全文获取类型
收费全文 | 1300篇 |
免费 | 39篇 |
国内免费 | 3篇 |
专业分类
化学 | 933篇 |
晶体学 | 5篇 |
力学 | 53篇 |
数学 | 55篇 |
物理学 | 296篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 41篇 |
2020年 | 32篇 |
2019年 | 30篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 35篇 |
2015年 | 37篇 |
2014年 | 56篇 |
2013年 | 96篇 |
2012年 | 94篇 |
2011年 | 105篇 |
2010年 | 67篇 |
2009年 | 59篇 |
2008年 | 81篇 |
2007年 | 83篇 |
2006年 | 74篇 |
2005年 | 67篇 |
2004年 | 57篇 |
2003年 | 44篇 |
2002年 | 50篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1342条查询结果,搜索用时 0 毫秒
941.
K.P. Ko R.K. Ko S.H. Moon S.S. Oh S.I. Yoo 《Physica C: Superconductivity and its Applications》2010,470(20):1275-1279
We report a successful fabrication of c-axis oriented GdBa2Cu3O7−δ (GdBCO) films on the BaSnO3 (BSO) buffer layers on ion-beam assisted deposition (IBAD)-MgO template by pulsed-laser deposition (PLD). The (0 0 l) growth and in-plane textures of BSO buffer layers were found sensitive to the substrate temperature (Ts). With increasing the BSO layer thickness up to ∼165 nm, in-plane texture (Δ? ∼ 6.2°) of BSO layers was almost unaltered while completely c-axis oriented BSO layers were obtainable from samples with the thickness below ∼45 nm. On the BSO buffer layers showing in-plane texture of 6.2° and RMS surface roughness of ∼8.6 nm, GdBCO films were deposited at 780–800 °C. All GdBCO films exhibited Δ? values of 4.6–4.7°, Tc,zero of ∼91 K, and critical current density (Jc) over 1 MA/cm2 at 77 K in a self-field. The highest Jc value of 1.82 MA/cm2 (Ic of 51 A/cm-width) was achieved from the GdBCO film deposited at Ts of 790 °C. These results support that BSO can be a promising buffer layer on the IBAD-MgO template for obtaining high-Jc GdBCO coated conductors. 相似文献
942.
A two-substrate method is developed to simultaneously determine emissivity, transmittance, and reflectance of semitransparent materials with a single measurement under the same environment at elevated temperature. The three quantities can be obtained through the emissivities of substrates and the apparent emissivities resulting from the radiance of the sample heated by substrates. The two-substrate method is compared with the conventional method by measuring sapphire samples with various thicknesses, resulting in good agreements for all the samples. The present method will be useful to measure the temperature dependence of optical properties of porous ceramic materials. 相似文献
943.
Hyoung Sun Yoo Won Bin Im Sung Wook Kim Byoung Hwa Kwon Duk Young Jeon 《Journal of luminescence》2010,130(1):153-156
In order to investigate the effects of the crystallite size on the photoluminescence (PL) properties of a phosphor, monodisperse spherical SiO2/Y2O3:Eu3+ phosphor core/shell particles were synthesized. On the surface of the core particles prepared by the Stöber method, the phosphor shell was continuously coated by a heterogeneous precipitation method. Because the growth of the crystallite was restricted by the shell thickness, the crystallite size could be successfully controlled at the same firing conditions. The PL intensity, the asymmetric ratio and thus the color purity were significantly decreased with the decrease of the crystallite size. In addition, the position of charge transfer band in the PL excitation spectrum was red-shifted with the decrease of the crystallite size. 相似文献
944.
Hydration or dehydration of a proton conducting oxide has been understood to be due to chemical diffusion of H2O. Hence, mass relaxation of the oxide has often been employed to determine the chemical diffusivity and saturation solubility of H2O. This paper shows that this approach is not correct. Applying thermogravimetric methods at 973 and 1073 K to BaCe0.95Yb0.05O2.975 as model system, the mass relaxes twofold (i.e., with two different chemical diffusivities for H and O) like the electrical conductivity, but monotonically unlike the conductivity which relaxes non-monotonically. The correlation of the mass relaxation with the conductivity relaxation is established. The closed-form solution for the mass relaxation is presented in comparison with that for the conductivity relaxation and its implication is discussed in connection to water saturation. 相似文献
945.
Sun‐Min Jung Jungmin Park Dongbin Shin Hu Young Jeong DongKyu Lee In‐Yup Jeon HyungJoon Cho Noejung Park Jung‐Woo Yoo Jong‐Beom Baek 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11796-11801
Ordered graphitic carbon nanosheets (GCNs) were, for the first time, synthesized by the direct condensation of multifunctional phenylacetyl building blocks (monomers) in the presence of phosphorous pentoxide. The GCNs had highly ordered structures with random hole defects and oxygenated functional groups, showing paramagnetism. The results of combined structural and magnetic analyses indicate that the hole defects and functional groups are associated with the appearance and stabilization of unpaired spins. DFT calculations further suggest that the emergence of stabilized spin moments near the edge groups necessitates the presence of functionalized carbon atoms around the hole defects. That is, both hole defects and oxygenated functional groups are essential ingredients for the generation and stabilization of spins in GCNs. 相似文献
946.
