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91.
92.
Anastasia D. Zubenko Bayirta V. Egorova Stepan N. Kalmykov Nikolai E. Shepel Valentina A. Karnoukhova Ivan V. Fedyanin Yuri V. Fedorov Olga A. Fedorova 《Tetrahedron》2019,75(19):2848-2859
A new series of macrocyclic diamides with carboxyl, pyridyl and picolinate pendant arms have been synthesized and the stability constants of their complexes with Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ in water were determined. Complexes with a stoichiometry of 1 : 1 (M: L) were found for all ligands with the exception of 15-membered crown ethers with one pendant carboxyl or pyridine group. The ligand containing two picolinate backbone groups exhibits the highest values of the stability constants for all studied cations (logβML?=?12.5–15.7). X-ray study of free ligands showed that the introduction of benzene and amide fragments into the macrocyclic moiety provides a flatten open structure of the ligand. The crystallographic analysis of Cu2+ and Zn2+ complexes revealed the external coordination of the metal atom by amine N atoms of the macrocycle and heteroatoms of the pendant groups. 相似文献
93.
Characterizing Polyoxovanadate-Alkoxide Clusters Using Vanadium K-Edge X-Ray Absorption Spectroscopy
Rachel L. Meyer Samuel M. Greer Anastasia V. Blake Samantha K. Cary Alexander S. Ditter Scott R. Daly Feng Li Stosh A. Kozimor Ellen M. Matson Veronika Mocko Gerald T. Seidler Benjamin W. Stein Samuel D. Weinstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1592-1597
A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron-functionalized and hexavanadium polyoxovanadate-alkoxide clusters, which we characterized here using V K-edge X-ray absorption spectroscopy. Substantial changes in the pre-edge peak intensities were observed that tracked with the V 3d-electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the FeIII cations were electronically isolated from the polyoxovanadate core. 相似文献
94.
The present paper reports on the study of the dephosphorylation of pyridoxal 5′-phosphate and four derived hydrazones (containing the residues of pyrazine, 2-furan, 2-thiophene, 3-pyridine carboxylic acids) induced by bovine alkaline phosphatase from intestinal mucosa at 298.2 K and pH 10 (0.05 m Tris–HCl buffer). We observed and discussed characteristic changes in the UV–vis and fluorescent spectra of substrates. Michaelis–Menten parameters of the enzymatic dephosphorylation are calculated. The stability of alkaline phosphatase in the presence of hydrazones is confirmed. The dephosphorylation of the Zn(II) complex with pyridoxal 5′-phosphate-derived hydrazone is analyzed. 相似文献
95.
The HIV-1 nucleocapsid protein (NC) is a desirable target in antiretroviral therapy due to its high conservation among HIV-1 strains, and to its multiple and crucial roles in the HIV-1 replication cycle. Natural products represent a valuable source of NC inhibitors, with the catechol group being a privileged scaffold in NC inhibition. By coupling molecular modeling with NMR spectroscopy and fluorescence-based assays, we disclosed lithospermic acid, a catechol derivative extracted from Salvia miltiorrhizza, as a potent and chemically stable non-covalent inhibitor of the NC. Being different from other catechol derivative reported so far, lithospermic acid does not undergo spontaneous oxidation in physiological conditions, thus becoming a profitable starting point for the development of efficient NC inhibitors. 相似文献
96.
Viktor A. Dmitriev Mariia M. Efremova Alexander S. Novikov Vladimir V. Zarubaev Alexander V. Slita Anastasia V. Galochkina Galina L. Starova Andrey V. Ivanov Alexander P. Molchanov 《Tetrahedron letters》2018,59(24):2327-2331
The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities. 相似文献
97.
Alexander A. Voronov Kseniia A. Alekseeva Elena A. Ryzhkova Vladimir V. Zarubaev Anastasia V. Galochkina Vladimir P. Zaytsev Mahesh S. Majik Santosh G. Tilve Atash V. Gurbanov Fedor I. Zubkov 《Tetrahedron letters》2018,59(12):1108-1111
The reaction between readily accessible N-aryl-3-phenylallylamines and maleic anhydride led to unexpected products – polysubstituted hydrogenated benzo[f]isoindole-4-carboxylic acids. This transformation proceeds through a previously unknown sequence of steps: N-acylation of the allylamine with maleic anhydride, intramolecular Diels-Alder reaction of the vinylarene in the intermediate N-maleamide, and Alder-ene reaction of the products of the previous two steps. Selected benzo[f]isoindoles displayed antiviral activity. 相似文献
98.
Egorin Andrei Sokolnitskaya Tatiana Azarova Yuliya Portnyagin Arseniy Balanov Mikhail Misko Darya Shelestyuk Evgeny Kalashnikova Anastasia Tokar Eduard Tananaev Ivan Avramenko Valentin 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):243-251
Sorption of micro- and microamounts of Sr from seawater has been studied using granulated Na-birnessite. Distribution coefficients of 90Sr in the natural seawater are 0.8–1.2?×?103 ml g?1, in the model seawater they are 1.6–1.8?×?103 ml g?1. Application of Na-birnessite was shown to be prospective in sorption–desorption–regeneration regime. In dynamic sorption conditions, over 150 bed volumes of seawater can be purified till 5% breakthrough occurs at feed rate 10 BV h?1. Na-birnessite can be used for 90Sr radionuclide removal from liquid radioactive wastes containing seawater.
相似文献99.
[reaction: see text] Two new and very efficient procedures (Procedures A and B) are reported for the Pd-catalyzed cross coupling of aryl electrophiles with terminal alkynes via their in situ conversion into alkynylzinc derivatives. Procedure A is particularly valuable in cases where electron-deficient alkynes are used, while Procedure B is operationally simple and very satisfactory in less demanding cases. 相似文献
100.
Vidal-Madjara C Cañada-Cañada F Jaulmes A Pantazaki A Taverna M 《Journal of chromatography. A》2005,1087(1-2):95-103
A numerical simulation of the direct zonal liquid chromatographic method is described for studying the binding of a ligand to a macromolecule by quantification of the interacting species present in a sample at equilibrium. The algorithm accounts for both the kinetic exchanges in solution and the dispersion effects depicted by the Fick law. Dimensionless variables are used for the concentrations which are expressed as a function of the equilibrium constant, KD. The free ligand concentration was varied in the injected samples from 0.1 to 20 KD, while that of the macromolecule was kept constant. An apparent binding isotherm was obtained from the total ligand chromatogram generated by the simulation run, when the amount emerging at almost column dead volume is plotted against that eluting at the free ligand retention time. As a continuous dissociation of the complex may occur during its migration, the apparent binding curve and the theoretical binding isotherm coincide at extremely low dissociating rates. At larger dissociation rates (0.001 s(-1) < kd <0.1 s(-1), for a first peak eluting in 1 min) the simulations were used to test various chromatographic conditions. The flow rate (or column volume) is the major effect which influences the on-column dissociation process as an exponential decay was found when the apparently bound fraction is plotted against the analysis time. The apparent equilibrium coefficient is close to the theoretical one for a binding curve generated with an initial solution containing a relatively low total concentration of binding sites (< or = KD). The apparent stoichiometric term is largely underestimated as its value decreases exponentially at increasing dissociation rates. An extrapolation at extremely short analysis times could be used to determine the stoichiometric coefficient characterizing the binding interaction. 相似文献