全文获取类型
收费全文 | 347篇 |
免费 | 99篇 |
国内免费 | 9篇 |
出版年
2024年 | 9篇 |
2023年 | 20篇 |
2022年 | 15篇 |
2021年 | 8篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 25篇 |
2017年 | 31篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 20篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 21篇 |
2010年 | 10篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 24篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有455条查询结果,搜索用时 31 毫秒
81.
Photoluminescence properties of Ca2Al2O5:RE3+ (RE = Eu,Dy and Tb) phosphors for solid state lighting 下载免费PDF全文
Atul N. Yerpude Vishal R. Panse Sanjay J. Dhoble Namdeo S. Kokode Mudavath Srinivas 《Luminescence》2017,32(7):1361-1364
Ca2Al2O5:Eu3+, Ca2Al2O5:Dy3+ and Ca2Al2O5:Tb3+ phosphors were synthesized using a combustion synthesis method. The prepared phosphors were characterized by X‐ray powder diffraction for phase purity, by scanning electron microscopy for morphology, and by photoluminescence for emission and excitation measurements. The Ca2Al2O5:Eu3+ phosphors could be efficiently excited at 396 nm and showed red emission at 594 nm and 616 nm due to 5D0 → 7F1 and 5D0 → 7F2 transitions. Dy3+‐doped phosphors showed blue emission at 482 nm and yellow emission at 573 nm. Ca2Al2O5:Tb3+ phosphors showed emission at 545 nm when excited at 352 nm. Concentration quenching occurred in both Eu3+ and Dy3+phosphors at 0.5 mol%. Photoluminescence results suggested that the aluminate‐based phosphor could be a potential candidate for application in environmentally friendly based lighting technologies. 相似文献
82.
Synthesis and luminescence characterization of Y2BaZnO5:RE (RE = Eu3+, Tb3+, Pr3+ and Sm3+) phosphors 下载免费PDF全文
Modified synthesis and luminescence of Y2BaZnO5 phosphors activated with the rare earths (RE) Eu3+, Tb3+, Pr3+ and Sm3+ are reported. RE2BaZnO5 phosphors have attracted attention because of their interesting magnetic and optical properties; and are usually prepared using a two‐step solid‐state reaction. In the first step, carbonates or similar precursors are thoroughly mixed and heated at 900°C to decompose them to oxides. To eliminate the unwanted phases like BaRE2O4, the resulting powders are reheated at 1100°C for a long time. We prepared Y2BaZnO5 phosphors activated with various activators by replacing the first step with combustion synthesis. The photoluminescence results are presented. The photoluminescence results for Eu3+, Tb3+ and Pr3+ are in good agreement with the literature. However, photoluminescence emission from Sm3+ has not been documented previously. The excitation spectrum of Eu3+ is dominated by a charge transfer band around 261 nm, and an additional band around 238 nm is always present, irrespective of the type of activator. The presence of this band for all these different types of activators was interpreted as host absorption. 相似文献
83.
Huttunen R Shweta Martikkala E Lahdenranta M Virta P Hänninen P Härmä H 《Analytical biochemistry》2011,415(1):27-31
Homogeneous luminescence-based microplate assays are desirable in high-throughput screening of new nuclear receptor regulators. Time-resolved fluorescence resonance energy transfer (TR–FRET) assays provide high sensitivity due to low background signal. The TR–FRET concept requires labeling of both ligand and receptor, making the assay format and its development relatively expensive and complex compared with single-label methods. To overcome the limitations of the multilabel methods, we have developed a single-label method for estrogen receptor (ER)–ligand binding based on quenching resonance energy transfer (QRET), where estradiol labeled with luminescent europium(III) chelate (Eu–E2) is quenched using soluble quencher molecules. The luminescence signal of Eu–E2 on binding to full-length ER is protected from quenching while increasing competitor concentrations displace Eu–E2 from the receptor, reducing the signal. The QRET method was paralleled with a commercial fluorescence polarization (FP) assay. The measured signal-to-background (S/B) values for estradiol, estrone, fulvestrant, and tamoxifen obtained for the QRET assay (5.8–9.2) were clearly higher than the S/B values for the FP assay (1.3–1.5). A Kd value of 30 nM was calculated for binding of Eu–E2 to ER from a saturation binding isotherm. The QRET method provides an attractive new single-label assay format for nuclear receptor ligand screening. 相似文献
84.
