全文获取类型
收费全文 | 124篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 79篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 32篇 |
物理学 | 16篇 |
出版年
2023年 | 4篇 |
2021年 | 2篇 |
2020年 | 8篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 2篇 |
2013年 | 15篇 |
2012年 | 4篇 |
2011年 | 5篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 3篇 |
2007年 | 6篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有130条查询结果,搜索用时 15 毫秒
11.
Abderrahmen Abdelli Oumayma Bejaoui Hajer Bougatef Sarra Ouni Assaâd Sila Hedi M'rabet Xavier Moreau Mohamed Lotfi Efrit Damien Prim 《Journal of heterocyclic chemistry》2023,60(1):96-105
An efficient synthesis of new γ,δ-insaturated δ-lactam and glutarimide derivatives bearing a phosphonomethyl group from a common allylphosphonate precursor is described. Our approach is based on a two-step procedure involving the preparation of phosphonated-1,5-ketoester and −1,5-diester followed by an amidation–heterocyclization sequence. The first step proceeds via Michael's addition of ethyl acetoacetate and diethyl malonate on an allylphosphonate starting material. The second step consists of a base-promoted intramolecular amidation-cyclization sequence with primary amines, which accounts for the construction of δ-lactams and glutarimide skeletons. We performed the evaluation of angiotensin I-converting enzyme (ACE) inhibition using an in vitro enzyme assay on six new compounds. Five compounds showed potent ACE inhibitory activity, with IC50 values ranging from 0.02 to 0.27 mg/ml. Compared with Captopril, used as a reference drug, two new glutarimide derivatives exhibited higher efficiency ACE inhibition activity. 相似文献
12.
13.
14.
Hedi Hannachi Naoual Anoune Christian Arnaud Pierre Lant ri R mi Longeray Henry Chermette 《Journal of Molecular Structure》1998,434(1-3):183-191
The Baeyer-Villiger reaction of polymethoxybenzaldehydes with peroxysuccinic acid (PSA) is studied theoretically. The semi-empirical SCF-MO/PM3 method has been used to study the reaction and to calculate the energy profiles. In addition, heat of formation computations and bond order analyses of the transition species along the reaction coordinates have been performed and are interpreted qualitatively in terms of electron flow through the system during aryl migration. Our results support the hypothesis that the second step is a concerted reaction. Our data support a definite effect of the substituent on the aryl migration. The theoretical predictions are in good agreement with experimental results. 相似文献
15.
EPR Studies of the Binding Properties,Guest Dynamics,and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule 下载免费PDF全文
Dr. Mehmet Menaf Ayhan Dr. Gilles Casano Dr. Hakim Karoui Prof. Antal Rockenbauer Dr. Valérie Monnier Dr. Micaël Hardy Prof. Paul Tordo Dr. David Bardelang Dr. Olivier Ouari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16404-16410
Nitroxide free radicals have been used to study the inner space of one of Rebek’s water‐soluble capsules. EPR and 1H NMR spectroscopy, ESI‐MS, and DFT calculations showed a preference for the formation of 1:2 complexes. EPR titrations allowed us to determine binding constants (Ka) in the order of 107 M ?2. EPR spectral‐shape analysis provided information on the guest rotational dynamics within the capsule. The interplay between optimum hydrogen bonding upon capsule formation and steric strain for guest accommodation highlights some degree of flexibility for guest inclusion, particularly at the center of the capsule where the hydrogen bond seam can be barely distorted or slightly disturbed. 相似文献
16.
Frontispiece: EPR Studies of the Binding Properties,Guest Dynamics,and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule 下载免费PDF全文
17.
F?rster resonance energy transfer (FRET), which involves the nonradiative transfer of excitation energy from an excited donor fluorophore to a proximal ground-state acceptor fluorophore, is a well-characterized photophysical tool. It is very sensitive to nanometer-scale changes in donor-acceptor separation distance and their relative dipole orientations. It has found a wide range of applications in analytical chemistry, protein conformation studies, and biological assays. Luminescent semiconductor nanocrystals (quantum dots, QDs) are inorganic fluorophores with unique optical and spectroscopic properties that could enhance FRET as an analytical tool, due to broad excitation spectra and tunable narrow and symmetric photoemission. Recently, there have been several FRET investigations using luminescent QDs that focused on addressing basic fundamental questions, as well as developing targeted applications with potential use in biology, including sensor design and protein conformation studies. Herein, we provide a critical review of those developments. We discuss some of the basic aspects of FRET applied to QDs as both donors and acceptors, and highlight some of the advantages offered (and limitations encountered) by QDs as energy donors and acceptors compared to conventional dyes. We also review the recent developments made in using QD bioreceptor conjugates to design FRET-based assays. 相似文献
18.
