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排序方式: 共有621条查询结果,搜索用时 15 毫秒
71.
Vanessa A. Béland Zhiqiang Wang Tsun-Kong Sham Paul J. Ragogna 《Journal of polymer science. Part A, Polymer chemistry》2022,60(16):2508-2517
In this work, we show that polymer networks composed of tertiary alkyl phosphines can be cleanly functionalized with phosphino-phosphonium or triphosphenium cations. Methods for functionalizing the polymers range from halide abstraction of commercially available reagents, to ligand exchange from simple to make reported compounds, and finally, macromolecular ligand design guided by observations made at the molecular level to accommodate the formation of kinetically favored triphosphenium cation functionalized networks. The synthesis, comprehensive characterization, and comparison of the new polymers to molecular analogues is outlined. It is shown the addition of the low valent phosphorus centers to the polymer network has the effect of tuning material physical properties. 相似文献
72.
Vanessa C. Lussini Dr. James P. Blinco Dr. Kathryn E. Fairfull‐Smith Prof. Steven E. Bottle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18258-18268
Novel profluorescent mono‐ and bis‐isoindoline nitroxides linked to napthalimide and perylene diimide structural cores are described. These nitroxide‐fluorophore probes display strongly suppressed fluorescence in comparison to their corresponding non‐radical diamagnetic methoxyamine derivatives. The perylene‐based probe possessing two isoindoline systems tethered through ethynyl linkages was shown to be the most photostable in solution, demonstrating significantly enhanced longevity over the 9,10‐bis(phenylethynyl)anthracene fluorophore used in previous profluorescent nitroxide probes. 相似文献
73.
Brian N. Figgis Alexandre N. Sobolev Edward S. Kucharski Vanessa Broughton 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):e228-e229
The crystal structure of tripotassium sodium hexachloroferrate(II) has been determined by X‐ray diffraction at 293, 84 and 9.5 K. The accurate and extensive data sets collected should be suitable for charge–density analysis studies. 相似文献
74.
Jasquer A. Sehnem Priscila Milani Vanessa Nascimento Leandro H. Andrade Luciano Dorneles Antonio L. Braga 《Tetrahedron: Asymmetry》2010,21(8):997-1003
N-Trifluoracyl β-chalcogeno amides and N-perfluoracyl β-thio amide ligands were prepared by a simple and efficient reaction sequence. These new ligands were evaluated in palladium-catalyzed alkylation of rac-(E)-1,3-diphenyl-2-propenyl acetate in the presence of dimethyl malonate and an enantioselectivity of up to 99% was obtained. After catalysis, the fluorous ligand can be easily recovered by liquid–liquid extraction and reused without loss in the activity. 相似文献
75.
Dialkyl phosphates determination by gas chromatography: Evaluation of a microwave‐assisted derivatization† 下载免费PDF全文
Alessandra Cristina Pupin Silvrio Simone Caetani Machado Vanessa Bergamin Boralli Isarita Martins 《Journal of separation science》2015,38(15):2664-2669
Dialkyl phosphates are organophosphate insecticide metabolites and their urinary analysis is useful for assessing human exposure to these compounds. This study presents a sample preparation method with microwave‐assisted derivatization for two dialkyl phosphates to make the process faster before gas chromatographic analysis. The optimized conditions for derivatization procedure were: 250 μL of 2,3,4,5,6‐pentafluorobenzyl bromide 3% in acetonitrile for derivative; microwave for 5 min with intensity of 160 W. The electron ionization mass spectrometric analysis was performed using a gas chromatography with mass spectrometry QP‐2010 from the Shimadzu® equipped with RTx®‐5MS capillary column. Ions were monitored at selected‐ion monitoring mode at m/z 350 for diethyl thiophosphate and m/z 366 for diethyl dithiophosphate. The developed method was linear for both metabolites. The intra‐assay precision was the values ranged between 1.1 and 9.1%, for diethyl thiophosphate, and between 4.06 and 6.9%, for diethyl dithiophosphate. The interassay precision showed relative standard deviation between 10.3 and 15.1%, for diethyl thiophosphate and between 4.9 and 11.9%, for diethyl dithiophosphate. The results obtained suggests that derivatization assisted by microwave, before gas chromatography with mass spectrometry analysis, can be applied to monitoring of exposure to organophosphates once is fast, sensible, and precise method to determinate dialkyl phosphates. 相似文献
76.
