全文获取类型
收费全文 | 222篇 |
免费 | 13篇 |
国内免费 | 30篇 |
专业分类
化学 | 259篇 |
数学 | 1篇 |
物理学 | 5篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 24篇 |
2012年 | 13篇 |
2011年 | 31篇 |
2010年 | 36篇 |
2009年 | 34篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
排序方式: 共有265条查询结果,搜索用时 15 毫秒
1.
Hiroshi Aoki Ken Hosoya Tomohisa Norisuye Nobuo Tanaka Daisuke Tokuda Norio Ishizuka Kazuki Nakanishi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(2):949-958
An investigation was made of the gelation of dimethacrylate‐type crosslinking agents in view of an application for separation media. The study mainly centered on a crosslinking agent, glycerol dimethacrylate (GDMA), which is relatively hydrophilic because of a hydroxyl group in the middle of its structure. The gelation of GDMA was compared with that of other hydrophobic crosslinking agents such as ethylene glycol dimethacrylate and 1,6‐hexanediol dimethacrylate. The diluents used in the study were toluene, toluene with methanol, and cyclohexanol. The gelation was observed in real time with a charge coupled device camera and dynamic light scattering (DLS). Also, the separated dry gels were extensively characterized with scanning electron microscopy, BET (N2 absorption and desorption isotherm), and Fourier transform infrared. DLS analysis showed a stronger molecular interaction of GDMA gelation in toluene, whereas this interaction was much weaker in an alcoholic solvent such as toluene with methanol or cyclohexanol. This indicated that GDMA gelation might proceed through hydrogen bonding as well as a crosslinking reaction of vinyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 949–958, 2006 相似文献
2.
Zeolite-based monoliths (Cu/ZSM-5 on cordierite) are prepared and used to catalyze direct decomposition of nitrogen monoxide. Two-dimensional heterogeneous model is applied to describe the behavior of the monolith reactor, with the emphasis on the features introduced due to coupling of flow, mass transfer and chemical reaction. The proposed model has been verified by comparing computer simulation data with laboratory experimental data. It is shown that both inter- and intraphase diffusion limitations have to be considered when modeling complex reactor configuration, such as monolith reactors, especially when monolith with thicker catalytic layer are used at higher temperatures. 相似文献
3.
A novel microcellular polyHIPE monolith of high functional group capacity has been prepared by a two-step process including the synthesis of the scaffold by polymerization of a highly concentrated emulsion and then the in situ surface polymerization of methacrylate monomers. Application of the resulting functionalized monolith is demonstrated in a scavenging reaction of poly(glycidyl methacrylate)-grafted polyHIPE with 1-hexylamine. The open-cellular structure of the core combined with the good accessibility of the grafted functional polymer chains allows total scavenging of the amine in a relatively short period. 相似文献
4.
Parawee Rattanakit Saisunee Liawruangrath 《International journal of environmental analytical chemistry》2013,93(7):739-754
A spectrophotometric microfluidic bioreactor system is described for the determination of organophosphorus pesticides. The glass chip was designed and fabricated for in situ monolithic preparation and subsequently acetlycholineserase (AChE) immobilization via a covalent bonding method. The porous polymer monolith was prepared using glycidyl methacrylate, ethylenedimethacrylate and 2,2-dimethoxy-1,2-diphenylethan-1-one in binary porogenic solvents of cyclohexanol and dodecanol. The epoxide groups of monolith were reacted with ethylenediamine and gluteraldehyde to allow immobilization of the enzyme using their amine groups. Organophosphorus pesticides can be determined by measuring their inhibition effect on the enzyme AChE using Ellman's reaction. A linear relationship between the absorbance and percentage inhibitions was obtained over the concentration range of 0.25 to 2.50?mg?L?1 paraoxon with a correlation coefficient (r 2) of 0.9974. The limit of detection (LOD) defined as 10% inhibition (I 10) was 0.17?mg?L?1 for paraoxon. The relative standard deviations (RSD) of 1.0?mg?L?1 paraoxon was 3.73% (n?=?5). The proposed µFI system incorporates efficient enzyme immobilization and reduces reagent consumption and waste production and could thus be considered to be more environmentally friendly. 相似文献
5.
Karine Vuignier Szabolcs Fekete Pierre‐Alain Carrupt Jean‐Luc Veuthey Davy Guillarme 《Journal of separation science》2013,36(14):2231-2243
In the present study, three types of silica‐based monoliths, i.e. the first and second generations of commercial silica monolithic columns and a wide‐pore prototype monolith were compared for the analysis of large biomolecules. These molecules possess molecular weights between 1 and 66 kDa. The gradient kinetic performance of the first‐generation monolith was lower than that of the second generation, for large biomolecules (>14 kDa) but very close with smaller ones (1.3–5.8 kDa). In contrast, the wide‐pore prototype column was particularly attractive with proteins larger than 19 kDa (higher peak capacity). Among these three columns, the selectivity and retention remained quite similar but a possible larger number of accessible and charged residual silanols was noticed on the wide‐pore prototype material, which led to unpredicted small changes in selectivity and slightly broader peaks than expected. The peak shapes attained with the addition of 0.1% formic acid in the mobile phase remained acceptable for MS coupling, particularly for biomolecules of less than 6 kDa. It was found that one of the major issues with all of these silica‐based monoliths is the possible poor recovery of large biomolecules (principally with monoclonal antibody fragments of more than 25 kDa). 相似文献
6.
