全文获取类型
收费全文 | 2142篇 |
免费 | 345篇 |
国内免费 | 137篇 |
专业分类
电工技术 | 14篇 |
综合类 | 138篇 |
化学工业 | 93篇 |
金属工艺 | 13篇 |
机械仪表 | 88篇 |
建筑科学 | 2篇 |
矿业工程 | 2篇 |
能源动力 | 4篇 |
轻工业 | 26篇 |
武器工业 | 11篇 |
无线电 | 1554篇 |
一般工业技术 | 589篇 |
冶金工业 | 8篇 |
原子能技术 | 11篇 |
自动化技术 | 71篇 |
出版年
2024年 | 6篇 |
2023年 | 48篇 |
2022年 | 49篇 |
2021年 | 84篇 |
2020年 | 78篇 |
2019年 | 79篇 |
2018年 | 77篇 |
2017年 | 109篇 |
2016年 | 69篇 |
2015年 | 94篇 |
2014年 | 164篇 |
2013年 | 228篇 |
2012年 | 188篇 |
2011年 | 177篇 |
2010年 | 160篇 |
2009年 | 178篇 |
2008年 | 191篇 |
2007年 | 160篇 |
2006年 | 147篇 |
2005年 | 104篇 |
2004年 | 86篇 |
2003年 | 50篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 14篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 2篇 |
排序方式: 共有2624条查询结果,搜索用时 125 毫秒
1.
设计了一种基于阿基米德螺线的新型螺旋光子晶体光纤,该光纤以二氧化硅为基底材料,包层由24个螺旋臂组成,每个螺旋臂包含11个小空气孔,纤芯设有大空气孔,包层与纤芯中间的环形区域用于传输轨道角动量模式。该结构在1300~1800 nm波段上可支持22种轨道角动量模式稳定传输,在1550 nm波长下,有效折射率差最高可达2.89×10^(-3),色散系数最低可达66.4 ps/(nm·km),非线性系数最低可达2.17 W^(-1)·km^(-1),且1500~1600 nm波段上的色散值变化均小于15.15 ps/(nm·km)。此螺旋光子晶体光纤不仅结构简单,且具有低非线性、色散平坦的性能,为螺旋光子晶体光纤的设计提供了思路。 相似文献
2.
Dimpi Paul Rajib Biswas Gunjan Saikia 《International Journal of Communication Systems》2021,34(1):e4669
We report here the development of two computational tools PCFPS (Photonic Crystal Fiber Parameter Study) and PCFPA (Photonic Crystal Fiber Parameter Analysis), equipped with graphical user interface (GUI) for modeling of photonic crystal fiber. The tools are based on different structural parameters, and they provide characteristic analysis of the modal parameters from the structural parameters. The main feature of PCFPS is that it enables the user to find out the values of each defining modal parameter that has an immense contribution towards the manufacture of photonic crystal fiber. Additionally, PCFPA allows the user to observe the variation in the modal parameters with respect to the changes in structural parameters (such as d, Λ, d/Λ, and λ/>Λ). Besides their ease of use, these two schemes have high computational precision and adaptability, giving a novel platform to optical engineers to modulate the microstructured fibers according to their requirement. 相似文献
3.
Patterned photonic crystals with structural colors on textile substrates have attracted a special attention due to the great advantages in application, which currently become a research hot-spot. This study utilized an ink-jet printing technology to prepare high-quality photonic crystal patterns with structural colors on polyester substrates. The self-assembly temperature of poly(styrene-N-methylol acrylamide) (P(St-NMA)) microspheres set to construct photonic crystals were deeply optimized. Moreover, the structural colors of prepared photonic crystal patterns were characterized and evaluated. When the mass fraction of P(St-NMA) microspheres was 1.0 wt.%, the pH value ranged from 5 to 7, and the surface tension was in the range of 63.79 to 71.20 mN/m, inks could present the best print performance. At 60 °C, prepared P(St-NMA) microsphere inks were good for printing to obtain patterned photonic crystals with regular arrangement and beautiful structural colors. Specifically, photonic crystals with different colors could be constructed by regulating the diameter of microspheres in inks, and prepared structural colors exhibited distinct iridescent phenomenon. The present results could provide a theoretical basis for the industrial realization of patterned photonic crystals by ink-jet printing technology. 相似文献
4.
为了研究电磁诱导透明效应在拓扑单向波导中的表现,设计了一种基于磁性光子晶体的耦合谐振腔波导。通过对谐振腔位置的调控实现了具有单向性质的电磁诱导透明效应,并利用有限时域差分仿真证明了电磁诱导透明效应在单向拓扑波导中的相关特性。该研究可为拓扑波导中实现光延迟、光开关等提供参考。 相似文献
5.
