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71.
Solid bisphenol-A epoxy
resin of medium molecular mass was cured using a Lewis acid initiator (ytterbium(III)
trifluoromethanesulfonate) in three different proportions (0.5, 1 and 2 phr).
A kinetic study was performed in a differential scanning calorimeter. The
complete kinetic triplet was determined (activation energy, pre-exponential
factor, and integral function of the degree of conversion) for each system.
A kinetic analysis was performed with an integral isoconversional procedure
(free model), and the kinetic model was determined both with the Coats-Redfern
method (the obtained isoconversional value being accepted as the effective
activation energy) and through the compensation effect. All the systems followed
the same isothermal curing model simulated from non-isothermal ones. The growth-of-nuclei
Avrami kinetic model A3/2 has been proposed as the
polymerization kinetic model. The addition of initiator accelerated the reaction
especially when 2 phr was added. 0.5 and 1 phr showed very few kinetic differences
between them. 相似文献
72.
Nordin SJ Roth P Tarnai T Alonso DA Brandt P Andersson PG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(7):1431-1436
A new generation of 2-aza-norbornyl amino alcohol ligands for the catalytic transfer hydrogenation reaction of aromatic ketones was synthesized. Extremely active catalysts were formed by introducing a ketal functionality at the rear end of the ligand. Acetophenone was reduced in 96% ee at low catalyst loading, substrate to catalyst ratio, S/C 5000, within 90 minutes with isopropyl alcohol as the hydrogen donor. It was found that the dioxolane substituent in the ligand increased the turnover frequency, TOF50, from 1050 h(-1) to 3000 h(-1) at an S/C ratio of 1000. Introduction of a methyl group at the carbinol carbon resulted in TOF50 as high as 8500 h(-1). Transfer hydrogenation of a range of aromatic ketones was evaluated and found to reach completion within 30 minutes at room temperature, and excellent enantioselectivity, up to 99 % ee, was obtained. A possible explanation for the enhanced activity was provided by density functional calculations, which showed that the presence of a remote dipole in the ligand lowered the transition state energy. 相似文献
73.
Syahrina Nur 'Ain Abdul Halim Fariza Juliana Nordin Mohd Ridzuan Mohd Abd Razak Nur Rahimah Fitrah Mohd Sofyan Siti Nadiah Abdul Halim Nor Fadilah Rajab 《Journal of Coordination Chemistry》2019,72(5-7):879-893
Five new silver(I) complexes were synthesized with mixed ligands of thiosemicarbazone derivatives and diphenyl(p-tolyl)phosphine in search of new biologically active compounds. A CHN elemental analysis, powder X-ray diffraction (PXRD) data and several spectroscopic techniques such as Fourier-transform infrared spectroscopy, energy-dispersive X-ray, 1H, 13C, and 31P{1H} NMR were performed to elucidate the structure of these complexes. Elemental analysis suggested that the stoichiometry of the complexes formed by the reaction of silver nitrate with thiosemicarbazone in the presence of (p-tolyl)PPh2 was indeed 1:2:1 molar ratio. The silver ions were discovered to be coordinated to the sulfur of thiosemicarbazone and phosphorus of (p-tolyl)PPh2, having a tetrahedral geometry based on the spectroscopic data obtained. The PXRD patterns were studied to see the degree of crystallinity of the complexes. The in vitro antiproliferative activity of these complexes was investigated toward the MDA-MB-231 and MCF-7 breast cancer cell lines, as well as the HT-29 colon cancer cell line, which yielded IC50 values in low micromolar range. The antiplasmodial activity of these complexes was also examined against chloroquine-resistant Plasmodium falciparum parasite which demonstrated good activity and further tested for their selectivity index. 相似文献
74.
