全文获取类型
收费全文 | 400篇 |
免费 | 45篇 |
国内免费 | 54篇 |
专业分类
化学 | 366篇 |
晶体学 | 12篇 |
力学 | 20篇 |
综合类 | 1篇 |
数学 | 31篇 |
物理学 | 69篇 |
出版年
2024年 | 1篇 |
2023年 | 19篇 |
2022年 | 47篇 |
2021年 | 24篇 |
2020年 | 27篇 |
2019年 | 43篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 25篇 |
2014年 | 20篇 |
2013年 | 26篇 |
2012年 | 37篇 |
2011年 | 29篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 20篇 |
2007年 | 7篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有499条查询结果,搜索用时 46 毫秒
131.
Dr. Xunkai Yin Zichun Zhang Kequan Yao Prof. Xinxin Xu Dr. Yun Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(34):8774-8781
Zn-air batteriesare a perspective power source for grid-storage. But, after they are discharged at1.1 to 1.2 V, large overpotential is required for their charging (usually 2.5 V). This is due to a sluggish oxygen evolution reaction (OER). Incorporating organic pollutants into the cathode electrolyte is a feasible strategy for lowering the required charging potential. In the discharge process, the related oxygen reduction reaction, hydrophobic electrocatalysts are more popular than hydrophilic ones. Here, a hydrophobic bifunctional polyoxometalate electrocatalyst is synthesized by precise structural design. It shows excellent activities in both bisphenol A degradation and oxygen reduction reactions. In bisphenol A containing electrolyte, to achieve 100 mA ⋅ cm−2, its potential is only 1.32 V, which is 0.34 V lower than oxygen evolution reaction. In the oxygen reduction reaction, this electrocatalyst follows the four-electron mechanism. In both bisphenol A degradation and oxygen reduction reactions, it shows excellent stability. With this electrocatalyst as cathode material and bisphenol A containing KOH as electrolyte, a Zn-air battery was assembled. When “charged” at 85 mA ⋅ cm−2, it only requires 1.98 V. Peak power density of this Zn-air battery reaches 120.5 mW ⋅ cm−2. More importantly, in the “charge” process, bisphenol A is degraded, which achieves energy saving and pollutant removal simultaneously in one Zn-air battery. 相似文献
132.
Prof. Xinxin Xu Dr. Xunkai Yin Dr. Jingnuo Fu Dr. Di Ke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14451-14460
As a H2O2 generator, a 2e− oxygen reduction reaction active electrocatalyst plays an important role in the advanced oxidation process to degrade organic pollutants in sewage. To enhance the tendency of NiCo2S4 towards the 2e− reduction reaction, N atoms are doped in its structure and replace S2−. The result implies that this weakens the interaction between NiCo2S4 and OOH*, suppresses O−O bond breaking and enhances H2O2 selectivity. This electrocatalyst also shows photothermal effect. Under photothermal heating, H2O2 produced by the oxidation reduction reaction can decompose and releaseOH, which degrades organic pollutants through the advanced oxidation process. Photothermal effect induced by the advance oxidation process shows obvious advantages over the traditional Fenton reaction, such as wide pH adaptation scope and low secondary pollutant due to its Fe2+ free character. With Zn as anode and the electrocatalyst as cathode material, a Zn−O2 battery is assembled. It achieves electricity generation and photothermal effect induced by the advance oxidation process simultaneously. 相似文献
133.
Li Hongbo Ke Fei An Yanli Hou Xinxin Zhang Hao Lin Mei Zhang Dongsheng 《Journal of nanoparticle research》2013,15(3):1-11
Journal of Nanoparticle Research - Given the ubiquity of silver nanoparticles (AgNPs) and their potential for toxic effects on both humans and the environment, it is important to understand their... 相似文献
134.
