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91.
Visualization of Heterogeneous Oxygen Storage Behavior in Platinum‐Supported Cerium‐Zirconium Oxide Three‐Way Catalyst Particles by Hard X‐ray Spectro‐Ptychography 下载免费PDF全文
Makoto Hirose Dr. Nozomu Ishiguro Kei Shimomura Dr. Nicolas Burdet Dr. Hirosuke Matsui Prof. Dr. Mizuki Tada Prof. Dr. Yukio Takahashi 《Angewandte Chemie (International ed. in English)》2018,57(6):1474-1479
The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce2Zr2Ox (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce2Zr2Ox particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts. 相似文献
92.
Yukio Yoshimura 《Journal of polymer science. Part A, Polymer chemistry》1986,24(9):2085-2099
Formaldehyde was reacted with both 2,4-dimethylphenol(2,4-xyenol) and 2,6-dimethylphenol(2,6-xylenol), which are model compounds of monofunctional phenols, and the reaction products were subjected to HLC analysis to elucidate details of the formation process and bonding manner of a formal group, which can greatly affect the performance of phenol–formaldehyde resins. As a result, formal compounds of dimethylphenols were successfully separated by HLC. It was further found, as a result of tracing the reactions by HLC, that the formation of a formal group occurs at either position of the ortho and para positions, and that methylol compounds were formed following formation of the formal compounds. Furthermore, as a result of NMR analysis as well as consideration of solvation on the basis of the relative elution volumes of the nonacetylated and acetylated reaction products it was found that the formal group was added to the phenol nuclei. 相似文献
93.
Atsuhiro Fujimori Hiroko Hoshizawa Satoshi Kobayashi Kaname Kanai Yukio Ouchi Kazuhiko Seki 《Journal of Polymer Science.Polymer Physics》2008,46(5):534-546
Comb copolymers containing both hydrogenated and fluorinated side‐chains were prepared by copolymerization using acrylic or methacrylic monomers in several ratios. The crystal structures of these copolymers and layer structures of their organized molecular films were investigated by wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and out‐of plane X‐ray diffraction. Further, to selectively estimate the regularity of shorter fluorocarbon side‐chains, organized molecular films of copolymers were investigated by polarized near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy. From the results of these measurements, it was inferred that these copolymers formed highly ordered layer structures, and a long spacing was predominantly determined by the arrangement of hydrogenated side‐chains, except in copolymers having extremely high fluorocarbon contents. In the case of the organized molecular films, the fluorinated side‐chains of methacrylate copolymers cannot form a highly ordered arrangement, whereas those of acrylate copolymers were oriented on monolayers. However, in both cases, the hydrogenated side‐chains predominantly formed layer structures in the organized films, and the fluorinated side‐chains did not contribute to the formation of the layer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 534–546, 2008 相似文献
94.
Nonlinear resonances and self-excited oscillations of a rotor caused by radial clearance and collision 总被引:1,自引:0,他引:1
This paper investigates oscillations in a flexible rotor system with radial clearance between an outer ring of the bearing
and a casing by experiments and numerical simulations. The mathematical model considers the collisions of the bearing with
the casing. The following phenomena are found: (1) Nonlinear resonances of subharmonic, super-subharmonic and combination
oscillation occur. (2) Self-excited oscillation of a forward whirling mode occurs in a wide range above the major critical
speed. (3) Entrainment phenomena from self-excited oscillation to nonlinear forced oscillation occur at these nonlinear resonance
ranges. Moreover, this study analyzes periodic solutions of the mathematical model by the Harmonic Balance Method (HBM). As
the results, the nonlinear resonances of subharmonic oscillation and its entrainment phenomenon can be explained theoretically
by investigating the stability of the periodic solutions. The influence of the static force and the bearing damping on these
oscillation are also clarified. 相似文献
95.
