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排序方式: 共有202条查询结果,搜索用时 953 毫秒
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I. El-Kady R. Biswas Y. Ye M. F. Su I. Puscasu Martin Pralle E. A. Johnson J. Daly A. Greenwald 《Photonics and Nanostructures》2003,1(1):69-77
In this work, we present both the theoretical basis as well as supporting experimental measurements for development of a novel mid-infrared thermally stimulated narrow band emitter with a spectral bandwidth of less than 10%. To achieve this, we utilize a metallized-surface 2D photonic crystal of air voids in a silicon background with hexagonal structure symmetry. Our results are based on the generation of discrete surface plasmon (SP) modes in the thin metallized layer residing on the top surface. This yields a series of adequately spaced discrete peaks in the reflection spectrum, dominated by a single sharp feature corresponding to the lowest plasmon order, in an otherwise uniform highly reflective spectrum (>90%) over most of the IR spectrum. This, in turn, gives rise to a sharp absorption feature with a correspondingly narrow thermal emission peak in the emission spectrum. Transfer matrix calculations simulate well both the position and strengths of the absorption peaks. By altering the period of the surface photonic lattice, the SP peak and emissive band can be tuned to the desired wavelength. These devices promise a new class of tunable infrared emitters with high power in a narrow spectral bandwidth. Such narrow band sources are critical to achieving high efficiency gas sensors. 相似文献
3.
The dipole moment and polarizability changes have been determined from electroabsorption (EA) spectroscopy of solid films of fac tris(2-(phenyl)pyridinato,N,C2′)iridium (III) [Ir(ppy)3]. The maximum changes in the dipole moment |Δμ|S=(5.0±0.5) D/f (f is the local field correction factor: 1.3–1.7) accompany ground state to the lowest singlet, and |Δμ|T=(1.7±0.5) D/f ground state to the lowest triplet metal-to-ligand charge transfer (MLCT) excited states formation, while the average polarizability change
Å3/f2 follows from the fitting procedure throughout the visible absorption spectrum range. The experimental values of |Δμ| as well as energy positions of the MLCT states correlate with the literature results of time-dependent density functional theory. 相似文献
4.
Oliver Back Dr. Christoph Förster Prof. Dr. Thomas Basché Prof. Dr. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6542-6552
2-Iminopyrroles [HtBuL, 4-tert-butyl phenyl(pyrrol-2-ylmethylene)amine] are non-fluorescent π systems. However, they display blue fluorescence after deprotonation with alkali metal bases in the solid state and in solution at room temperature. In the solid state, the alkali metal 2-imino pyrrolates, M(tBuL), aggregate to dimers, [M(tBuL)(NCR)]2 (M=Li, R=CH3, CH(CH3)CNH2), or polymers, [M(tBuL)]n (M=Na, K). In solution (solv=CH3CN, DMSO, THF, and toluene), solvated, uncharged monomeric species M(tBuL)(solv)m with N,N′-chelated alkali metal ions are present. Due to the electron-rich pyrrolate and the electron-poor arylimino moiety, the M(tBuL) chromophore possesses a low-energy intraligand charge-transfer (ILCT) excited state. The chelated alkali cations rigidify the chromophore, restricting intramolecular motions (RIM) by the chelation-enhanced fluorescence (CHEF) effect in solution and, consequently, switch-on a blue fluorescence emission. 相似文献
5.
In this study, the electronic structures and optical properties of a cyclometalated Pt(II) complex (M1) and a series of derivatives (M1–F, M1–CF3, and M1–CN) with electron-withdrawing substituents (–F, –CF3, and –CN) at the carbazole moiety were theoretically investigated by density functional theory and time-dependent density functional theory. The calculation results reveal that these Pt complexes display deep red phosphorescence emission above Λ = 640 nm. When the 3MLCT/π → π* to triplet metal-centered 3MC/d–d state decay mechanism is taken into consideration, the nonradiative decay rate constant (knr) decreased in the order M1 > M1–CF3 > M1–F > M1–CN. The <T1|HSOC|Sm> and kr values of M1-F are similar with those of M1, however the Knr rate ofM1-F is larger than that of M1. M1–F is expected to have improved quantum yields. Moreover, through the analyses of the HOMO/LUMO level and triplet energy, it is found that the introduction of –F and –CN substituents in M1 results in efficient energy transfer from the host material 4,4′-N,N′-dicarbazole-biphenyl to these complexes. In view of the electroluminescent applications in organic light-emitting diodes, M1–F can serve as efficient deep-red guest materials with improved electron injection and transport ability. 相似文献
6.
