首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   415篇
  免费   130篇
  国内免费   25篇
综合类   21篇
化学工业   96篇
金属工艺   13篇
机械仪表   5篇
建筑科学   1篇
矿业工程   1篇
能源动力   1篇
轻工业   11篇
武器工业   1篇
无线电   145篇
一般工业技术   215篇
冶金工业   57篇
自动化技术   3篇
  2024年   2篇
  2023年   15篇
  2022年   15篇
  2021年   30篇
  2020年   36篇
  2019年   45篇
  2018年   30篇
  2017年   43篇
  2016年   42篇
  2015年   33篇
  2014年   37篇
  2013年   30篇
  2012年   38篇
  2011年   16篇
  2010年   21篇
  2009年   18篇
  2008年   19篇
  2007年   14篇
  2006年   22篇
  2005年   13篇
  2004年   9篇
  2003年   8篇
  2002年   2篇
  2001年   7篇
  2000年   6篇
  1999年   4篇
  1998年   3篇
  1997年   5篇
  1996年   4篇
  1995年   2篇
  1994年   1篇
排序方式: 共有570条查询结果,搜索用时 0 毫秒
1.
The Y2O3: Yb3 , Er3 microstructures were fabricated by a hydrothermal method without surfactants.The microstructures structure was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM,KYKY 1000B).The up-conversion luminescence spectra were studied under 978 nm laser diode excitation.In Yb3 and Er3 codoped Y2 O3 microcrystals, the relative intensity of green emission became stronger as the morphology of sample changed from wires to films.  相似文献   
2.
以9-蒽甲酸(9-ACA)为发光剂,八乙基卟啉钯(Pd OEP)为光敏剂,在二者最佳配比〔n(9-ACA)∶n(Pd OEP)=80∶1〕下,构建了对溶液中氢离子和氢氧根离子具备灵敏响应性的上转换发光体系9-ACA/PdOEP。当pH处于4~8以及8~11时,上转换发光强度均与pH呈现良好的线性关系。参比实验中,单一组分9-ACA本身的荧光强度与pH没有呈现线性关系,证明了9-ACA/Pd OEP体系对于pH的宽范围响应来源于光敏剂与发光剂之间的三线态-三线态能量转移(TTET)过程。  相似文献   
3.
4.
5.
6.
Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) assays reveal that the as-synthesized Ba2ErF7 nanocrystals are of the cubic structure with the cell parameter of 5.943 A, instead of the reported orthorhombic and tetragonal structure. Two emission bands originated from 2Hwj4H3/2 → 4F5/2 and 4F9/2 ----+ 4115,2 of Er3+ can be observed under a 980 nm laser excitation. The magnetic mass susceptibility of the as-synthesized BazErF7 nanocrystals reaches 4.293 × 10-5 emu g-1 Oe-1.  相似文献   
7.
To date, the increase in reactive oxygen species (ROS) production for effectual photodynamic therapy (PDT) treatment still remains challenging. In this study, a facile and effective approach is utilized to coat mesoporous silica (mSiO2) shell on the ligand-free upconversion nanoparticles (UCNPs) based on the LiYF4 host material. Two kinds of mesoporous silica-coated UCNPs (UCNP@mSiO2) that display green emission (doped with Ho3+) and red emission (doped with Er3+), respectively, were successfully synthesized and well characterized. Three photosensitizers (PSs), merocyanine 540 (MC 540), rose bengal (RB), and chlorin e6 (Ce6), with the function of absorption of green or red emission, were selected and loaded into the mSiO2 shell of both UCNP@mSiO2 nanomaterials. A comprehensive study for the three UCNP@mSiO2/PS donor/acceptor pairs was performed to investigate the efficacy of fluorescence resonance energy transfer (FRET), ROS generation, and in vitro PDT using a MCF-7 cell line. ROS generation detection showed that as compared to the oleate-capped and ligand-free UCNP/PS pairs, the UCNP@mSiO2/PS nanocarrier system demonstrated more pronounced ROS generation due to the UCNP@mSiO2 nanoparticles in close vicinity to PS molecules and a higher loading capacity of the photosensitizer. As a result, the three LiYF4 UCNP@mSiO2/PS nanoplatforms displayed more prominent therapeutic efficacies in PDT by using in vitro cytotoxicity tests.  相似文献   
8.
The effect of the localized surface plasmon resonance (SPR) on optical absorption and photoluminescence of Sm3+-doped sodium borosilicate glass containing reduced silver nanoparticles (NPs) is reported (Ag+  Ag0). The interaction of ultraviolet light by metallic NPs and its effect on the optical properties of samarium in proposed glass were investigated by absorption and photoluminescence spectra analysis. The existence of the NPs was pursued by transmission electron microscopy technique, revealing the existence of Ag NPs with average size of ∼8–14 nm. The largest enhancement was achieved for emission at 561 nm. Such improvements were attributed and discussed by enhanced electric field around metallic NPs and energy transfer (ET) between Sm3+ ions and silver NPs.  相似文献   
9.
《Ceramics International》2022,48(21):31344-31353
Highly thermally stable Er3+/Tm3+/Yb3+ tri-doped bismuth lanthanum tungstate phosphors were prepared by high temperature solid-state reaction method. The structural and morphological properties of the prepared phosphors were analysed by X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM) coupled with energy dispersion spectrum (EDS). Visible upconversion (UC) luminescence was measured by exciting the phosphors with 980 nm laser radiation. The dependence of the UC intensity of each emission band of Er3+ and Tm3+ ions as a function of temperature in the range from 30 to 300 K was monitored. Fluorescence intensity ratios (FIR) of thermally coupled levels (TCL) and non-thermally coupled levels (NTCL) were analysed and verified with appropriate theoretical validation. The absolute (SA) and relative sensitivities (SR) were estimated and compared with the reported systems. In the present case of BiLaWO6: Er3+/Tm3+/Yb3+, SR (0.43 % K?1) related to TCL of Er3+ UC is found to have maximum sensitivity compared to any of the NTCL combinations at 300 K. From this study we inferred that the SR values estimated from NTCL are smaller than that of TCL involved in BLW: Er3+/Tm3+/Yb3+ phosphor. The temperature dependent CIE color coordinates were also evaluated in the cryogenic temperature region.  相似文献   
10.
A series of Sr2.99-x(PO4)2:.01Er3+/xYb3+ (x = .02, .04, .06, .08, .10) phosphors in the presence of impurity Tm3+ were synthesized by high temperature solid-state method, and X-ray diffraction results show that these samples are pure R-3 m(166) space group phase. The upconversion luminescence (UCL) of Er3+ and impurity Tm3+ under 980-nm laser excitation were investigated, and the results show that the intense blue UCL of impurity Tm3+ and thermal enhancement of 2H11/24I15/2 of Er3+ simultaneously exist. When Er3+ doping concentration is kept at .01, both the blue UCL intensity of impurity Tm3+ and green and red UCL intensity of Er3+ reach the maximum at Yb3+ doping concentration of .08. The thermal enhancement effect of 2H11/24I15/2 of Er3+ was observed as high as 3.27 times from 303 to 723 K, which is because of lattice distortion and phonon-assisted transition. In addition, the optical temperature performance of Sr2.91(PO4)2:.01Er3+/.08Yb3+ sample was studied, and the maximum absolute temperature sensitivity was calculated as .00623 K−1 at 538 K. This study suggests that Sr3(PO4)2:Er3+/Yb3+ phosphors in the presence of impurity Tm3+ have a promising application prospect as optical temperature sensor at high temperature.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号