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81.
James Guo Sheng Moo Zaenal Awaludin Takeyoshi Okajima Takeo Ohsaka 《Journal of Solid State Electrochemistry》2013,17(12):3115-3123
Through the use of XPS and controlled Ar+ etching, the surface composition and oxide species of tantalum oxides (TaO x ), which were electrodeposited on glassy carbon electrodes by cyclic voltammetric and constant-potential electrolyses, are quantified along the depth profile. Electrodeposition exhibits efficacy in depositing TaO x with a distribution of various TaO x : TaO, TaO2, and Ta2O5. The distribution gradient from the outer surface of TaO x is such that Ta2O5?>?TaO2?>?TaO. TaO is found to be the dominant species in the underlying layer of TaO x . Such a unique structure of the electrode surface is analogous to that of nanoparticles with a core–shell structure, with the core being suboxides and the surface being that of the saturated pentoxide, Ta2O5. The electrochemically induced nonhydrolytic condensation route is proposed to be capable of producing TaO x with a distribution gradient of Ta2O5, TaO2, and TaO in the depth direction. 相似文献
82.
Farhana S. Saleh Mohammad R. Rahman Takeyoshi Okajima Lanqun Mao Takeo Ohsaka 《Bioelectrochemistry (Amsterdam, Netherlands)》2011,80(2):121-127
The electrochemical regeneration of NADH/NAD+ redox couple has been studied using poly(phenosafranin) (PPS)-modified carbon electrodes to evaluate the formal potential and catalytic rate constant for the oxidation of NADH. The PPS-modified electrodes were prepared by electropolymerization of phenosafranin onto different carbon substrates (glassy carbon (GC) and basal-plane pyrolytic graphite (BPPG)) in different electrolytic solutions. The formal potential was estimated to be ? 0.365 ± 0.002 V vs. SHE at pH 7.0. As for the bare carbon electrodes, the oxidation of NADH at the BPPG electrode was found to be enhanced compared with the GC electrode. For the PPS-modified electrodes, it was found that the electrocatalysis of PPS-modified electrodes for the oxidation of NADH largely depends on the carbon substrate and electrolyte solution employed for their preparation, i.e., the PPS-modified BPPG electrode prepared in 0.2 M NaClO4/acetonitrile solution exhibits an excellent and persistent electrocatalytic property toward NADH oxidation in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of about 740 and 670 mV compared with those at the bare GC electrode and the PPS-modified GC electrode prepared in 0.2 M H2SO4 solution, respectively. A quantitative analysis of the electrocatalytic reaction based on rotating disk voltammetry gave the electrocatalytic reaction rate constants of the order of 103–104 M?1 s? 1 depending on the preparation conditions of the PPS-modified electrodes. 相似文献
83.
Yukihiro Kuge Hideo Nakazawa Toru Kometani Toru Sugaya Kenichi Mochida Shinji Tomioka 《合成通讯》2013,43(6):759-766
A one-pot synthesis of vinpocetine from vincamine was established. Lewis acids caused transesterification and/or dehydration of vincamine in EtOH. FeCl3 catalyzed both transesterification and dehydration while Ti(OEt)4 selectively catalyzed transesterification. 相似文献
84.
Anomalous Enhancement of Proton Conductivity for Water Molecular Clusters Stabilized in Interstitial Spaces of Porous Molecular Crystals 下载免费PDF全文
Prof. Makoto Tadokoro Yuki Ohhata Yuriko Shimazaki Prof. Shin'ichi Ishimaru Prof. Teppei Yamada Prof. Yuki Nagao Dr. Tomoaki Sugaya Dr. Kyosuke Isoda Yuta Suzuki Prof. Hiroshi Kitagawa Prof. Hiroshi Matsui 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13698-13709
In an investigation into the proton conductivity of crystallized water clusters confined within low‐dimensional nanoporous materials, we have found that water‐stable nanoporous crystals are formed by complementary hydrogen bonding between [CoIII(H2bim)3]3+ (H2bim: 2,2′‐biimidazole) and TATC3? (1,3,5‐ tricarboxyl‐2,4,6‐triazinate); the O atoms in the ?COO? groups of TATC3? in the porous outer wall are strongly hydrogen bonded with H2O, forming two types of WMCs (water molecular clusters): a spirocyclic tetramer chain (SCTC) that forms infinite open 1D channels, and an isolated cyclic tetramer (ICT) present in the void space. The ICT is constructed from four H2O molecules as a novel C2‐type WMC, which are hydrogen bonded with four‐, three‐, and two‐coordination spheres, respectively. The largest structural fluctuation is observed at elevated temperatures from the two‐coordinated H2O molecules, which begin to rapidly and isotropically fluctuate on heating. This behavior can be rationalized by a simple model for the elucidation of pre‐melting phenomena, similar to those in ice surfaces as the temperature increases. Moreover, high proton conductivity of SCTCs (ca. 10?5 S cm?1 at 300 K with an activation energy of 0.30 eV) through a proton‐hole mechanism was observed for pellet samples using the alternating impedance method. The proton conductivity exhibits a slight enhancement of about 0.1×10?5 S cm?1 at 274 K due to a structural transition upon approaching this temperature that elongates the unit cell along the b‐axis. The proton‐transfer route can be predicted in WMCs, as O(4) of an H2O molecule at the center of an SCTC shows a motion that rotates the dipole in the b‐axis direction, but not the c‐axis; the thermal ellipsoids of O(4) based on anisotropic temperature factors obtained by X‐ray crystallography reflect a structural fluctuation along the b‐axis direction induced by [CoIII(H2bim)3]3+. 相似文献
85.
