全文获取类型
收费全文 | 216篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 175篇 |
晶体学 | 7篇 |
力学 | 6篇 |
数学 | 6篇 |
物理学 | 34篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 15篇 |
2013年 | 15篇 |
2012年 | 16篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有228条查询结果,搜索用时 0 毫秒
131.
Shashank M. Patil Reshma Mary Martiz A. M. Satish Abdullah M. Shbeer Mohammed Ageel Mohammed Al-Ghorbani Lakshmi Ranganatha V Saravanan Parameswaran Ramith Ramu 《Molecules (Basel, Switzerland)》2022,27(12)
Coumarin derivatives are proven for their therapeutic uses in several human diseases and disorders such as inflammation, neurodegenerative disorders, cancer, fertility, and microbial infections. Coumarin derivatives and coumarin-based scaffolds gained renewed attention for treating diabetes mellitus. The current decade witnessed the inhibiting potential of coumarin derivatives and coumarin-based scaffolds against α-glucosidase and α-amylase for the management of postprandial hyperglycemia. Hyperglycemia is a condition where an excessive amount of glucose circulates in the bloodstream. It occurs when the body lacks enough insulin or is unable to correctly utilize it. With open-source and free in silico tools, we have investigated novel 80 coumarin derivatives for their inhibitory potential against α-glucosidase and α-amylase and identified a coumarin derivative, CD-59, as a potential dual inhibitor. The ligand-based 3D pharmacophore detection and search is utilized to discover diverse coumarin-like compounds and new chemical scaffolds for the dual inhibition of α-glucosidase and α-amylase. In this regard, four novel coumarin-like compounds from the ZINC database have been discovered as the potential dual inhibitors of α-glucosidase and α-amylase (ZINC02789441 and ZINC40949448 with scaffold thiophenyl chromene carboxamide, ZINC13496808 with triazino indol thio phenylacetamide, and ZINC09781623 with chromenyl thiazole). To summarize, we propose that a coumarin derivative, CD-59, and ZINC02789441 from the ZINC database will serve as potential lead molecules with dual inhibition activity against α-glucosidase and α-amylase, thereby discovering new drugs for the effective management of postprandial hyperglycemia. From the reported scaffold, the synthesis of several novel compounds can also be performed, which can be used for drug discovery. 相似文献
132.
N. Manikandan 《Journal of Non》2009,355(1):58-60
The thermal diffusivity (α) of As20Te80−xGax glasses (7.5 ? x ? 18.5) has been measured using photo-thermal deflection (PTD) technique. It is found that the thermal diffusivity is comparatively lower for As20Te80−xGax glasses, which is consistent with the memory type of electrical switching exhibited by these samples. Further, the thermal diffusivity of As20Te80−xGax glasses is found to increase with the incorporation of gallium initially (for x ? 9), which is consistent with the metallicity of the additive. This increase in α results in a maximum at the composition x = 9; beyond x = 9, a decrease is seen in α leading to a minimum at the composition x = 15. The observed composition dependence of thermal diffusivity of As20Te80−xGax glasses has been found to be similar to that of Al20AsxTe100−x glasses, based on which it is proposed that As20Te80−xGax glasses exhibit an extended stiffness transition with compositions x = 9 and x = 15 being its onset and completion, respectively. Also, the composition x = 17.5 at which a second maximum is seen in the thermal diffusivity has been identified to be the chemical threshold (CT) of the As20Te80−xGax glassy system, as at CT, the glass is configurationally closest to the crystalline state and the scattering of the diffusing thermal waves is minimal for the chemically ordered phase. 相似文献
133.
