全文获取类型
收费全文 | 176篇 |
免费 | 11篇 |
专业分类
化学 | 142篇 |
晶体学 | 1篇 |
数学 | 4篇 |
物理学 | 40篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 18篇 |
2011年 | 15篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 11篇 |
2007年 | 18篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1995年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 15 毫秒
151.
Debashis Banerjee Sanjib Bagchi Shampa Mondal Sanjib Ghosh 《Journal of photochemistry and photobiology. A, Chemistry》1995,90(2-3):171-176
The fluorescence characteristics of two ketocyanine dyes have been studied in six mixed binary solvents. Several parameters such as the maximum energy E12(F) of fluorescence, the quantum yield Φ12 of fluorescence and the normalized intensity of the fluorescence have been investigated as functions of solvent composition. In protic+aprotic binary mixtures a dramatic change at the aprotic end has been observed. The results point to a preferential solvation of the solute by the protic component. 相似文献
152.
Solvation characteristics of 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridino)phenolate in completely miscible ternary solvent mixtures (viz., methanol + acetone + water, methanol + acetone + benzene, and methanol + chloroform + benzene) have been studied by using an electronic spectroscopic procedure. The transition energy (E) corresponding to the charge-transfer band maximum of the solute in a ternary solvent mixture differs significantly from the average E-values in the component solvents weighted by the mole fraction of the solvents. A two-phase model of solvation has been invoked to explain the results. The excess or deficit of solvent components in the local region of the solute molecule over that in the bulk has been estimated using the knowledge of solvation in binary solvent mixtures. 相似文献
153.
Basu JK Shannigrahi M Ray N Bagchi S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(11-12):2539-2542
Interaction between 3d-transition metal ions (Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) and the E(T)(30) dye, 2,6-diphenyl-4-(2,4,6-triphenyl 1-pyridino)phenolate in aqueous medium have been studied by distributing the dye between the aqueous and micellar phase formed by cationic surfactant cetyltrimethylammonium bromide(CTAB). Values of equilibrium constant K for the dye-metal ion interaction and the partition coefficient of the dye between the micellar and the aqueous phase have been determined. K values show a systematic correlation with ionic potential of metal ions. 相似文献
154.
Banerjee D Das PK Singha H Bagchi S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1109-1113
Interaction of merbromin with trypsin is of bovine origin has been studied by monitoring the absorption steady-state and time-resolved fluorescence spectral properties of the dye. Studies have been done in media of varying pH at different trypsin concentrations. It has been observed that trypsin brings about a quenching of fluorescence of the dye. The quenching is static in nature and the equilibrium constant of dye-trypsin interaction in the ground-state has been determined from quenching studies. Steady-state anisotropy of the dye increases in presence of trypsin in the medium. Values of micro-viscosity in the vicinity of the fluorophore in media containing trypsin have been determined from measurements of fluorescence anisotropy. Time-resolved fluorescence studies indicate the existence of two decaying states for the dye. The fractional contribution to the time-resolved decay changes with pH. The average lifetime, however, does not depend on the concentration of trypsin. 相似文献
155.
Solvation characteristics in ternary solvent mixtures have been studied by monitoring the solvent-sensitive electronic absorption band of a ketocyanine dye in two ternary solvent mixtures, water + ethanol + benzene and water + ethanol + cyclohexane, in which one of the pairs are partially miscible. Investigations have been done in a completely miscible region including the binodal curve. The maximum energy of absorption (E) of the solute in a ternary solvent mixture differs significantly from the mole fraction average of the E-values in the component solvents. Results in the corresponding binary solvent mixtures also show a deviation of the E-value from the mole fraction averaged E-values, indicating preferential solvation by a component solvent. The results in ternary solvent mixture have been explained in terms of a realistic model of solvation using the results on binary solvation. 相似文献
156.