A new family of mononuclear Zn(II) complexes [Zn(Pyimpy)2](ClO4)2 (1), [Zn(Pyimpy)(Cl)2] (2), [Zn(Pyimpy)(SCN)2] (3) and [Zn(Pyimpy)(N3)2] (4) were synthesized using designed tridentate ligand Pyimpy having NNN donors (Pyimpy: (2-((2-phenyl-2-(pyridin-2-l)hydazono)methyl)pyridine)). Complexes were characterized by different spectroscopic studies and it has been found out that all complexes exhibited strong fluorescent emission at room temperature. Molecular structures of [Zn(Pyimpy)2](ClO4)2·C6H5CH3·0.5H2O (1·C6H5CH3·0.5H2O) and [Zn(Pyimpy)(Cl)2]·CH3CN (2·CH3CN) were determined by X-ray crystallography and ligand coordinated Zn(II) ions was described as distorted octahedral and distorted square pyramidal, respectively. DNA binding properties of these complexes were investigated by absorption spectral, fluorescence quenching and circular dichroism spectral studies. 相似文献
85.
Two triorganotin(IV) carboxylates [nBu3SnOL]n (KK1) and [Ph3SnOL]n (KK2) have been prepared by the reactions of (E)-3-(4-(diphenylamino)phenyl)acrylic acid (HL) with n(Bu3Sn)2O and Ph3Sn(OH), respectively. Complexes KK1 and KK2 have been structurally characterized by IR, elemental analysis and X-ray crystallography, confirming that both complexes possess infinite 1D chain structures. It’s exciting to discover that KK1 and KK2 exhibit strong solid-state luminescence emission while the HL almost quenches. Furthermore, both complexes were assayed for in vitro antibacterial activity against two Gram-positive bacterial strains (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 6538) and two Gram-negative bacterial strains (Pseudomonas aeruginosa ATCC 13525 and Escherichia coli ATCC 35218) by MTT method. Complex KK2 exhibited powerful antibacterial activities against S. aureus with MIC value of 0.78 μg/mL, which was superior to the positive controls penicillin G. On the basis of the biological results, structure-activity relationships were discussed. 相似文献
86.
87.
Ca3(PO4)2:Eu3+ phosphor preparation with different morphologies and their fluorescence properties 下载免费PDF全文
Ca3(PO4)2:Eu3+ phosphor was prepared using a facile chemistry method in the presence of surfactants. The effects of surfactants on the morphology and photoluminescence properties of Ca3(PO4)2:Eu3+ phosphor were investigated. The morphology of the phosphor was significantly influenced by the surfactants employed. When nonionic surfactant glyceryl monostearate and anionic surfactant sodium dodecylbenzene sulfonate were employed, the phospor powders are composed of a large number of homogeneous spherical particles with sizes of 0.3–0.6 µm and 2–3 µm, respectively. By contrast, when cationic surfactant cetyltrimethylammonium bromide was used, the morphology of the phosphor is completely different. The product is an excellent cuboid, and the phosphor prepared with 2.5 mmol cetyltrimethylammonium bromide showed higher luminescent intensity than phosphors prepared with the other two types of surfactants. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
88.
