全文获取类型
收费全文 | 193篇 |
免费 | 43篇 |
国内免费 | 52篇 |
专业分类
化学 | 174篇 |
晶体学 | 1篇 |
力学 | 5篇 |
综合类 | 5篇 |
数学 | 31篇 |
物理学 | 72篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 22篇 |
2009年 | 21篇 |
2008年 | 12篇 |
2007年 | 13篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 17篇 |
2003年 | 13篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有288条查询结果,搜索用时 562 毫秒
1.
Yang Wang Weizhe Gao Kangzhou Wang Xinhua Gao Baizhang Zhang Heng Zhao Qingxiang Ma Peipei Zhang Guohui Yang Mingbo Wu Noritatsu Tsubaki 《Chemical science》2021,12(22):7786
Even though the transformation of syngas into aromatics has been realized via a methanol-mediated tandem process, the low product yield is still the bottleneck, limiting the industrial application of this technology. Herein, a tailor-made zeolite capsule catalyst with Ga doping and SiO2 coating was combined with the methanol synthesis catalyst Cr2O3 to boost the synthesis of value-added aromatics, especially para-xylene, from syngas. Multiple characterization studies, control experiments, and density functional theory (DFT) calculation results clarified that Ga doped zeolites with strong CO adsorption capability facilitated the transformation of the reaction intermediate methanol by optimizing the first C–C coupling step under a high-pressure CO atmosphere, thereby driving the reaction forward for aromatics synthesis. This work not only reveals the synergistic catalytic network in the tandem process but also sheds new light on principles for the rational design of a catalyst in terms of oriented conversion of syngas.The single-pass conversion of syngas into para-xylene was realized using a bifunctional catalyst Cr2O3/Ga-ZSM-5@SiO2. The Ga species facilitates the methanol consumption process by C–C coupling optimization, enhancing the yield of the target aromatics. 相似文献
2.
尼龙—6/丙烯酸接枝膜的结构与性能 总被引:3,自引:0,他引:3
应用IR确定了尼龙-6与丙烯酸接枝反应的接枝点位于尼龙大分子酰胺键的N原子上,用X射线衍射研究了接枝膜的结晶状况,探讨了接枝率对接枝膜的电阻、离子交换容量、强度等性能的影响. 相似文献
3.
Qingxiang Zhou Zhenwen Zheng Junping Xiao Huili Fan Xiuyi Yan 《Analytical and bioanalytical chemistry》2016,408(19):5211-5220
4.
A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a computer running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments’ graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization. 相似文献
5.
TiO2 nanotube arrays prepared by anodization as an adsorbent in micro‐solid‐phase extraction to preconcentrate and determine nitrogen‐containing polycyclic aromatic hydrocarbons in water samples
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this study, a simultaneous determination method for nitrogen‐containing polycyclic aromatic hydrocarbons including 7‐methylquinoline, acridine, 5,6‐benzoquinoline, carbazole, and 9‐methylcarbazole was developed. This method is based on a micro‐solid phase extraction using TiO2 nanotube arrays as an adsorbent in combination with HPLC. Some factors that had an effect on the enrichment were optimized, such as sample pH, surfactant concentration, ion strength, type of eluent, equilibrium time, and desorption time. Under the optimized conditions, the linear ranges and LODs were in the range of 0.01–100 and 0.0035–0.81 μg/L, respectively. The precisions of the proposed method were <9.51% (RSD, n = 6). The developed method was validated with four real samples, and the spiked recoveries were in the range of 77–109.6%. All these results demonstrated that this novel micro‐solid‐phase extraction technique was a reliable alternative to conventional preconcentration method for the extraction and analysis of such nitrogen‐containing polycyclic aromatic hydrocarbons in complex samples. 相似文献
6.