Dr. Ludovic Bretin Yurii Husiev Dr. Vadde Ramu Liyan Zhang Matthijs Hakkennes Selda Abyar Andrew C. Johns Dr. Sylvia E. Le Dévédec Dr. Tania Betancourt Dr. Alexander Kornienko Dr. Sylvestre Bonnet 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(5):e202316425
Photoactivated chemotherapy (PACT) is a promising cancer treatment modality that kills cancer cells via photochemical uncaging of a cytotoxic drug. Most ruthenium-based photocages used for PACT are activated with blue or green light, which penetrates sub-optimally into tumor tissues. Here, we report amide functionalization as a tool to fine-tune the toxicity and excited states of a terpyridine-based ruthenium photocage. Due to conjugation of the amide group with the terpyridine π system in the excited state, the absorption of red light (630 nm) increased 8-fold, and the photosubstitution rate rose 5-fold. In vitro, red light activation triggered inhibition of tubulin polymerization, which led to apoptotic cell death both in normoxic (21 % O2) and hypoxic (1 % O2) cancer cells. In vivo, red light irradiation of tumor-bearing mice demonstrated significant tumor volume reduction (45 %) with improved biosafety, thereby demonstrating the clinical potential of this compound. 相似文献
134.
Muhammad Taha Sadia Sultan Muhammad Herizal M. Qaiser Fatmi Manikandan Selvaraj Kalavathy Ramasamy Sobia Ahsan Halim Siong Meng Lim Fazal Rahim Kamran Ashraf Adeeb Shehzad 《Journal of Saudi Chemical Society》2019,23(8):1168-1179
To find out effective anticancer compounds we synthesized (1–30) derivatives of 4-isopropylbenzoylhydrazone and evaluated for anticancer potential. The compounds 3, 9, 12, 23, 26 and 28 showed better activities ranging (0.39–1.1 µg/ml) than the standard (1.53 ± 0.01 µg/ml). In line with this, compounds 2, 6, 24, 25 and 29 exhibited better activities compared to the second standard (5FU 4.60 ± 0.01 µg/ml). The best molecular docked complex between the BRCA1 structure and the 1–30 derivatives were analyzed based on the Glide docked score and binding orientation for both the SP and XP mode. The 2D-QSAR analysis reflected a significant correlation between the experimental and the predicted biological activities. The above-mentioned compounds were also assessed by various spectroscopic techniques. 相似文献
135.
Biswanath Das Joydeep BanerjeeR. Ramu Rammohan PalN. Ravindranath C. Ramesh 《Tetrahedron letters》2003,44(29):5465-5468
Aromatic acetates were selectively deprotected in the presence of aliphatic acetates to the corresponding phenols in excellent yields using Amberlyst-15 or iodine as catalysts in methanol at room temperature. The first catalyst can be recovered. 相似文献
136.
E. Rajanarendar K. Ramu D. Karunakar P. Ramesh 《Journal of heterocyclic chemistry》2005,42(4):711-715
Trimolecular condensation of N‐(3‐meihyl‐5‐styryl‐isoxazol‐4‐yl)‐N'‐aryl thioureas ( 2 ), paraformaldehyde and primary amines using montmorillonite K‐10 in dry media under microwave irradiation leads to isoxazolyl triazinethiones ( 3 ) in high yield. Condensation of 2 with paraformaldehyde alone under similar conditions provide isoxazolyl oxadiazinethiones ( 4 ) in excellent yield. 相似文献
137.
New lathyrane and podocarpane diterpenoids from Jatropha curcas 总被引:5,自引:0,他引:5
Ravindranath N Ravinder Reddy M Ramesh C Ramu R Prabhakar A Jagadeesh B Das B 《Chemical & pharmaceutical bulletin》2004,52(5):608-611
Chemical investigation on Jatropha curcas resulted in the isolation of twenty constituents among which four diterpenoids were unknown and six compounds, tetradecyl-(E)-ferulate, 3-O-(Z)-coumaroyl oleanolic acid, heudelotinone, epi-isojatrogrossidione, 2alpha-hydroxy-epi-isojatrogrossidione, and 2-methyanthraquinone had not been reported earlier from this species. The structures of the new compounds were established by extensive studies of their 1D- and 2D-NMR spectra. 相似文献
138.