A facile two-step approach has been used for the synthesis of porous SnO2 rods: the initial room-temperature precipitation of precursor SnC2O4 and its subsequent thermal decomposition at 550 °C. Both the as-obtained porous SnO2 microrods (length ~10.0?±?3.5 μm, diameter ~1.1?±?0.4 μm) and submicrorods (length ~5.8?±?1.9 μm, diameter ~0.4?±?0.1 μm) are the crystalline mixtures of major tetragonal and minor orthorhombic crystal phases, showing a tetragonal fraction of 84.7 and 87.0 %, respectively. When applied as a lithium-ion battery anode, the porous submicrorods (specific surface area ~13.6 m2 g?1) can deliver an initial discharge capacity of 1,730.7 mAh g?1 with a high coulombic efficiency of 61.6 % and show the 50th discharge capacity of 662.8 mAh g?1 at 160 mA g?1 within a narrow potential range of 10.0 mV to 2.0 V. Similarly, even the anode of porous microrods (specific surface area ~11.8 m2 g?1) can still exhibit an initial discharge capacity of 1,661.1 mAh g?1 at 160 mA g?1 with a coulombic efficiency of 60.9 %. Regardless of the polymorphic nature, the acquired porosity may only alleviate the huge volume change of anodes for the first cycle; thus, the structural parameters of average size and specific surface area can be feasibly associated with the enhanced lithium storage capability. Anyway, these indicate a facile oxalate precursor method for the controlling synthesis and high performance of rodlike SnO2 for lithium-ion batteries. 相似文献
135.
Surface modification with EDTA molecule: A feasible method to enhance the adsorption property of ZnO
Chong Sun Xuanwei WuHao Meng Xinxin XuJunli Xu Xia Zhang 《Journal of Physics and Chemistry of Solids》2014
Surface-functionalized zinc oxide (ZnO) nanoparticles were synthesized with ethylene diamine tetraacetic acid (EDTA) as a modification agent, which were used as adsorbents in the adsorption of Cu2+ at certain conditions. The transmission electron microscopy (TEM) results show that the average size of ZnO particles is about 45 nm, and it exhibits hexagonal wurtzite structure. Fourier transform infrared (FTIR) spectra reveal that the EDTA species are chemically bonded on the surface of ZnO. Compared with bare ZnO particles, the functionalized ZnO nanoparticles have a better activity in the Cu2+ adsorption. The maximum adsorption capacity of functionalized ZnO nanoparticles is 20.97 mg/g, while it is 17.93 mg/g for the bare ZnO. The adsorption isotherm of bare ZnO particles is in accordance with the Freundlich model, and the chemical adsorption is in a dominant position in the adsorption process of Cu2+ on functionalized ZnO particles. 相似文献
136.
Feng Zhou James D. Blocher Xinxin Hu H. Sebastian Heese 《European Journal of Operational Research》2014
We consider the problem of scheduling products with components on a single machine, where changeovers incur fixed costs. The objective is to minimize the weighted sum of total flow time and changeover cost. We provide properties of optimal solutions and develop an explicit characterization of optimal sequences, while showing that this characterization has recurrent properties. Our structural results have interesting implications for practitioners, primarily that the structure of optimal sequences is robust to changes in demand. 相似文献
137.
A time-dependent wavepacket diffusion method is proposed to deal with charge transport in organic crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent fluctuations which are generated from the corresponding spectral density functions. The numerical demonstrations reveal that the present approach predicts the consistent charge carrier dynamics with the rigorous quantum approaches. In addition, the diffusion coefficients obtained from the Marcus formula are well reproduced at the weak electronic coupling and high temperature limits. It is also found that the charge mobility feature of the crossover from the band-like to the hopping-type cannot be predicted from the fluctuations induced by the linear electron-phonon interactions with an Ohmic spectral density; however, it indeed appears as the electronic coupling fluctuation exponentially depends on the nuclear coordinates. Finally, it should be noted that although the present approach neglects the imaginary fluctuation, it essentially incorporates the coherent motion of the charge carrier and quantum effect of the phonon motion with a broad regime of the fluctuations for symmetric systems. Besides, the approach can easily be applied to systems having thousands of sites, which allows one to investigate charge transport in nanoscale organic crystals. 相似文献
138.
