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101.
Pratik?K.?SenEmail author Purabi?R.?Samaddar Kaushik?Das 《Transition Metal Chemistry》2005,30(7):907-914
The kinetics of the oxidation of propan-1-ol and propan-2-ol by KMnO4 in HClO4 medium has been studied in absence and presence of Tween-20. In the absence of Tween-20 the reaction is of first order with
respect to each of permanganate and H+, but of complex order with respect to substrate. The active oxidant species HMnO4 reacts with the alkanol molecule to form an intermediate complex, which decomposes in the rate-determining step to form the
respective product and Mnv. In the presence of Tween-20, both the oxidant and the substrate are distributed between the aqueous phase and the micellar
pseudo-phase and then react. Different kinetic and thermodynamic parameters have been evaluated. Compensation between water
structure destruction and substrate–micelle interaction plays an important role in the presence of the surfactant. 相似文献
102.
Acrylonitrile/pentyl acrylate (A/P) copolymers of different monomer composition were prepared by solution polymerization using benzoyl peroxide as initiator. Copolymer compositions were determined by elemental analysis and quantitative 13C1H‐NMR spectroscopy. The comonomer reactivity ratios, determined by both Kelen Tudos (KT) and nonlinear error in variables (EVM) methods are rA = 0.75 and rp = 0.45. 2‐D heteronuclear correlation spectroscopy (HSQC) was used to simplify the complex 1H spectra of A/P copolymers in terms of configurational and compositional sequences. The microstructure was obtained in terms of the distribution of A‐ and P‐ centered triad sequences from 13C1H‐NMR spectra of the copolymers. The copolymerization mechanism was found to follow a first order Markov Model. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 533–543, 1999 相似文献
103.
Summary Ionic chelate complexes of the type, [(5-R)2ML][dtz] [R=cyclopentadienyl (Cp) or indenyl (C9H7); M=TiIV, ZrIV or HfIV; HL=oxine; dtz=phenyldithiocarbazate (PhNHNHCS2)] have been synthesised and characterised. Conductance measurements indicate that the complexes are 11 electrolytes. From i.r. and u.v. spectral studies we conclude that the oxinato-group is chelating. Consequently there is tetrahedral coordination around the metal ion.1H and13C N.m.r. studies are consistent with the stoichiometries. X-ray powder diffraction studies have been made for [(5-Cp)2ZrL][dtz]. For [(5-Cp)2TiL][dtz] and [(5-Cp)2ZrL][dtz] thermal (t.g. and d.t.a.) and mass spectral studies have been carried out. 相似文献
104.
Polymer‐supported palladium was synthesized by applying a single‐step wet chemical synthesis route and the resultant composite material was characterized by means of various techniques. Infrared and UV–visible spectra provided information on the chemical structure of the polymer. Microscopy techniques showed the general morphology of the polymer. The oxidation state of palladium was determined using the X‐ray photoelectron spectroscopy method. The synthesized material was applied as a heterogeneous catalyst for the Heck coupling reaction and also as an electrocatalyst for the oxidation of cysteine. 相似文献
105.
106.
Sirish Kaushik Lakkaraju Justin A. Lemkul Jing Huang Alexander D. MacKerell Jr. 《Journal of computational chemistry》2016,37(4):416-425
The conformational dynamics of a macromolecule can be modulated by a number of factors, including changes in environment, ligand binding, and interactions with other macromolecules, among others. We present a method that quantifies the differences in macromolecular conformational dynamics and automatically extracts the structural features responsible for these changes. Given a set of molecular dynamics (MD) simulations of a macromolecule, the norms of the differences in covariance matrices are calculated for each pair of trajectories. A matrix of these norms thus quantifies the differences in conformational dynamics across the set of simulations. For each pair of trajectories, covariance difference matrices are parsed to extract structural elements that undergo changes in conformational properties. As a demonstration of its applicability to biomacromolecular systems, the method, referred to as DIRECT‐ID, was used to identify relevant ligand‐modulated structural variations in the β2‐adrenergic (β2AR) G‐protein coupled receptor. Micro‐second MD simulations of the β2AR in an explicit lipid bilayer were run in the apo state and complexed with the ligands: BI‐167107 (agonist), epinephrine (agonist), salbutamol (long‐acting partial agonist), or carazolol (inverse agonist). Each ligand modulated the conformational dynamics of β2AR differently and DIRECT‐ID analysis of the inverse‐agonist vs. agonist‐modulated β2AR identified residues known through previous studies to selectively propagate deactivation/activation information, along with some previously unidentified ligand‐specific microswitches across the GPCR. This study demonstrates the utility of DIRECT‐ID to rapidly extract functionally relevant conformational dynamics information from extended MD simulations of large and complex macromolecular systems. © 2015 Wiley Periodicals, Inc. 相似文献
107.
108.
Mishra AK Manav N Kaushik NK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3097-3101
Some new organotin(IV) complexes with salicylaldehyde aniline-N-thiohydrazone (L1) and cinamaldehyde aniline-N-thiohydrazone (L2) of the type (p-ClC6H4)3Sn[L] Cl and (p-ClC6H4)2Sn[L]Cl2 have been synthesized (where L = L1 and L2). The complexes and ligands were characterized by elemental analysis and spectral (UV-vis, IR and 1H NMR) studies. In all the complexes, ligands act as bidentate, coordination through sulphur and azomethane nitrogen. Complexes are 1:1 metal ligands complexes. Antifungal studies of some complexes against Rhizoctonia bataticola fungal strain have been carried out. 相似文献
109.
Xin-Cindy Wang Thomas Blesgen Kaushik Bhattacharya Michael Ortiz 《Archive for Rational Mechanics and Analysis》2016,221(2):1035-1075
We reformulate the Kohn–Sham density functional theory (KSDFT) as a nested variational problem in the one-particle density operator, the electrostatic potential and a field dual to the electron density. The corresponding functional is linear in the density operator and thus amenable to spectral representation. Based on this reformulation, we introduce a new approximation scheme, termed spectral binning, which does not require smoothing of the occupancy function and thus applies at arbitrarily low temperatures. We prove convergence of the approximate solutions with respect to spectral binning and with respect to an additional spatial discretization of the domain. 相似文献
110.
Prabal Bandyopadhyay Sumit K. Agrawal Manisha Sathe Pratibha Sharma M.P. Kaushik 《Tetrahedron》2012,68(20):3822-3827
N-Bromo succinimide (NBS) was found to be an efficient and regioselective reagent in combination with AIBN for an unprecedented, facile and rapid one-step synthesis of 8-substituted xanthine derivatives at room temperature. The inexpensive, nontoxic and readily available NBS efficiently promoted the condensation of several aryl/cycloaryl/heteroaryl aldehydes with 5,6-diamino-1,3-dimethyluracils in presence of catalytic amount of AIBN in a single step via radical chain reaction. The notable advantages of this protocol were short reaction time, milder reaction conditions, simple work-up procedure, no requirement for chromatographic separation, use of non-hazardous reagent/solvent and applicable to a variety of substrates. 相似文献