The effects of a magnetic force on magnetic particles linked by cysteamine to a silver colloid plate were analyzed with surface-enhanced Raman scattering spectroscopy. Cysteamine molecules were stretched by a force exerted on the magnetic particles with the external magnetic field gradients generated by two Nd-Fe-B magnets. The spectra showed that the relative intensity ratio of C-S (trans) to C-S (gauche) of cysteamine was increased 2 - 3 times within 30 min under the application of magnetic field gradients. Also, the shift of C-S (T) was observed up to 4 cm(-1) to higher frequency. These results suggested that an extension of the distance between a magnetic particle and a silver colloid induced isomerization from the gauche conformation to the trans conformation, accompanied by probable thiolate migration on the silver colloid surface. 相似文献
86.
The polarographic streaming maxima and cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) in room-temperature ionic liquid (RTIL) have been studied for the first time using cyclic voltammetric, potential step chronoamperometric and pulse voltammetric techniques. The reversible redox reaction of the 2,1,3-benzothiadiazole (BTD)/BTD*- (an anion radical of BTD) couple with a formal potential (E0') of -1.36 V versus Ag/AgCl/NaCl(saturated) in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) RTIL was typically employed for this purpose. A maximum was observed at the rising part of the normal pulse voltammogram for the reduction of BTD to BTD*- as well as of the reversed pulse voltammogram for the reoxidation of BTD*- to BTD at the HMDE. The conditions of the initiation and control of the CVACO at the HMDE in EMIBF4 were extensively investigated. Generally, the CVACO was enhanced by increasing the concentration of BTD at a given potential scan rate (upsilon) and was attenuated by increasing upsilon. An electrocapillary curve was measured using a dropping mercury electrode in EMIBF4, and the potential of zero charge was determined to be -0.23 V. On the basis of the modern theory of the polarographic streaming maxima of the first kind, the observed streaming maxima and CVACO phenomena are successfully explained to originate from the macroscopic instability at the electrode/solution interface wherein the oscillating mode creates the CVACO. 相似文献
87.
Experimental results are presented for a behavior of the electrostatic ion cyclotron waves excited in an ion beam-plasma system. This wave appears as forward and backward waves with respect to the propagating component along the magnetic field. 相似文献
88.
Yoshio Imai Mitsuru Ueda Takeyoshi Takahashi 《Journal of polymer science. Part A, Polymer chemistry》1976,14(10):2391-2397
Aromatic and aliphatic polybenzodipyrrolediones have been synthesized directly by the solution cyclopolycondensation of two dibenzylidenebenzodifurandiones with four different diamines in refluxing m-cresol or o-phenylphenol in the presence of boric acid. The polymerizations proceeded smoothly in a homogeneous solution and afforded the heterocyclic polymers having inherent viscosities as high as 1.0 almost quantitatively. All the polymers were readily soluble in a wide range of solvents, including N-methyl-2-pyrrolidone (NMP), hot m-cresol, and hot pyridine. Tough, transparent, yellow films could be cast from NMP solutions of the polymers. Thermogravimetric analysis of the aromatic polybenzodipyrrolediones showed a 10% weight loss temperature of 460–500°C under nitrogen. The results also indicated that the aromatic polymers were somewhat less thermally stable than wholly aromatic polypyromellitimides. 相似文献
89.
Md. Motahar Hossain Md. Mominul Islam Sara Ferdousi Takeyoshi Okajima Takeo Ohsaka 《Electroanalysis》2008,20(22):2435-2441
The simple, fast and highly sensitive anodic stripping voltammetric detection of As(III) at a gold (Au) nanoparticle‐modified glassy carbon (GC) (nano‐Au/GC) electrode in HCl solution was extensively studied. The Au nanoparticles were electrodeposited onto GC electrode using chronocoulometric technique via a potential step from 1.1 to 0 V vs. Ag|AgCl|NaCl (sat.) in 0.5 M H2SO4 containing Na[AuCl4] in the presence of KI, KBr, Na2S and cysteine additives. Surfaces of the resulting nano‐Au/GC electrodes were characterized with cyclic voltammetry. The performances of the nano‐Au/GC electrodes, which were prepared using different concentrations of Na[AuCl4] (0.05–0.5 mM) and KI additive (0.01–1.0 mM) at various deposition times (10–30 s), for the voltammetric detection of As(III) were examined. After the optimization, a high sensitivity of 0.32 mA cm?2 μM?1 and detection limit of 0.024 μM (1.8 ppb) were obtained using linear sweep voltammetry. 相似文献
90.
Shigefusa F. Chichibu Takuya Ohmori Naoyuki Shibata Takahiro Koyama Takeyoshi Onuma 《Journal of Physics and Chemistry of Solids》2005,66(11):1868-1871
Greenish-white electroluminescence (EL) was observed from the heterojunction light-emitting diodes (LEDs) composed of p-type (001) CuGaS2 chalcopyrite semiconductor epilayers and preferentially (0001)-oriented polycrystalline n-type ZnO thin films. The CuGaS2 layers were grown on a (001) GaP substrate by metalorganic vapor phase epitaxy and the ZnO films were deposited by the surface-damage-free helicon-wave-excited-plasma sputtering method. The n-ZnO/p-CuGaS2 LED structure was designed to enable an electron injection from the n-type wider band gap material forming a TYPE-I heterojunction. The EL spectra exhibited emission peaks and bands between 1.6 and 2.5 eV, although their higher energy portions were absorbed by the GaP substrate. Since the spectral lineshape resembled that of the photoluminescence from identical CuGaS2 epilayers, the EL was assigned to originate from p-CuGaS2. 相似文献