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11.
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Evaluating the accuracy of theoretical one‐bond 13C─13C scalar couplings and their ability to predict structure in a natural product 下载免费PDF全文
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
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Harley Cohen 《Meccanica》1996,31(5):527-546
A number of simple solutions are obtained which are universal for an homogeneous monotropic elastic rod whose theory is based on a Cosserat-type model.
Sommario Si ottengono alcune soluzioni semplici che sono universali per una trave omogenea monotropica la cui teoria è basata su un modello alla Cosserat.相似文献
15.
Delong CM Au WW Lemonds DW Harley HE Roitblat HL 《The Journal of the Acoustical Society of America》2006,119(3):1867-1879
The focus of this study was to investigate how dolphins use acoustic features in returning echolocation signals to discriminate among objects. An echolocating dolphin performed a match-to-sample task with objects that varied in size, shape, material, and texture. After the task was completed, the features of the object echoes were measured (e.g., target strength, peak frequency). The dolphin's error patterns were examined in conjunction with the between-object variation in acoustic features to identify the acoustic features that the dolphin used to discriminate among the objects. The present study explored two hypotheses regarding the way dolphins use acoustic information in echoes: (1) use of a single feature, or (2) use of a linear combination of multiple features. The results suggested that dolphins do not use a single feature across all object sets or a linear combination of six echo features. Five features appeared to be important to the dolphin on four or more sets: the echo spectrum shape, the pattern of changes in target strength and number of highlights as a function of object orientation, and peak and center frequency. These data suggest that dolphins use multiple features and integrate information across echoes from a range of object orientations. 相似文献
16.
C. Harley 《Applied mathematics and computation》2010,217(8):4065-4075
Numerical solutions to the Frank-Kamenetskii partial differential equation modelling a thermal explosion in a cylindrical vessel are obtained using the hopscotch scheme. We observe that a nonlinear source term in the equation leads to numerical difficulty and hence adjust the scheme to accommodate such a term. Numerical solutions obtained via MATLAB, MATHEMATICA and the Crank-Nicolson implicit scheme are employed as a means of comparison. To gain insight into the accuracy of the hopscotch scheme the solution is compared to a power series solution obtained via the Lie group method. The numerical solution is also observed to converge to a well-known steady state solution. A linear stability analysis is performed to validate the stability of the results obtained. 相似文献
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Alexander Ovchinnikov Dr. Matej Bobnar Dr. Yurii Prots Dr. Horst Borrmann Dr. Jörg Sichelschmidt Prof. Yuri Grin Dr. Peter Höhn 《Angewandte Chemie (International ed. in English)》2018,57(36):11579-11583
Two new calcium nitridomanganates, Ca12[Mn19N23] (P3, a=11.81341(3) Å, c=5.58975(2) Å, Z=1) and Ca133[Mn216N260] ( , a=39.477(1) Å, c=5.5974(2) Å, Z=1), were obtained by a gas–solid reaction of Ca3N2 and Mn with N2 at 1273 K and 1223 K, respectively. The crystal structure of Ca12[Mn19N23] was determined from high‐resolution X‐ray synchrotron powder diffraction data, whereas single‐crystal X‐ray diffraction was employed to establish the crystal structure of the Ca133[Mn216N260] phase, which classifies as a complex metallic alloy (CMA). Both crystal structures have 2D nitridomanganate layers containing similar building blocks but of different levels of structural complexity. Bonding analysis as well as magnetic susceptibility and electron spin resonance measurements revealed that only a fraction of the Mn atoms in both structures carries a localized magnetic moment, while for most Mn species the magnetism is quenched as a result of metal–metal bond formation. 相似文献
19.
Dr. Nahyun Kwon Gabriel O. Jasinevicius Dr. Giulia Kassab Lili Ding Jiachuan Bu Letícia P. Martinelli Dr. Vinicius G. Ferreira Alexander Dhaliwal Dr. Harley H. L. Chan Yulin Mo Dr. Vanderlei S. Bagnato Prof. Dr. Cristina Kurachi Dr. Juan Chen Prof. Dr. Gang Zheng Prof. Dr. Hilde H. Buzzá 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305564
Indocyanine green (ICG) is the only near-infrared (NIR) dye approved for clinical use. Despite its versatility in photonic applications and potential for photothermal therapy, its photobleaching hinders its application. Here we discovered a nanostructure of dimeric ICG (Nano-dICG) generated by using ICG to stabilize nanoemulsions, after which ICG enabled complete dimerization on the nanoemulsion shell, followed by J-aggregation of ICG-dimer, resulting in a narrow, red-shifted (780 nm→894 nm) and intense (≈2-fold) absorbance. Compared to ICG, Nano-dICG demonstrated superior photothermal conversion (2-fold higher), significantly reduced photodegradation (−9.6 % vs. −46.3 %), and undiminished photothermal effect (7 vs. 2 cycles) under repeated irradiations, in addition to excellent colloidal and structural stabilities. Following intravenous injection, Nano-dICG enabled real-time tracking of its delivery to mouse tumors within 24 h by photoacoustic imaging at NIR wavelength (890 nm) distinct from the endogenous signal to guide effective photothermal therapy. The unprecedented finding of nanostructure-driven ICG dimerization leads to an ultra-stable phototheranostic platform. 相似文献
20.
Renan Borsoi Campos Fernando Wypych Harley Paiva Martins Filho 《International journal of quantum chemistry》2009,109(3):594-604
Calculations at AM1, PM3, and HF/6‐31G levels of part of the IR spectrum of the water–kaolinite intercalated system based on a 96‐atom cluster of kaolinite with one water molecule are reported. Only the water molecule conformation is optimized. Frequencies and intensities for just the water vibrations and stretchings of four cluster hydroxyls were calculated through partial Hessian matrices and polar tensors obtained by numerical differentiation of energy gradients and dipole moment. The water molecule was found to attach to the cluster mainly through a double hydrogen bond to the siloxane inner surface, partially entering the siloxane ring hexagonal hole. Though the theoretical results predict that the water OH stretching frequencies decrease from the gas‐phase state to the intercalated state, they are still higher than expected with respect to the observed spectrum. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献