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91.
Deb Shankar Roy Kankan Bhattacharyya Subhas C. Bera Mihir Chowdhury 《Chemical physics letters》1980,69(1):134-140
A time-resolved study of the emission from benzil and naphthyl in semi-solid glasses (e.g. alcoholic glass near the melting point) using a pulsed N2-laser as an excitation source is reported. The emission from the relaxed excited triplet shows a growth followed by a decay. This growth provides a convincing proof of geometrical relaxation occurring in the excited states of benzil and naphthyl. 相似文献
92.
Sourabh Bera Dr. Sushmita Basu Prof. Biman Jana Prof. Parthasarathi Dastidar 《Angewandte Chemie (International ed. in English)》2023,62(7):e202216447
Supramolecular assemblies such as tubules/helix/double helix/helical tape etc. are usually submicron objects preventing direct observation under optical microscope. Chiral-pure form of these assemblies is important for potential applications. Herein, we report a rare phenomenon wherein a DMSO gel of a simple terpyridine derivative [(4-CNPhe)4PyTerp] produced macroscopic helical morphologies (μm length scale) which could be observed under optical microscope, formation of which could be monitored by optical videography, stable enough to withstand acidic vapour, robust enough to display reversible gel↔sol in response to acidic and ammonia vapour and sturdy enough to be maneuvered with a needle. These properties appeared to be unique to the title compound as the other related derivatives failed to display such assembly structures. SXRD and MD simulation studies suggested that weak interactions (π-π stacking) played a crucial role in the self-assembly process. 相似文献
93.
Tishyasoumya Bera Bandana Singh Prof. Vincent Gandon Prof. Dr. Jaideep Saha 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(62):e202201208
Herein, development and detailed investigation of a SN′-type intramolecular aromatic substitution reaction involving α-arylazaoxyallyl cation intermediate, is disclosed. The study showcased that while α-aryl-α-chlorohydroxamate could be activated by a combination of base and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) into the corresponding azaoxyallyl cations, it could further emerge into a π-extended species involving the adjacent α-aryl moiety, and this transition is contingent on electronic effects of the aromatic ring as well as on α-substituents. An effective activation of the α-aromatic ring could pave the path for intramolecular Ar(Csp2)-N bond formation towards oxindoles. Control experiments and DFT calculations suggested that a non-pericyclic nucleophilic amination pathway is most likely operative and precluded the possibility of concerted or electrophilic amination mechanism. HFIP as the reaction solvent plays pivotal roles in the transformation. 相似文献
94.
Metal–Ligand Cooperation on a Diruthenium Platform: Selective Imine Formation through Acceptorless Dehydrogenative Coupling of Alcohols with Amines 下载免费PDF全文
Biswajit Saha S. M. Wahidur Rahaman Prosenjit Daw Gargi Sengupta Prof. Jitendra K. Bera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6542-6551
Metal?metal singly‐bonded diruthenium complexes, bridged by naphthyridine‐functionalized N‐heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single‐pot reaction of [Ru2(CH3COO)2(CO)4] with 1‐benzyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (BIN ? HBr) or 1‐isopropyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (PIN ? HBr), TlBF4, and substituted benzaldehyde containing an electron‐withdrawing group. The modified NHC‐naphthyridine‐hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4‐diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p‐nitrobenzaldehyde). A similar complex [Ru2(CO)4(CH3COO)(3‐PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a , obtained by deprotonation of the hydroxy arm in 1 , is found to be active for the ADHC of alcohols and amines under base‐free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal–hydroxyl/hydroxide and metal–metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β‐hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation. 相似文献
95.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献
96.
Bera JK Schelter EJ Patra SK Bacsa J Dunbar KR 《Dalton transactions (Cambridge, England : 2003)》2006,(33):4011-4019
Fully and partially solvated triply-bonded [Re2]4+ complexes have been synthesized and their X-ray structures are described. A fully solvated dirhenium salt with BArf [tetrakis(3,5-bis(trifluoromethyl)phenyl)borate] as the counter anion [Re2(CH3CN)10][BArf]4 () has been characterized. The solubility of the complex in CH2Cl2 and THF in addition to CH3CN offers the possibility of improved reactivity. The structure of [Re2(micro-O)(CH3CN)10][BF4]4 () that possesses a linear [Re(III)-O-Re(III)]4+ unit is reported. Protonation reactions of cis-Re2Cl2(dppm)2(O2CCH3)2 and trans-Re2Cl4(dppm)2 with HBF4.Et2O in acetonitrile afforded cis and trans [Re2(dppm)2(CH3CN)6][BF4]4 ( and ), respectively. Prolonging the reaction time, however, does not lead to fully solvated complex [Re2(CH3CN)10][BF4]4. The neutral nitrogen donor ligands pynp (2-(2-pyridyl)-1,8-naphthyridine) and tznp (2-(2-thiazolyl)-1,8-naphthyridine) react readily with [Re2(CH3CN)10][BF4]4 to provide trans-[Re2(pynp)2(CH3CN)4][BF4]4 and trans-[Re2(tznp)2(CH3CN)4][BF4]4. The X-ray structures trans-[Re2(pynp)2(CH3CN)4][BF4]4 () and trans-[Re2(tznp)2(CH3CN)4][BF4]3[PF6] () have been determined. 相似文献
97.
