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51.
Optical encryption and verification technique for information coding in multiple-wavelengths in Fresnel domain 总被引:1,自引:0,他引:1
We propose a new optical encryption and verification technique in which multiple frames of images recorded by different wavelengths can be synchronously encrypted into double pure phase masks (PMs). The height distributions of the two surface-relief PMs are designed by using an iterative phase-retrieval algorithm in combination with the conjugate-gradient method. Two PMs are located at the predesigned positions in the verification system. When a plane wave with a correct wavelength illuminates the optical verification system, the corresponding image is extracted to display on the output plane. Another incident plane wave with other different wavelength which was used in recording can produce another image. Only when all the frames of images recorded by different wavelengths are obtained, the user can then pass through the verification procedure. Compared with the previous encryption and verification technique, these predesigned wavelengths can be used as additional verification keys, which should significantly enhance the security of system. Numerical simulation shows that the proposed technique can successfully reconstruct the verification images for the authorized user having all the correct keys, but never for any unauthorized intruder. 相似文献
52.
Goutam Chattopadhyay Frank Maiwald Erich Schlecht Robert J. Dengler John C. Pearson Imran Mehdi 《International Journal of Infrared and Millimeter Waves》2003,24(9):1485-1498
Heterodyne instruments at millimeter and submillimeter wavelengths often use wideband fixed-tuned frequency multipliers, in conjunction with broadband power amplifiers driven by frequency synthesizers, as the local oscillator (LO) source. At these frequencies the multipliers use Gallium Arsenide (GaAs) based Schottky varactor diodes as the nonlinear element, and like most other harmonic generators are susceptible to spurious signal interference. The state-of-the-art LO sources at these wavelengths use high power MMIC amplifiers at the initial stages, and are used to drive the subsequent multiplier stages to have enough LO power to pump the mixers. Because of the high input power environment and the presence of noise in the system, the multipliers become vulnerable to spurious signal interference. As the spurious signals propagate through the receiver system, they generate inter-modulation products which might fall in the passband of the heterodyne instrument and seriously degrade its performance. In this paper spurious signal response of solid-state frequency multipliers at millimeter and submillimeter wavelengths is investigated. Results of numerical harmonic balance simulations and laboratory experiments, which were found to show good agreement, are presented here. 相似文献
53.
E. C. C. Vasconcellos J. Wyss K. M. Evenson 《International Journal of Infrared and Millimeter Waves》1987,8(6):647-651
We have measured the frequencies of 12 known and 3 new submillimeter laser lines obtained by pumping12CH3OH with a cw waveguide CO2 laser in a Fabry-Perot far infrared resonator. We have also measured the relative polarization and the pumping CO2 frequency offset for each line.Supported in part by a joint grant with the U.S. National Science Foundation # INT80-19014 and the Brazilian Conselho Nacional de Pesquisas (CNPq).Work of the U.S. Government; not subject to U.S. copyright. 相似文献
54.
Energy levels and transition data of 3p63d8 and 3p53d9 configurations in Fe-like ions (Z = 57, 60, 62, 64, 65)
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Bao-Ling Shi 《中国物理 B》2022,31(5):53102-053102
Atomic data of highly charged ions (HCIs) offer an attractive means for plasma diagnostic and stars identification, and the investigations on atomic data are highly desirable. Herein, based on the fully relativistic multi-configuration Dirac-Hartree-Fock (MCDHF) method, we have performed calculations of the fine-structure energy levels, wavelengths, transition rates, oscillator strengths, and line strengths for the lowest 21 states of 3p63d8-3p53d9 electric dipole (E1) transitions configurations in Fe-like ions (Z = 57, 60, 62, 64, 65). The correlation effects of valence-valence (VV) and core-valence (CV) electrons were systematically considered. In addition, we have taken into account transverse-photon (Breit) interaction and quantum electrodynamics (QED) corrections to treat accurately the atomic state wave functions in the final relativistic configuration interaction (RCI) calculations. Our calculated energy levels and transition wavelengths are in excellent agreement with the available experimental and theoretical results. Most importantly, we predicted some new transition parameters that have not yet been reported. These data would further provide critical insights into better analyzing the physical processes of various astrophysical plasmas. 相似文献
55.
用准相对论Hartree-Fock方法对Nb XIII离子二电子激发组态3d94s2, 3d94s4p, 3d94p2 的能级结构做了全面系统的理论计算研究.在对已有研究结果分析的基础上, 运用最小二乘方法对径向积分参数进行了优化计算, 得到了与这些组态有关的电偶极允许跃迁的谱线波长和跃迁概率.计算结果与最新的实验值做了对比分析, 表明本文计算结果是准确的. 研究发现, 波长40.92 nm的谱线, 属于3d94s(1D)4p2F7/2–3d9 (2D)4s2 2D5/2 的跃迁谱线, 而不属于3d94s (1D)4p4D7/2–3d9(2D)4s2 2D5/2 的跃迁谱线, 即上谱项能级为2F7/2, 而不是4D7/2.
关键词:
Nb XIII离子
二电子激发组态
谱线波长
跃迁概率 相似文献
56.