77.
Collins KE Collins CH Maroneze CM Cappovila V Custodio R 《Langmuir : the ACS journal of surfaces and colloids》2011,27(1):187-195
Nitrogen adsorption isotherms of silicas and other oxidic materials are distorted by the presence of micropore adsorption and capillary condensation. This distortion affects the determination of the specific area of the material, depending on the chosen calculation procedure. Correction of the initial (total) isotherm for micropore capacity decreases or eliminates this source of error to give a useful estimate of the external surface area. In the present work, 26 silica-based adsorbent materials were studied to obtain total and external specific surface areas by the Brunauer-Emmett-Teller (BET), I-point, and α-plot procedures, using the micropore capacities from the α-plots to obtain the corrected (external) isotherms. Errors in the specific surface areas due to the presence of micropores are given by the equation ΔsA = 3.267 (m(2)/cm(3) STP) sV(mic), where sA is the specific surface area in m(2)/g and sV(mic) is the micropore capacity in cm(3) STP/g. A consistent set of conversion factors was obtained by which the external specific surface area obtained using one of these procedures can be converted, with part-per-thousand precision, to either of the others. Although the I-point procedure presents the advantage of not requiring a defined p/p(0) range, the α-plot procedure is recommended for routine determinations of external specific areas of silicas and other oxidic materials, except for cases in which the shapes of the adsorption isotherms of the sample and the reference differ significantly from one another in the p/p(0) range used for the determination. 相似文献
78.
Molecular photonics is a rapidly developing and multi-disciplinary field of research involving the construction of molecular assemblies comprising photoactive building blocks that are responsive to a light stimulus. A salient challenge in this field is the controlled assembly of these building blocks with nanoscale precision. DNA exhibits considerable promise as an architecture for the templated assembly of photoactive materials. In this Concept Article we describe the progress that has been made in the area of DNA photonics, in which DNA acts as a platform for the construction of optoelectronic assemblies, thin films and devices. 相似文献
79.
Amundson LM Owen BC Gallardo VA Habicht SC Fu M Shea RC Mossman AB Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2011,22(4):670-682
Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS
n
) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant
protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer.
Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation
patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers
was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction
products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some
of the reactions were examined by H/D exchange reactions and molecular orbital calculations. 相似文献
80.
Paulovich FV Maki RM de Oliveira MC Colhone MC Santos FR Migliaccio V Ciancaglini P Perez KR Stabeli RG Perinoto AC Oliveira ON Zucolotto V 《Analytical and bioanalytical chemistry》2011,400(4):1153-1159
Recent advances in the control of molecular engineering architectures have allowed unprecedented ability of molecular recognition in biosensing, with a promising impact for clinical diagnosis and environment control. The availability of large amounts of data from electrical, optical, or electrochemical measurements requires, however, sophisticated data treatment in order to optimize sensing performance. In this study, we show how an information visualization system based on projections, referred to as Projection Explorer (PEx), can be used to achieve high performance for biosensors made with nanostructured films containing immobilized antigens. As a proof of concept, various visualizations were obtained with impedance spectroscopy data from an array of sensors whose electrical response could be specific toward a given antibody (analyte) owing to molecular recognition processes. In addition to discussing the distinct methods for projection and normalization of the data, we demonstrate that an excellent distinction can be made between real samples tested positive for Chagas disease and Leishmaniasis, which could not be achieved with conventional statistical methods. Such high performance probably arose from the possibility of treating the data in the whole frequency range. Through a systematic analysis, it was inferred that Sammon's mapping with standardization to normalize the data gives the best results, where distinction could be made of blood serum samples containing 10(-7) mg/mL of the antibody. The method inherent in PEx and the procedures for analyzing the impedance data are entirely generic and can be extended to optimize any type of sensor or biosensor. 相似文献