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281.
Mithlesh Kumar A. R. Dhobale Mukesh Kumar M. D. Sastry 《Journal of Polymer Science.Polymer Physics》1997,35(1):187-192
Photoacoustic (PA) spectra of Ho3+, Er3+, and Sm3+ doped PVA films were obtained in 350–800 nm range. PA spectra were also obtained for the respective dopant oxides: Ho2O3, Er2O3, and Sm2O3 for comparison. It was found that in PVA the PA sensitivity has increased considerably compared to pure rare earth oxides. The relative intensities of absorption bands at 540 and 637 nm of Ho3+: PVA have shown distinct enhancement, indicating the increase in nonradiative relaxation at these excitations. Furthermore, the PA signals at wavelengths for different PA absorption bands were monitored as a function of chopping frequency. These experiments have shown that PA signal varies w−1 both for oxides and PVA samples, suggesting that they behave as thermally thin samples. © 1997 John Wiley & Sons, Inc. 相似文献
282.
Two phthalein dyes in aqueous polyvinyl alcohol solutions of pH 8.5 have been investigated: fluorescein and phenolphthalein. Competitive pathways of deactivation of their energetically excited states have been followed by the use of spectroscopic and photoelectric techniques. Radiative, nonradiative, and charge separation processes followed by electron transfer have been measured by absorption, fluorescence, and photoacoustic spectroscopy accompanied by photovoltage/photocurrent generation in a photoelectrochemical cell. It is shown that, despite their being only a slight difference in molecular structure between the two dyes, their spectral as well as photoelectric behavior is significantly different. 相似文献
283.
《Analytical letters》2012,45(7):1150-1162
Fourier-transform mid-infrared photoacoustic spectroscopy was utilized for rapid and nondestructive determination of nitrogen in rapeseeds. Rapeseed spectra were characterized by independent component analysis for quantitative calibration. A calibration model was built by using independent components as the input for partial least squares. Compared to full-spectrum partial least squares, the combined model achieved higher prediction accuracy with a residual predictive deviation of 2.06. Moreover, a genetic algorithm coupled with partial least squares was adopted to optimize the independent components for partial least square modeling and provide a further refined model with the highest residual predictive deviation of 2.12. A t-test verified a high congruence between results obtained by calibration models and the reference Kjeldahl method. This study demonstrated the promise of Fourier-transform mid-infrared photoacoustic spectroscopy for the determination of nitrogen in rapeseeds and the applicability of independent components for multivariate calibration. 相似文献
284.
285.
利用室温下单模运行的近红外半导体二极管激光,报导了波长调制共振光声光谱结合二次谐波探测技术.实验系统应用到乙炔探测,在1个标准大气压和3毫瓦平均光功率以及3毫秒锁相积分时间条件下其探测灵敏度可达10ppm(体积比),归一化到激光功率和系统带宽最小可探测吸收为4.0×10-8Wcm-1/Hz,并且实验中发现系统最佳压力响应值在2.66×104Pa附近.本实验装置可有效的消除光声光谱系统中常见的窗片和光声腔壁吸收入射光而引起的背景噪声.此外,相对于其他方法我们描述的基于半导体激光共振光声光谱具有很大的优点,为进一步发展便利、实用、便携式环境监测仪器奠定了坚实的基础. 相似文献
286.
研究了四(对-硝基)苯基卟啉及其Cr(Ⅲ)、Mn(Ⅲ)、Fe(Ⅲ)、Co(Ⅱ)、Ni(I)、Cu(Ⅱ)、Zn(Ⅱ)配合物的3500-225 cm-1范围的傅立叶变换红外光声光谱.对主要谱带进行经验归属.金属敏感谱带出现在-1489、-1076、-737和-250 cm-1等附近.-250 cm-1谱带是M—N伸缩振动和卟啉环变形的复合振动. 相似文献
287.
288.
Yuanqin Yu Yuxi Wang Ke Lin Xiaoguo Zhou Shilin Liu Jin Sun 《Journal of Raman spectroscopy : JRS》2016,47(11):1385-1393
The C―H stretching vibration serves as an important probe for characterizing molecular structures and properties of hydrocarbons. In this work, we present a detailed study on gas‐phase Raman spectrum of n‐propanol in the C―H stretching region using stimulated photoacoustic Raman spectroscopy. A complete assignment was carried out with the aid of quantum chemistry calculations and depolarization ratio measurement as well as isotope substitutions, i.e. CH3CD2CD2OH, CD3CH2CD2OH and CD3CD2CH2OH. It is shown that the spectra of three C―H groups of n‐propanol overlap each other because of Fermi resonance coupling and different molecular conformations, leading to complex features that were not determined previously. In addition, the comparisons between the spectra of three isotopologues reveal that the C―H vibrations at different sites of carbon chain exhibit different sensitivity to conformational change of n‐propanol. The CH3 stretching vibration at terminated γ‐carbon is not sensitive whereas the CH2 stretching vibrations at both α‐carbon and β‐carbon atoms are sensitive. Furthermore, Raman spectra of liquid propanol recorded by conventional spontaneous Raman technique are reassigned on the basis of gas‐phase analysis. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献