Design of organic supercapacitors with high performances using pore size controlled active materials
Inchan Yang Dahye Kwon Jihoon Yoo Myung-Soo Kim Ji Chul Jung 《Current Applied Physics》2019,19(2):89-96
In this study, we thoroughly investigate the required properties of active materials for organic supercapacitors with high performances. In this regard, we synthesize carbon xerogels with different physical properties, including specific surface area and pore size. The carbon xerogels are prepared via the sol-gel reaction of resorcinol and formaldehyde under different gelation temperature conditions. Through Fourier-transform infrared, nitrogen adsorption–desorption, and scanning electron microscopy analysis, we can confirm that carbon xerogels with different physical properties can be successfully synthesized. We apply the prepared carbon xerogels to organic supercapacitor electrodes. As a result of electrochemical experiments, carbon xerogels with high surface area exhibit high electrochemical performances at low-rate charge?discharge processes. However, as the charge–discharge rate increases, carbon xerogels with low surface area and high conductivity exhibit higher performances. Therefore, the surface area of active materials is a key factor for supercapacitors with high performances at low-rate charge–discharge processes. However, the effects of conductivity can be more crucial as compared with those of surface area as the charge–discharge rates increase. In addition, we suggest that the physical properties of active materials should be differently optimized as the charge–discharge rate is employed. 相似文献
947.
Trilochan Sahoo Jung-Hun Choi Ju-Wan Yoo Yeon-Tae Yu Seong-Ran Jeon Jong-Hyeob Baek Hyung-Do Yoon Sung-Min Hwang In-Hwan Lee 《Journal of Crystal Growth》2010,312(20):2857-2860
ZnO nanorod arrays are grown on a-plane GaN template/r-plane sapphire substrates by hydrothermal technique. Aqueous solutions of zinc nitrate hexahydrate and hexamethylenetetramine were employed as growth precursors. Electron microscopy and X-ray diffraction measurements were carried out for morphology, phase and growth orientation analysis. Single crystalline nanorods were found to have off-normal growth and showed well-defined in-plane epitaxial relationship with the GaN template. The 〈0 0 0 1〉 axis of the ZnO nanorods were observed to be parallel to the 〈1 0 1¯ 0〉 of the a-plane GaN layer. Optical property of the as-grown ZnO nanorods was analyzed by room temperature photoluminescence measurements. 相似文献
948.
Tae Hoon Kim Kyeongnan Kwon Dae Sung Yoo Seung-Jun Lee Choong Je Ma Juhee Ahn 《Journal of Dispersion Science and Technology》2019,40(1):119-127
Monoolein (MO) cubic phase including alginate and cystamine in its water channel controlled the release of epidermal growth factor (EGF) by responding to changes in pH value and the reductive conditions of the release medium. The crosslinking degree of alginate gel with cystamine and the complex coacervation of alginate and EGF were investigated by using light scattering. TEM micrographs of cubic phases revealed MO bilayers along with water channels. Differential scanning calorimetry indicated that the cubic-to-hexagonal phase transition took place at 60.2?°C. Additives such as stearyl trimethyl ammonium chloride and cystamine decreased the transition temperature by a few to more than 10?°C. The release of EGF loaded in cubic phases was completed in 5?h and, thereafter, no significant additional release was observed. The release % of EGF loaded in MO cubic phase containing alginate and cystamine increased not only with the increase of pH but also glutathione concentration. The MO cubic phase containing alginate/cystamine gel can be used as a carrier for the delivery of peptide and protein drugs. 相似文献
949.
Joo-Sik Yoo 《International Journal of Heat and Fluid Flow》1996,17(6):587-593
Dual steady solutions in natural convection in an annulus between two horizontal concentric cylinders are numerically investigated for a fluid of Prandtl number 0.7. It is found that, when the Rayleigh number based on the gap width exceeds a certain critical value, dual steady two-dimensional (2-D) flows can be realized: one being the crescent-shaped eddy flow commonly observed and the other the flow consisting of two counter-rotating eddies and their mirror images. The critical Rayleigh number decreases as the inverse relative gap width increases. 相似文献
950.
Min Ku Jeon Tae-Sic Yoo Eun-Young Choi Jin-Mok Hur 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(1):155-163
This paper discusses the development of a separation method for isolation of 171Tm from a half-gram irradiated erbium target in support of stockpile stewardship and astrophysics research. The developed procedure is based on cation exchange separation using alpha-hydroxyisobutyric acid (α-HIBA) as chelating agent. It is able to achieve either a decontamination factor of 1.4(4) × 105 with 68.9(3) % recovery or 95.4(3) % recovery with a decontamination factor of 5.82(7) × 103 for a mock 500-mg target containing 17.9 mg thulium in a single pass-through at room temperature. 相似文献