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排序方式: 共有186条查询结果,搜索用时 15 毫秒
1.
Red/near infrared (NIR) long persistent phosphors have received extensive attentions in biomedical, food inspection, iris recognition, biological imaging, etc. Herein, a new phosphor, Li2ZnGe3O8:Cr3+, is reported with deep red persistent luminescence peaking at 708 nm. By adjusting the Cr3+ doping concentration, the competitive site occupation at [ZnO6] and [GeO6] polyhedral enables different traps behaviors including trap types, trap concentration and trap depth, which in turn leads to different afterglow duration time from 2 to 20 h. The persistent luminescence mechanisms originated from different trap models have been discussed, and it is found that they can cooperate or inhibit each other, enabling different luminescence depending on time. The dynamic anti-counterfeiting applications have been demonstrated, which provides a new way to rationally designing for multi-functional luminescent materials.  相似文献   
2.
以柠檬酸钠为碳源、氨水为氮源,采用一步水热法制备了氮掺杂碳点(NCDs),对其制备条件进行了优化.采用荧光光谱仪、TEM、AFM、XPS及FTIR对制备的NCDs进行了表征,并探索了NCDs在Fe3+检测及荧光防伪中的应用.结果表明,NCDs的最优制备条件为柠檬酸钠浓度为0.1 mol/L、氨水浓度为1.8 mol/L、反应温度为200℃、反应时间6 h、装载体积25 mL.在最优条件下制备的NCDs的荧光为典型的非激发波长依赖型,最佳激发波长为343 nm,最佳发射波长为443 nm,荧光量子产率可达54.9%.NCDs为球形结构,平均粒径为4.96 nm,碳核为类石墨烯结构且其表面含有—NH2、—OH及—COOH.NCDs的荧光可被Fe3+选择性猝灭,且荧光猝灭程度与Fe3+浓度在0.1~87.5μmol/L范围内线性关系良好,检测限为50 nmol/L.此外,将NCDs配制成荧光墨水,利用喷墨打印机打印出的图案整体饱满、边缘细节清晰具有很强的可识别性.  相似文献   
3.
《Ceramics International》2022,48(24):36201-36209
The persistent luminescence (PersL) materials Ca2Sb2O7:Pr3+ were prepared by traditional high-temperature solid-state method. We systematically investigated the crystal structure, band structure, photoluminescence, PersL performance by X-ray diffraction diagrams, Materials Studio calculation, photoluminescence (PL) spectra, PersL spectra and CIE coordinate analysis. The PL and PersL are attributed to the Sb5+ → O2? transition of the matrix and the 4f-4f transition of Pr3+ ion. For the sake of explaining the impact of various traps on PersL performance, thermoluminescence (TL) tests were performed on the optimal sample after diverse charging and discharging times. It was concluded that shallow traps have priority over deep traps in capturing electrons, and the electrons in the shallow traps were preferentially released. The highlight of this work is that the PL and PersL color can be adjusted by regulating the Pr3+ doping concentration when these samples were excited by a single excitation wavelength, so as to achieve a double anti-counterfeiting effect. Furthermore, the color change of PersL is different from that of PL. The luminescent patterns can make a difference as the change of concentration and time, forming a dynamic anti-counterfeiting mark that distinguishes in color and time. Thus, Ca2Sb2O7:Pr3+ has a bright application prospect in dynamic anti-counterfeiting field.  相似文献   
4.
郝晓秀  尹兴  孙诚  杨淑惠 《包装工程》2015,36(3):6-9,21
目的研究不同造纸助留剂CPAM,APAM,高取代度淀粉和变性淀粉对紫外光致变色防伪纸的物理性能和防伪性能的影响。方法系统研究了4种常用造纸助留剂对光致变色材料在防伪纸中的留着量的影响,评定防伪纸的物理性能和防伪性能,从而确定了不同助留剂在浆料中的最佳用量。结果光致变色防伪纸的抄造特性和防伪性能与纸料体系中所用助留剂的种类和性能密切相关。在一定的光致变色材料体系下,不同助留剂的最佳加入量为变性淀粉的质量分数1.5%,CPAM的质量分数0.005%,APAM的质量分数0.015%,高取代度淀粉的质量分数0.15%。结论在浆料中加入助留剂后,紫外光致变色材料在防伪纸中的留着量显著增加,且加入助留剂的种类不同时,其纸张的相对荧光强度值也不同,从而保证了紫外光致变色纸张的防伪效果。  相似文献   
5.
