全文获取类型
收费全文 | 71329篇 |
免费 | 18077篇 |
国内免费 | 2348篇 |
专业分类
电工技术 | 3460篇 |
技术理论 | 2篇 |
综合类 | 3021篇 |
化学工业 | 21684篇 |
金属工艺 | 2247篇 |
机械仪表 | 2919篇 |
建筑科学 | 4353篇 |
矿业工程 | 910篇 |
能源动力 | 1757篇 |
轻工业 | 10697篇 |
水利工程 | 1036篇 |
石油天然气 | 1478篇 |
武器工业 | 410篇 |
无线电 | 11029篇 |
一般工业技术 | 14874篇 |
冶金工业 | 1888篇 |
原子能技术 | 473篇 |
自动化技术 | 9516篇 |
出版年
2024年 | 157篇 |
2023年 | 679篇 |
2022年 | 1303篇 |
2021年 | 1872篇 |
2020年 | 2651篇 |
2019年 | 4090篇 |
2018年 | 4076篇 |
2017年 | 4574篇 |
2016年 | 4883篇 |
2015年 | 5452篇 |
2014年 | 5793篇 |
2013年 | 7177篇 |
2012年 | 5395篇 |
2011年 | 4950篇 |
2010年 | 5161篇 |
2009年 | 4794篇 |
2008年 | 4376篇 |
2007年 | 4158篇 |
2006年 | 3558篇 |
2005年 | 2926篇 |
2004年 | 2512篇 |
2003年 | 2303篇 |
2002年 | 2266篇 |
2001年 | 2019篇 |
2000年 | 1735篇 |
1999年 | 930篇 |
1998年 | 404篇 |
1997年 | 314篇 |
1996年 | 259篇 |
1995年 | 202篇 |
1994年 | 192篇 |
1993年 | 116篇 |
1992年 | 105篇 |
1991年 | 63篇 |
1990年 | 68篇 |
1989年 | 52篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1959年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
采用直流磁控溅射和后退火氧化工艺在p型GaAs单晶衬底上成功制备了n-VO_2/pGaAs异质结,研究了不同退火温度和退火时间对VO_2/GaAs异质结性能的影响,并分析其结晶取向、化学组分、膜层质量以及光电特性。结果表明,在退火时间2 h和退火温度693 K下能得到相变性能最佳的VO_2薄膜,相变前后电阻变化约2个数量级。VO_2/GaAs异质结在308 K、318 K和328 K温度下具有较好的整流特性,对应温度下的阈值跳变电压分别为6.9 V、6.6 V和6.2 V,该结果为基于VO_2相变特性的异质结光电器件的设计与应用提供了可行性。 相似文献
2.
摘 要:核心网业务模型的建立是5G网络容量规划和网络建设的基础,通过现有方法得到的理论业务模型是静态不可变的且与实际网络存在偏离。为了克服现有5G核心网业务模型与现网模型适配性较差以及规划设备无法满足用户实际业务需求的问题,提出了一种长短期记忆(long short-term memory,LSTM)网络与卷积LSTM (convolution LSTM,ConvLSTM)网络双通道融合的 5G 核心网业务模型预测方法。该方法基于人工智能(artificial intelligence,AI)技术以实现高质量的核心网业务模型的智能预测,形成数据反馈闭环,实现网络自优化调整,助力网络智能化建设。 相似文献
4.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
5.
Bijan Nasri‐Nasrabadi Akif Kaynak Shayan Seyedin Zahra Komeily‐Nia Abbas Z Kouzani 《Polymer International》2019,68(5):922-928
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry 相似文献
6.
Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films are attracting famous applications in antistatic coating, energy storage and conversion, printed electronics, and biomedical fields due to their conductivity, optical transparency and flexibility. However, PEDOT:PSS has poor dispersion stability during long-term storage and transport. Moreover, the dried PEDOT:PSS films are insoluble in any solvent and cannot be redispersed again. In comparison to bake drying, here, a feasible strategy to achieve mechanically redispersed PEDOT:PSS with the help of freeze-drying process was reported. The redispersed PEDOT:PSS can recover not only the initial characters such as pH, chemical composition, viscosity, and particle size under similar solid contents, but also conductivity and surface morphology of treated films. In addition, the treated film exhibits self-healing properties similar to pristine film in terms of mechanical and electrical properties. This technology enables reuse and overcomes the technical problems of PEDOT:PSS dispersion, realizing real-time processing to meet variable applications. 相似文献
7.
Chenglai Xin Rong Yuan Jiang Wu Qingyuan Wang Yanan Zhou 《Ceramics International》2021,47(3):3411-3420
A novel method for fabricating a nano-Cu/Si3N4 ceramic substrate is proposed. The nano-Cu/Si3N4 ceramic substrate is first fabricated using spark plasma sintering (SPS) with the addition of nanoscale multilayer films (Ti/TiN/Ti/TiN/Ti) as transition layers. The microstructures of the nano-Cu metal layer and the interface between Cu and Si3N4 are investigated. The results show that a higher SPS temperature increases the grain size of the nano-Cu metal layer and affects the hardness. The microstructure of the transition layer evolves significantly after SPS. Ti in the transition layer can react with Si3N4 and with nano-Cu to form interfacial reaction layers of TiN and Ti–Cu, respectively; these ensure stronger bonding between nano-Cu and Si3N4. Higher SPS temperatures improve the diffusion ability of Ti and Cu, inducing the formation of Ti3Cu3O compounds in the nano-Cu metal layer and Ti2Cu in the transition layer. This study provides an important strategy for designing and constructing a new type of ceramic substrate. 相似文献
8.
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique... 相似文献
9.
10.
Yuan-Cheng Meng Hua-Feng Zhang Xiao-Xiao Pan Nan Chen Hui-Fang Hu Saeed ul Haq Abid Khan Ru-Gang Chen 《International journal of molecular sciences》2021,22(6)
Dehydrins (DHNs) play an important role in abiotic stress tolerance in a large number of plants, but very little is known about the function of DHNs in pepper plants. Here, we isolated a Y1SK2-type DHN gene “CaDHN3” from pepper. To authenticate the function of CaDHN3 in salt and drought stresses, it was overexpressed in Arabidopsis and silenced in pepper through virus-induced gene silencing (VIGS). Sub-cellular localization showed that CaDHN3 was located in the nucleus and cell membrane. It was found that CaDHN3-overexpressed (OE) in Arabidopsis plants showed salt and drought tolerance phenotypic characteristics, i.e., increased the initial rooting length and germination rate, enhanced chlorophyll content, lowered the relative electrolyte leakage (REL) and malondialdehyde (MDA) content than the wild-type (WT) plants. Moreover, a substantial increase in the activities of antioxidant enzymes; including the superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and lower hydrogen peroxide (H2O2) contents and higher O2•− contents in the transgenic Arabidopsis plants. Silencing of CaDHN3 in pepper decreased the salt- and drought-stress tolerance, through a higher REL and MDA content, and there was more accumulation of reactive oxygen species (ROS) in the CaDHN3-silenced pepper plants than the control plants. Based on the yeast two-hybrid (Y2H) screening and Bimolecular Fluorescence Complementation (BiFC) results, we found that CaDHN3 interacts with CaHIRD11 protein in the plasma membrane. Correspondingly, the expressions of four osmotic-related genes were significantly up-regulated in the CaDHN3-overexpressed lines. In brief, our results manifested that CaDHN3 may play an important role in regulating the relative osmotic stress responses in plants through the ROS signaling pathway. The results of this study will provide a basis for further analyses of the function of DHN genes in pepper. 相似文献