
47.
S Ogasahara T Mandai A Yamatodani T Watanabe H Wada T Seki 《Journal of chromatography. A》1979,180(1):119-126
A simple method for the simultaneous determination of noradrenaline, dopamine and serotonin using a short column of Amberlite CG-50 is described. Noradrenaline and dopamine were eluted from the column with phosphate buffers containing 1.5 and 4.0% boric acid, respectively, and then serotonin was eluted with 1.0 N HCl. Catecholamines were determined by a modification of the ethylenediamine condensation method using potassium ferricyanide as oxidant and isobutanol for extraction of the fluorophores. Serotonin was measured by the acidic o-phthalaldehyde method. The method was applied to the simultaneous determination of noradrenaline, dopamine and serotonin in discrete regions of rat brain. 相似文献
48.
Aminopolycarboxylic acid-type cellulose (Chelest Fiber Iry) has been studied for its sorption efficiencies with respect to lead from acidic solution. The influence pH and other properties related to sorption kinetic, isotherm, maximum capacity, stability and the mechanism of the sorption were discussed.Lead was quantitatively retained on the proposed adsorbent in the pH range of 2.5-5.5 (studied pH range 1.5-5.5). The maximum sorption capacity was found to be 0.86±0.06 mmol/g adsorbent. The decline in the efficiency of the adsorbent was not observed for repeated adsorption-desorption cycles. It was found that the preconcentration factor of 200 can be achieved. The limit of determination was found to be about 1 μg Pb/2 l. The method was applied to the determination of lead in water samples. 相似文献
49.
Yusuke Asakuma Kyuya Nakagawa Kouji Maeda Keisuke Fukui 《Polymer Degradation and Stability》2009,94(2):240-245
The depolymerization reaction of polyethylene terephthalate (PET) was analyzed using a computational chemistry approach. The reaction is a type of transesterification reaction using alkoxide. In this study we employed the calculated optimum structure, electrostatic potential distribution, activation energy, electric charges and pathway to investigate the mechanism. We found that the tetrahedral intermediate produced by ring formation with alkoxide is an essential feature of the depolymerization process. Moreover, there is a possibility that a PET molecule is depolymerized by multiple alkoxides at the same time. However, the effects of degree of polymerization and the position of attack by the alkoxides do not strongly influence the reactivity. 相似文献
50.
Akira Kotani Kouji Takahashi Hideki Hakamata Satoshi Kojima Fumiyo Kusu 《Analytical sciences》2007,23(2):157-163
Attomole quantities of catechins were determined by a capillary liquid chromatography system with electrochemical detection (CLC-ECD) and the system is applied to the determination of catechins in human plasma. The eight catechins: catechin (C), epicatechin (EC), gallocatechin (GC), epigallocatechin (EGC), catechin gallate (Cg), epicatechin gallate (ECg), gallocatechin gallate (GCg), and epigallocatechin gallate (EGCg), were separated within 10 min using a capillary column (0.2 mm i.d.) and a mobile phase of phosphoric acid (85%)-methanol-water (0.5:27.5:72.5, v/v/v), and were detected at +0.85 V vs. Ag/AgCl. Peak heights were found to be linearly related to the amount of catechins injected, from 200 amol to 500 fmol (r > 0.998). The detection limits of the catechins were 61 amol for EGC, 75 amol for EC, 54 amol for GC, 61 amol for C, 67 amol for GCg, 75 amol for EGCg, 75 amol for ECg and 89 amol for Cg (S/N = 3). Because the present method is highly sensitive and allows facile pretreatment for plasma sample, the time courses of concentrations of catechins (GCg, EC, EGCg, ECg, and Cg) and their conjugates in human plasma obtained from a 10 microl plasma sample after ingestion of green tea could be determined. 相似文献