全文获取类型
收费全文 | 287篇 |
免费 | 10篇 |
专业分类
化学 | 201篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 23篇 |
物理学 | 66篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 13篇 |
2021年 | 13篇 |
2020年 | 24篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 6篇 |
2014年 | 16篇 |
2013年 | 17篇 |
2012年 | 17篇 |
2011年 | 24篇 |
2010年 | 17篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 1篇 |
1999年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有297条查询结果,搜索用时 15 毫秒
21.
Sengupta J Mukhopadhyay R Bhattacharjya A Bhadbhade MM Bhosekar GV 《The Journal of organic chemistry》2005,70(21):8579-8582
3,5'-ether-linked pseudooligopentose derivatives were synthesized for the first time from readily available carbohydrate precursors. The 1,2-isopropylidene-protected ether-linked oligopentoses are potentially important as precursors of novel RNA analogues. Intramolecular cycloaddition of the nitrile oxides prepared from these derivatives led to the diastereoselective formation of chiral isoxazolines fused to 10-16-membered oxacycles. The stereochemistry of some of these isoxazolines was established by X-ray diffraction and NOESY analysis. 相似文献
22.
This paper presents a multiobjective analog/RF circuit sizing tool using an improved brain storm optimization (IMBSO) algorithm with the purpose of analyzing the tradeoffs between competing performance specifications of analog/RF circuit block. A number of improvements are incorporated into IMBSO algorithm at different steps. At first, the clustering step of IMBSO algorithm is augmented with k-means\(++\) seeding technique to select the initial cluster centroids while clustering using k-means clustering technique. As a second improvement, the proposed IMBSO algorithm makes use of random probabilistic decision-making of river formation dynamics scheme to select optimal cluster centroids during population generation step. As a third improvement, an adaptive mutation operator is incorporated inside the IMBSO algorithm to generate new population. Finally, two separate constraint handling techniques are employed to handle both boundary and functional constraints during analog/RF circuit optimization. The performance of the proposed IMBSO algorithm is demonstrated in finding optimal Pareto fronts among different performance specifications of a two-stage operational amplifier circuit, a folded cascode amplifier circuit and a low noise amplifier circuit. 相似文献
23.
Gobind Kumar Pule Seboletswe Neha Manhas Parvesh Singh Gaurav Bhargava Jaspreet Kaur Rajput Rupesh Kumar 《Journal of heterocyclic chemistry》2024,61(2):347-357
A safer, greener, and more effective reaction methodology for the synthesis of dihydroquinazolinones (DHQs) has been developed. The deep eutectic solvent (DES) ZnCl2/urea employed in this study efficiently accelerated the cyclization of 2-aminobenzamide with different aldehydes (aromatic and heteroaromatic) to afford the target scaffolds without the generation of any oxidized product. This method has exhibited remarkable advantages such as quick reaction time, mild reaction conditions, high yield (82%–98%), operational simplicity, and selectivity. The approach was observed to be tolerant to electron-donating and electron-withdrawing functional groups. Green metric parameters (AEf, OE, AE, RME, CE, etc.) determined further aided this greener chemical approach. 相似文献
24.
Maruthibabu Paidikondala Vignesh Kumar Rangasami Ganesh N. Nawale Tommaso Casalini Giuseppe Perale Sandeep Kadekar Gaurav Mohanty Turkka Salminen Oommen P. Oommen Oommen P. Varghese 《Angewandte Chemie (International ed. in English)》2019,58(9):2815-2819
Circulating nucleic acids, such as short interfering RNA (siRNA), regulate many biological processes; however, the mechanism by which these molecules enter the cell is poorly understood. The role of extracellular‐matrix‐derived polymers in binding siRNAs and trafficking them across the plasma membrane is reported. Thermal melting, dynamic light scattering, scanning electron microscopy, and computational analysis indicate that hyaluronic acid can stabilize siRNA via hydrogen bonding and Van der Waals interactions. This stabilization facilitated HA size‐ and concentration‐dependent gene silencing in a CD44‐positive human osteosarcoma cell line (MG‐63) and in human mesenchymal stromal cells (hMSCs). This native HA‐based siRNA transfection represents the first report on an anionic, non‐viral delivery method that resulted in approximately 60 % gene knockdown in both cell types tested, which correlated with a reduction in translation levels. 相似文献
25.