Srinivasa Rao Jada Katherine McMillan Ahmad S. Hamzah Mohammad S. Saad Nordin H. Lajis Malcolm F.G. Stevens Carl H. Schwalbe Johnson Stanslas 《Journal of chemical crystallography》2006,36(2):93-97
The title compound, 3-{2-[decahydro-6-hydroxy-5-(hydroxymethyl)-5,8a-dimethyl-2-methylene-1-napthalenyl]ethylidene}dihydro-4-acetoxy-2(3H)-furanone, C22H32O6, was synthesised from andrographolide. It crystallizes in the orthorhombic system with a = 7.4219(12), b = 11.8411(10), c = 23.777(4) Å in space group P212121. While the stereochemical relation between rings is slightly changed from the starting material, acetylation of the hydroxyfuranone moiety completely abolishes O--HO hydrogen bonding there, leaving a C--HO interaction. The hydrogen-bonded chains at the opposite end of the andrographolide molecule persist but reverse direction. 相似文献
75.
76.
Norsyafikah Asyilla Nordin Vannessa Lawai Ainaa Nadiah Abd Halim Siaw San Hwang Reagan Entigu Linton 《Natural product research》2020,34(11):1505-1514
AbstractIn searching for drugs from natural product scaffolds has gained interest among researchers. In this study, a series of twelve halogenated thiourea (ATX 1-12) via chemical modification of aspirin (a natural product derivative) and evaluated for cytotoxic activity against nasopharyngeal carcinoma (NPC) cell lines, HK-1 via MTS-based colorimetric assay. The cytotoxicity studies demonstrated that halogens at meta position of ATX showed promising activity against HK-1 cells (IC50 value ≤15?µM) in comparison to cisplatin, a positive cytotoxic drug (IC50 value =8.9?±?1.9?µM). ATX 11, bearing iodine at meta position, showed robust cytotoxicity against HK-1 cells with an IC50 value of 4.7?±?0.7?µM. Molecular docking interactions between ATX 11 and cyclooxygenase-2 demonstrated a robust binding affinity value of ?8.1?kcal/mol as compared to aspirin’s binding affinity value of ?6.4?kcal/mol. The findings represent a promising lead molecule from natural product with excellent cytotoxic activity against NPC cell lines. 相似文献
77.
Lee KH Abas F Alitheen NB Shaari K Lajis NH Ahmad S 《Molecules (Basel, Switzerland)》2011,16(11):9728-9738
Our preliminary screening had shown that the curcumin derivative [2,6-bis(2,5-dimethoxybenzylidene)cyclohexanone] or BDMC33 exhibited improved anti-inflammatory activity by inhibiting nitric oxide synthesis in activated macrophage cells. In this study, we further investigated the anti-inflammatory properties of BDMC33 on PGE(2 )synthesis and cyclooxygenase (COX) expression in IFN-γ/LPS-stimulated macrophages. We found that BDMC33 significantly inhibited PGE(2) synthesis in a concentration-dependent manner albeit at a low inhibition level with an IC(50) value of 47.33 ± 1.00 μM. Interestingly, the PGE(2) inhibitory activity of BDMC33 is not attributed to inhibition of the COX enzyme activities, but rather BDMC33 selectively down-regulated the expression of COX-2. In addition, BDMC33 modulates the COX expression by sustaining the constitutively COX-1 expression in IFN-γ/LPS-treated macrophage cells. Collectively, the experimental data suggest an immunodulatory action of BDMC33 on PGE(2) synthesis and COX expression, making it a possible treatment for inflammatory disorders with minimal gastrointestinal-related side effects. 相似文献
78.
Patricelli MP Nomanbhoy TK Wu J Brown H Zhou D Zhang J Jagannathan S Aban A Okerberg E Herring C Nordin B Weissig H Yang Q Lee JD Gray NS Kozarich JW 《Chemistry & biology》2011,18(6):699-710
Protein kinases are intensely studied mediators of cellular signaling, yet important questions remain regarding their regulation and in?vivo properties. Here, we use a probe-based chemoprotemics platform to profile several well studied kinase inhibitors against >200 kinases in native cell proteomes and reveal biological targets for some of these inhibitors. Several striking differences were identified between native and recombinant kinase inhibitory profiles, in particular, for the Raf kinases. The native kinase binding profiles presented here closely mirror the cellular activity of these inhibitors, even when the inhibition profiles differ dramatically from recombinant assay results. Additionally, Raf activation events could be detected on live cell treatment with inhibitors. These studies highlight the complexities of protein kinase behavior in the cellular context and demonstrate that profiling with only recombinant/purified enzymes can be misleading. 相似文献