Guyon F Hameau A Khatyr A Knorr M Amrouche H Fortin D Harvey PD Strohmann C Ndiaye AL Huch V Veith M Avarvari N 《Inorganic chemistry》2008,47(17):7483-7492
The dinuclear gold complexes [{Au(PPh 3)} 2(mu- dmid)] ( 1) ( dmid = 1,3-dithiole-2-one-4,5-dithiolate) and [{Au(PPh 3)} 2(mu- dddt)] ( 2) ( dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) were synthesized and characterized by X-ray crystallography. Both complexes exhibit intramolecular aurophilic interactions with Au...Au distances of 3.1984(10) A for 1 and 3.1295(11) A for 2. A self-assembly reaction between 4,5-bis(2-hydroxyethylthio)-1,3-dithiole-2-thione ( (HOCH 2 CH 2 ) 2 dmit) and [AuCl(tht)] affords the complex [AuCl{ (HOCH 2 CH 2 ) 2 dmit}] 2 ( 4), which possesses an antiparallel dimeric arrangement resulting from a short aurophilic contact of 3.078(6) A. This motif is extended into two dimensions due to intra- and intermolecular hydrogen bonds via the hydroxyethyl groups, giving rise to a supramolecular network. Three compounds were investigated for their rich photophysical properties at 298 and 77 K in 2-MeTHF and in the solid state; [Au 2(mu- dmid)(PPh 3) 2] ( 1), [Au 2(mu- dddt)(PPh 3) 2] ( 2), and [AuCl{( HOCH 2 CH 2 ) 2 dmit}] ( 4). 1 exhibits relatively long-lived LMCT (ligand-to-metal charge transfer) emissions at 298 K in solution (370 nm; tau e approximately 17 ns, where M is a single gold not interacting with the other gold atom; i.e., the fluxional C-SAuPPh 3 units are away from each other) and in the solid state (410 nm; tau e approximately 70 mus). At 77 K, a new emission band is observed at 685 nm (tau e = 132 mus) and assigned to a LMCT emission where M is representative for two gold atoms interacting together consistent with the presence of Au...Au contacts as found in the crystal structure. In solution at 77 K, the LMCT emission is also red-shifted to 550 nm (tau e approximately 139 mus). It is believed to be associated to a given rotamer. 2 also exhibits LMCT emissions at 380 nm at 298 K in solution and at 470 nm in the solid state. 4 exhibits X/MLCT emission (halide/metal to ligand charge transfer) where M is a dimer in the solid state with obvious Au...Au interactions, resulting in red-shifted emission band, and is a monomer in solution in the 10 (-5) M concentration (i.e., no Au...Au interactions) resulting in blue-shifted luminescence. Both fluorescence and phosphorescence are observed for 4. 相似文献
19.
Hedi Zhao Miao Qi Yuan Gong Han Chen Dan Wang Jing Fan Yanmin Wang Jingjuan Wang 《Journal of separation science》2023,46(6):2200794
Danggui Buxue Decoction is a classic formula containing Astragali Radix and Angelicae Sinensis Radix in a 5:1 ratio and has been extensively used to treat blood deficiency for thousands of years. The aim of the study was to investigate the differences in plasma protein binding, pharmacokinetics, and tissue distribution of Danggui Buxue Decoction in normal and blood-deficient rats by ultra-performance liquid chromatography-tandem mass spectrometry. The effects on peripheral blood routine were verified. The compounds exhibited higher plasma protein binding and absorption in the model group compared to the control group, except formononetin. The six ingredients were distributed widely, and the highest concentrations were detected in the heart and uterus. As has been demonstrated in the previous study of the effect of Danggui Buxue Decoction, its potential is to serve as an effective traditional Chinese medicine formula for treating cardiovascular diseases and impacting estrogenic properties, which reveals the potential target organs of Danggui Buxue Decoction the heart and uterus. Our findings suggested that the absorption and distribution of different components in Danggui Buxue Decoction varies depending on the pathological state, molecular weight, lipid solubility, transporter-mediated efflux, and other factors. 相似文献
20.
Abderrazek Karoui 《Journal of Mathematical Analysis and Applications》2006,317(1):364-379
In this paper, we study a method for the construction of orthonormal wavelet bases with dilation factor 4. More precisely, for any integer M>0, we construct an orthonormal scaling filter mM(ξ) that generates a mother scaling function ?M, associated with the dilation factor 4. The computation of the different coefficients of 2|mM(ξ)| is done by the use of a simple iterative method. Also, this work shows how this construction method provides us with a whole family of compactly supported orthonormal wavelet bases with arbitrary high regularity. A first estimate of α(M), the asymptotic regularity of ?M is given by α(M)∼0.25M. Examples are provided to illustrate the results of this work. 相似文献