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41.
Tiny azacryptand 1,4,7,10,13,16,21,24-octaazabicyclo[8.8.8]hexacosane (L) upon reaction with 48% hydrobromic acid (containing <0.05% chloride contamination) forms hexabromide salt (1). Single crystal X-ray crystallographic investigation of the hexaprotonated bromide (1) shows no guest encapsulation inside the tiny cage. This bromide salt 1 with an empty proton cage has been utilized as the receptor for encapsulation of chloride (2) and fluoride (3). Crystallographic results of mixed chloride/bromide (2) and fluoride/bromide (3) complexes of L are examined, which show monotopic recognition of chloride in the case of 2 and fluoride in the case of 3 inside the proton cage with five bromide and three water molecules outside the cavity. Single crystals obtained from an experiment on mixed anionic system (chloride and fluoride), 1 shows selective encapsulation of fluoride, which supports the formation of complex 3 and crystals obtained upon treatment of 2 with tetrabutyl ammonium fluoride also yields complex 3. In a separate reaction between L and 49% hydrobromic acid containing higher chloride contamination (<0.2%) forms chloride/bromide salt (2). 1H NMR studies of 1 with sodium chloride and fluoride support the encapsulation of the respective anions inside the proton cage. 相似文献
42.
Coordinatively Unsaturated Lanthanide(III) Helicates: Luminescence Sensors for Adenosine Monophosphate in Aqueous Media 下载免费PDF全文
Jashobanta Sahoo Rajendran Arunachalam Dr. Palani S. Subramanian Dr. Eringathodi Suresh Dr. Arto Valkonen Prof. Dr. Kari Rissanen Prof. Dr. Markus Albrecht 《Angewandte Chemie (International ed. in English)》2016,55(33):9625-9629
Coordinatively unsaturated double‐stranded helicates [(H2L)2Eu2(NO3)2(H2O)4](NO3)4, [(H2L)2Tb2(H2O)6](NO3)6, and [(H2L)2Tb2(H2O)6]Cl6 (H2L=butanedioicacid‐1,4‐bis[2‐(2‐pyridinylmethylene)hydrazide]) are easily obtained by self‐assembly from the ligand and the corresponding lanthanide(III) salts. The complexes are characterized by X‐ray crystallography showing the helical arrangement of the ligands. Co‐ligands at the metal ions can be easily substituted by appropriate anions. A specific luminescence response of AMP in presence of ADP, ATP, and other anions is observed. Specificity is assigned to the perfect size match of AMP to bridge the two metal centers and to replace quenching co‐ligands in the coordination sphere. 相似文献
43.
44.
Víctor González-Ruiz Yamisley González-Cuevas Sankaralingam Arunachalam M. Antonia Martín Ana I. Olives Pascual Ribelles M. Teresa Ramos J. Carlos Menéndez 《Journal of luminescence》2012,132(9):2468-2475
Luotonin A is an alkaloid structurally related to the natural anti-tumour agent camptothecin. The fluorescence behaviour of luotonin A and a series of six analogues is described in the present work. The influence of solvent polarity and pH on the native fluorescence properties of these alkaloids was studied, finding that in organic solvents or in aqueous solutions (pH 5.5–7.2) the neutral form of the luotonin derivatives emit in the region of 410–450 nm but, in both media, acidification to pH values below 3.0 causes a new emission band to appear at about 500 nm. An ESPT reaction occurs due to the protonation of the basic nitrogen atoms of the pentacyclic ring. Acid-base titrations of luotonin A and its derivatives in aqueous and acetonitrile media were carried out in order to determine their pKa? values which were around 2, showing these compounds to be very weak bases. In aqueous media, the absence of an iso-emissive point in the emission spectra suggests the existence of more than two species in the proton transfer equilibria. The basicity of the luotonin A derivatives is increased in organic media, and a good correlation between the pKa? values and the chemical structure was found. The protonation of luotonin A was also studied by 1H-NMR and 13C-NMR experiments, which proved the protonation of the nitrogen atoms at the positions 5 and 6 of the pentacyclic ring. The fluorescence quantum yields were determined in ethanol and in aqueous solutions under neutral and acidic conditions. The fluorescence quantum yields were higher in water for the case of the more polar compounds, and the opposite result was obtained for the more hydrophobic ones. The remarkable and interesting fluorescence properties of luotonin A prompted the development of its fluorimetric analytical quantitation, obtaining very good analytical features. 相似文献
45.
[reaction: see text] A tin(II) chloride-mediated short, efficient, and practical regioselective synthesis of biheterocyclic 5,6-dihydro-quinazolino[4,3-b]quinazolin-8-ones with three-point diversity is reported. A one-step reductive transformation of 2-(2-nitrophenyl)-3H-quinazolin-4-one in various alcohols furnished the desired tetracyclic product in good yields with high purity. 相似文献
46.