Maity AN Schwederski B Sarkar B Zális S Fiedler J Kar S Lahiri GK Duboc C Grunert M Gütlich P Kaim W 《Inorganic chemistry》2007,46(18):7312-7320
The complexes {(mu4-TCNX)[Fe(CO)2(C5H5)]4}(BF4)4 were prepared as light-sensitive materials from [Fe(CO)2(C5H5) (THF)](BF4) and the corresponding TCNX ligands (TCNE = tetracyanoethene, TCNQ=7,7,8,8-tetracyano-p-quinodimethane, TCNB=1,2,4,5-tetracyanobenzene). Whereas the TCNE and TCNQ complexes are extremely easily reduced species with reduction potentials>+0.3 V vs ferrocenium/ferrocene, the tetranuclear complex of TCNB exhibits a significantly more negative reduction potential at about -1.0 V. Even for the complexes with strongly pi-accepting TCNE and TCNQ, the very positive reduction potentials, the unusually high nitrile stretching frequencies>2235 cm(-1), and the high-energy charge-transfer transitions indicate negligible metal-to-ligand electron transfer in the ground state, corresponding to a largely unperturbed (TCNX degrees)(FeII)4 formulation of oxidation states as caused by orthogonality between the metal-centered HOMO and the pi* LUMO of TCNX. M?ssbauer spectroscopy confirms the low-spin iron(II) state, and DFT calculations suggest coplanar TCNE and TCNQ bridging ligands in the complex tetracations. One-electron reduction to the 3+ forms of the TCNE and TCNQ complexes produces EPR spectra which confirm the predominant ligand character of the then singly occupied MO through isotropic g values slightly below 2, in addition to a negligible g anisotropy of frozen solutions at frequencies up to 285 GHz and also through an unusually well-resolved solution X band EPR spectrum of {(mu4-TCNE)[Fe(CO)2(C5H5)]4}3+ which shows the presence of four equivalent [Fe(CO)2(C5H5)]+ moieties through 57Fe and 13C(CO) hyperfine coupling in nonenriched material. DFT calculations reproduce the experimental EPR data. A survey of discrete TCNE and TCNQ complexes [(mu4-TCNX)(MLn)4] exhibits a dichotomy between the systems {(mu4-TCNX)[Fe(CO)2(C5H5)]4}4+ and {(mu4-TCNQ)[Re(CO)3(bpy)]4}4+ with their negligible metal-to-ligand electron transfer and several other compounds of TCNE or TCNQ with Mn, Ru, Os, or Cu complex fragments which display evidence for a strong such interaction, i.e., an appreciable value delta in the formulation {(mu4-TCNXdelta-)[Mx+delta/4Ln]4}. Irreversibility of the first reduction of {(mu4-TCNB)[Fe(CO)2(C5H5)]4}(BF4)4 precluded spectroelectrochemical studies; however, the high-energy CN stretching frequencies and charge transfer absorptions of that TCNB analogue also confirm the exceptional position of the complexes {(mu4-TCNX)[Fe(CO)2(C5H5)]4}(BF4)4. 相似文献
157.
Electronic absorption and emission spectral characteristics of two ketocyanine dyes have been studied in solution in the presence of alkaline earth metal ions. Absorption spectral studies indicate complex formation between the ions and the dyes in the ground state. Values of the equilibrium constant and the enthalpy change characterizing dye (S0)-metal ion interaction have been determined from the absorption spectral data. In the presence of the metal ions the fluorescence spectrum of the dyes shows two bands pointing to the existence of two emitting species, viz., the solvated and the complexed dye in solution. Time-resolved studies of the dyes in solution containing the metal ions can be explained by a two-state model and indicate the presence of two emitting species in equilibrium. Values of the equilibrium constant for the interaction of metal ion and the dyes in the S1 state have also been estimated. 相似文献
158.
Experimental and Theoretical Investigations of the Existence of CuII,CuIII, and CuIV in Copper Corrolato Complexes
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Woormileela Sinha Michael G. Sommer Naina Deibel Fabian Ehret Prof. Dr. Matthias Bauer Prof. Dr. Biprajit Sarkar Dr. Sanjib Kar 《Angewandte Chemie (International ed. in English)》2015,54(46):13769-13774
The most common oxidation states of copper in stable complexes are +I and +II. CuIII complexes are often considered as intermediates in biological and homogeneous catalysis. More recently, CuIV species have been postulated as possible intermediates in oxidation catalysis. Despite the importance of these higher oxidation states of copper, spectroscopic data for these oxidation states remain scarce, with such information on CuIV complexes being non‐existent. We herein present the synthesis and characterization of three copper corrolato complexes. A combination of electrochemistry, UV/Vis/NIR/EPR spectroelectrochemistry, XANES measurements, and DFT calculations points to existence of three distinct redox states in these molecules for which the oxidation states +II, +III, and +IV can be invoked for the copper centers. The present results thus represent the first spectroscopic and theoretical investigation of a CuIV species, and describe a redox series where CuII, CuIII, and CuIV are discussed within the same molecular platform. 相似文献
159.
Paul Dipayan Mahanta Saurov Tag Hui Das Sanjib Kumar Das Gupta Debmalya Tanti Bhaben Ananthan Rajendran Das Ranjan Jambhulkar Sanjay Hui Pallabi Kalita 《Molecular diversity》2022,26(4):1933-1955
Molecular Diversity - Breast and stomach cancer is reported as a leading cause for human mortality across the world. The overexpression of receptor tyrosine kinase (RTK) proteins, namely the human... 相似文献
160.
Mitrali Biswas Sanchaita Dey Abhishek Das Prof. Dr. Tapan Kanti Paine Dr. Sanjib Panda Prof. Dr. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202088
The unexplored ‘actor’ behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac)2} (acac= acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2−), and bis(carboxamido) (L32−)-bridged isovalent {RuII(μ-L1)RuII}, 1/ {RuIII(μ-L32−)RuIII}, 3 and mixed-valent {RuII(μ-L2−)RuIII}, 2 . Authentication of the complexes along with the redox non-innocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations. Kinetic and isotope labelling experiments together with DFT analyzed transition states justified the consideration of redox shuttling at metal/L1 interface for 3O2 activation despite of the closed shell configuration of 1 (S=0) to give carboxamido derived 2 / 3 . 相似文献