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A series of imidazolium chlorides for the formation of tridentate CNO‐donor palladium(II) complexes featuring N‐heterocyclic carbene moieties have been developed from cheap and readily available starting materials with high yields. Their palladium complexes were prepared by reactions between the ligand precursors and PdCl2 using K2CO3 as base in pyridine with reasonable yields. These air‐stable metal complexes were characterized using 1H NMR and 13C{1H} NMR spectroscopy and elemental analyses. Heteronuclear multiple bond correlation experiments were performed to identify key NMR signals of these compounds. The structures of two of the complexes were also established by single‐crystal X‐ray diffraction analysis. One of these complexes was successfully applied in the direct C―H functionalization reactions between heterocyclic compounds and aryl bromides, producing excellent yields of coupled products. The coupling reactions were scalable, allowing grams of coupled products to be obtained with a mere 2 mol% of Pd loading. The catalyst system developed allowed the large‐scale preparation of several push–pull chromophores straightforwardly. Photophysical properties based on UV–visible and fluorescence spectroscopy for these chromophores were investigated. Deep blue photoluminescence with moderate quantum efficiency and twisted intramolecular charge transfer excited state were observed for these chromophores. Density functional theory (DFT) and time‐dependent DFT calculations were performed to support the experimental results.  相似文献   
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Abstract

Functional imaging of biologic parameters like in vivo tissue metabolism is made possible by Positron Emission Tomography (PET). Many techniques have been suggested for extracting such images from dynamic time-course sequences of reconstructed PET scans. Quantitating the precision of these estimates is important for drawing inferences on the biologic parameters. Analytic variance formulas are not immediate owing to the nonlinear methods used in extraction. The usual resampling approach is infeasible because each image reconstruction in PET is a computationally demanding solution to a high-dimensional linear inverse problem. We suggest an alternative simulation approach that approximates the distribution of reconstructed PET scans and performs a parametric bootstrap in the imaging domain. Results on a simplified model chosen to match the characteristics of PET reconstruction are very encouraging. Mixture analysis is used to estimate functional images; however, the suggested approach is general enough to extend to other techniques or imaging methods.  相似文献   
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S. Maitra  R. Singh  A. Sinha  S. Lahiri 《合成通讯》2013,43(13-14):2363-2370
Short and convenient syntheses of 1,2-cis-dibenzoyl-1-ary 1-ethylenes 5a-e, 6 and 8a-d from the corresponding aryl ethers and dibenzoyl acetylene have been developed using boron trifluoride-etherate or aluminium chloride as catalyst.  相似文献   
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As a polycation with diverse applications in biomedical and environmental engineering, polyethylenimine (PEI) can be synthesized with varying degrees of branching, polymerization, and can exist in different protonation states. There have been some interests in molecular modeling of PEI at all-atom or coarse-grained (CG) levels, but present CG models are limited to linear PEIs. Here we present the methodology to systematically categorize bond lengths, bond angles and dihedral angles, which allows us to model branched PEIs. The CG model was developed under the Martini scheme based on eight ~600 Da PEIs, with four different degree of branching at two different protonation states. Comparison of the CG model with all-atom simulations shows good agreement for both local (distributions for bonded interactions) and global (end-to-end distance, radius of gyration) properties, with and without salt. Compatibility of the PEI model with other CG bio-molecules developed under the Martini scheme will allow for large-scale simulations of many PEI-enabled processes. © 2018 Wiley Periodicals, Inc.  相似文献   
6.
In this paper, we consider the multi-bit Differential Power Analysis (DPA) in the Hamming weight model. In this regard, we revisit the definition of Transparency Order (\(\mathsf {TO}\)) from the work of Prouff (FSE 2005) and find that the definition has certain limitations. Although this work has been quite well referred in the literature, surprisingly, these limitations remained unexplored for almost a decade. We analyse the definition from scratch, modify it and finally provide a definition with better insight that can theoretically capture DPA in Hamming weight model for hardware implementation with precharge logic. At the end, we confront the notion of (revised) transparency order with attack simulations in order to study to what extent the low transparency order of an s-box impacts the efficiency of a side channel attack against its processing. To the best of our knowledge, this is the first time that such a critical analysis is conducted (even considering the original notion of Prouff). It practically confirms that the transparency order is indeed related to the resistance of the s-box against side-channel attacks, but it also shows that it is not sufficient alone to directly achieve a satisfying level of security. Regarding this point, our conclusion is that the (revised) transparency order is a valuable criterion to consider when designing a cryptographic algorithm, and even if it does not preclude to also use classical countermeasures like masking or shuffling, it enables to improve their effectiveness.  相似文献   
7.
Graphene analogues of TaS2 and TiS2 (3–4 layers), prepared by Li intercalation followed by exfoliation in water, were characterized. Nanocomposites of CdS with few‐layer TiS2 and TaS2 were employed for the visible‐light‐induced H2 evolution reaction (HER). Benzyl alcohol was used as the sacrificial electron donor, which was oxidized to benzaldehyde during the reaction. Few‐layer TiS2 is a semiconductor with a band gap of 0.7 eV, and its nanocomposite with CdS showed an activity of 1000 μmol h?1 g?1. The nanocomposite of few‐layer TaS2, in contrast, gave rise to higher activity of 2320 μmol h?1 g?1, which was attributed to the metallic nature of few‐layer TaS2. The amount of hydrogen evolved after 20 and 16 h for the CdS/TiS2 and CdS/TaS2 nanocomposites was 14833 and 28132 μmol, respectively, with turnover frequencies of 0.24 and 0.57 h?1, respectively.  相似文献   
8.
The adiabatic approximation in time-dependent density functional theory (TDDFT) yields reliable excitation spectra with great efficiency in many cases, but fundamentally fails for states of double-excitation character. We discuss how double-excitations are at the root of some of the most challenging problems for TDDFT today. We then present new results for (i) the calculation of autoionizing resonances in the helium atom, (ii) understanding the nature of the double excitations appearing in the quadratic response function, and (iii) retrieving double-excitations through a real-time semiclassical approach to correlation in a model quantum dot.  相似文献   
9.
In this paper, we study HC-128 in detail from cryptanalytic point of view. First, we use linear approximation of the addition modulo 2 n of three n-bit integers to identify linear approximations of g 1, g 2, the feedback functions of HC-128. This, in turn, shows that the process of keystream output generation of HC-128 can be well approximated by linear functions. In this direction, we show that the ??least significant bit?? based distinguisher (presented by the designer himself) of HC-128 works for the complete 32-bit word. Using the above linear approximations of g 1, g 2, we present a new distinguisher for HC-128 which is slightly weaker than Wu??s distinguisher. Finally, in the line of Dunkelman??s observation, we also study how HC-128 keystream words leak secret state information of the cipher due to the properties of the functions h 1, h 2 and present improved results.  相似文献   
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