Kaleeswari Kalairajan Tamil Selvi Arunachalam 《Research on Chemical Intermediates》2022,48(4):1495-1513
Research on Chemical Intermediates - A straightforward and suitable protocol is described for the conversion of substituted styrene to alkylbenzenes in the presence of Al2O3 nanoparticles... 相似文献
47.
Narayanasamy Kumaraguru Sankarlingam Arunachalam Mahadevimanglam Narayanasamy Arumugham Kannappan Santhakumar 《Transition Metal Chemistry》2006,31(2):250-255
A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)2(A)X]2+ and cis-α-[Cr(trien)(A)X]2+ (A = Dodecyl or Cetylamine; X = F−, Cl−, Br−) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous
solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution
were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the
temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ Gm0, Δ Hm0 and Δ Sm0). 相似文献
48.
Winaki P. Sohtun Themmila Khamrang Arunachalam Kannan Gowdhami Balakrishnan Dhandayutham Saravanan Mohammad Abdulkader Akhbarsha Marappan Velusamy Mallayan Palaniandavar 《应用有机金属化学》2020,34(5):e5593
A series of iron(III) bis-complexes of the type [FeL2]X 1-4 , X = OH− ( 1 ), Cl¯ ( 3 ), and FeCl4¯ ( 2 , 4 ), where LH is a tridentate (N,N,S) ligands such as N′-(1-pyridin-2-ylethylidene)-hydrazinecarbodithioic acid methyl ester ( HL1 ), N′-(phenylpyridin-2-ylmethylene)-hydrazinecarbodithioic acid methyl ester ( HL2 ), N′-quinolin-2-ylmethylene-hydrazinecarbodithioic acid methyl ester ( HL3 ), or N′-(1-methyl-1H-imidazol-2-yl-methylene)hydrazinecarbodithioic acid methyl ester ( HL4 ) has been isolated in moderate to good yields and completely characterized by elemental analyses, conductivity studies, and infrared and UV-visible spectral measurements. The single crystal X-ray structures of 1 , 2 and 4 revealed that two deprotonated tridentate (NNS) ligands are meridionally coordinated to constitute a distorted octahedral coordination geometry around iron(III). In acetonitrile solution, all the complexes show quasi-reversible Fe(III)/Fe(II) redox behavior. The in vitro cytotoxicity of the ligands HL1–HL4 (IC50: HL1 , 64.5; HL2 , 51.0; HL3 , 124.0; HL4 , 45.0 μM at 24 h) and complexes 1–4 (IC50: 1 , 84.5; 2 , 40.0; 3 , 168.5; 4 , 50.5 μM at 24 h) towards A549 lung cancer cell lines are similar to cisplatin (69.0 μM), revealing that free ligands cause cancer cell death with potency higher than the corresponding iron(III) complexes. Also, both the ligands and the complexes cause cell death mainly through apoptotic mode, as revealed by the observation of a higher percentage of apoptotic cells in acridine orange (AO)/ ethidium bromide (EB), and Annexin V-Cy3 stained cancer cells. 相似文献
49.
Kannappan Santhakumar Narayanasamy Kumaraguru Sankarlingam Arunachalam Mahadevimanglam Narayanasamy Arumugham 《Transition Metal Chemistry》2006,31(4):475-481
The kinetics and mechanism of iron(II) reduction of cis- α-chloro/bromo(cetylamine)(triethylenetetramine) cobalt(III) surfactant complex ions were studied spectrophotometrically
in an aqueous acid medium by following the disappearance of CoIII using an excess of the reductant under pseudo-first-order conditions: [FeII = 0.25 mol dm−3, [H+ = 0.1 mol dm−3, [μ = 1.0 mol dm−3 ionic strength in a nitrogen atmosphere at 303, 308 and 313 K. The reaction was found to be second order and showed acid
independence in the range [H+ = 0.05−0.25 mol dm−3. The second order rate constant increased with CoIII concentration and the presence of aggregation of the complex itself altered the reaction rate. The effects of [FeII], [H+] and [ μ] on the rate were determined. Activation and thermodynamic parameters were computed. It is suggested that the reaction of
Fe2+(aq) with CoIII complex proceeds by an inner-sphere mechanism. 相似文献
50.
A new C3-symmetric drum-shaped homoditopic haxaamino bicyclic cyclophane and its hexachloride and hexaiodide complexes have been synthesized and characterized and dual recognition of guests has been demonstrated. Single-crystal X-ray analysis illustrates that bicyclic cyclophane has a cavity and side pockets for acetone molecules. The hexaprotonated state of this bicycle shows encapsulation of an iodide inside its cavity, and in hexachloride complex, chloride is recognized as Cl(-)...H2O in each of the three side pockets which are in extensive hydrogen bonding interactions with the water and chlorides. (1)H NMR experiments have also been carried out on hexatosylated cyclophane with the halides to study solution state binding. 相似文献