Preparation and up‐conversion luminescence properties of LaOBr:Yb3+/Er3+ nanofibers via electrospinning 下载免费PDF全文
LaOBr:Yb3+/Er3+ nanofibers were synthesized for the first time by calcinating electrospun PVP/[La(NO3)3 + Er(NO3)3 + Yb(NO3)3 + NH4Br] composites. The morphology and properties of the final products were investigated in detail using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X‐ray diffractometry (XRD) and fluorescence spectroscopy. The results indicate that LaOBr:Yb3+/Er3+ nanofibers are tetragonal in structure with a space group of P4/nmm. The diameter of LaOBr:Yb3+/Er3+ nanofibers is ~ 147 nm. Under the excitation of a 980‐nm diode laser, LaOBr:Yb3+/Er3+ nanofibers emit strong green and red up‐conversion emission centering at 519, 541 and 667 nm, ascribed to the 2H11/2, 4S3/2 → 4I15/2 and 4 F9/2 → 4I15/2 energy‐level transitions of Er3+ ions, respectively. The up‐conversion luminescent mechanism of LaOBr:Yb3+/Er3+ nanofibers is advanced. Moreover, near‐infrared emission of LaOBr:Yb3+/Er3+ nanofibers is obtained under the excitation of a 532‐nm laser. The formation mechanism of LaOBr:Yb3+/Er3+ nanofibers is proposed. LaOBr:Yb3+/Er3+ nanofibers could be important up‐conversion luminescent materials. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
89.
Sensitization enhancement of europium in ZnSe/ZnS core/shell quantum dots induced by efficient energy transfer 下载免费PDF全文
Ni Liu Ling Xu Hongyu Wang Jun Xu Weining Su Zhongyuan Ma Kunji Chen 《Luminescence》2014,29(8):1095-1101
Eu‐doped ZnSe:/ZnS quantum dots (formed as ZnSe:Eu/ZnS QDs) were successfully synthesized by a two‐step wet chemical method: nucleation doping and epitaxial shell growing. The sensitization characteristics of Eu‐doped ZnSe and ZnSe/ZnS core/shell QD are studied in detail using photoluminescence (PL), PL excitation spectra (PLE) and time‐resolved PL spectroscopy. The emission intensity of Eu ions is enhanced and that of ZnSe QDs is decreased, implying that energy was transferred from the excited ZnSe host materials (the donor) to the doped Eu ions (the acceptor). PLE reveals that the ZnSe QDs act as an antenna for the sensitization of Eu ions through an energy transfer process. The dynamics of ZnSe:Eu/ZnS core/shell quantum dots with different shell thicknesses and doping concentrations are studied via PL spectra and fluorescence lifetime spectra. The maximum phosphorescence efficiency is obtained when the doping concentration of Eu is approximately 6% and the sample showed strong white light under ultraviolet lamp illumination. By surface modification with ZnS shell layer, the intensity of Eu‐related PL emission is increased approximately three times compared with that of pure ZnSe:Eu QDs. The emission intensity and wavelength of ZnSe:Eu/ZnS core/shell quantum dots can be modulated by different shell thickness and doping concentration. The results provide a valuable insight into the doping control for practical applications in laser, light‐emitting diodes and in the field of biotechnology. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
90.
Strontium–aluminium–bismuth–borate glasses (SAlBiB) doped with different concentrations of Ho3+ were prepared using conventional melt quenching technique and their structural and optical properties investigated. X‐ray diffraction and scanning electron microscopy analysis were used to study the structural properties. Optical properties were studied by measuring the optical absorption and visible luminescence spectra. The Judd–Ofelt (J‐O) theory was applied to evaluate J‐O intensity parameters, Ωλ (λ = 2, 4 and 6). Using J‐O intensity parameters, radiative properties such as spontaneous transition probabilities (AR), branching ratios (βR) and radiative lifetimes (τR) were determined. From the emission spectra, a strong green emission nearly at 549 nm corresponding to the transition, 5S2(5F4)→5I8 was observed. Emission peak positions (λP), effective bandwidths (Δλeff) and stimulated emission cross‐sections (σp) were calculated for the observed emission transitions, 5F3→5I8, 5S2(5F4)→5I8 and 5F5→5I8 of Ho3+ in all the glass matrices. Chromaticity color coordinates were calculated using the emission spectra. The experimental results suggest that SAlBiB glass matrix with 1.5 mol% of Ho3+ has better emission properties. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献