全文获取类型
收费全文 | 181篇 |
免费 | 13篇 |
专业分类
化学 | 178篇 |
力学 | 6篇 |
数学 | 6篇 |
物理学 | 4篇 |
出版年
2023年 | 2篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 12篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有194条查询结果,搜索用时 93 毫秒
91.
Rapid determination of vitamin E in vegetable oils by reversed-phase high-performance liquid chromatography 总被引:5,自引:0,他引:5
Gimeno E Castellote AI Lamuela-Raventós RM de la Torre MC López-Sabater MC 《Journal of chromatography. A》2000,881(1-2):251-254
A quick and direct method for measuring tocopherols (alpha, beta+gamma and delta) in vegetable oils has been developed using RP-HPLC with UV detection. Previous extraction of tocopherols is not required. The oil is diluted in hexane and an aliquot is mixed with ethanol containing an internal standard (alpha-tocopherol acetate). The chromatographic system consists of an ODS-2 column with a methanol-water mobile phase. Tocopherols are detected at 292 nm in less than 5 min after injection. The method is precise (RSD=2.69%) and has a high mean recovery (98.14%). 相似文献
92.
Carlos D. L. Lima Dr. Helena Coelho Dr. Ana Gimeno Filipa Trovão Ana Diniz Dr. Jorge S. Dias Prof. Dr. Jesús Jiménez-Barbero Prof. Dr. Francisco Corzana Dr. Ana Luísa Carvalho Prof. Dr. Eurico J. Cabrita Dr. Filipa Marcelo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(29):7951-7958
Interactions of glycan-specific epitopes to human lectin receptors represent novel immune checkpoints for investigating cancer and infection diseases. By employing a multidisciplinary approach that combines isothermal titration calorimetry, NMR spectroscopy, molecular dynamics simulations, and X-ray crystallography, we investigated the molecular determinants that govern the recognition of the tumour and pathogenic glycobiomarker LacdiNAc (GalNAcβ1-4GlcNAc, LDN), including their comparison with the ubiquitous LacNAc epitope (Galβ1-4GlcNAc, LN), by two human immune-related lectins, galectin-3 (hGal-3) and the macrophage galactose C-type lectin (hMGL). A different mechanism of binding and interactions was observed for the hGal-3/LDN and hMGL/LDN complexes, which explains the remarkable difference in the binding specificity of LDN and LN by these two lectins. The new structural clues reported herein are fundamental for the chemical design of mimetics targeting hGal-3/hMGL recognition process. 相似文献
93.
Summary A method for determining aromatic sulfonates in sea water is presented. Ion-pair solid phase extraction is coupled on-line
to ion-pair liquid chromatography with UV detection. In the enrichment step, the recoveries from 100 mL of sea water were
higher than 65% for most analytes. Linearity was good and detection limits were between 0.02 and 1 μgL−1. The repeatability of the method, expressed as % of relative standard deviation (n=3) was between 1 and 15%. The method was
checked in coastal water near the commercial port of Tarragona, where effluents from the petrochemical industry are discharged.
All the samples taken were found to contain 2-naphthalenesulfonate. 相似文献
94.
Lea Gimeno Dr. Errol Blart Dr. Jean-Noël Rebilly Marina Coupeau Magali Allain Thierry Roisnel Alexis Quarré de Verneuil Dr. Christophe Gourlaouen Prof. Chantal Daniel Dr. Yann Pellegrin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11887-11899
A strategy is presented to improve the excited state reactivity of homoleptic copper–bis(diimine) complexes CuL2+ by increasing the steric bulk around CuI whereas preserving their stability. Substituting the phenanthroline at the 2-position by a phenyl group allows the implementation of stabilizing intramolecular π stacking within the copper complex, whereas tethering a branched alkyl chain at the 9-position provides enough steric bulk to rise the excited state energy E00. Two novel complexes are studied and compared to symmetrical models. The impact of breaking the symmetry of phenanthroline ligands on the photophysical properties of the complexes is analyzed and rationalized thanks to a combined theoretical and experimental study. The importance of fine-tuning the steric bulk of the N–N chelate in order to stabilize the coordination sphere is demonstrated. Importantly, the excited state reactivity of the newly developed complexes is improved as demonstrated in the frame of a reductive quenching step, evidencing the relevance of our strategy. 相似文献
95.
96.
Victorio Cadierno Josefina Díez Sergio E. García-Garrido Jos Gimeno Antonio Pizzano 《Polyhedron》2010,29(18):1-3386
A series of cationic rhodium(I) complexes [Rh(diene)(N^N)][BF4] (diene = 1,5-cyclooctadiene (cod), norbornadiene (nbd), tetrafluorobenzobarralene (tfb)), containing the optically pure bis(sulfoximine) ligand 1,2-bis(S-methyl-S-phenylsulfonimidoyl)benzene, have been synthesized and fully characterized. The structure of the R,R enantiomer of the ligand, and that of its cyclooctadiene–Rh(I) complex, were confirmed by means of single-crystal X-ray diffraction techniques. Studies on the catalytic activity of these complexes in acetophenone hydrosilylation and dimethyl itaconate hydrogenation are also reported. 相似文献
97.
