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排序方式: 共有244条查询结果,搜索用时 703 毫秒
71.
Rongrong Tang 《分析论及其应用》2006,22(3):254-261
In this paper, using the theory of differential inequalities, we study the nonlinear boundary value problem for a class of integro-differential system. Under appropriate assumptions, the existence of solution is proved and the uniformly valid asymptotic expansions for arbitrary n-th order approximation and the estimation of remainder term are obtained simply and conveniently. 相似文献
72.
73.
Jiali Liu Rongrong Gao Xuejing Gu Bin Yu Yan Wu Qiushi Li Ping Xiang Hui Xu 《Molecules (Basel, Switzerland)》2022,27(6)
Colchicine (COL) is a well-known plant alkaloid long used for medical purposes due to the selective anti-inflammatory effect on acute gouty arthritis. It is also a kind of mitosis toxin with strong inhibitory effects of cell division and is therefore being applied to the treatment of various cancers. However, this product shows a variety of adverse effects that are significantly correlated with the dosage and have attracted much attention. For the first time, the present work obtained a new insight into the gastrointestinal toxicity of colchicine analogues by molecular docking analysis, which was based on the 3D structure of intestinal tight junction protein ZO-1 and the ligand library containing dozens of small-molecule compounds with the basic skeleton of COL and its metabolites. The binding energy and mode of protein–ligand interaction were investigated to better understand the structure–toxicity relationships of COL analogues and the mechanism of action as well. Cluster analysis clearly demonstrated the strong correlation between the binding energy and toxicity of ligand molecules. The interaction mode further revealed that the hydrogen bonding (via the C-7 amide or C-9 carbonyl group) and hydrophobic effect (at ring A or C) were both responsible for ZO-1-related gastrointestinal toxicity of COL analogues, while metabolic transformation via phase I and/or phase II reaction would significantly attenuate the gastrointestinal toxicity of colchicine, indicating an effective detoxication pathway through metabolism. 相似文献
74.
Rongrong Li Shiting Wang Yuan Hu Hong Chen Jingjing Chen Chu Chu Jianli Zheng 《Chemical Papers》2018,72(10):2425-2432
Pd catalysts supported on N-doped-ordered mesoporous carbons (NOMC) have been prepared and tested for selective hydrogenation of 4-chlorophenol (4-CP) with H2. The difference from the previous methods is that the NOMC was synthesized using urea as nitrogen source via one-pot route. The rate constant of Pd/NOMC for hydrodechlorination of 4-CP was about 135.9 h?1 which were higher than Pd/OMC (65.6 h?1) and Pd/AC (20.8 h?1). It could be attributed to the synergetic effects of mesoporous structure, N-doped supports, and the stabilized small PdNPs. The conversion changed from 100 to 90.2% after the sixth reaction using Pd/NOMC which could be caused by the palladium leaching. 相似文献
75.
Identification of metabolites of gardenin A in rats by combination of high‐performance liquid chromatography with linear ion trap–Orbitrap mass spectrometer based on multiple data processing techniques 下载免费PDF全文
Jiayu Zhang Fang Wang Wei Cai Qian Zhang Ying Liu Yun Li Rongrong Liu Guangshang Cao 《Biomedical chromatography : BMC》2015,29(3):379-387
Gardenin A is one of the less abundant hydroxylated polymethoxyflavonoids (OH‐PMFs) in nature, and has many potential significant health benefits. In the present study, an efficient strategy was established using high‐performance liquid chromatography coupled with linear ion trap–Orbitrap mass spectrometer to profile the in vivo metabolic fate of gardenin A in rat plasma and various tissues. First, an online LC‐MSn data acquisition method was developed to trace all the probable metabolites. Second, a combination of offline data processing methods including extracted ion chromatography and multiple mass defect filters was employed to screen the common and uncommon metabolites from the background noise and endogenous components. Finally, structures of the metabolites were elucidated based on an accurate mass measurement, the diagnostic product ions of PMFs, and relevant drug biotransformation knowledge. Based on the proposed strategy, a total of 26 metabolites were observed and characterized. The results indicate that some biotransformations, such as methylation, demethoxylation, demethylation, glucuronide conjugation, sulfate conjugation and their composite reactions, have been discovered for OH‐PMFs. Moreover, some diagnostic biotransformation pathways are summarized. Overall, this study gives us a first insight into the in vivo metabolism of gardenin A. The study also provides a practical strategy for rapidly screening and identifying metabolites, which can be widely applied for the other biotransformations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
76.
Dr. Rongrong Hu Dr. Jacky W. Y. Lam Yi Liu Xiaoa Zhang Prof. Ben Zhong Tang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(18):5617-5624
A series of nonplanar tetraphenylethene (TPE)–hexaphenylbenzene (HPB) adducts was designed and synthesized by Diels–Alder reaction of the acetylene precursors and tetraphenylcyclopentadienone. All of the adducts showed aggregation‐induced emission features. The twisting amplitude and steric hindrance of the TPE and HPB units were found to play a crucial role in their fluorescence behaviors in the aggregated state. 相似文献
77.