(Ni0.25Cu0.20Zn0.55)LaxFe2−xO4 ferrite with x=0.00, 0.025, 0.050 and 0.075 compositions were synthesized through nitrate–citrate auto-combustion method. Crystalline spinel ferrite phase with about 16–19 nm crystallite size was present in the as-burnt ferrite powder. These powders were calcined, compacted and sintered at 950 °C for 4 h. Initial permeability, magnetic loss and AC resistivity of different compositions were measured in the frequency range from 10 Hz to 10 MHz. Saturation magnetization and hysteresis parameters were measured at room temperature with a maximum magnetic field of 10 kOe. Permeability and AC resistivity were found to increase and magnetic loss decreased with La substitution for Fe, up to x=0.025. Saturation magnetization and coercive field also increases up to that limit. The electromagnetic properties were found best in the ferrite composition of x=0.025, which would be better for more miniaturized multi layer chip inductor. 相似文献
98.
P. K. Sinha P. M. Satyasai R. Shankar R. Muthiah S. Bera S. V. Narasimhan A. N. Pandey A. Jaleel 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(2):341-348
An intermediate level liquid waste (ILLW or Category III waste) stream was treated for the removal of radioactive Cs in pilot
scale experiments, using three different ion exchange media. Results indicated that the polyacrylic fibre coated with cupric
ferric hexacyanoferrate (CuFeHCF-fibre composite) was the most efficient, followed by cupric hexacyanoferrate loaded ion exchange
resin (CuHCF-resin) and mixed zeolites (AR-1, 4A and 13X in the ratio 6:1:1). The mixed zeolites column and the CuFeHCF-fibre
column were used in series in order to get a high total decontamination factor (DF). Leaching studies on the CuFeHCF-fibre
composite loaded with137Cs, in demineralised (DM) water, tap water and ground water media indicated a release of about 19.3%, 25.5% and 41.3% of137Cs, respectively, in a period of about 8 months. XPS studies with CuFeHCF-fibre composite indicated some chemical interaction
between the CuFeHCF precipitate and the polyacrylic fibre. Some of the possible disposal options for the CuFeHCF-fibre composite
have also been discussed. 相似文献
99.
I. Bhattacharyya N. C. Bera A. K. Das 《International journal of quantum chemistry》2008,108(3):447-455
Stability, structural properties, and dissociation pathways of silylidyne‐amines FSiN, ClSiN, their isomers, and silylidyne‐phosphanes FSiP and ClSiP have been studied in detail using ab initio MP2, CCSD, and CCSD(T) and density functional B3LYP methods. After dissociation of FSiN, ClSiN, FSiP, and ClSiP, the fragmented atoms have been considered to be either in their ground state or in their metastable state in various dissociation channels. The dissociation energy for various dissociation pathways has been compared and interesting results have been obtained for the dissociation channels where the fragmented atoms are in their metastable states. The structure properties of these molecules agree well with the theoretical results wherever available. The NBO atomic charges of these molecules have been analyzed. The isomerization energy has been compared with existing theoretical data. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
100.
G.K. Paul R. Ghosh S.K. Bera S. Bandyopadhyay T. Sakurai K. Akimoto 《Chemical physics letters》2008,463(1-3):117-120
Deep levels in polycrystalline p-Cu2O/i-ZnO/n-ZnO/glass photovoltaic structures were studied by deep level transient spectroscopy (DLTS). Post-deposition crown-ether cyanide (CN) treatments of the samples were performed with the variation of time. DLTS spectra for all samples showed the presence of two traps localized at 0.2 eV and 0.5 eV from the top of the valence band. Effects of defect passivation and improvement of cell performance were demonstrated with the cyanide treated samples. Optimum time of cyanide treatment was found to be 3 min. Cell performance was increased from 0.4% to 0.7% for the samples undergoing the optimum post-deposition cyanide treatment. 相似文献