全文获取类型
收费全文 | 182篇 |
免费 | 12篇 |
专业分类
化学 | 137篇 |
晶体学 | 11篇 |
力学 | 2篇 |
数学 | 14篇 |
物理学 | 30篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 11篇 |
2008年 | 3篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1961年 | 1篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有194条查询结果,搜索用时 15 毫秒
91.
Mari Annadhasan Durga Prasad Karothu Ragaverthini Chinnasamy Luca Catalano Ejaz Ahmed Soumyajit Ghosh Pan
e Naumov Rajadurai Chandrasekar 《Angewandte Chemie (International ed. in English)》2020,59(33):13821-13830
Flexible organic single crystals are evolving as new materials for optical waveguides that can be used for transfer of information in organic optoelectronic microcircuits. Integration in microelectronics of such crystalline waveguides requires downsizing and precise spatial control over their shape and size at the microscale, however that currently is not possible due to difficulties with manipulation of these small, brittle objects that are prone to cracking and disintegration. Here we demonstrate that atomic force microscopy (AFM) can be used to reshape, resize and relocate single‐crystal microwaveguides in order to attain spatial control over their light output. Using an AFM cantilever tip, mechanically compliant acicular microcrystals of three N‐benzylideneanilines were bent to an arbitrary angle, sliced out from a bundle into individual crystals, cut into shorter crystals of arbitrary length, and moved across and above a solid surface. When excited by using laser light, such bent microcrystals act as active optical microwaveguides that transduce their fluorescence, with the total intensity of transduced light being dependent on the optical path length. This micromanipulation of the crystal waveguides using AFM is non‐invasive, and after bending their emissive spectral output remains unaltered. The approach reported here effectively overcomes the difficulties that are commonly encountered with reshaping and positioning of small delicate objects (the “thick fingers” problem), and can be applied to mechanically reconfigure organic optical waveguides in order to attain spatial control over their output in two and three dimensions in optical microcircuits. 相似文献
92.
Eliott Le Du Nieves P. Ramirez Stefano Nicolai Rosario Scopelliti Farzaneh Fadaei-Tirani Matthew D. Wodrich Durga Prasad Hari Jerome Waser 《Helvetica chimica acta》2023,106(3):e202200175
First synthesized in 1991, EthynylBenziodoXolones (EBXs) – cyclic hypervalent iodine reagents derived from 2-iodobenzoic acid – are now among the most versatile electrophilic alkynylation reagents. Due to their cyclic structure, these reagents exhibit enhanced stability compared to previously used alkynyl iodonium salts. Over the last decade, both the iodoheterocycle and the arene ring have been extensively modified to fine-tune the reactivity of the reagents, resulting in new analogues such as Ethynylbenziodoxoles (EBxs) or N-heterocyclic reagents. In this article, we have for the first time compiled the structural data available for EBXs and their analogues, focusing especially on X-Ray and NMR data. For selected compounds, molecular electrostatic potentials (MEP) have also been calculated. When considering the tight relationship between structure and reactivity in hypervalent iodine reagents, the collected data is expected to be highly useful for further developments in the field. 相似文献
93.
94.
Yashpal S. Chhonker Chandra P. Pandey Hardik Chandasana Tulsankar Sachin Laxman Yarra Durga Prasad V. S. Narain Madhu Dikshit Rabi S. Bhatta 《Biomedical chromatography : BMC》2016,30(3):466-473
The interest in therapeutic drug monitoring has increased over the last few years. Inter‐ and intra‐patient variability in pharmacokinetics, plasma concentration related toxicity and success of therapy have stressed the need of frequent therapeutic drug monitoring of the drugs. A sensitive, selective and rapid liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS) method was developed for the simultaneous quantification of acetylsalicylic acid (aspirin), salicylic acid, clopidogrel and carboxylic acid metabolite of clopidogrel in human plasma. The chromatographic separations were achieved on Waters Symmetry ShieldTM C18 column (150 × 4.6 mm, 5 µm) using 3.5 mm ammonium acetate (pH 3.5)–acetonitrile (10:90, v/v) as mobile phase at a flow rate of 0.75 mL/min. The present method was successfully applied for therapeutic drug monitoring of aspirin and clopidogrel in 67 patients with coronary artery disease. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
95.