AbstractIn this research, hydrophilic molecularly imprinted microspheres (HMIPs) for azoxystrobin were successfully synthesized through precipitation polymerization. The adsorption capacities of HMIPs for azoxystrobin in water medium were higher than ordinary molecularly imprinted microspheres (MIPs), and HMIPs exhibited good hydrophilic properties. HMIPs and non-imprinted microspheres (HNIPs) were characterized by FT-IR, SEM, laser particle size analyzer and TGA. Comparing with HNIPs, azoxystrobin had a significant influence on morphologys and sizes of HMIPs. The Langmuir adsorption isotherm illustrated each binding site of HMIPs had the same adsorption capacity. The Lagergran pseudo-second-order kinetic model indicated the adsorption process between azoxystrobin and HMIPs was chemical adsorption. BET test illustrated HMIPs had bigger specific surface areas than HNIPs. Selective adsorption indicated that HMIPs had highly specific recognition of azoxystrobin. HMIPs successfully exhibited high selectivity and high hydrophilicity in water medium. 相似文献
139.
Jinru Liang Yoichiro Ito Xinxin Zhang Jiao He Wenji Sun 《Journal of separation science》2013,36(24):3934-3940
A rapid method combining microwave‐assisted extraction (MAE) and high‐speed counter‐current chromatography (HSCCC) was applied for preparative separation of six bioactive compounds including loganic acid ( I ), isoorientin‐4′‐O‐glucoside ( II ), 6′‐O‐β‐d ‐glucopyranosyl gentiopicroside ( III ), swertiamarin ( IV ), gentiopicroside ( V ), sweroside ( VI ) from traditional Tibetan medicine Gentiana crassicaulis Duthie ex Burk. MAE parameters were predicted by central composite design response surface methodology. That is, 5.0 g dried roots of G. crassicaulis were extracted with 50 mL 57.5% aqueous ethanol under 630 W for 3.39 min. The extract (gentian total glycosides) was separated by HSCCC with n‐butanol/ethyl acetate/methanol/1% acetic acid water (7.5:0.5:0.5:3.5, v/v/v/v) using upper phase mobile in tail‐to‐head elution mode. 16.3, 8.8, 12., 25.1, 40.7, and 21.8 mg of compounds I–VI were obtained with high purities in one run from 500 mg of original sample. The purities and identities of separated components were confirmed using HPLC with photo diode array detection and quadrupole TOF‐MS and NMR spectroscopy. The study reveals that response surface methodology is convenient and highly predictive for optimizing extraction process, MAE coupled with HSCCC could be an expeditious method for extraction and separation of phytochemicals from ethnomedicine. 相似文献
140.
Lijun Wang Chao Han Wenjun Sui Mei Wang Xinxin Lu 《Analytical and bioanalytical chemistry》2013,405(15):5259-5266
Laboratory identification of carbapenemase-producing clinical isolates is crucial to limit the spread of the bacteria. In this study, we shall first develop the matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) assay in automatic identification of carbapenemase producers. A total of 143 well-characterized isolates were studied. After an incubation of bacteria with meropenem trihydrate, the mixture was centrifuged and the supernatant analyzed by MALDI-TOF MS. A genetic algorithm model with ClinProTools software was built using spectra of 43 carbapenemase-positive isolates and 40 carbapenemase-negative isolates after 2 h of incubation. This model was externally validated using 60 test isolates. All spectra of supernatants of the carbapenemase-negative isolates showed peak profiles comparable to that of pure meropenem (m/z 384.159, 406.140, and 428.122 of its two sodium salt variants) regardless of the incubation time tested. For the carbapenemase-positive isolates, the specific peak for meropenem at m/z 384.159 disappeared during the incubation time, two products of meropenem degradation were identified with m/z 358.18 (the decarboxylated product) and 380.161 (sodium salt of the decarboxylated product), and other degradation products were observed (native molecule with disrupted amide bond with m/z 402.169, three sodium salt variants with m/z 424.151, 446.133, and 468.115). Sixty test isolates were 100 % correctly classified as carbapenemase positive and carbapenemase negative with the genetic algorithm model. MALDI-TOF MS coupled with ClinProTools is capable of rapidly, accurately, and automatically identifying carbapenemase producers. Figure
The average spectra of the carbapenemase-positive (red) and carbapenemasenegative isolates (green) were shown. Nine peaks differentiating the two classes are highlighted by arrows. x axis, mass per charge [m/z (in daltons)]; y axis, intensity(arbitrary units [arb.u.]). 相似文献