全文获取类型
收费全文 | 46574篇 |
免费 | 4105篇 |
国内免费 | 2214篇 |
专业分类
电工技术 | 2565篇 |
技术理论 | 3篇 |
综合类 | 3223篇 |
化学工业 | 7818篇 |
金属工艺 | 2375篇 |
机械仪表 | 2964篇 |
建筑科学 | 3781篇 |
矿业工程 | 1272篇 |
能源动力 | 1467篇 |
轻工业 | 2708篇 |
水利工程 | 834篇 |
石油天然气 | 3201篇 |
武器工业 | 353篇 |
无线电 | 5399篇 |
一般工业技术 | 5737篇 |
冶金工业 | 2058篇 |
原子能技术 | 572篇 |
自动化技术 | 6563篇 |
出版年
2024年 | 204篇 |
2023年 | 743篇 |
2022年 | 1293篇 |
2021年 | 1804篇 |
2020年 | 1368篇 |
2019年 | 1201篇 |
2018年 | 1300篇 |
2017年 | 1496篇 |
2016年 | 1355篇 |
2015年 | 1673篇 |
2014年 | 2192篇 |
2013年 | 2588篇 |
2012年 | 2698篇 |
2011年 | 2980篇 |
2010年 | 2584篇 |
2009年 | 2448篇 |
2008年 | 2492篇 |
2007年 | 2337篇 |
2006年 | 2506篇 |
2005年 | 2076篇 |
2004年 | 1519篇 |
2003年 | 1704篇 |
2002年 | 1963篇 |
2001年 | 1703篇 |
2000年 | 1356篇 |
1999年 | 1431篇 |
1998年 | 1037篇 |
1997年 | 880篇 |
1996年 | 883篇 |
1995年 | 689篇 |
1994年 | 595篇 |
1993年 | 457篇 |
1992年 | 316篇 |
1991年 | 232篇 |
1990年 | 183篇 |
1989年 | 157篇 |
1988年 | 157篇 |
1987年 | 95篇 |
1986年 | 56篇 |
1985年 | 38篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1976年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
该文设计了一款温度补偿型声表面波(TC-SAW)滤波器,建立了弹性材料及压电材料温度方程,对滤波器的温度场进行仿真分析。通过在压电材料(128°YX-LiNbO3)上沉积SiO2作为温度补偿层,降低了滤波器的频率温度系数。为了解决在沉积SiO2温度补偿层后,谐振器的反谐振频率处出现杂散响应,通过增加电极厚度,降低了谐振器杂散响应对滤波器性能的影响。采用四阶级联提高滤波器的带外抑制。仿真结果表明,设计的TC-SAW滤波器中心频率为2 497 MHz,频率温度系数为-9.89×10-6/℃,-30~85 ℃工作温度范围内的带内最大插损为1.95 dB,带外抑制大于30 dB,-3 dB损耗带宽大于97 MHz。 相似文献
983.
Jiefeng Hai Yuanxia Song Ling Li Xin Liu Xiaoyu Shi Zhuoyue Huang Guangming Qian Zhenhuan Lu Jiangsheng Yu Huawei Hu Shangshang Chen 《Advanced functional materials》2023,33(19):2213429
The elaborate balance between the open-circuit voltage (VOC) and the short-circuit current density (JSC) is critical to ensure efficient organic solar cells (OSCs). Herein, the chalcogen containing branched chain engineering is employed to address this dilemma. Three novel nonfullerene acceptors (NFAs), named BTP-2O , BTP-O-S , and BTP-2S , featuring different peripheral chalcogen containing branched chains are synthesized. Compared with symmetric BTP-2O and BTP-2S grafting two alkoxy or alkylthio branched chains, the asymmetric BTP-O-S grafting one alkoxy and one alkylthio branched chains shows mediate absorption range, applicable miscibility, and favorable crystallinity. Benefiting from the enhanced π–π stacking and charge transport, an optimal power conversion efficiency (PCE) of 17.3% is obtained for the PM6: BTP-O-S -based devices, with a good balance between VOC (0.912 V) and JSC (24.5 mA cm−2), and a high fill factor (FF) of 0.775, which is much higher than those of BTP-2O (16.1%) and BTP-2S -based (16.4%) devices. Such a result represents one of the highest efficiencies among the binary OSCs with VOC surpassing 0.9 V. Moreover, the BTP-O-S -based devices fabricated by using green solvent yield a satisfactory PCE of 17.1%. This work highlights the synergistic effect of alkoxy and alkylthio branched chains for high-performance OSCs by alleviating voltage loss and enhancing FF. 相似文献
984.
Rui-Qi Yao Yi-Tong Zhou Hang Shi Wu-Bin Wan Qing-Hua Zhang Lin Gu Yong-Fu Zhu Zi Wen Xing-You Lang Qing Jiang 《Advanced functional materials》2021,31(10):2009613
Electrocatalytic hydrogen evolution in alkaline and neutral media offers the possibility of adopting platinum-free electrocatalysts for large-scale electrochemical production of pure hydrogen fuel, but most state-of-the-art electrocatalytic materials based on nonprecious transition metals operate at high overpotentials. Here, a monolithic nanoporous multielemental CuAlNiMoFe electrode with electroactive high-entropy CuNiMoFe surface is reported to hold great promise as cost-effective electrocatalyst for hydrogen evolution reaction (HER) in alkaline and neutral media. By virtue of a surface high-entropy alloy composed of dissimilar Cu, Ni, Mo, and Fe metals offering bifunctional electrocatalytic sites with enhanced kinetics for water dissociation and adsorption/desorption of reactive hydrogen intermediates, and hierarchical nanoporous Cu scaffold facilitating electron transfer/mass transport, the nanoporous CuAlNiMoFe electrode exhibits superior nonacidic HER electrocatalysis. It only takes overpotentials as low as ≈240 and ≈183 mV to reach current densities of ≈1840 and ≈100 mA cm−2 in 1 m KOH and pH 7 buffer electrolytes, respectively; ≈46- and ≈14-fold higher than those of ternary CuAlNi electrode with bimetallic Cu–Ni surface alloy. The outstanding electrocatalytic properties make nonprecious multielemental alloys attractive candidates as high-performance nonacidic HER electrocatalytic electrodes in water electrolysis. 相似文献
985.
