全文获取类型
收费全文 | 325篇 |
免费 | 27篇 |
专业分类
化学 | 276篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 12篇 |
物理学 | 57篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 45篇 |
2021年 | 63篇 |
2020年 | 21篇 |
2019年 | 21篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 28篇 |
2015年 | 14篇 |
2014年 | 15篇 |
2013年 | 26篇 |
2012年 | 23篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1917年 | 2篇 |
排序方式: 共有352条查询结果,搜索用时 15 毫秒
71.
This paper presents a chemometrics-assisted optimization study to improve the separation of tocopherol (-T) and tocotrienol (-TT) homologues on a C30 stationary phase in reversed-phase HPLC. The HPLC settings were optimized using a central composite design and the response surface methodology. Flow rate, column temperature, and mobile phase composition were chosen as independent variables. Peak resolution (Rs), analysis time (tR), and peak symmetries of the tocopherol isomers were chosen as response variables. Optimum performance in terms of Rs was obtained at a flow rate of 0.31 mL min?1, a temperature of 8.70 °C, and % B content (methyl tert-butyl ether: methanol: water, 80:18:2, v/v/v) in the mobile phase of 38.12%. The analysis of variance and regression analysis gave adjusted R2 values of 0.9841 for Rs, 0.9850 for tR-(α-T), 0.9853 for tR-(β-T), and 0.9204 for the peak symmetry of β-T. This confirms the good agreement of experimental data with predicted values. The close eluting peaks of β-/γ-tocol could be baseline separated at the optimized conditions at a minimized analysis time. Empirical second-order polynomial models were derived that gave statistically high significances (P?<?0.0001). Hence, the models can be successfully employed to predict the optimum separation conditions of co-eluting peaks of β-/γ-tocols. The optimized method was successfully applied to determine the individual tocol homologues in various cold pressed edible oils. Total contents ranged from 15 to almost 2600 mg tocol kg?1 oil. 相似文献
72.
A photocatalytic degradation method was developed for polychlorobiphenyl (PCB) and organochloride pesticide (OCP) discrimination and quantification. A mixture of Aroclor 1260 and p,p′-DDT was irradiated at 254 nm by UV lamp (40 W) in the presence of TiO2 (30 mg mL−1 non-aqueous solution). Comparison of gas chromatograms showed that p,p′-DDT signals decreased significantly after irradiation, while Aroclor 1260s chromatograms did not show any difference before and after irradiation. Detection limits were 0.30 mg L−1 and 0.15 mg L−1 for p,p′-DDT and Aroclor 1260, respectively. The method was applied to spiked egg samples, the recoveries were found as 72% for DDT and 82.01% for Aroclor 1260. 相似文献
73.
Yun Hau Ng Izan Izwan Hadi Nur Mohd Nazlan Mohd Muhid Halimaton Hamdan 《Journal of fluorine chemistry》2007,128(1):12-16
A series of amphiphilic fluorinated zirconia containing titanium was prepared by titanium impregnation followed by fluorination and alkylsilylation of zirconium oxide. Physical properties of the resulting samples were characterized by XRD analysis, UV-vis spectroscopy, BET surface area analysis and EDAX analysis. The effects of fluorine and alkylsilane groups on the samples were studied by the epoxidation of 1-octene with aqueous hydrogen peroxide. The epoxidation of alkenes is one of the most important methods of functionalizing simple hydrocarbons. The amphiphilic fluorinated catalysts were more active and more efficient than the conventional titania-silica and zirconia-silica mixed oxides in linear alkene epoxidation; enhanced by the presence of alkylsilane and fluorine groups in the catalysts. Modification with alkylsilane successfully induces the hydrophobic behavior of zirconia which is hydrophilic in nature; whereas fluorine was chosen for its electron-withdrawing effect which further activates the titanium active sites. 相似文献
74.
Alraqa Shaya Y. Kaya Esra Nur Taşci Neşe Erbahar Dogan Durmuş Mahmut 《Journal of fluorescence》2022,32(5):1801-1813
Journal of Fluorescence - In this current study, the novel bis[4,5-(pyrene-2-yl)-3,6-(hexyloxy)] phthalonitrile (SPN) fluorophore has been successfully synthesized. Structural characterization of... 相似文献
75.
Mat Mohamad Nur Hidayat Asmuin Nor Zelawati Md Basir Md Faisal Abbas Tehseen Mohd Kasihmuddin Mohd Shareduwan Goodarzi Marjan 《Journal of Thermal Analysis and Calorimetry》2021,143(3):2343-2354
Journal of Thermal Analysis and Calorimetry - In this paper, a numerical study was performed to examine the effect of divergent nozzle length of single-hose dry ice blasting on the development of... 相似文献
76.
Ridhuan Nur Syafinaz Mohamad Nor Noorhashimah Abdul Razak Khairunisak Lockman Zainovia Zakaria Nor Dyana 《Journal of Solid State Electrochemistry》2021,25(3):1065-1072
Journal of Solid State Electrochemistry - This work demonstrated the property enhancement of Pt nanodendrite (PtNDs)-decorated ZnO nanorods (ZnONRs) modified indium tin oxide (ITO) electrode for an... 相似文献
77.
78.
79.
Dilsat Ozkan‐Ariksoysal Ozlem Akgul Seyma Aydinlik Seda Nur Topkaya Nilay Aladag Mehmet Ozsoz 《Electroanalysis》2010,22(19):2225-2234
In this work, an electrochemical DNA‐based sensor was developed for the detection of the interaction between the anticonvulsant compounds 2‐phthalimido‐N‐substituted phenylethanesulfonamides (PMPES‐derivatives) and 24‐mer short DNA sequences by using differential pulse voltammetry (DPV) based on both compound and guanine oxidation signals at the renewable carbon graphite electrode (CGE) surface. The influence of compounds on DNA showed differences depending on the nature and position of the substituent on the N‐phenyl ring. Compounds bearing 3‐methoxy, 4‐chloro and 2,6‐dimethyl substituents bind to single stranded probe DNA more strongly than the other derivatives of PMPES. Thus, these compounds were evaluated for use as an electrochemical hybridization label (indicator). 相似文献
80.
Yongjun Liu Nur Fadhilah Ibrahim 《Journal of Computational and Applied Mathematics》2010,235(1):286-292
In this paper we propose an iterative method to calculate the largest eigenvalue of a nonnegative tensor. We prove this method converges for any irreducible nonnegative tensor. We also apply this method to study the positive definiteness of a multivariate form. 相似文献