全文获取类型
收费全文 | 240篇 |
免费 | 13篇 |
国内免费 | 36篇 |
专业分类
化学 | 108篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 1篇 |
物理学 | 174篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 9篇 |
2011年 | 18篇 |
2010年 | 9篇 |
2009年 | 18篇 |
2008年 | 13篇 |
2007年 | 26篇 |
2006年 | 17篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有289条查询结果,搜索用时 15 毫秒
131.
Jiunn-Woei Liaw Chi-San Chen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(3):454-465
The plasmonic effects of a metallic (Au or Ag) nanodimer on the excitation and emission of a single emitter placed within the gap of the nanodimer are studied to identify its overall performance (enhancement or quenching) for the spontaneous emission. The process of a spontaneous emission is divided into two stages for analysis: the excitation and the subsequent emission stages. For the excitation stage, the amplification of the local electric field around the gap region is studied to show the converging-lens effect of the nanodimer for focusing an incident light. For the emission stage, the apparent quantum yield of an electric dipole (the excited emitter) in the presence of the nanodimer is studied in terms of its radiative and nonradiative decay rates. Both models are simulated by the multiple multi-pole methods for solving Maxwell's equations. The results indicate that the overall enhancement factor of a metallic nanodimer on the spontaneous emission depends not only on its dimension (radius and gap) but also on the absorption and emission spectra of the emitter. Moreover, there is an optimal dimension (radius and gap) of a nanodimer for obtaining the maximum enhancement to a specific spontaneous emission. In addition, the observed emission spectrum of the emitter can be modified by the nearby nanodimer (a low-pass filter), and its lifetime can be reduced by two or three orders of magnitude due to the energy transfer between them. 相似文献
132.
压缩真空态的激发态及其在非耗散介观含源电路的应用 总被引:5,自引:0,他引:5
借助逆算符的性质,提出了压缩真空态激发态的概念,作为应用,导出了非耗散介观含源电路在该激发态下其电荷和电流的量子零点涨落,数值计算表明,在不同的激发量子数下,电荷和电流均存在压缩效应,它们的不确定度之积分别趋向于一个最小值。 相似文献
133.
You Osanai Hirotake Ishikawa Nobuaki Miura Takeshi Noro 《Theoretical chemistry accounts》2001,105(6):437-445
Configuration interaction calculations were carried out for neutral ground and excited states and positively and negatively
ionized states of the V, Cr and Mn atoms. Energy convergence with respect to systematic expansion of both the one-electron
and configuration bases was investigated for valence correlation. Contributions from core electrons to the differential correlation
energies and relativistic effects were evaluated separately. Assuming additivity of these contributions, excitation energies,
electron affinities and ionization potentials of the atoms were obtained. All calculated values were in excellent agreement
with the observed values within a deviation of 0.056 eV except for the electron affinity of the V atom, which had a calculated
value 0.110 eV larger than the experimental value.
Received: 9 August 2000 / Accepted: 26 October 2000 / Published online: 3 April 2001 相似文献
134.
Rosalba Sortino Marina Cunquero Gustavo Castro-Olvera Ricard Gelabert Miquel Moreno Fabio Riefolo Carlo Matera Noèlia Fernàndez-Castillo Luca Agnetta Michael Decker José M. Lluch Jordi Hernando Pablo Loza-Alvarez Pau Gorostiza 《Angewandte Chemie (International ed. in English)》2023,62(51):e202311181
To interrogate neural circuits and crack their codes, in vivo brain activity imaging must be combined with spatiotemporally precise stimulation in three dimensions using genetic or pharmacological specificity. This challenge requires deep penetration and focusing as provided by infrared light and multiphoton excitation, and has promoted two-photon photopharmacology and optogenetics. However, three-photon brain stimulation in vivo remains to be demonstrated. We report the regulation of neuronal activity in zebrafish larvae by three-photon excitation of a photoswitchable muscarinic agonist at 50 pM, a billion-fold lower concentration than used for uncaging, and with mid-infrared light of 1560 nm, the longest reported photoswitch wavelength. Robust, physiologically relevant photoresponses allow modulating brain activity in wild-type animals with spatiotemporal and pharmacological precision. Computational calculations predict that azobenzene-based ligands have high three-photon absorption cross-section and can be used directly with pulsed infrared light. The expansion of three-photon pharmacology will deeply impact basic neurobiology and neuromodulation phototherapies. 相似文献
135.