A carboxy precursor monolithic column, namely poly(carboxy ethyl acrylate-co-ethylene glycol dimethacrylate) was first produced in a 100 μm i.d. fused-silica capillary and subsequently surface bonded with n-octadecyl (C18) ligands by a post-polymerization functionalization process with octadecylamine in the presence of N,N´-dicyclohexylcarbodiimide. The bonding of octadecyl ligands was achieved via an amide linkage between the carboxy functions of the precursor monolith and the amino group of the octadecylamine compound. The resulting C18 monolith exhibited a very low electroosmotic flow (EOF), a fact that required the incorporation of small amounts of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) in the polymerization solution to produce a precursor monolith with fixed negative charges of sulfonate groups. This may indicate that the conjugation of the carboxy functions with octadecylamine occurred to a large extent so that the amount of residual carboxy functions was sparsely dispersed and not enough to produce a desirable EOF. The EOF velocity of the C18 column having fixed negative charges provided by the incorporated AMPS increased with increasing ACN content of the mobile phase signaling an increased binding of mobile phase ions to the polar amide linkages near the monolithic surface, and a decreased viscosity of the mobile phase, both of which would result in increased EOF velocity. The C18 monolithic column constituted a novel nonpolar sorbent for reversed-phase capillary electrochromatography for nonpolar solutes, e.g., alkylbenzenes, alkylphenyl ketones, and polyaromatic hydrocarbons, and slightly polar compounds including phenol and chlorophenols. The C18 monolithic column exhibited relatively high selectivity toward chlorophenols differing by one chloro substituent. 相似文献
7.
Hui-Juan Zhang 《Analytica chimica acta》2006,565(2):129-135
In this study, a polymer monolith microextraction (PMME) using a poly (methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith in conjunction with high-performance liquid chromatography (HPLC) was developed for the determination of 2,4-dinitrophenylhydrazine (DNPH) derivatives of several aldehydes in human saliva. The conditions for the labeling reactions of aldehydes with DNPH and followed extraction of the derivatives were optimized. The precision, recovery and detection limits were evaluated with spiked saliva. The limits of detection ranged from 0.43 to 1.40 μg/L. The inter-and intra-day relative standard deviations were less than 10%. The proposed method was successfully applied to the determination of aldehydes in saliva samples from a non-smoker, a passive smoker and a heavy smoker. 相似文献
8.
9.
One-pot synthesis of porous polymer monolith decorated with N-methylimidazolium in a capillary was described. The polymer matrix was synthesized by in situ copolymerization and quaterization of 3-chloro-2-hydroxylpropyl methacrylate (CHPMA), ethylene dimethacrylate (EDMA), and N-methylimidazole (N-MIz). The influencing factors including amount of cross-linkers, composition of porogenic solvents, and polymerization temperature on the formation of the monolithic column were investigated. The monolithic column exhibited high column efficiency for thiourea, up to 135 000 plates per meter, and phenylmethanol, up to 102 000 plates per meter. Different types of compounds including alkylbenzenes, phenols, and inorganic anions were successfully baseline separated by capillary electrochromatography (CEC). The separation of theses analytes on the column indicated typical reversed-phase and anion-exchange chromatographic retention mechanism. 相似文献
10.
A carbon monolith was synthesized via a polymerization–carbonization method, styrene and divinylbenzene being adopted as precursors and dodecanol as a porogen during polymerization. The resultant monolith had bimodal porous substructure, narrowly distributed nano skeleton pores and uniform textural pores or throughpores. The carbon monolith was directly used as an extracting fiber, taking place of the coated silica fibers in commercially available solid-phase microextraction device, for the extraction of phenols followed by gas chromatography–mass spectrometry. Under the studied conditions, the calibration curves were linear from 0.5 to 50 ng mL−1 for phenol, o-nitrophenol, 2,4-dichlorophenol and p-chlorophenol. The limits of detection were between 0.04 and 0.43 ng mL−1. The recoveries of the phenols spiked in real water samples at 10 ng mL−1 were between 85% and 98% with the relative standard deviations below 10%. Compared with the commercial coated ones (e.g. PDMS, CW/DVB and DVB/CAR/PDMS), the carbon monolith-based fiber had advantages of faster extraction equilibrium and higher extraction capacity due to the superior pore connectivity and pore openness resulting from its bimodal porous substructure. 相似文献