Kensuke Okusa Yuki Suita Yukio Otsuka Mineo Tahara Tohru Ikegami Nobuo Tanaka Masayoshi Ohira Masakazu Takahashi 《Journal of separation science》2010,33(3):348-358
The effectiveness of several basic compounds for testing silica‐based stationary phases was reviewed by applying them to recent columns for reversed‐phase HPLC. Most octadecylsilylated (C18) stationary phases, prepared as a base‐deactivated material from high‐purity silica gel with endcapping, provided excellent peak shape and column efficiency for the bases including benzylamine and amitriptyline that once caused problems and were subsequently employed for testing silanol activities. However, a cyclic tertiary amine, dextrometorphan, was eluted as an acceptable peak from only a few columns at neutral pH. Such a more sensitive probe is expected to contribute to further improvement of the stationary phase for reversed‐phase HPLC. 相似文献
96.
It was shown that ubiquinone (CoQ10) and ubiquinol (CoQ10H2) produce fluorescence products under alkaline conditions when reacted with 2-cyanoacetamide. The reaction mixture from CoQ10 gave fluorescence with excitation and emission maximum wavelengths at 442 nm and 549 nm, respectively. This reaction was
considered to proceed via Craven’s reaction. Moreover, 2-cyanoacetamide was shown to be a useful reagent for high-performance
liquid chromatography (HPLC) with post-column fluorescence derivatization of CoQ10 and CoQ10H2 in blood. CoQ10 showed a linear response in the range of 0.32–1276 ng, and the detection limit (S/N = 3) was 0.16 ng. Moreover, the sample
pretreatment by deproteinization and extraction of CoQ10 and CoQ10H2 from plasma using 1-propanol with potassium formate was effective for excellent separation of CoQ10 and CoQ10H2 from other fluorescent substances in the blood. This simple and rapid pretreatment was considered to minimize the oxidation
of CoQ10H2. On the other hand, CoQ10 and CoQ10H2 in plasma samples obtained by finger prick were detected, as in venous blood obtained by venipuncture. Our method involving
the simple and rapid collection of plasma by finger prick and sample pretreatment is thought to be applicable for the determination
of CoQ10H2/total CoQ10 ratio as a biomarker of oxidative stress. 相似文献
97.
Sasaki S Kriener M Segawa K Yada K Tanaka Y Sato M Ando Y 《Physical review letters》2011,107(21):217001
A topological superconductor (TSC) is characterized by the topologically protected gapless surface state that is essentially an Andreev bound state consisting of Majorana fermions. While a TSC has not yet been discovered, the doped topological insulator Cu(x)Bi(2)Se(3), which superconducts below ~3 K, has been predicted to possess a topological superconducting state. We report that the point-contact spectra on the cleaved surface of superconducting Cu(x)Bi(2)Se(3) present a zero-bias conductance peak (ZBCP) which signifies unconventional superconductivity. Theoretical considerations of all possible superconducting states help us conclude that this ZBCP is due to Majorana fermions and gives evidence for a topological superconductivity in Cu(x)Bi(2)Se(3). In addition, we found an unusual pseudogap that develops below ~20 K and coexists with the topological superconducting state. 相似文献
98.
F. Shimojo S. Ohmura A. Nakano R. K. Kalia P. Vashishta 《The European physical journal. Special topics》2011,196(1):53-63
A linear-scaling algorithm based on a divide-and-conquer (DC) scheme is designed to perform large-scale molecular-dynamics
simulations, in which interatomic forces are computed quantum mechanically in the framework of the density functional theory
(DFT). This scheme is applied to the thermite reaction at an Al/Fe2O3 interface. It is found that mass diffusion and reaction rate at the interface are enhanced by a concerted metal-oxygen flip
mechanism. Preliminary simulations are carried out for an aluminum particle in water based on the conventional DFT, as a target
system for large-scale DC-DFT simulations. A pair of Lewis acid and base sites on the aluminum surface preferentially catalyzes
hydrogen production in a low activation-barrier mechanism found in the simulations. 相似文献
99.
100.