In this paper, the nonreciprocal properties of a novel kind of 1D magnetized plasma photonic crystals(MPPCs) with the Fibonacci sequence are investigated. The isolation of the proposed 1D MPPCs is also used to analyze the nonreciprocal properties. Compared to the conventional 1D MPPCs with periodic structure, the nonreciprocal performance can be significantly improved.The effects of several parameters of the proposed 1D MPPCs on the nonreciprocal properties are studied by the transfer matrix method, which includes the incident angle, order of the Fibonacci sequence, plasma frequency, plasma cyclotron frequency and plasma filling factor. The obtained results show that the nonreciprocal propagation properties can be improved by increasing the values of the plasma cyclotron frequency and incident angle, but they will worsen by blindly increasing the order of the Fibonacci sequence, plasma frequency and filling factor of plasma.The peaks of transmittance also are obviously reduced. In addition, the value of isolation will increase with increasing the incident angle, order of Fibonacci sequence, plasma frequency and plasma filling factor. However, when the plasma cyclotron frequency is increased, the value of isolation will be increased at lower frequencies, but is almost unchanged at higher frequencies. 相似文献
6.
Yuemei Wang Wei Feng Meiqi Chang Jiacai Yang Yuedong Guo Li Ding Luodan Yu Hui Huang Yu Chen Jianlin Shi 《Advanced functional materials》2021,31(6):2005093
2D monoelemental nanomaterials (Xenes) have shown tremendous potential for versatile biomedical applications. Bismuth, as a heavy element in pnictogens, has acquired massive research interest due to its unique optical performance, high biocompatibility, stability, and relatively low cost. However, the utilization of 2D bismuthene in nanomedicine has not been achieved because of the difficulty in engineering bismuthene with crucial structural/compositional characteristics for satisfying strict biomedical requirements. Herein, to address this Gordian knot, a facile strategy to intercalate and delaminate Bi bulk for generating mass few-layered 2D bismuthene with high yield by employing a water molecule mediated freezing–thawing process and sodium borohydride-triggered reduction treatment is proposed. The resulting 2D bismuthene displays good optical performance in the near-infrared (NIR) biowindow and can be excited via red light for reactive oxygen species generation, enabling applications in multiple photonic cancer nanomedicine settings, including photothermal hyperthermia and photodynamic therapy. Utilizing the intrinsic desirable optical absorbance and strong X-ray attenuation of bismuthene, dual photonic therapy can be conducted under the supervision of photoacoustic/computed tomography guided multimodal imaging. This research not only offers a potential mass-production ready, cost-effective, and eco-efficient methodology for engineering 2D Xenes, but also exploits an innovative 2D bismuthene based photonic cancer nanomedicine. 相似文献
7.
8.
9.
Inki Kim Muhammad Afnan Ansari Muhammad Qasim Mehmood Won-Sik Kim Jaehyuck Jang Muhammad Zubair Young-Ki Kim Junsuk Rho 《Advanced materials (Deerfield Beach, Fla.)》2020,32(50):2004664
Flat optics, realized by the artificially created 2D material platform called optical metasurfaces, is currently undergoing a science-to-technology transition. However, “real-time” active operations of such flat optical devices remain yet unresolved. Here, liquid crystals (LCs)-integrated metaholograms for ultracompact dynamic holographic displays are proposed. The anisotropic nature of the LCs allows facile and repeatable manipulation of the polarization of light. Specifically designed (“designer”) LCs and efficient helicity-encoded metaholograms are combined to realize stimuli-responsive dynamic displays. The designer LC modulators are used as switches that enable a variety of external stimuli (e.g., electric field, heat, surface pressure) to operate holographic images in real-time. Such a dynamic metaholographic platform will provide a path to external stimuli-driven “smart” sensing and display applications such as hologram labels for temperature/pressure/touch monitoring and interactive holographic displays with haptic motion recognition. 相似文献
10.
Saeid Salimzadeh 《Journal of Modern Optics》2018,65(17):2017-2024
In this paper, a 3 to 8 optical decoder was proposed using nonlinear photonic crystal ring resonators. For realizing the 3 to 8 decoder, we combined seven 1 to 2 optical decoders. In the proposed structure, X, Y and Z serve as input ports. By combination of these ports, one can control which output port to be ON. The maximum time delay of the proposed structure is about 6?ps. 相似文献