全文获取类型
收费全文 | 307篇 |
免费 | 15篇 |
国内免费 | 6篇 |
专业分类
化学 | 207篇 |
力学 | 11篇 |
数学 | 47篇 |
物理学 | 63篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 23篇 |
2011年 | 21篇 |
2010年 | 22篇 |
2009年 | 18篇 |
2008年 | 30篇 |
2007年 | 22篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1986年 | 5篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有328条查询结果,搜索用时 31 毫秒
41.
42.
Dr. Song Song Vincent Fung Kin Yuen Dr. Lu Di Dr. Qiming Sun Prof. Dr. Kang Zhou Prof. Dr. Ning Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20018-20022
Production of renewable, high-value N-containing chemicals from lignocellulose will expand product diversity and increase the economic competitiveness of the biorefinery. Herein, we report a single-step conversion of furfural to pyrrole in 75 % yield as a key N-containing building block, achieved via tandem decarbonylation–amination reactions over tailor-designed Pd@S-1 and H-beta zeolite catalytic system. Pyrrole was further transformed into dl -proline in two steps following carboxylation with CO2 and hydrogenation over Rh/C catalyst. After treating with Escherichia coli, valuable d -proline was obtained in theoretically maximum yield (50 %) bearing 99 % ee. The report here establishes a route bridging commercial commodity feedstock from biomass with high-value organonitrogen chemicals through pyrrole as a hub molecule. 相似文献
43.
Dia Zeidan Chi Kin Chau Tzon-Tzer Lu Wei-Quan Zheng 《Mathematical Methods in the Applied Sciences》2020,43(5):2171-2188
In this paper, a novel Adomian decomposition method (ADM) is developed for the solution of Burgers' equation. While high level of this method for differential equations are found in the literature, this work covers most of the necessary details required to apply ADM for partial differential equations. The present ADM has the capability to produce three different types of solutions, namely, explicit exact solution, analytic solution, and semi-analytic solution. In the best cases, when a closed-form solution exists, ADM is able to capture this exact solution, while most of the numerical methods can only provide an approximation solution. The proposed ADM is validated using different test cases dealing with inviscid and viscous Burgers' equations. Satisfactory results are obtained for all test cases, and, particularly, results reported in this paper agree well with those reported by other researchers. 相似文献
44.
Nelwamondo Aubrey N. Colletti Lisa P. Lindvall Rachel E. Vesterlund Anna Xu Ning Tan Angela Hiong Jun Eppich Gary R. Genetti Victoria D. Kokwane Banyana L. Lagerkvist Petra Pong Boon Kin Ramebäck Henrik Tandon Lav Rasmussen Gert Varga Zsolt Wallenius Maria 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(2):379-394
Journal of Radioanalytical and Nuclear Chemistry - An international group of laboratories participating in CMX-4 subjected three samples to comparative nuclear forensic analysis using uranium assay... 相似文献
45.
Tam TK Zhou J Pita M Ornatska M Minko S Katz E 《Journal of the American Chemical Society》2008,130(33):10888-10889
A switchable bioelectrocatalytic system for glucose oxidation controlled by external biochemical signals exemplifies interfacing between bioelectronic and biochemical ensembles. 相似文献
46.
An in situ analytical approach to the measurement of supported liquid membrane permeability is reported. The method consists of a spectrophotometric method to measure transport through a membrane-supported lipid solution, using a rotating-diffusion cell configuration to overcome limits arising from transport through the aqueous solution boundary layer in stationary systems. Rotation frequencies are almost two orders of magnitude higher than those employed previously for rotating-diffusion studies of membrane transport. The method is illustrated with the transport of warfarin [1-(4'-hydroxy-3'-coumarinyl)-1-phenyl-3-butanone]. The use of the rotating-diffusion approach permits accurate calculation of the aqueous phase boundary layer thickness, which has hitherto been treated as an adjustable parameter in studies of membrane permeability. Further, it is shown that the analyte diffusion coefficient can be determined readily using liquid-liquid electrochemistry. 相似文献
47.
This paper reports the design and optimization of a double-stranded molecular probe for homogeneous detection of specific nucleotide sequences. The probes are labeled with either a fluorophore or a quencher such that the probe hybridization brings the two labels into close proximity, and this diminishes the fluorescence signal in the absence of a target. In the presence of a target, the fluorophore probe is thermodynamically driven to unzip from its hybridized form and bind with the target. An equilibrium analysis, which successfully describes all the major features of the assay without any fitting parameter, is performed to generalize the design of the probe. Several key parameters affecting the performance of the assay are examined. We show that the dynamic range and the signal-to-noise ratio of the assay can be optimized by the probe concentration, the quencher-to-fluorophore ratio, and the probe strand sequence. By proper design of the sequence, the probe discriminates single nucleotide mismatches in a single step without any separation step or measurement of melting profile. 相似文献
48.
49.
Di Liu Jia Zhao Youchao Kong Haoqiang Ai Haoyun Bai Chon Chio Leong Kin Ho Lo Shuangpeng Wang Weng Fai Ip Sen Lin Hui Pan 《Chemphyschem》2023,24(11):e202200937
Carbon neutrality has drawn increasing attention for realizing the carbon cyclization and reducing the greenhouse effect. Although the C1 products, such as CO, can be achieved with a high Faraday efficiency, the targeted production of C2 fuels as well as the mechanism have not been systematically investigated. In this work, we carry out a first-principles study to screen dual-atom catalysts (DACs) for producing C2 fuels through the electrocatalytic carbon monoxide reduction reaction (e-CORR). We find that methanol, ethanol and ethylene can be produced on both DAC−Co and DAC−Cu, while acetate can be achieved on DAC−Cu only. Importantly, methanol and ethylene are preferred on DAC−Co, while acetate and ethylene on DAC−Cu. Furthermore, we show that the explicit solvent can enhance the adsorption and influence the protonation steps, which subsequently affects the protonation and dimerization behavior as well as the performance and selectivity of e-CORR on DACs. We further demonstrate that the C−C coupling is easy to be formed and stabilized if the Integrated Crystal Orbital Hamilton Population (ICOHP) is low because of the low energy barrier. Our findings provide not only guidance on the design of novel catalysts for e-CORR, but an insightful understanding on the reduction mechanism. 相似文献
50.
Lianghui Chen Dechao Niu Cheng Hao Lee Yuan Yao Ki Lui Kin Man Ho Pei Li 《Particle & Particle Systems Characterization》2016,33(10):756-763
A scalable synthesis of magnetic core–shell nanocomposite particles, acting as a novel class of magnetic resonance (MR) contrast agents, has been developed. Each nanocomposite particle consists of a biocompatible chitosan shell and a poly(methyl methacrylate) (PMMA) core where multiple aggregated γ‐Fe2O3 nanoparticles are confined within the hydrophobic core. Properties of the nanocomposite particles including their chemical structure, particle size, size distribution, and morphology, as well as crystallinity of the magnetic nanoparticles and magnetic properties were systematically characterized. Their potential application as an MR contrast agent has been evaluated. Results show that the nanocomposite particles have good stability in biological media and very low cytotoxicity in both L929 mouse fibroblasts (normal cells) and HeLa cells (cervical cancer cells). They also exhibited excellent MR imaging performance with a T2 relaxivity of up to 364 mMFe?1 s?1. An in vivo MR test performed on a naked mouse bearing breast tumor indicates that the nanocomposite particles can localize in both normal liver and tumor tissues. These results suggest that the magnetic core–shell nanocomposite particles are an efficient, inexpensive and safe T2‐weighted MR contrast agent for both liver and tumor MR imaging in cancer therapy. 相似文献