Vanessa Rück Mikkel B. Liisberg Christian Brinch Mollerup Yanmei He Junsheng Chen Cecilia Cerretani Tom Vosch 《Angewandte Chemie (International ed. in English)》2023,62(39):e202309760
DNA-stabilized silver nanoclusters (DNA-AgNCs) are easily tunable emitters with intriguing photophysical properties. Here, a DNA-AgNC with dual emission in the red and near-infrared (NIR) regions is presented. Mass spectrometry data showed that two DNA strands stabilize 18 silver atoms with a nanocluster charge of 12+. Besides determining the composition and charge of DNA2[Ag18]12+, steady-state and time-resolved methods were applied to characterize the picosecond red fluorescence and the relatively intense microsecond-lived NIR luminescence. During this process, the luminescence-to-fluorescence ratio was found to be excitation-intensity-dependent. This peculiar feature is very rare for molecular emitters and allows the use of DNA2[Ag18]12+ as a nanoscale excitation intensity probe. For this purpose, calibration curves were constructed using three different approaches based either on steady-state or time-resolved emission measurements. The results showed that processes like thermally activated delayed fluorescence (TADF) or photon upconversion through triplet-triplet annihilation (TTA) could be excluded for DNA2[Ag18]12+. We, therefore, speculate that the ratiometric excitation intensity response could be the result of optically activated delayed fluorescence. 相似文献
136.
This paper describes the evaluation of synchronous fluorescence spectroscopy (SFS) and excitation emission matrix fluorescence (EEMF) spectroscopy as means of monitoring transformer oil degradation. When accelerated thermal ageing method is used, the onset of degradation of transformer oil on 17th day and transformer oil with polypropylene and cellulosic paper on 23rd and 27th days is sensitively reflected in the SFS and EEMF fluorescence spectral characteristics. 相似文献
137.
Zhi-qiang Wang Qun-qing Hao Chuan-yao Zhou Dong-xu Dai Xue-ming Yang 《化学物理学报(中文版)》2015,28(4):459-464
Post-irradiation temperature-programmed desorption (TPD) has been used to study the photocatalyzed oxidation of methanol on TiO2(110) surface under the irradiation of 360, 380 and 400 nm light. The photocatalytic process initiated by ultraviolet light of different wavelength are similar. Methanol has been photocatalytically converted into formaldehyde, and the released hydrogen atoms transfer to the neighboring twofold coordinated oxygen to form bridging hydroxyls. The reaction rate, however, is strongly wavelength dependent. The reaction rate under 360 nm light irradiation is 4.8 times of that in the case of 400 nm exposure, consistent with a previous femtosecond time-resolved absorption measurement on TiO2 which shows the faster charge carrier recombination in the near-band-gap than the over-band-gap excitation. So far, the underlying factors which govern the excitation wavelength dependence of photocatalytic activity of TiO2 and other photocatalysts remain unclear, and future studies are needed to address this important issue. 相似文献
138.
用解析代数方法研究了分子转动和激光脉冲对双原子分子多光子激发控制的影响并推导得到不同转动通道下的分子振动激发几率的解析表达式.为了考察转动能级和考虑分子转动后与激光场夹角的变化对分子多光子振动激发和振动激发控制的影响,我们计算并比较了分子纯振动和加入分子转动两种情况,并分别给出了分子与极化激光场在不同取向角下三光子选择激发的图像.研究发现分子的转动能级对多光子非共振激发有修正作用,但是分子转动会降低多光子激发的选择性,而选择合适的激光脉冲形状有利于目标多光子激发控制的实现.文中还进一步讨论了激光脉冲初相位对分子多光子激发控制的影响,发现脉冲初相位对多光子激发过程有明显的调制作用. 相似文献
139.
Azuma Matsuura Hiroyuki Sato Wataru Sotoyama Atsuya Takahashi Minoru Sakurai 《Journal of Molecular Structure》2008,860(1-3):119-127
The absorption maxima, λmax, of various organic dyes such as indigo, azobenzene, phenylamine, hydrazone, anthraquinone, naphthoquinone, and malachite green were calculated using the AM1, PM3, and PM5 semiempirical molecular orbital theories with the configuration interaction singles (CIS) and random phase approximation (RPA) approaches. The calculated λmax were then compared with the values obtained by CNDO/S, INDO/S, ab initio CIS, and time-dependent density functional theory (TD-DFT). We found that the λmax values calculated by AM1, PM3, and PM5 were in good correlation with the observed λmax values. When B3LYP/cc-pVDZ optimized geometries were used, the square of the correlation coefficients between the calculated and observed λmax, , at the AM1-RPA, PM3-RPA, and PM5-RPA levels were 0.891, 0.897, and 0.927, respectively. In particular, at PM5-RPA//B3LYP/cc-pVDZ was the largest among those obtained from all the other calculations including TD/B3LYP/cc-pVDZ//B3LYP/cc-pVDZ . Accordingly, the standard deviation of the difference between observed and calculated λmax by the linear regression function at PM5-RPA//B3LYP/cc-pVDZ was the smallest. It was therefore concluded that this method was the most promising for the prediction of λmax of various dyes among the computational methods studied here. When AM1 optimized geometries were used, at the AM1-RPA, PM3-RPA, and PM5-RPA levels were 0.822, 0.841, and 0.901, respectively, and they were also comparable to that at TD/B3LYP/cc-pVDZ//B3LYP/cc-pVDZ. Therefore, although some calibration efforts may be needed for AM1 geometries, PM5-RPA(CIS)//AM1 may be a second candidate available for the prediction of the absorption maxima of dyes, especially in the case of emphasizing computational cost. 相似文献
140.