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51.
Brian E. Broderick Wim P. Cofino Rita Cornelis Kaj Heydorn William Horwitz David T. E. Hunt Robert C. Hutton Howard M. Kingston Herbert Muntau Renato Baudo Daria Rossi Jacobus G. van Raaphorst Tjip T. Lub Peter Schramel Frank T. Smyth David E. Wells Allan G. Kelly 《Mikrochimica acta》1991,104(1-6):523-542
The Euroanalysis VII conference in Vienna included a two-day session: Quality Assurance in Analytical Chemistry. The contributions comprised 15 lectures devoted to: intra-laboratory quality measures, inter-laboratory control, formal aspects and accreditation and implementation. The paper presents an overview of the main items developed by the contributors.A survey on the session on Quality Assurance in Analytical Chemistry of Euroanalysis VIIThe authors thank the organizers of EUROANALYSIS VII and in particular Dr. B. Griepink and Dr. E. Maier of the Community Bureau of Reference (BCR) of the CEC for their support and considerable contributions. 相似文献
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Skarpos H Vorob'eva DV Osipov SN Odinets IL Breuer E Röschenthaler GV 《Organic & biomolecular chemistry》2006,4(19):3669-3674
Convenient routes to methyl 2-oxalylimino- and 2-(phosphonoformimido)-3,3,3-trifluoropropanoates have been elaborated, based on the reaction of methyl trifluoropyruvate with ethyl oxamate or diethyl carbamoylphosphonate, respectively, followed by dehydration. The compounds obtained are useful synthetic intermediates toward a variety of novel 3,3,3-trifluoroalanine derivatives that are potential drug candidates. 相似文献
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Andreeva DV Ip B Gurinov AA Tolstoy PM Denisov GS Shenderovich IG Limbach HH 《The journal of physical chemistry. A》2006,110(37):10872-10879
The ability of strongly sterically hindered pyridines to form hydrogen bonded complexes was inspected using low-temperature 1H and 15N NMR spectroscopy in a liquefied Freon mixture. The proton acceptors were 2,6-di(tert-butyl)-4-methyl- and 2,6-di(tert-butyl)-4-diethylaminopyridine; the proton donors were hydrogen tetrafluoroborate, hydrogen chloride, and hydrogen fluoride. The presence of the tert-butyl groups in the ortho positions dramatically perturbed the geometry of the forming hydrogen bonds. As revealed by experiment, the studied crowded pyridines could form hydrogen bonded complexes with proton donors exclusively through their protonation. Even the strongest small proton acceptor, anion F-, could not be received by the protonated base. Instead, the simplest hydrogen bonded complex involved the [FHF]- anion. This complex was characterized by the shortest possible N...F distance of about 2.8 A. Because the ortho tert-butyl groups did not prevent the hydrogen bond interaction between the protonated center and the anion completely, an increase of the pyridine basicity caused a further shortening of the N-H distance and a weakening of the hydrogen bond to the counterion. 相似文献
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Treatment of α-imino esters derived from glycine esters and benzophenone or benzaldehydes with potassium tert butoxide in DMSO gave persistent solutions of carbanions at 20?°C. The kinetics of their reactions with quinone methides and benzylidene malonates (reference electrophiles) have been followed photometrically under pseudo-first order conditions. The reactions followed second-order rate laws. Since addition of 18-crown-6 ether did not affect the reaction rates, the measured rate constants correspond to the reactions of the non-paired carbanions. Plots of the second-order rate constants against the electrophilicity parameters E of the electrophiles are linear, which allowed us to derive the nucleophile-specific parameters N and sN, according to the linear Gibbs energy relationship lg k2(20?°C)?=?sN(N + E). The Ph2C?=?N- and PhCH?=?N- groups act as very weak electron acceptors with the consequence that Ph2C?=?N-CH–-CO2R and PhCH?=?N-CH–-CO2R have a similar nucleophilicity as Ph-CH–-CO2Et, the anion of ethyl phenylacetate. 相似文献
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Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smithsonites from different origins. An intense sharp band at 1092 cm−1 is assigned to the CO32− symmetric stretching vibration. Impurities of hydrozincite are identified by a band around 1060 cm−1. An additional band at 1088 cm−1 which is observed in the 298 K spectra but not in the 77 K spectra is attributed to a CO32− hot band. Raman spectra of smithsonite show a single band in the 1405–1409 cm−1 range assigned to the ν3 (CO3)2− antisymmetric stretching mode. The observation of additional bands for the ν3g modes for some smithsonites is significant in that it shows distortion of the ZnO6 octahedron. No ν2 bending modes are observed for smithsonite. A single band at 730 cm−1 is assigned to the ν4 in phase bending mode. Multiple bands be attributed to the structural distortion are observed for the carbonate ν4 in phase bending modes in the Raman spectrum of hydrozincite with bands at 733, 707 and 636 cm−1. An intense band at 304 cm−1 is attributed to the ZnO symmetric stretching vibration. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Raluca Borlan Daria Stoia Luiza Gaina Andreea Campu Gabriel Marc Maria Perde-Schrepler Mihaela Silion Dana Maniu Monica Focsan Simion Astilean 《Molecules (Basel, Switzerland)》2021,26(15)
In recent times, researchers have aimed for new strategies to combat cancer by the implementation of nanotechnologies in biomedical applications. This work focuses on developing protein-based nanoparticles loaded with a newly synthesized NIR emitting and absorbing phthalocyanine dye, with photodynamic and photothermal properties. More precisely, we synthesized highly reproducible bovine serum albumin-based nanoparticles (75% particle yield) through a two-step protocol and successfully encapsulated the NIR active photosensitizer agent, achieving a good loading efficiency of 91%. Making use of molecular docking simulations, we confirm that the NIR photosensitizer is well protected within the nanoparticles, docked in site I of the albumin molecule. Encouraging results were obtained for our nanoparticles towards biomedical use, thanks to their negatively charged surface (−13.6 ± 0.5 mV) and hydrodynamic diameter (25.06 ± 0.62 nm), favorable for benefitting from the enhanced permeability and retention effect; moreover, the MTT viability assay upholds the good biocompatibility of our NIR active nanoparticles. Finally, upon irradiation with an NIR 785 nm laser, the dual phototherapeutic effect of our NIR fluorescent nanoparticles was highlighted by their excellent light-to-heat conversion performance (photothermal conversion efficiency 20%) and good photothermal and size stability, supporting their further implementation as fluorescent therapeutic agents in biomedical applications. 相似文献
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Laser-induced breakdown spectroscopy (LIBS) was applied to the preliminary examination of Polish documents – passports and identity cards – for forensic purposes. Several security features of potentially high discrimination capability were selected at both the passports (Alphagram, serial number, the contour map of Europe, and emblem) and identity cards (kinegram, the date of birth, and emblem). Different elemental compositions were identified after comparing the spectra recorded from various measurement locations. It was possible to identify characteristic atomic emission from several elements (such as Ti, Ca, K, Fe, Cr, Mg, Na, La, Cd, Li, V, Al, Mn, Ni, and Cu) based on the type of document, issue date, and evaluated area. In the case of passports, the potentially good discriminators with unique elemental composition were identified, e.g., the serial number and the contour map of Europe printed with the use of intaglio printing technique. Identity cards with the cover of polycarbonate foil constitute a very difficult sample to analyze because of the foil’s influence on the laser ablation phenomenon. This study presents the potential of LIBS as an effective and useful technique to analyze Polish passports for forensic purposes. Its many advantages provide a good alternative to the analytical methods routinely used for the examination of these objects. 相似文献