全文获取类型
收费全文 | 112篇 |
免费 | 3篇 |
国内免费 | 6篇 |
专业分类
化学 | 52篇 |
力学 | 5篇 |
数学 | 28篇 |
物理学 | 36篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
排序方式: 共有121条查询结果,搜索用时 15 毫秒
21.
Effective and rapid assessment of pork freshness is significant for monitoring pork quality. However, a traditional sensory evaluation method is subjective and physicochemical analysis is time-consuming. In this study, the near-infrared spectroscopy (NIRS) technique, a fast and non-destructive analysis method, is employed to determine pork freshness. Considering that commonly used statistical modeling methods require preprocessing data for satisfactory performance, this paper presents a one-dimensional squeeze-and-excitation residual network (1D-SE-ResNet) to construct the complex relationship between pork freshness and NIRS. The developed model enhances the one-dimensional residual network (1D-ResNet) with squeeze-and-excitation (SE) blocks. As a deep learning model, the proposed method is capable of extracting features from the input spectra automatically and can be used as an end-to-end model to simplify the modeling process. A comparison between the proposed method and five popular classification models indicates that the 1D-SE-ResNet achieves the best performance, with a classification accuracy of 93.72%. The research demonstrates that the NIRS analysis technique based on deep learning provides a promising tool for pork freshness detection and therefore is helpful for ensuring food safety. 相似文献
22.
In E & Liu (SIAM J Numer. Anal., 1995), we studied convergence and the structure of the error for several projection methods when the spatial variable was kept continuous (we call this the semi-discrete case). In this paper, we address similar questions for the fully discrete case when the spatial variables are discretized using a staggered grid. We prove that the numerical solution in velocity has full accuracy up to the boundary, despite the fact that there are numerical boundary layers present in the semi-discrete solutions.
23.
The electronic structure of a smoothly deformed crystal is analyzed using a minimalist model in quantum many‐body theory, the nonlinear tight‐binding model. An extension of the classical Cauchy‐Born rule for crystal lattices is established for the electronic structure under sharp stability conditions. A nonlinear elasticity model is rigorously derived. The onset of instability is briefly examined. © 2010 Wiley Periodicals, Inc. 相似文献
24.
25.
Zhe Sui Mengqing Liu Weinan Wang Hui Chen Guoqing Wang Ran An Xingguo Liang Makoto Komiyama 《化学:亚洲杂志》2019,14(19):3251-3254
Circular single‐stranded DNA (c‐ssDNA) has significant applications in DNA detection, the development of nucleic acid medicine, and DNA nanotechnology because it shows highly unique features in mobility, dynamics, and topology. However, in most cases, the efficiency of c‐ssDNA preparation is very low because polymeric byproducts are easily formed due to intermolecular reaction. Herein, we report a one‐pot ligation method to efficiently prepare large c‐ssDNA. By ligating several short fragments of linear single‐stranded DNA (l‐ssDNA) in one‐pot by using T4 DNA ligase, longer l‐ssDNAs intermediates are formed and then rapidly consumed by the cyclization. Since the intramolecular cyclization reaction is much faster than intermolecular polymerization, the formation of polymeric products is suppressed and the dominance of intramolecular cyclization is promoted. With this simple approach, large‐sized single‐stranded c‐ssDNAs (e.g., 200‐nt) were successfully synthesized in high selectivity and yield. 相似文献
26.
Kelley AM Leng W Blanchard-Desce M 《Journal of the American Chemical Society》2003,125(35):10520-10521
Resonance hyper-Raman spectra have been obtained using 1064 nm excitation for several electron donor-acceptor-substituted, pi-conjugated "push-pull" molecules that have large second harmonic hyperpolarizabilities. The hyper-Raman spectra are nearly identical to the resonance Raman spectra measured with 532 nm excitation. This indicates that both the second harmonic hyperpolarizability and the linear absorption are dominated by the same, single electronic transition that is both one- and two-photon allowed. Comparison of resonance Raman and resonance hyper-Raman spectra is proposed as an experimental test of the common two-electronic-state model for the first hyperpolarizability. 相似文献
27.
The finite-temperature string method proposed by E, et al. [W. E, W. Ren, and E. Vanden-Eijnden, Phys. Rev. B 66, 052301 (2002)] is a very effective way of identifying transition mechanisms and transition rates between metastable states in systems with complex energy landscapes. In this paper, we discuss the theoretical background and algorithmic details of the finite-temperature string method, as well as the application to the study of isomerization reaction of the alanine dipeptide, both in vacuum and in explicit solvent. We demonstrate that the method allows us to identify directly the isocommittor surfaces, which are approximated by hyperplanes, in the region of configuration space where the most probable transition trajectories are concentrated. These results are verified subsequently by computing directly the committor distribution on the hyperplanes that define the transition state region. 相似文献
28.
We study stationary measures for the two-dimensional Navier–Stokes equation with periodic boundary condition and random forcing.
We prove uniqueness of the stationary measure under the condition that all “determining modes” are forced. The main idea behind
the proof is to study the Gibbsian dynamics of the low modes obtained by representing the high modes as functionals of the
time-history of the low modes.
Received: 21 November 2000 / Accepted: 9 December 2000 相似文献
29.
We study the connection between atomistic and continuum models for the elastic deformation of crystalline solids at zero temperature.
We prove, under certain sharp stability conditions, that the correct nonlinear elasticity model is given by the classical
Cauchy–Born rule in the sense that elastically deformed states of the atomistic model are closely approximated by solutions
of the continuum model with stored energy functionals obtained from the Cauchy–Born rule. The analysis is carried out for
both simple and complex lattices, and for this purpose, we develop the necessary tools for performing asymptotic analysis
on such lattices. Our results are sharp and they also suggest criteria for the onset of instabilities of crystalline solids. 相似文献
30.
Yijing Chen Weinan Chen Yanjun Qiao Xuefeng Lu Gang Zhou 《Angewandte Chemie (International ed. in English)》2020,59(18):7122-7130
BN‐embedded oligomers with different pairs of BN units were synthesized by electrophilic borylation. Up to four pairs of BN units were incorporated in the large polycyclic aromatic hydrocarbons (PAHs). Their geometric, photophysical, electrochemical, and Lewis acidic properties were investigated by X‐ray crystallography, optical spectroscopy, and cyclic voltammetry. The B?N bonds show delocalized double‐bond characteristics and the conjugation can be extended through the trans‐orientated aromatic azaborine units. Calculations reveal the relatively lower aromaticity for the inner azaborine rings in the BN‐embedded PAH oligomers. The frontier orbitals of the longer oligomers are delocalized over the inner aromatic rings. Consequently, the inner moieties of the BN‐embedded PAH oligomers are more active than the outer parts. This is confirmed by a simple oxidation reaction, which has significant effects on the aromaticity and the intramolecular charge‐transfer interactions. 相似文献