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701.
Rui Tamura Hiroki Takahashi Hideyuki Miura Zsolt Lepp Yoshitaka Nakajima Ken Hirotsu 《Supramolecular chemistry》2013,25(1):71-78
Abstract The crystal structures of (±)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]ethyl] trimethylammonium p-chlorobenzenesulfonate [(±)-NCMe3] and its terminal methoxy derivative, (±)-NCMe3-OMe, are compared. The former racemate exhibited the phenomenon of Preferential Enrichment, whereas the latter failed to do so. Crystal data, (±)-NCMe3: CuKα radiation, space group P 1, Z = 2, a = 9.848(5), b = 14.823(3), c = 9.147(1) Å, α = 97.81(1), β = 92.68(3), γ = 105.92(2)°, D calc = 1.355 g/cm3, R = 0.056 for 3213 observed reflections; (±)-NCMe3-OMe: CuKα radiation, space group P 1, Z = 2, a = 11.350(1), b = 14.568(2), c = 8.2981(4) Å, α = 94.346(7), β = 112.376(5), γ = 78.622(9)°, D calc = 1.343 g/cm3, R = 0.069 for 1519 observed reflections. 相似文献
702.
Ícaro A. Simon Bernardo B. Vacaro Michael R. Nunes Edilson V. Benvenutti Silvio L. P. Dias Yoshitaka Gushikem Jacqueline Arguello 《Electroanalysis》2013,25(11):2501-2506
Gold nanoparticles of different morphologies have been synthesized on a silica‐based organic‐inorganic hybrid material for catalytic applications. The gold nanoparticles formations proceed through in situ chemical reduction of the AuCl4? anions previously adsorbed on 3‐(1‐imidazolyl)propyl‐silsesquioxane, which plays the role of substrate and stabilizer. Two distinct reducing agents, sodium citrate and sodium borohydride, were employed to generate gold nanoparticles of different sizes. UV‐vis diffuse reflectance as well as transmission electron microscopy were employed to evaluate the particle’s morphology. Modified carbon paste electrodes were prepared from these materials and their electrochemical behavior investigated using potassium ferrocyanide and 4‐nitrophenol as redox model compounds. Both AuNPs‐modified electrodes decreased the overpotential of 4‐nitrophenol reduction by around 90 mV compared to the unmodified electrode as evidenced by cyclic voltammetry experiment. However, the smaller diameter particles (borohydride‐reduced) produced more significant catalytic effect as a consequence of their large surface area. Regarding the sensing parameters, the sensitivity is higher for the borohydride‐reduced AuNPs while the values of limit of detection are of the same order of magnitude. Thus, the detection limit and sensitivity are 70.0±0.6 nM and 187 µA/mM for the citrate‐reduced AuNPs; and 75.0±2.2 nM and 238 µA/mM for the borohydride‐reduced AuNPs. 相似文献
703.
Masaaki Hori Satoshi Tsutsumi Yukimasa Yasumoto Masanori Ito Michimasa Suzuki Fumine S. Tanaka Shinsuke Kyogoku Masanobu Nakamura Takashi Tabuchi Issei Fukunaga Yuriko Suzuki Koji Kamagata Yoshitaka Masutani Shigeki Aoki 《Magnetic resonance imaging》2014
Introduction
We investigated microstructural changes in the spinal cord, separately for white matter and gray matter, in patients with cervical spondylosis by using diffusional kurtosis imaging (DKI).Methods
We studied 13 consecutive patients with cervical myelopathy (15 affected sides and 11 unaffected sides). After conventional magnetic resonance (MR) imaging, DKI data were acquired by using a 3 T MR imaging scanner. Values for fractional anisotropy (FA), apparent diffusion coefficient (ADC), and mean diffusional kurtosis (MK) were calculated and compared between unaffected and affected spinal cords, separately for white matter and gray matter.Results
Tract-specific analysis of white matter in the lateral funiculus showed no statistical differences between the affected and unaffected sides. In gray matter, only MK was significantly lower in the affected spinal cords than in unaffected spinal cords (0.60 ± 0.18 vs. 0.73 ± 0.13, P = 0.0005, Wilcoxon’s signed rank test).Conclusions
MK values in the spinal cord may reflect microstructural changes and gray matter damage and can potentially provide more information beyond that obtained with conventional diffusion metrics. 相似文献704.
Takumi Kobayashi Tatsuki ShimuraYuzuru Kurita Yoshitaka KatsumataSatoko Kezuka 《Tetrahedron letters》2014
Optically active cobalt(II) salen complexes were found to be effective Lewis acid catalysts for the enantioselective Michael addition of O-alkylhydroxylamines to nitroalkenes to afford the corresponding N-alkylhydroxyl-1,2-nitroamines in high yields and with good to high enantioselectivities. This study represents the first example of a transition-metal-catalyzed asymmetric Michael addition of amines to nitroalkenes. 相似文献
705.
Total syntheses of (+)-coronarin A (1), (+)-coronarin E (2), (+)-austrochaparol (3) and (+)-pacovatinin A (4) were achieved from the synthetic (+)-albicanyl acetate (6). Dess-Martin oxidation of (+)-albicanol (5) derived from the chemoenzymatic product (6) gave an aldehyde (7), which was subjected to Julia one-pot olefination using beta-furylmethyl-heteroaromatic sulfones (8 or 9 ) gave (+)-trans coronarin E (2) and (+)-cis coronarin E (12) with high cis-selectivity. The synthesis of (+)-coronarin A (1) from (+)-trans coronarin E (2) was achiev-ed, while (+)-cis coronarin E (12) was converted to the natural products (+)-(5S,9S,10S)-15,16-epoxy-8(17),13(16),14-labdatriene (13) and (+)-austrochaparol (3). By the asymmetric synthesis of (+)-3, the absolute structure of (+)-3 was determined to be 5S, 7R, 9R, 10S configurations. Homologation of (+)-albicanol (5) followed by allylic oxidation gave (7 alpha)-hydroxy nitrile (17), which was finally converted to the natural (+)-pacovatinin A (4) in 8 steps from (+)-albicanol (5). 相似文献
706.