提出了一种以样品光谱类间相关系数之和最小为准则进行光谱波长逐步筛选的方法(stepwise selection basing on minimum sum of correlation coefficients, SMCC),以类间距离与类内距离和的比值最大化(符合分析者主观预期目标)作为定性分析中特征波长筛选效果的评价依据,并使用红塔集团提供的2012年17种不同类型工业分级烟叶作为试验样品,以验证筛选方法的有效性。研究表明,采用CO1分级烟叶光谱作为参照类别,筛选出10个特征波长点:采用特征波长计算得到的类内欧氏距离的平均值为采用全部波长计算得到的平均值的1.69倍,采用特征波长计算得到的类间欧氏距离的平均值为采用全部波长计算得到的平均值的3.70倍,采用特征波长计算得到的类间欧氏距离与类内欧氏距离和的比值的平均值为采用全部波长计算得到的平均值的2.21倍。特征波长的类间与类内欧氏距离和的比值增大,说明筛选出来的特征波长能更加有效的表达不同类间的远近关系以及同一类内的离散度,SMCC算法是一种有效的、可应用于近红外光谱定性分析中的特征波长筛选方法。 相似文献
57.
58.
高光谱技术结合特征波长筛选和支持向量机的哈密瓜成熟度判别研究 总被引:2,自引:0,他引:2
可溶性固形物含量(SSC)和硬度是哈密瓜划分等级的重要指标,同时也是其成熟度的表征因子。因此,为满足哈密瓜自动化分级和适宜采摘,采用高光谱技术结合特征波长筛选的方法,同时对哈密瓜的可溶性固形物含量、硬度及成熟度进行了无损检测研究。对多元散射校正(MSC)处理后的光谱分别利用连续投影算法(SPA)、竞争性自适应重加权算法(CARS)和CARS-SPA方法筛选了哈密瓜可溶性固形物和硬度的特征波长,并将原始光谱、MSC预处理后的光谱和所筛选的特征波长作为输入变量分别建立哈密瓜可溶性固形物和硬度的支持向量机(SVM)预测模型及成熟度判别模型。结果显示,MSC-CARS-SPA方法所建立的可溶性固形物和硬度SVM预测模型最优,其Rpre, RMSEP和RPD分别为0.940 4, 0.402 7, 2.94 1和0.825 3, 35.22, 1.771。同时对哈密瓜成熟度进行了判别分析,并分别建立了基于全光谱、单一的可溶性固形物或硬度特征波长和主成分分析(PCA)特征融合的哈密瓜成熟度SVM判别模型。结果显示,CARS-PCA-SVM模型的判别结果与全光谱SNV-SVM模型相同,其校正集和预测集判别正确率分别为95%和94%。研究表明,利用高光谱技术结合特征波长筛选方法可实现同时对哈密瓜可溶性固形物和硬度的定量预测及成熟度判别。 相似文献
59.
不同波长提取方法的高光谱成像技术检测番茄叶片早疫病的研究 总被引:1,自引:0,他引:1
提出了基于连续投影算法(successive projections algorithm,SPA)、载荷系数法(x-loading weights,x-LW)和格拉姆-施密特正交(gram-schmidt orthogonalization,GSO)提取特征波长的高光谱成像技术检测番茄叶片早疫病的方法。首先获取380~1 023 nm波段范围内70个健康和70个染病番茄叶片的高光谱图像信息,然后提取健康和染病叶片感兴趣区域(region of interest, ROI)的光谱反射率值,建立番茄叶片早疫病的最小二乘-支持向量机(least squares-support vector machine,LS-SVM)鉴别模型,建模集和预测集的鉴别率都是100%。再通过SPA 、x-LW和GSO提取特征波长(effective wavelengths,EW),并建立EW-LS-SVM和特征波长-线性判别分析(ew-linear discriminant analysis,EW-LDA)鉴别模型。结果显示,每个模型的鉴别效果都很好,EW-LS-SVM模型中预测集的鉴别率都达到了100%,EW-LDA模型中预测集的鉴别率分别是100%, 100%和97.83%。基于SPA, x-LW和GSO所建模型的输入变量分别是4个(492,550,633和680nm),3个(631,719和747 nm)和2个(533和657 nm),较少的特征波长便于实时检测仪器的开发。结果表明,高光谱成像技术检测番茄叶片早疫病是可行的,SPA,x-LW和GSO都是非常有效的特征波长提取方法。 相似文献
60.
A number of researchers have reported discrepancies between surface
resistance (SR) measurements and classical theoretical predictions in
normal metals for millimetre wavelengths (MW). In this paper, a
rigorous model is developed for analysing SR of normal metals. This
model is based on quantum mechanical analysis of the spatial
dispersion within the metal. We use the model to predict SR and
eliminate the discrepancies between SR measurements and classical
theoretical predictions in normal metals for MW. Moreover, we have
compared the results of this model with that of the classical
skin-effect model and classical relaxation-effect model. Our analysis
shows that the conductivity is not only frequency- but also
wave-vector-dependent for MW. We demonstrate that our model has good
quantitative agreement with the published experimental data for the
room temperature surface resistance of normal metals for MW. 相似文献