Density profiles are the most common measure of inhomogeneous structure in confined fluids, but their connection to transport coefficients is poorly understood. We explore via simulation how tuning particle-wall interactions to flatten or enhance the particle layering of a model confined fluid impacts its self-diffusivity, viscosity, and entropy. Interestingly, interactions that eliminate particle layering significantly reduce confined fluid mobility, whereas those that enhance layering can have the opposite effect. Excess entropy helps to understand and predict these trends. 相似文献
26.
Christina Heroven Victoria Georgi Gaurav K. Ganotra Prof. Paul Brennan Finn Wolfreys Prof. Dr. Rebecca C. Wade Amaury E. Fernández‐Montalván Apirat Chaikuad Prof. Dr. Stefan Knapp 《Angewandte Chemie (International ed. in English)》2018,57(24):7220-7224
Prolonged drug residence times may result in longer‐lasting drug efficacy, improved pharmacodynamic properties, and “kinetic selectivity” over off‐targets with high drug dissociation rates. However, few strategies have been elaborated to rationally modulate drug residence time and thereby to integrate this key property into the drug development process. Herein, we show that the interaction between a halogen moiety on an inhibitor and an aromatic residue in the target protein can significantly increase inhibitor residence time. By using the interaction of the serine/threonine kinase haspin with 5‐iodotubercidin (5‐iTU) derivatives as a model for an archetypal active‐state (type I) kinase–inhibitor binding mode, we demonstrate that inhibitor residence times markedly increase with the size and polarizability of the halogen atom. The halogen–aromatic π interactions in the haspin–inhibitor complexes were characterized by means of kinetic, thermodynamic, and structural measurements along with binding‐energy calculations. 相似文献
27.
Flora JW Edmiston J Secrist R Li G Rana GS Langston TB McKinney W 《Analytical and bioanalytical chemistry》2008,391(8):2845-2856
28.
Gaurav Bhargava 《Tetrahedron》2008,64(13):3017-3024
The chemo- as well as regioselective imino Diels-Alder reactions of 5-dienyl pyrimidinones with N-aryl as well as N-naphthyl imines in the presence of a different Lewis acid catalysts resulting in novel quinoline and benzoquinoline derivatives are reported. 相似文献
29.
Gaurav Sharma 《Tetrahedron letters》2008,49(27):4269-4271
An efficient synthesis of 1,3-diaryl-2,3-dihydro-1,5-benzothiazepines has been developed by the reaction of various 1,3-diaryl-2-propenones with 2-aminothiophenol in water under neutral conditions catalysed by SDS. Excellent chemoselectivity was observed for substrates possessing halogen atoms or nitro/alkoxy/thioalkyl groups which did not undergo competitive aromatic nucleophilic substitution of the halogen atoms or the nitro group, reduction of the nitro or the α,β-unsaturated carbonyl group, or dealkylation of the alkoxy/thioalkoxy groups. 相似文献
30.
Maity J Shakya G Singh SK Ravikumar VT Parmar VS Prasad AK 《The Journal of organic chemistry》2008,73(14):5629-5632
Candida antarctica lipase-B (CAL-B) immobilized on lewatite selectively acylated the primary hydroxyl group of the furanosyl nucleoside in a mixture of 1-(alpha-D-arabinofuranosyl)thymine and 1-(alpha-D-arabinopyranosyl)thymine. This selective biocatalytic acylation of furanosyl nucleoside has enabled us an easy separation of arabinofuranosyl thymine from an inseparable mixture with arabinopyranosyl thymine. The primary hydroxyl selective acylation methodology of arabinonucleoside has also been successfully used for the separation of 1-(beta-D-xylofuranosyl)thymine and 1-(beta-D-xylopyranosyl)thymine from a mixture of the two, which demonstrate the generality of the enzymatic methodology for separation of furanosyl and pyranosyl nucleosides. 相似文献