Novel hydrophilic NaYF4:Yb3+,Tm3+@NaGdF4:Ce3+,Eu3+ double-jacket microtubes (DJMTs) with upconversion/ downconversion dual-mode luminescence were designed and prepared through epitaxial growth of NaGdF4:Ce3+, Eu3+ shell onto the NaYF4:Yb3+,Tm3+ microtube via poly(acrylic acid) (PAA) mediated hydrothermal method. It is demonstrated that PAA ligand played an important role in guiding the direct growth of NaGdF4:Ce3+,Eu3+ shell onto the surface of NaYF4:Yb3+,Tm3+ parent microtubes. The growth of NaGdF4:Ce3+,Eu3+ shell experienced a crystal phase transition from β-NaGdF4 and β-NaYF4 mixture to β-NaYF4@NaGdF4 composite crystal, and morphology evolution from mixture of β-NaGdF4:Ce3+,Eu3+ nanorods and β-NaYF4:Yb3+,Tm3+ microtubes to NaYF4:Yb3+,Tm3+@NaGdF4: Ce3+,Eu3+ DJMTs. The formation mechanism of DJMTs was the dissolution−renucleation of β-NaGdF4:Ce3+,Eu3+ nanorods and the growth of β-NaGdF4:Ce3+,Eu3+ shell via the classical Ostwald ripening mechanism. The as-prepared DJMTs could exhibit blue upconversion and red downconversion luminescence, which was further made into environmentally benign luminescent inks for creating highly secured and fluorescent-based anti-counterfeiting patterns via inkjet printing.  相似文献   
6.
The construction of invisible patterns via high-resolution printing and the independent encoding/decoding of complex information can lead to promising applications in steganography and watermarking for optical encryption. Herein, a rewritable chiral photonic paper formed by cholesteric cellulose nanocrystals and polycation is reported. The chemically crosslinked polycation network interpenetrates in the cholesteric structure while retaining the optical properties of the photonic crystals. The film exhibits controllable wettability via anion exchange, leading to extremely low contrast in the dry state but high contrast by a rapid wetting response. Triple invisible information is independently encoded on the films, including invisible patterns caused by reversible counterion-controlled wettability, permanent fluorescent labels based on fluorescent counterions, and polarization-dependent structural colors based on cholesteric structures. Full color patterns can be reversibly constructed via inkjet printing, with a high resolution of 100 µm. In addition, the circular polarization characteristics of the cellulose nanocrystals, liquid crystals, endow the system with complex and independent responses, realizing a wetting/polarization double-key decryption. This work provides a simple and effective optical technique for coding complex information on a single material platform and expands the techniques available to achieve invisible patterns for sensing and anti-counterfeiting.  相似文献   
7.
周荣勇  唐正宁 《包装工程》2012,33(3):121-124
使用Q-switched Nd:YAG激光对普通塑料薄膜上多层彩色油墨进行了激光烧蚀,从而产生了全触觉多色图像。研究表明这种方法产生的图像是具有防伪功能的。  相似文献   
8.
马小娜  韩颖 《黑龙江造纸》2012,40(1):33-37,40
从八种不同的防伪纸类型分别阐述了我国常用的防伪纸的特点及应用并简述了它们的制造工艺,探讨了防伪纸的发展前景。  相似文献   
9.
针对纹理防伪标签在光线不足、视力不佳的情况下难以鉴别的问题,提出了一种基于DCT、感知哈希和视觉特征向量的纹理防伪标签鉴别算法.首先通过DCT和感知哈希提取图像的特征向量;然后建立特征数据库,通过特征向量之间的归一化相关系数(NC)实现纹理防伪标签的自动鉴别.实验结果表明,该方法可以有效抵抗常规攻击和几何攻击,可实现自动鉴别技术.与现有的纹理防伪技术相比,该算法可以减小占据的数据库存储空间,具有更好的实用性.  相似文献   
10.
无线射频识别技术作为一种自动识别技术的高级形式,具有适应环境能力强、抗干扰强、读取方便和读取数据量大等诸多优点。将RFID技术应用于军车号牌及驾驶证防伪管理中,以提高军车号牌及驾驶证管理各环节的自动化水平和效率。  相似文献   
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