全文获取类型
收费全文 | 90859篇 |
免费 | 8485篇 |
国内免费 | 4314篇 |
专业分类
电工技术 | 5767篇 |
技术理论 | 10篇 |
综合类 | 6448篇 |
化学工业 | 15131篇 |
金属工艺 | 5052篇 |
机械仪表 | 5869篇 |
建筑科学 | 7061篇 |
矿业工程 | 2925篇 |
能源动力 | 2564篇 |
轻工业 | 6402篇 |
水利工程 | 1606篇 |
石油天然气 | 6043篇 |
武器工业 | 898篇 |
无线电 | 10398篇 |
一般工业技术 | 10207篇 |
冶金工业 | 4201篇 |
原子能技术 | 1235篇 |
自动化技术 | 11841篇 |
出版年
2024年 | 488篇 |
2023年 | 1707篇 |
2022年 | 3140篇 |
2021年 | 4133篇 |
2020年 | 3195篇 |
2019年 | 2632篇 |
2018年 | 2914篇 |
2017年 | 3157篇 |
2016年 | 2836篇 |
2015年 | 3752篇 |
2014年 | 4636篇 |
2013年 | 5413篇 |
2012年 | 5776篇 |
2011年 | 6254篇 |
2010年 | 5455篇 |
2009年 | 5262篇 |
2008年 | 5332篇 |
2007年 | 4907篇 |
2006年 | 4919篇 |
2005年 | 4264篇 |
2004年 | 2770篇 |
2003年 | 2586篇 |
2002年 | 2538篇 |
2001年 | 2272篇 |
2000年 | 2142篇 |
1999年 | 2189篇 |
1998年 | 1588篇 |
1997年 | 1403篇 |
1996年 | 1268篇 |
1995年 | 1050篇 |
1994年 | 899篇 |
1993年 | 671篇 |
1992年 | 548篇 |
1991年 | 370篇 |
1990年 | 301篇 |
1989年 | 230篇 |
1988年 | 195篇 |
1987年 | 131篇 |
1986年 | 91篇 |
1985年 | 52篇 |
1984年 | 47篇 |
1983年 | 46篇 |
1982年 | 36篇 |
1981年 | 24篇 |
1980年 | 22篇 |
1979年 | 8篇 |
1978年 | 1篇 |
1959年 | 6篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Guankui Long Yecheng Zhou Mingtao Zhang Randy Sabatini Abdullah Rasmita Li Huang Girish Lakhwani Weibo Gao 《Advanced materials (Deerfield Beach, Fla.)》2019,31(17)
Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics. 相似文献
62.
63.
Qiang Wang Lei Shen Tong Xue Gao Cheng Cheng Zhi Huang Hong Jin Fan Yuan Ping Feng 《Advanced functional materials》2021,31(2):2002187
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures. 相似文献
64.
65.
66.
Lin Gao Stefano Selleri Giorgio Battistelli Luigi Chisci Giuseppe Pelosi 《国际射频与微波计算机辅助工程杂志》2020,30(9)
This paper presents a novel approach to the localization of moving targets in a complex environment based on the measurement of the perturbations induced by the target presence on an independently‐generated time‐varying electromagnetic field. Field perturbations are measured via a set of sensors deployed over the domain of interest and used to detect and track a possible target by resorting to a particle Bernoulli filter (PBF). To comply with real‐time operation, the PBF works along with an artificial neural network (ANN) model of the environment trained offline via finite elements (FEs). The performance of the proposed algorithm is assessed via simulation experiments. 相似文献
67.
正进入21世纪以来,国际水泥混凝土产业经历了17年的科研试验、工业生产与工程应用等大量的实践,促使人们对过去曾被视为"低标号"的32.5水泥的认知发生了的逆转。非但一扫早先那种"水泥要向高标号发展"的旧传统理念,进而开始青睐于32.5水泥的新发展,并寄于厚望。这是国际水泥混凝土工业的一项重大技术进步,对发展方向具有重要指导意义,我国应予密切关注。(1)须要再次澄清一个重要的基本概念和现今 相似文献
68.
69.
针对在灰度图像着色领域中,传统算法信息提取率不高、着色效果不理想的问题,提出了基于密集神经网络的灰度图像着色算法,以实现改善着色效果,让人眼更好地观察图片信息的目的。利用密集神经网络的信息提取高效性,构建并训练了一个端到端的深度学习模型,对图像中的各类信息及特征进行提取。训练网络时与原图像进行对比,以逐渐减小网络输出结果的信息、分类等各类型的损失。训练完成后,只需向网络输入一张灰度图片,即可生成一张颜色饱满、鲜明逼真的彩色图片。实验结果表明,引入密集网络后,可有效改善着色过程中的漏色、细节信息损失、对比度低等问题,所提算法着色效果较基于VGG网络及U-Net、双流网络结构、残差网络(ResNet)等性能优异的先进着色算法而言取得了显著的改进。 相似文献
70.
Dujuan Li Wei Yan Ronghui Qi Li-Zhi Zhang 《International Journal of Hydrogen Energy》2021,46(14):9267-9279
PEM-based electrolytic air dehumidification is innovative in dehumidification that requires high precision and small space due to its high efficiency, compactness, and cleanness. However, the system dehumidification performance and durability are limited by using commercial Anatase-IrO2 catalysts. In this study, two types of structurally modified OER catalyst materials, ATO-IrO2 and ND-MnO2-IrO2, are developed to improve the performance of the system. System experiments showed that, compared to the commercial catalysts, the use of ATO-IrO2 and ND-MnO2-IrO2 as the anode catalyst can improve the dehumidification performance by 45% and 20%, respectively. Furthermore, in 50-h accelerated aging tests, the attenuation rates of the ATO-IrO2 and ND-MnO2-IrO2 systems are 3% and 8% respectively, which are far lower than the 35% attenuation of commercial catalyst. The results indicate that, as catalysts with a classic core-shell structure, ATO-IrO2 and ND-MnO2-IrO2 still have a significant impact on improving the performance of the electrolytic dehumidification systems. 相似文献