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51.
Evaluating the accuracy of theoretical one‐bond 13C─13C scalar couplings and their ability to predict structure in a natural product
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Jacob Powell Domenic Valenti Harley Bobnar Erika Drain Blaine Elliott Sydney Frank Tyler McCullough Sean Moore Andrew Kettring Robbie Iuliucci James K. Harper 《Magnetic resonance in chemistry : MRC》2017,55(11):979-989
This study explores the feasibility of using a combination of experimental and theoretical 1‐bond 13C─13C scalar couplings (1JCC) to establish structure in organic compounds, including unknowns. Historically, nJCC and nJCH studies have emphasized 2 and 3‐bond couplings, yet 1JCC couplings exhibit significantly larger variations. Moreover, recent improvements in experimental measurement and data processing methods have made 1JCC data more available. Herein, an approach is evaluated in which a collection of theoretical structures is created from a partial nuclear magnetic resonance structural characterization. Computed 1JCC values are compared to experimental data to identify candidates giving the best agreement. This process requires knowledge of the error in theoretical methods, thus the B3LYP, B3PW91, and PBE0 functionals are evaluated by comparing to 27 experimental values from INADEQUATE. Respective errors of ±1.2, ±3.8, and ±2.3 Hz are observed. An initial test of this methodology involves the natural product 5‐methylmellein. In this case, only a single candidate matches experimental data with high statistical confidence. This analysis establishes the intramolecular hydrogen‐bonding arrangement, ring heteroatom identity, and conformation at one position. This approach is then extended to hydroheptelidic acid, a natural product not fully characterized in prior studies. The experimental/theoretical approach proposed herein identifies a single best‐fit structure from among 26 candidates and establishes, for the first time, 1 configuration and 3 conformations to complete the characterization. These results suggest that accurate and complete structural characterizations of many moderately sized organic structures (<800 Da) may be possible using only 1JCC data. 相似文献
52.
Veronika Nagy Erika Turcsi Péter Molnár Zoltán Szabó József Deli 《Tetrahedron letters》2007,48(51):9012-9014
Latoxanthin was isolated as a minor carotenoid from the ripe fruits of yellow tomato shaped paprika (Capsicum annuum var. lycopersiciforme flavum) and identified as (all-E,3S,5R,6R,3′S,5′R,6′S)-5′,6′-epoxy-5,6,5′,6′-tetrahydro-β,β-carotene-3,5,6,3′-tetrol based on spectral data. 相似文献
53.
Erika Szunyogová Katarína Györyová Daniela Hudecová Lenka Piknová J. Chomič Zuzanna Vargová V. Zeleňák 《Journal of Thermal Analysis and Calorimetry》2007,88(1):219-223
The thermal decomposition of the complexes Zn(form)2⋅2phen
(I), Zn(ac)2⋅2phen
(II), Zn(prop)2⋅2phen
(III), Zn(but)2⋅2phen
(IV), where phen=phenazone, form=formiate,
ac=acetate, prop=propionate, but=butyrate has been studied in air by TG/DTG
and DTA methods. The possible mechanism of the thermal decomposition was proposed.
The final product of thermal decomposition was ZnO. IR data show unidentate
coordination of carboxylate group to Zn(II) ion. The complexes were tested
against various strains of microorganisms and their efficiency decrease in
the sequence yeasts >bacteria>filamentous fungi. 相似文献
54.
Erika G. Kisvarsanyi N.S. Sullivan 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,127(2):192-198
The theory of the formation of NMR multiple echoes for isotopic impurities (HD) in solid para-H2has been developed for the case of weak quantum tunneling of the impurities. The results show that even for low tunneling rates (100–1000 Hz), NMR multiple echoes can be observed for experimentally accessible nuclear spin polarizations and can be used to provide an independent test for the existence of tunneling in the solid hydrogens. 相似文献
55.
Ohne Zusammenfassung 相似文献
56.
A Hot‐Segment‐Based Approach for the Design of Cross‐Amyloid Interaction Surface Mimics as Inhibitors of Amyloid Self‐Assembly
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Dr. Erika Andreetto Dipl.‐Chem. Eleni Malideli Dr. Li‐Mei Yan Dipl.‐Ing. Michael Kracklauer MSc. Karine Farbiarz Dipl.‐Chem. Marianna Tatarek‐Nossol Prof. Dr. Gerhard Rammes M. Sc. Elke Prade Tatjana Neumüller Dr. Andrea Caporale M. Sc. Anna Spanopoulou B. Sc. Maria Bakou Prof. Dr. Bernd Reif Prof. Dr. Aphrodite Kapurniotu 《Angewandte Chemie (International ed. in English)》2015,54(44):13095-13100
The design of inhibitors of protein–protein interactions mediating amyloid self‐assembly is a major challenge mainly due to the dynamic nature of the involved structures and interfaces. Interactions of amyloidogenic polypeptides with other proteins are important modulators of self‐assembly. Here we present a hot‐segment‐linking approach to design a series of mimics of the IAPP cross‐amyloid interaction surface with Aβ (ISMs) as nanomolar inhibitors of amyloidogenesis and cytotoxicity of Aβ, IAPP, or both polypeptides. The nature of the linker determines ISM structure and inhibitory function including both potency and target selectivity. Importantly, ISMs effectively suppress both self‐ and cross‐seeded IAPP self‐assembly. Our results provide a novel class of highly potent peptide leads for targeting protein aggregation in Alzheimer’s disease, type 2 diabetes, or both diseases and a chemical approach to inhibit amyloid self‐assembly and pathogenic interactions of other proteins as well. 相似文献
57.
58.
Erika N. Daley Christopher M. Vogels Dr. Stephen J. Geier Dr. Andreas Decken Dr. Simon Doherty Prof. Dr. Stephen A. Westcott 《Angewandte Chemie (International ed. in English)》2015,54(7):2121-2125
The synthesis of phosphinoboronate esters containing a single P? B bond is reported, together with preliminary reactivity studies towards a range of organic substrates. These compounds add readily to aldehydes, ketones, aldimines, and α,β‐unsaturated enones to give primarily the corresponding 1,2‐addition products containing a new P? C bond. The first examples of transition‐metal‐catalyzed phosphinoborations of C‐C multiple bonds in which P? C and B? C bonds are formed in a single step are also disclosed; allenes react by a highly regioselective 1,2‐addition whereas terminal alkynes undergo a formal 1,1‐addition. 相似文献
59.
György Keglevich Alajos Grün Erika Bálint Nóra Zsuzsa Kiss Péter Bagi László Tőke 《Structural chemistry》2017,28(2):431-443
Application of the microwave (MW) technique offers many advantages in organophosphorus syntheses. Reluctant reactions may take place on MW irradiation. In most cases, MWs make the reactions more efficient in respect of rate, selectivity and yield. The benefits are shown via representative examples. MW irradiation may replace a catalyst, or simplify catalytic systems. The synthesis of catalysts incorporating heterocyclic P-ligands is also discussed. Where it was relevant, structural chemical details were also provided. 相似文献
60.