Dr. Chandra B. KC Gary N. Lim Prof. Dr. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13301-13311
Subphthalocyanine (SubPc), a unique ring‐reduced member of the common phthalocyanines family, although known for its higher absorptivity, reveals narrow absorption with peak maxima around 570 nm thus limiting its utility in light‐energy‐harvesting applications. In the present study, by peripheral thio–aryl substitution of SubPc macrocycle, the spectral properties have been modulated to extend the absorption and emission well into the visible/near‐IR region. Additionally, for α‐ring‐substituted derivatives, facile oxidation of SubPc was witnessed, thus making these derivatives better electron donors. Next, the preparation of donor–acceptor dyads containing the well‐known electron acceptor C60 connected to the central boron atom of SubPc was accomplished by making use of the 1,3‐dipolar cycloaddition reaction. Control experiments and free‐energy calculations using the redox and spectral data suggested that the observed fluorescence quenching of SubPc in these dyads is due to electron transfer. Accordingly, transient spectral studies performed both in polar and nonpolar solvents conclusively proved electron transfer to be the quenching mechanism in these dyads. The measured rate constants by fitting kinetic data revealed efficient charge separation and charge recombination processes, suggesting that these dyads could be useful materials for the construction of light‐to‐electricity or light‐to‐fuel production devices. 相似文献
96.
This article describes the synthesis of a series of aromatic amide-amines and their potential use as epoxy hardeners. These amines were synthesized by the reaction of L-phenylalanine(PA) with diamines of different structures i.e.1,4- phenylene diamine(PD),1,5-diamino naphthalene(N),4,4’-(9-fluorenyllidene)-dianiline(F),4,4’-diaminodiphenyl sulphide (DS) and 3,4’-oxydianiline(O) in a stoichiometric ratio(1:1).Structural characterization of synthesized amide-amines was done with the help of elemental analysis and spectroscopic techniques viz.FT-IR,1H-NMR and 13C-NMR.An epoxy blend was prepared by mixing tris(glycidyloxy) phosphine oxide(TGPO) with conventional epoxy i.e.diglycidyl ether of bisphenol-A(DGEBA) in an equivalent ratio of 2:3 to incorporate phosphorous into the main chain.The curing kinetics of the epoxy blend with synthesized aromatic amide-amines was investigated by non-isothermal DSC technique using multiple heating rate method(5,10,15 and 20 K/min.).The activation energies were determined by fitting the experimental data into Kissinger and Ozawa kinetic models.The activation energies obtained through Ozawa method were slightly higher than those of Kissinger method but were comparable.However,both the energies were found to be dependent on the structure of amines.The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis(TGA) in nitrogen atmosphere.All the samples showed improved thermal stability in terms of char yield than using only amines as hardeners. 相似文献
97.
Rathna Durga R.S. Manian Jayadevan Jayashankaran Raghavachary Raghunathan 《Tetrahedron》2006,62(52):12357-12362
A versatile one-pot method for the synthesis of new dispiro heterocycles is described using an intermolecular [3+2] cycloaddition reaction. The reaction gives excellent yields when carried out under solvent-free microwave irradiation. 相似文献
98.
In this paper it is shown that (i) there exists an alternative definition of the superoperator resolvent for calculation of
difference energy satisfying linked cluster theorem for a coupled-cluster choice of the ground-state function which may even
be approximate; (ii) the pole-structure of this propagator-like function in superoperator form is shown to contain information
similar to that contained in the conventional propagator. (iii) It is demonstrated that suitable “Killer conditions” and completeness
of the “operator manifold”—essential for understanding the pole-structure of the propagator—can be established both for an
exact and an approximate ground state function in a coupled-cluster form. (iv) It is also demonstrated that difference energies
calculated with these propagator-like functions are identical to those obtained from a linear response theory in a coupled-cluster
form put forward recently by Mukherjeeet al and Monkhorst. 相似文献
99.
D. Durga Rao N. V. Satyanarayana S. S. Sait Y. Ramakoti Reddy K. Mukkanti 《Chromatographia》2009,70(3-4):647-651
A stability-indicating UPLC method was developed for the simultaneous quantitative determination of losartan potassium, atenolol, and hydrochlorothiazide in pharmaceutical dosage forms in the presence of degradation products. The separation was achieved on a simple isocratic method (water: acetonitrile: triethyl amine: ortho phosphoric acid (60:40:0.1:0.1, v/v) at 0.7 mL min?1, a detection wavelength of 225 nm). The retention times of losartan potassium, atenolol, and hydrochlorothiazide were 2.3, 0.6 and 0.9 min. The total runtime was 3 min. Losartan potassium, atenolol, and hydrochlorothiazide were subjected to different ICH prescribed stress conditions. The method was validated with respect to linearity, accuracy, precision, robustness and ruggedness. 相似文献
100.
The first stereocontrolled and enantiospecific formal synthesis of antiplatelet drug beraprost has been achieved from readily available 1-tetralone. 相似文献