Arenas LT Pinheiro AC Ferreira JD Livotto PR Pereira VP Gallas MR Gushikem Y Costa TM Benvenutti EV 《Journal of colloid and interface science》2008,326(1):96-102
Anisotropic self-organized hybrid silica based xerogels were obtained. The ordered structure was imposed by the double charged 1,4-diazoniabicycle[2.2.2]octane chloride group bonded in a bridged way. This was confirmed by the presence of well defined X-ray diffraction peaks corresponding to an interplanar distance with the same length estimated for the organic bridged groups. The material was characterized by elemental analysis using CHN technique and the chloride ion was analyzed by a potentiometric titration. (13)C and (29)Si CP MAS solid state NMR spectroscopy and thermogravimetric analysis were also performed. The material that can be obtained in the form of powders and transparent monoliths or films, is thermally stable up to 260 degrees C and the samples with high organic content presented birefringence properties. 相似文献
707.
THP (tetrahydropyran) has been found to show an excellent stability towards autooxidation, compared with THF. Tributyltin hydride mediated radical cyclization, when conducted in THF as a solvent, suffers from competition of hydrogen abstraction from the solvent, whereas the use of THP resulted in the course to negligible degree. Tributyltin hydride, TTMSS, and hexanethiol mediated radical reactions were carried out successfully using THP as a solvent. 相似文献
708.
Dr. Liang Wang Dr. Qingqing Miao Dr. Dandan Wang Dr. Mengmeng Chen Dr. Huan Bi Dr. Jiaqi Liu Dr. Ajay Kumar Baranwal Dr. Gaurav Kapil Dr. Yoshitaka Sanehira Dr. Takeshi Kitamura Prof. Tingli Ma Dr. Zheng Zhang Prof. Qing Shen Prof. Shuzi Hayase 《Angewandte Chemie (International ed. in English)》2023,62(33):e202307228
The photoelectric properties of nontoxic Sn-based perovskite make it a promising alternative to toxic Pb-based perovskite. It has superior photovoltaic performance in comparison to other Pb-free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi-interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long-term stability. 相似文献
709.
Eliana W. de Menezes Michael R. Nunes Leliz T. Arenas Silvio L. P. Dias Irene T. S. Garcia Yoshitaka Gushikem Tania M. H. Costa Edilson V. Benvenutti 《Journal of Solid State Electrochemistry》2012,16(12):3703-3713
In this work, gold nanoparticles lower than 10?nm were prepared in an aqueous medium using two charged silsesquioxanes, the propylpyridinium chloride and propyl-1-azonia-4-azabicyclo[2.2.2]octane chloride, as stabilizer agents which revealed to be water-soluble. This stabilization method is innovative allowing thin films containing gold nanoparticles to be obtained, and it was used for the first time in the preparation of carbon paste electrodes (CPEs). The charged silsesquioxanes were characterized by liquid 13C NMR. The gold nanoparticle/silsesquioxane systems were characterized by ultraviolet–visible spectroscopy (UV–Vis) and transmission electron microscopy. In sequence, they were immobilized on silica matrix coated with aluminum oxide. The resulting solid materials designated as Au-Py/AlSi and Au-Db/AlSi were characterized by infrared spectroscopy and N2 adsorption/desorption isotherms. The results showed that the gold nanoparticle/silsesquioxane systems are strongly adhered to the surface-forming thin films. The Au-Py/AlSi and Au-Db/AlSi materials were used to prepare CPEs for the electrooxidation of nitrite (NO 2 ? ) using cyclic voltammetry and differential pulse voltammetry. The Au-Py/AlSi and Au-Db/AlSi CPEs showed high sensitivity and detection limits of 71.87 and 53.66?μA?mmol–1?L and 1.3 and 3.0?μmol?L–1, respectively. 相似文献
710.
Andréia de Morais Gustavo Silveira Paulo César Mendes Villis Camila Marchetti Maroneze Yoshitaka Gushikem Fábio Luiz Pissetti Alzira Maria Serpa Lucho 《Journal of Solid State Electrochemistry》2012,16(9):2957-2966
A simple preparation methodology able to stabilize gold nanoparticles and to obtain an electrode which detects ascorbic acid, uric acid, and dopamine by different techniques is presented. A 3-mercaptopropyl-functionalized silica network was synthesized using the sol–gel method. Gold nanoparticles (nAu) were immobilized on the material at synthesis by adding a sol of these previously prepared particles to the reaction mixture. The electrochemical behavior of the SiO2/MPTS/Au carbon paste electrode was studied using cyclic voltammetry in the presence of a hexacyanoferrate probe molecule. The presence of nAu in the functionalized silica network changes the electrochemical characteristics of the material, favoring the electron transfer process of this complex ion. The SiO2/MPTS/Au electrode was proven to be an efficient tool in the simultaneous determination of ascorbic acid (H2AA), dopamine (DA), and uric acid (UA) using square wave voltammetry techniques. With the nAu on the electrode, an increase in the peak current related to the redox process of the H2AA, DA, and UA was observed. The separations of the anodic peak potentials between DA/H2AA and UA/H2AA were 310 and 442?mV, respectively. The results obtained show that the SiO2/MPTS/Au electrode can be used in the simultaneous determination of H2AA, DA, and UA. 相似文献