Yanfang Liu Yuehong Li Chunhui Zhang Rongrong Wang Mingtao Run Hongzan Song 《Journal of Polymer Science.Polymer Physics》2016,54(13):1255-1266
A siloxane‐containing diphenol is synthesized from 1,1,3,3‐tetramethyldisiloxane and o‐allylphenol, followed by the Mannich condensation with aniline, methylamine, and formaldehyde yielding two siloxane‐containing benzoxazines. The onset polymerization temperature of aniline‐based benzoxazine is higher than that of the methylamine counterpart. The dynamic mechanical properties of the polybenzoxazines depend on the structure of the starting primary amines. Both polybenzoxazines exhibit one‐way dual‐shape memory behavior in response to changes in temperature, and they show excellent shape fixity ratios in bending, tension, and tensile stress–strain tests, high shape recovery ratios in bending and tension tests, but relatively low shape recovery ratios in tensile stress–strain test. The network chain segments including the alkylsiloxane units serve as a thermal control switch based on the glass transition temperatures (39 and 53 °C) for the polybenzoxazines. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1255–1266 相似文献
78.
Hexaaquaaluminum methanesulfonate crystals, [Al(H2O)6][CH3SO3]3 were synthesized by a hydrothermal reaction of Al(OH)3 with methanesulfonic acid. Single-crystal diffraction determination revealed that Al3+ was coordinated by six water molecules in octahedral geometry, while the CH3SO3– anion connected with Al3+ through coordinated water molecules by hydrogen bonds. The six-coordinate environment of Al was also determined by 27Al MAS NMR measurement. Thermogravimetric analysis and Fourier transform infrared spectroscopy showed that the decomposition intermediate at 265–365 °C was Al2(μ-OH)(CH3SO3)5 and the final product was amorphous Al2O3 residue with about 0.8 wt% SO3 at 520–800 °C. A pure phase of [Al(H2O)6][CH3SO3]3 was confirmed by powder X-ray diffraction analysis. Esterification of n-butyric acid with n-butanol and ketalization of cyclohexanone with glycol catalyzed by [Al(H2O)6][CH3SO3]3 and Al2(μ-OH)(CH3SO3)5, respectively, proceeded in 100% yield by continuously removing the produced water. In the case of tetrahydropyranylation of n-butanol at room temperature in dichloromethane, the catalytic activity of [Al(H2O)6][CH3SO3]3 was much lower than that of Al2(μ-OH)(CH3SO3)5. Furthermore, both [Al(H2O)6][CH3SO3]3 precursor and Al2(μ-OH)(CH3SO3)5 catalysts could be recycled. 相似文献
79.
Ixone Esnal Arlette Urías‐Benavides Dr. C. F. Azael Gómez‐Durán Dr. Carlos A. Osorio‐Martínez Prof. Inmaculada García‐Moreno Prof. Angel Costela Dr. Jorge Bañuelos Nerea Epelde Prof. Iñigo López Arbeloa Dr. Rongrong Hu Prof. Ben Zhong Tang Prof. Eduardo Peña‐Cabrera 《化学:亚洲杂志》2013,8(11):2691-2700
A thorough study of the photophysical and laser properties of 8‐aminoboron dipyrromethene dyes was undertaken to determine the role of amine substitution and spatial disposition on the properties of the dyes. It was found that the fluorescent and laser response varied significantly. Although primary amines give rise to highly fluorescent products at the blue edge of the visible region, secondary amines yield nonfluorescent analogues in polar media. The crystal structures of two analogues are reported and described. Steric hindrance and the higher electron‐releasing ability of the amine favor the formation of a quenching intramolecular charge‐transfer state. Accordingly, boron dipyrromethene derivatives with primary amines exhibited laser emission with efficiencies of up to 44 %. Besides, the more efficient derivative was also the most photostable, leading to a significant improvement in the lasing performance with regard to previously reported 8‐aminoboron dipyrromethene derivatives. An increase in the solvent polarity, and mainly the presence of tertiary cyclic amines, led to a dramatic decrease or even the loss of the laser action. 相似文献
80.
Guoqiang Shen Rongrong Zhang Lun Pan Fang Hou Yingjie Zhao Zeyu Shen Wenbo Mi Chengxiang Shi Qingfa Wang Xiangwen Zhang Ji‐Jun Zou 《Angewandte Chemie (International ed. in English)》2020,59(6):2313-2317
Ferric oxides and (oxy)hydroxides, although plentiful and low‐cost, are rarely considered for oxygen evolution reaction (OER) owing to the too high spin state (eg filling ca. 2.0) suppressing the bonding strength with reaction intermediates. Now, a facile adsorption–oxidation strategy is used to anchor FeIII atomically on an ultrathin TiO2 nanobelt to synergistically lower the spin state (eg filling ca. 1.08) to enhance the adsorption with oxygen‐containing intermediates and improve the electro‐conductibility for lower ohmic loss. The electronic structure of the catalyst is predicted by DFT calculation and perfectly confirmed by experimental results. The catalyst exhibits superior performance for OER with overpotential 270 mV @10 mA cm?2 and 376 mV @100 mA cm?2 in alkaline solution, which is much better than IrO2/C and RuO2/C and is the best iron‐based OER catalyst free of active metals such as Ni, Co, or precious metals. 相似文献