Ahmed Kamal R. Ramu Mohd. Ameruddin Azhar G.B. Ramesh Khanna 《Tetrahedron letters》2005,46(15):2675-2677
Copper(II) tetrafluoroborate catalyzes efficiently the selective opening of epoxides by amines leading to the synthesis of β-amino alcohols. The reaction works well with aromatic and aliphatic amines in high yields under solvent-free conditions. 相似文献
139.
Ramu Rajasekaran Prakash Rao Aruna Dornadula Koteeswaran Loganathan Padmanabhan Kulandaivel Muthuvelu Ram Rathan Rai Palraj Thamilkumar Chilakapati Murali Krishna Singaravelu Ganesan 《Photochemistry and photobiology》2013,89(2):483-491
Urine is one of the diagnostically important bio fluids, as it has different metabolites in it, where many of them are native fluorophores. Native fluorescence characteristics of human urine samples were studied using excitation–emission matrices (EEMs) over a range of excitation and emission wavelengths, and emission spectra at 405 nm excitation, to discriminate patients with cancer from the normal subjects. The fluorescence spectra of urine samples of cancer patients exhibit considerable spectral differences in both EEMs and emission spectra with respect to normal subjects. Different ratios were calculated using the fluorescence intensity values of the emission spectra and they were used as input variables for a multiple linear discriminant analysis across different groups. The discriminant analysis classifies 94.7% of the original grouped cases and 94.1% of the cross‐validated grouped cases correctly. Based on the fluorescence emission characteristics of urine and statistical analysis, it may be concluded that the fluorophores nicotinamide adenine dinucleotide (NADH) and flavins may be considered as metabolomic markers of cancer. 相似文献
140.
Sougandi Ilango Mahalakshmi Rajaram Kannappan Ramu Rajendiran Thekkelnayackanpatti M. Venkatesan Rangarajan Sambasiva Rao Pillutla 《Transition Metal Chemistry》2002,27(5):512-519
The synthesis, reduction, optical and e.p.r. spectral properties of a series of new binuclear copper(II) complexes, containing bridging moieties (OH–, MeCO2
–, NO2
–, and N3
–), with new proline-based binuclear pentadentate Mannich base ligands is described. The ligands are: 2,6-bis[(prolin-1-yl)methyl]4-bromophenol [H3L1], 2,6-bis[(prolin-1-yl)methyl]4-t-butylphenol [H3L2] and 2,6-bis[(prolin-1-yl)methyl]4-methoxyphenol [H3L3]. The exogenous bridging complexes thus prepared were hydroxo: [Cu2L1(OH)(H2O)2] · H2O (1a), [Cu2L2(OH)(H2O)2] · H2O (1b), [Cu2L3(OH)(H2O)2] · H2O (1c), acetato [Cu2L1(OAc)] · H2O (2a), [Cu2L2(OAc)] · H2O (2b), [Cu2L3(OAc)] · H2O (2c), nitrito [Cu2L1(NO2)(H2O)2] · H2O (3a), [Cu2L2(NO2)(H2O)2] · H2O (3b), [Cu2L3(NO2)(H2O)2] · H2O (3c) and azido [Cu2L1(N3)(H2O)2] · H2O (4a), [Cu2L2(N3)(H2O)2] · H2O (4b) and [Cu2L3(N3)(H2O)2] · H2O (4c). The complexes were characterized by elemental analysis and by spectroscopy. They exhibit resolved copper hyperfine e.p.r. spectra at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. The strength of the antiferromagnetic coupling lies in the order: NO2 N3 OH OAc. Cyclic voltammetry revealed the presence of two redox couples CuIICuII CuIICuI CuICuI. The conproportionality constant K
con for the mixed valent CuIICuI species for all the complexes have been determined electrochemically. 相似文献