Hélène Beucher Dr. Sudhir Kumar Dr. Roopender Kumar Dr. Estíbaliz Merino Wei-Hsu Hu Gerrit Stemmler Sergio Cuesta-Galisteo Dr. Jorge A. González Léonard Bezinge Dr. Jakub Jagielski Dr. Chih-Jen Shih Prof. Dr. Cristina Nevado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17604-17612
Efficient OLED devices have been fabricated using organometallic complexes of platinum group metals. Still, the high material cost and low stability represent central challenges for their application in commercial display technologies. Based on its innate stability, gold(III) complexes are emerging as promising candidates for high-performance OLEDs. Here, a series of alkynyl-, N-heterocyclic carbene (NHC)- and aryl-gold(III) complexes stabilized by a κ3-(N^C^C) template have been prepared and their photophysical properties have been characterized in detail. These compounds exhibit good photoluminescence quantum efficiency (ηPL) of up to 33 %. The PL emission can be tuned from sky-blue to yellowish green colors by variations on both the ancillary ligands as well as on the pincer template. Further, solution-processable OLED devices based on some of these complexes display remarkable emissive properties (ηCE 46.6 cd.A−1 and ηext 14.0 %), thus showcasing the potential of these motifs for the low-cost fabrication of display and illumination technologies. 相似文献
7.
Optimizing Optoelectronic Properties of Pyrimidine‐Based TADF Emitters by Changing the Substituent for Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 25 % and Slow Efficiency Roll‐Off
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Kailong Wu Tao Zhang Lisi Zhan Dr. Cheng Zhong Prof. Shaolong Gong Prof. Nan Jiang Prof. Zheng‐Hong Lu Prof. Chuluo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10860-10866
A series of green butterfly‐shaped thermally activated delayed fluorescence (TADF) emitters, namely PXZPM , PXZMePM , and PXZPhPM , are developed by integrating an electron‐donor (D) phenoxazine unit and electron‐acceptor (A) 2‐substituted pyrimidine moiety into one molecule via a phenyl‐bridge π linkage to form a D –π–A–π–D configuration. Changing the substituent at pyrimidine unit in these emitters can finely tune their emissive characteristics, thermal properties, and energy gaps between the singlet and triplet states while maintaining frontier molecular orbital levels, and thereby optimizing their optoelectronic properties. Employing these TADF emitters results in a green fluorescent organic light‐emitting diode (OLED) that exhibits a peak forward‐viewing external quantum efficiency (EQE) close to 25 % and a slow efficiency roll‐off characteristic at high luminance. 相似文献
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9.
Investigation of fill factor losses on 20.2% efficient n‐type mono‐like silicon solar cells with laser contact opening
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Alexander Frey Josh Engelhardt Gabriel Micard Giso Hahn Barbara Terheiden 《固体物理学:研究快报》2016,10(2):143-147
Large area (243.36 cm2) back‐junction passivated emitter, rear totally diffused (PERT) solar cells with laser contact opening (LCO) on n‐type mono‐like crystalline Si with efficiencies of 20.2% are presented. Boron emitters with high electrical quality (implied open circuit voltage iVOC up to 700 mV) are formed during a co‐diffusion step using SiOx:B layers. Increasing the rear metal contact coverage, we observed a decrease in fill factor (FF) instead of the expected increase due to the decrease of the back side series resistance. We show that it can be attributed to recombination centers (RCs) in the space charge region underneath the contact spots inducing an increasing second diode contribution. The presented empirical model for the RCs implemented in Synopsys Sentaurus TCAD allows for a successful reproduction of the FF, pseudo FF and VOC behaviour with contact coverage. According to this model, the RCs induced by laser ablation and subsequently evaporation of Al have a shallow exponential distribution with a characteristic length of LT = 0.2 µm and an effective surface density of N *T0 = 25 cm–1. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
10.
研究用于癌症诊断与治疗的光敏剂血卟啉(hematoporphyrin derivative,HPD)的超快光动力学过程。采用超短脉冲激光光谱技术和皮秒时间相关单光子计数系统,测量经血卟啉培养的活体癌细胞与正常细胞的荧光光谱、荧光寿命特性及荧光峰值强度随时间的变化,观测到:癌细胞样品在645nm处具有特征发射光谱峰;癌细胞与正常细胞样品荧光寿命的快成分分别为150,300ps;癌细胞与正常细胞的荧光峰值强度经12h分别衰减10%和55%。对测量所得的荧光光谱曲线及时间分辨荧光衰减曲线分析,计算出:在癌细胞内部血卟啉浓度增大了约2个数量级;癌细胞与正常细胞的荧光寿命分别为824,1798ps;血卟啉在癌细胞与正常细胞样品中滞留时间分别为17,6d。测量结果确认了荧光光谱技术诊断与治疗癌症的可行性,并对发展超短脉冲激光光谱技术早期诊断与治疗癌症具有重要的指导意义和临床应用价值。 相似文献