Wolf-Walther du Mont Roxana Bîrzoi Delia Bugnariu Constantin G. Daniliuc Christine Goers Rafael Guerrero Gimeno Thorsten Gust Daniela Lungu Antje Riecke Rainer Bartsch Laszlo Nyulászi Zoltan Benkõ Laszlo Könczöl 《Comptes Rendus Chimie》2010,13(8-9):1111-1126
An overview is given on synthesis and structures of new bidentate phosphaalkene ligands [(RMe2Si)2CP]2E (E = O, NR, N?) and (RMe2Si)2CPN(R′)PR′′2. Exceptional properties of these ligands, extending beyond predictable properties of phosphaalkenes are: (i) the NSi bond cleavage of [(iPrMe2Si)2CP]2NSiMe3 with AuI and RhI chloro complexes under mild conditions leading to binuclear complexes of the 6π-delocalised imidobisphosphaalkene anion [(iPrMe2Si)2CP]2N?, and (ii) the chlorotropic formation of molecular 1:2 PdII and PtII metallochloroylid complexes with novel ylid-type ligands [(RMe2Si)2CP(Cl)N(R)PR2]?, and the transformation of a P-platina-P-chloroylid complex into a C-platina phosphaalkene by intramolecular chlorosilane elimination. Properties of the heavier congeners [(RMe2Si)2CP]2E (E = S, Se, Te, PR, P?, As?) and (RMe2Si)2CPEPR′′2 (E = S, Se, Te) are also described. 相似文献
98.
Peris-Vicente J Gimeno Adelantado JV Carbó MT Castro RM Reig FB 《Journal of chromatography. A》2006,1101(1-2):254-260
A study attempted to characterize natural waxes used in pictorial works of art was carried out by means of gas chromatography. The analytical treatment requires prior hydrolysis of the waxes to release the fatty acids (FA) (myristic (myr), palmitic (pal), oleic (ole), stearic (ste), araquidic (ara), behenic (beh), lignoceric (lig), cerotic (cer)) from the main esters of the waxes. The formation of volatile derivatives of the fatty acids was carried out by derivatization with ethyl choroformate (ECF). This derivatization reagent was chosen due to the speed, safety and quantitativity of the reaction. The analyzed hydrocarbons were n-eicosane, n-heneicosane, n-docosane, n-tricosane, n-tetracosane, n-pentacosane, n-hexacosane, n-heptacosane, n-octacosane, n-nonacosane, n-tricontane n-hentriacontane, n-dotriacontane, n-tritriacontane, n-tetratriacontane, n-pentatriacontane, main constituents of the waxes. No derivatization is needed to analyze the hydrocarbons. Ethyl ester derivatives and hydrocarbons are adequately separated by gas chromatography, identified by flame ionization detection and confirmed by mass spectrometry. To characterize natural waxes, peak area ratios of each fatty acids with respect to the palmitic acid and peak area ratios of each hydrocarbons with respect to n-heptacosane were calculated. The proposed method provides a good characterization of different waxes most frequently used in artworks, such as beeswax, carnauba wax and ceresin, and has been successfully applied to real samples. This is the first report on the application of ECF to the analysis of fatty acids in wax. 相似文献
99.
The alkenylaminoallenylidene complex [Ru(η5-C9H7){CCC(NEt2)[C(Me)CPh2]}{κ(P)-Ph2PCH2CHCH2}(PPh3)][PF6] (2) has been prepared by the reaction of the allenylidene [Ru(η5-C9H7)(CCCPh2){κ(P)-Ph2PCH2CHCH2}(PPh3)][PF6] (1) with the ynamine MeCCNEt2. The reaction proceeds regio- and stereoselectively, and the insertion of the ynamine takes place exclusively at the CβCγ bond of the unsaturated chain. The secondary allenylidene [Ru(η5-C9H7){CCC(H)[C(Me)CPh2]}{κ(P)-Ph2PCH2CHCH2}(PPh3)][PF6] (3) is obtained, in a one-pot synthesis, from the reaction of aminoallenylidene 2 with LiBHEt3 and subsequent treatment with silica. Moreover, the addition of an excess of NaBH4 to a solution of the complex 2 in THF at room temperature gives exclusively the alkynyl complex [Ru(η5-C9H7){CCCH2[C(Me)CPh2]}{κ(P)-Ph2PCH2CHCH2}(PPh3)] (5). The heating of a solution of allenylidene derivative 3 in THF at reflux gives regio- and diastereoselectively the cyclobutylidene complex [Ru(η5-C9H7) (PPh3)][PF6](4) through an intramolecular cycloaddition of the CC allyl and the CαCβ bonds in the allenylidene complex 3. The structure of complex 4 has been determined by single crystal X-ray diffraction analysis. 相似文献
100.
Structural and Photophysical Study on Heterobimetallic Complexes with d8–d10 Interactions Supported by Carborane Ligands: Theoretical Analysis of the Emissive Behaviour
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Olga Crespo Prof. M. Concepción Gimeno Prof. Antonio Laguna Dr. Olli Lehtonen Dr. Isaura Ospino Prof. Pekka Pyykkö Dr. M. Dolores Villacampa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(11):3120-3127
Heterobimetallic complexes of formula [M{(PPh2)2C2B9H10}(S2C2B10H10)M′(PPh3)] (M=Pd, Pt; M′=Au, Ag, Cu) and [Ni{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] were obtained from the reaction of [M{(PPh2)2C2B10H10}(S2C2B10H10)] (M=Pd, Pt) with [M′(PPh3)]+ (M′=Au, Ag, Cu) or by one‐pot synthesis from [(SH)2C2B10H10], (PPh2)2C2B10H10, NiCl2 ? 6 H2O, and [Au(PPh3)]+. They display d8–d10 intermetallic interactions and emit red light in the solid state at 77 K. Theoretical studies on [M{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] (M=Pd, Pt, Ni) attribute the luminescence to ligand (thiolate, L)‐to‐“P2‐M‐S2” (ML′) charge‐transfer (LML′CT) transitions for M=Pt and to metal (M)‐to‐“P2‐M‐S2” (ML′) charge‐transfer (MML′CT) transitions for M=Ni, Pd. 相似文献