Tao Cheng Yi-Zhou Zhang Shi Wang Ya-Li Chen Si-Ya Gao Feng Wang Wen-Yong Lai Wei Huang 《Advanced functional materials》2021,31(24):2101303
Stretchable self-healing supercapacitors (SCs) can operate under extreme deformation and restore their initial properties after damage with considerably improved durability and reliability, expanding their opportunities in numerous applications, including smart wearable electronics, bioinspired devices, human–machine interactions, etc. It is challenging, however, to achieve mechanical stretchability and self-healability in energy storage technologies, wherein the key issue lies in the exploitation of ideal electrode and electrolyte materials with exceptional mechanical stretchability and self-healing ability besides conductivity. Conductive hydrogels (CHs) possess unique hierarchical porous structure, high electrical/ionic conductivity, broadly tunable physical and chemical properties through molecular design and structure regulation, holding tremendous promise for stretchable self-healing SCs. Hence, this review is innovatively constructed with a focus on stretchable and self-healing CH based electrodes and electrolytes for SCs. First, the common synthetic approaches of CHs are introduced; then the stretching and self-healing strategies involved in CHs are systematically elaborated; followed by an explanation of the conductive mechanism of CHs; then focusing on CH-based electrodes and electrolytes for stretchable self-healing SCs; subsequently, application of stretchable and self-healing SCs in wearable electronics are discussed; finally, a conclusion is drawn along with views on the challenges and future research directions regarding the field of CHs for SCs. 相似文献
986.
Jinqiang Shi Tianjiang Sun Junquan Bao Shibing Zheng Haihui Du Lin Li Xuming Yuan Tao Ma Zhanliang Tao 《Advanced functional materials》2021,31(23):2102035
Aqueous Zn-ion batteries have been considered as promising alternatives to Li-ion batteries due to their abundant reserves, low price, and high safety. However, Zn anode shows poor reversibility and cycling stability in most conventional aqueous electrolytes. Here, a new type of aqueous Zn-ion electrolyte based on ZnCl2–acetamide deep eutectic solvent with both environmental and economic friendliness has been prepared. The water molecule introduced in the “water-in-deep eutectic solvent” electrolyte could reduce the Zn2+ desolvation energy barrier by regulating Zn2+ solvation structure to promote uniform Zn nucleation. Zn anode shows improved electrochemical performance (≈98% Coulombic efficiency over 1000 cycles) in the electrolyte whose molar ratio of ZnCl2:acetamide:H2O is 1:3:1. The assembled full battery composed of phenazine cathode and Zn anode could stably cycle over 10 000 cycles with a high capacity retention of 85.7%. Overall, this work offers new insights into exploring new green electrolyte systems for Zn-ion batteries. 相似文献
987.
Lowering Internal Friction of 0D–1D–2D Ternary Nanocomposite‐Based Strain Sensor by Fullerene to Boost the Sensing Performance 下载免费PDF全文
Xinlei Shi Shuiren Liu Yang Sun Jiajie Liang Yongsheng Chen 《Advanced functional materials》2018,28(22)
The development of strain sensors with both large strain range (>50%) and high gauge factor (>100) is a grand challenge. High sensitivity requires material to perform considerable structural deformation under tiny strain, whereas high stretchability demands structural connection or morphological integrity for materials upon large deformation, yet both features are hard to be achieved in one thin film. A new 0D–1D–2D ternary nanocomposite–based strain sensor is developed that possesses high sensitivity in broad working strain range (gauge factor 2392.9 at 62%), low hysteresis, good linearity, and long‐term durability. The skin‐mountable strain sensor, fabricated through one‐step screen‐printing process, is made of 1D silver nanowire offering high electrical conductivity, 2D graphene oxide offering brittle layered structure, and 0D fullerene offering lubricity. The fullerene constitutes a critical component that lowers the friction between graphene oxide–based layers and facilitates the sliding between adjacent layers without hurting the brittle nature of the nanocomposite film. When stretching, layer slippage induced by fullerene can accommodate partial applied stress and boost the strain, while cracks originating and propagating in the brittle nanocomposite film ensure large resistance change over the whole working strain range. Such high comprehensive performance renders the strain sensor applicable to full‐spectrum human motion detection. 相似文献
988.
基于红外图像的行人检测技术在夜间场景监控、汽车夜间辅助驾驶等相关领域具有重要的作用,然而受红外图像分辨率低、信噪比高等因素影响,当前的很多方法性能不佳。提出了一种基于图像特征通道的红外行人检测算法。利用快速特征金字塔技术在红外图像上进行了滑动窗口检测。实验结果证明,相对于其他常规算法,该算法在实时性和鲁棒性上都有很大的提升。 相似文献
989.
经济社会和科学技术的发展,有效推动了智能化技术的发展,其在越来越多的领域中得到广泛应用,尤其是电气工程自动化控制领域.智能化技术的应用,既可以提高电气工程自动化控制的整体效果,而且还可以推动整个电气工程行业的发展.本文将会对智能化技术的基础理论、主要特点给予介绍,重点分析了在电气工程自动化控制中智能化技术的应用效果及未... 相似文献
990.