全文获取类型
收费全文 | 473篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 323篇 |
晶体学 | 4篇 |
力学 | 27篇 |
数学 | 37篇 |
物理学 | 91篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 19篇 |
2019年 | 14篇 |
2018年 | 8篇 |
2017年 | 19篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 19篇 |
2013年 | 40篇 |
2012年 | 34篇 |
2011年 | 44篇 |
2010年 | 16篇 |
2009年 | 19篇 |
2008年 | 26篇 |
2007年 | 29篇 |
2006年 | 14篇 |
2005年 | 18篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 2篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有482条查询结果,搜索用时 10 毫秒
101.
Daniel M. Walden Yogesh Bundey Aditya Jagarapu Victor Antontsev Kaushik Chakravarty Jyotika Varshney 《Molecules (Basel, Switzerland)》2021,26(1)
Amorphous solid dispersions (ASDs) have emerged as widespread formulations for drug delivery of poorly soluble active pharmaceutical ingredients (APIs). Predicting the API solubility with various carriers in the API–carrier mixture and the principal API–carrier non-bonding interactions are critical factors for rational drug development and formulation decisions. Experimental determination of these interactions, solubility, and dissolution mechanisms is time-consuming, costly, and reliant on trial and error. To that end, molecular modeling has been applied to simulate ASD properties and mechanisms. Quantum mechanical methods elucidate the strength of API–carrier non-bonding interactions, while molecular dynamics simulations model and predict ASD physical stability, solubility, and dissolution mechanisms. Statistical learning models have been recently applied to the prediction of a variety of drug formulation properties and show immense potential for continued application in the understanding and prediction of ASD solubility. Continued theoretical progress and computational applications will accelerate lead compound development before clinical trials. This article reviews in silico research for the rational formulation design of low-solubility drugs. Pertinent theoretical groundwork is presented, modeling applications and limitations are discussed, and the prospective clinical benefits of accelerated ASD formulation are envisioned. 相似文献
102.
Anirudh Pratap Singh Raman Pallavi Jain Ajay Kumar Jaya Tomar Neha Kaushik Eun Ha Choi Nagendra Kumar Kaushik Latifa Negadi Prashant Singh 《印度化学会志》2022,99(8):100570
In this work, DFT calculations for the designed eutectic mixtures (EMs) using oxoazolidine 2,4-dione (OZD) and zinc chloride (ZnCl2) are done. The interaction between the hydrogen bond donor and hydrogen bond acceptor at atomic level to get EMs are studied using DFT calculations. At room temperature, the stability of these various systems have been investigated using thermodynamic values or parameters such as enthalpy, free energy and others. DFT calculations is used to investigate the possibility of forming the systems (EMs). Further, the impact of varying the temperature on each system was also investigated (323K, 348K). Various other thermodynamic parameters are studied like dipole moment, hardness, chemical potential of the systems (individual molecules and EMs) at different temperatures. The results of the calculations showed that O1Z4 and O4Z1 have maximum dipole moment having values 8.1291, 9.8801 respectively, indicating maximum polarizability. Change in free energy for O1Z4 is least and was found to be ?37.2496 kcal/ mol. Further on changing the temperature, the parameters do not show much variation. Additionally, we have analyzed structure activity relationship (SAR) method to understand the physico-chemical properties of designed EMs and predict their regression and correlation to optimized energy. From the calculated values of pOE model, the value of r2 is 0.9995 confirms the validity of the equation obtained. The results of this study suggest a link between the structures that have been utilized to describe the intermolecular interaction between the hydrogen bond donor and acceptor, as well as the stability of the EMs. 相似文献
103.
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
104.
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
105.
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
106.
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
107.
108.
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
109.
110.
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