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511.
512.
Zhang S Féret A Lefebvre H Tessier M Fradet A 《Chemical communications (Cambridge, England)》2011,47(39):11092-11094
The polyetherification of diols with 4-12 methylene units was studied in Br?nsted Acid Ionic Liquids (BAILs). High molar mass poly(oxyalkylene)s were obtained at relatively low temperatures (130 °C), except in the cases of 1,4-butanediol and 1,6-hexanediol where cyclic ether formation was observed. 相似文献
513.
Regiospecific thermal C-acylation of imidazo [1,2-a] pyridines via an N-acylimidazolium intermediate
Saïd Chayer Martine Schmitt Valérie Collot Jean-Jacques Bourguignon 《Tetrahedron letters》1998,39(52):99-9688
Direct acylation of imidazo [1,2-a] pyridines in a sealed tube at 130°C and without catalyst gave various 3-acyl derivatives in satisfactory yields. 相似文献
514.
César A. Urbina-Blanco Safia Z. Jilani Isaiah R. Speight Michael J. Bojdys Tomislav Friščić J. Fraser Stoddart Toby L. Nelson James Mack Renã A. S. Robinson Emanuel A. Waddell Jodie L. Lutkenhaus Murrell Godfrey Martine I. Abboud Stephen O. Aderinto Damilola Aderohunmu Lučka Bibič João Borges Vy M. Dong Lori Ferrins Fun Man Fung Torsten John Felicia P. L. Lim Sarah L. Masters Dickson Mambwe Pall Thordarson Maria-Magdalena Titirici Gabriela D. Tormet-González Miriam M. Unterlass Austin Wadle Vivian W.-W. Yam Ying-Wei Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18462-18466
515.
Linda Chikh Xavier Arnaud Céline Guillermain Martine Tessier Alain Fradet 《Macromolecular Symposia》2003,199(1):209-222
Hyperbranched aliphatic polyesters of 2,2′-bis-(hydroxymethyl) propanoic acid and hyperbranched aliphatic polyamides obtained from new carboxy- and amino-functionalized caprolactams were studied by NMR spectroscopy and MALDI-TOF mass spectrometry. Ring-chain equilibria taking place through intramolecular hydroxy-ester, carboxy-amide or amine-amide interchanges and leading to the formation of cyclic branches or end-groups were found to exert a predominant influence on the molar mass of these hyperbranched polymers. A number of intra- or intermolecular side reactions, such as the formation of ethers in polyesters and the formation of anhydrides, imides, amidines and secondary amines in polyamides were also detected and resulted in polymer crosslinking on prolonged heating. The existence of such ring-chain equilibria and side-reactions make the control of hyperbranched polymer structure much more difficult than generally accepted. 相似文献
516.
517.
Nicolas Trcera Stphanie Rossano Martine Tarrida 《Journal of Raman spectroscopy : JRS》2011,42(4):765-772
The presence of magnesium in glasses of geological, medical, and technological interests influences their physicochemical and durability properties. However, the understanding of the role of magnesium is dependent on the combined knowledge of the structural environment of magnesium in the glass or melt and of the silicate network connectivity of the studied systems. In this article, we present a Raman spectroscopic study of the network connectivity of 10 ternary silicate glasses in the system Na2O MgO SiO2 and one Mg‐free binary silicate glass Na2O SiO2. Results obtained at constant polymerization suggest the existence of various Qn units according to the nature of the modifying cation. As polymerization decreases for Na2O MgO αSiO2 glasses (labeled as NMSα with α decreasing from 10 to 2), the band associated with Si O Si bending in fully polymerized region disappears being gradually replaced by a band attributed to Si O Si bending in region containing mainly Q2 and Q3 species. For highly polymerized glasses (NMS10‐NMS4), the coexistence of these two bands suggests the presence of two interconnected networks. Concomitantly, the signal associated with Q3 species first increases. For a further decrease of the polymerization, the high wavenumber part of the signal associated with Q3 species decreases, while the intensity of the high wavenumber part of the band related to Q2 species increases. This result strongly suggests that magnesium charge‐balances preferentially Q2 species rather than Q3 species. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
518.
The surface of polyurethane based catheter material or of silicon wafers as model surfaces were modified by spin coating of solutions of poly(ethylene oxide) or poly(vinyl alcohol) in water. For the incorporation of silver ions, silver nitrate was added to some of the solutions or the as-cast surfaces were dipped into AgNO3 solution. Furthermore, samples coated with a thin layer of metallic silver were prepared by deposition of silver vapor in vacuum. The as-prepared surfaces were studied by atomic force microscopy and X-ray photoelectron spectroscopy. During the spin coating of the solutions containing AgNO3, clusters of the silver component were formed. They were well dispersed in a poly(vinyl alcohol) matrix but act as nucleation agents in poly(ethylene oxide) where then large spherulites are formed. The surface compositions of coated samples and the depth profiling were carried out by angle dependent X-ray photoelectron spectroscopy. 相似文献
519.
The properties of a composite material are gouverned by the fibre, the matrix and the interface properties. However, in a test, used to determine a composite property, the influence of the interface is often muffled by other influences (fibre volume fraction, inhomogeneity, voids, defects,). To understand the relation between the composite performance and the fibre-matrix interface properties, it is necessary to work in several steps. In a first step, a thorough understanding of the fibre-matrix interface behaviour is needed. This not only involves the determination of the interface properties using micromechanical test methods, but also the fundamental study of the stresses at the interface and of the failure events occuring during the test. In this paper, the fragmentation, the pull-out and the micro-indentation test will be elaborated. The former test is used to explain the importance of an accurate data reduction model. In a second step, the influence of these interface properties on the composite performance is investigated. It is well known that an improved interface quality is beneficial for the transverse tensile and the interlaminar shear strength. However, a strong fibre-matrix interface is not favourable for all composite properties. This is illustrated by an overview of micromechanical models, developed to understand the macromechanical behaviour of composites. Three properties are addressed: the longitudinal tensile strength, the interlaminar fracture toughness, and the damage development in cross-ply laminates. 相似文献
520.