Feng Gao Juan Song Bin Zhang Hidekazu Tanaka Fei Gao Weiwei Qiu Qingxiang Wang 《中国化学快报》2020,31(1):181-184
The core-shell structured Au@Bi2S3 nanorods have been prepared through direct in-situ growth of Bi2S3 at the surface of pre-synthesized gold nanorods.The product was characterized by X-ray diffraction,transmission electron microscopy and energy-dispersive X-ray spectroscopy.Then the obtained Au@Bi2S3 nanorods were coated onto glassy carbon electrode to act as a scaffold for fabrication of electrochemical DNA biosensor on the basis of the coordination of-NH2 modified on 5’-end of probe DNA and Au@Bi2S3.Electrochemical characterization assays demonstrate that the Au@Bi2S3 nanorods behave as an excellent electronic transport channel to promote the electron transfer kinetics and increase the effective surface area by their nanosize effect.The hybridization experiments reveal that the Au@Bi2S3 matrix-based DNA biosensor is capable of recognizing complementary DNA over a wide concentration ranging from 10 fmol/L to 1 nmol/L.The limit of detection was estimated to be 2 fmol/L(S/N=3).The biosensor also presents remarkable selectivity to distinguish fully complementa ry sequences from basemismatched and non-complementary ones,showing great promising in practical application. 相似文献
7.
8.
Qingxiang Wang Yingtao Ding Feng Gao Shulian Jiang Bin Zhang Jiancong Ni Fei Gao 《Analytica chimica acta》2013
A novel DNA biosensor was fabricated through a facile sulfamide coupling reaction. First, the versatile sulfonic dye molecule of 1-amino-2-naphthol-4-sulfonate (AN-SO3−) was electrodeposited on the surface of a glassy carbon electrode (GCE) to form a steady and ordered AN-SO3− layer. Then the amino-terminated capture probe was covalently grafted to the surface of SO3−-AN deposited GCE through the sulfamide coupling reaction between the amino groups in the probe DNA and the sulfonic groups in the AN-SO3−. The step-by-step modification process was characterized by electrochemistry and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Using Ru(NH3)63+ as probe, the probe density and the hybridization efficiency of the biosensor were determined to be 3.18 × 1013 strands cm−2 and 86.5%, respectively. The hybridization performance of the biosensor was examined by differential pulse voltammetry using Co(phen)33+/2+ (phen = 1,10-phenanthroline) as the indicator. The selectivity experiments showed that the biosensor presented distinguishable response after hybridization with the three-base mismatched, non-complementary and complementary sequences. Under the optimal conditions, the oxidation peak currents of Co(phen)33+/2+ increased linearly with the logarithm values of the concentration of the complementary sequences in the range from 1.0 × 10−13 M to 1.0 × 10−8 M with a regression coefficient of 0.9961. The detection limit was estimated to be 7.2 × 10−14 M based on 3σ. 相似文献
9.
Prof. Dr. Qingxiang Wang Yingtao Ding Liheng Wang Jiancong Ni Zhanglong Yu Haibin Lin Feng Gao 《化学:亚洲杂志》2013,8(7):1455-1462
An electrically neutral cobalt complex, [Co(GA)2(phen)] (GA=glycollic acid, phen=1,10‐phenathroline), was synthesized and its interactions with double‐stranded DNA (dsDNA) were studied by using electrochemical methods on a glassy carbon electrode (GCE). We found that [Co(GA)2(phen)] could intercalate into the DNA duplex through the planar phen ligand with a high binding constant of 6.2(±0.2)×105 M ?1. Surface studies showed that the cobalt complex could electrochemically accumulate within the modified dsDNA layer, rather than within the single‐stranded DNA (ssDNA) layer. Based on this feature, the complex was applied as a redox‐active hybridization indicator to detect 18‐base oligonucleotides from the CaMV35S promoter gene. This biosensor presented a very low background signal during hybridization detection and could realize the detection over a wide kinetic range from 1.0×10?14 M to 1.0×10?8 M , with a low detection limit of 2.0 fM towards the target sequences. The hybridization selectivity experiments further revealed that the complementary sequence, the one‐base‐mismatched sequence, and the non‐complementary sequence could be well‐distinguished by the cobalt‐complex‐based biosensor. 相似文献
10.
DNA repair has received heightened attention in recent years as ozone depletion threatens to significantly increase DNA damage by UVB radiation[1—6]. The major lesions formed in DNA by this radiation are cis-syn cyclobutane pyrimidine dimers, which are created by the linkage of two neighboring pyrimidine bases in DNA via C5-C5 and C6-C6 atoms by [2+2] cycloaddition[2,5—8]. This potentially lethal or mutagenic damage can be repaired either by the removal of the damaged bases by excisio… 相似文献