全文获取类型
收费全文 | 9963篇 |
免费 | 387篇 |
国内免费 | 106篇 |
专业分类
电工技术 | 252篇 |
综合类 | 194篇 |
化学工业 | 1950篇 |
金属工艺 | 369篇 |
机械仪表 | 364篇 |
建筑科学 | 335篇 |
矿业工程 | 102篇 |
能源动力 | 404篇 |
轻工业 | 600篇 |
水利工程 | 113篇 |
石油天然气 | 155篇 |
武器工业 | 16篇 |
无线电 | 1138篇 |
一般工业技术 | 2259篇 |
冶金工业 | 1130篇 |
原子能技术 | 112篇 |
自动化技术 | 963篇 |
出版年
2023年 | 97篇 |
2022年 | 163篇 |
2021年 | 235篇 |
2020年 | 213篇 |
2019年 | 164篇 |
2018年 | 274篇 |
2017年 | 213篇 |
2016年 | 242篇 |
2015年 | 217篇 |
2014年 | 289篇 |
2013年 | 602篇 |
2012年 | 409篇 |
2011年 | 485篇 |
2010年 | 407篇 |
2009年 | 393篇 |
2008年 | 382篇 |
2007年 | 345篇 |
2006年 | 313篇 |
2005年 | 264篇 |
2004年 | 241篇 |
2003年 | 219篇 |
2002年 | 201篇 |
2001年 | 174篇 |
2000年 | 220篇 |
1999年 | 228篇 |
1998年 | 304篇 |
1997年 | 264篇 |
1996年 | 237篇 |
1995年 | 202篇 |
1994年 | 181篇 |
1993年 | 174篇 |
1992年 | 148篇 |
1991年 | 150篇 |
1990年 | 102篇 |
1989年 | 109篇 |
1988年 | 112篇 |
1987年 | 108篇 |
1986年 | 92篇 |
1985年 | 127篇 |
1984年 | 121篇 |
1983年 | 134篇 |
1982年 | 96篇 |
1981年 | 96篇 |
1980年 | 84篇 |
1979年 | 88篇 |
1978年 | 74篇 |
1977年 | 65篇 |
1976年 | 72篇 |
1975年 | 57篇 |
1974年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Silicon - This paper presents, analytical modeling of surface potential,threshold voltage and DIBL for a Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET considering the parabolic... 相似文献
3.
4.
利用模糊控制和比例积分微分(PID)控制相结合的手段对注塑机料筒温度进行了控制,同时以Matlab 6.0软件为仿真平台,对料筒温度控制进行了模拟仿真研究。实验发现,在注塑机料筒升温过程中利用CHR整定的PID控制手段和模糊控制手段,恒温过程中利用人工整定的PID控制手段,可保证快速的料筒升温响应速率和稳定的保温过程。通过实际注塑实验对该仿真结果进行了验证,在十组实验中,料筒温度误差不超过2%,产品翘曲变形量不超过0.059 mm。 相似文献
5.
Nur Lina Rashidah Mohd Rashid Abdullah Abdul Samat Abdul Azim Jais Mahendra Rao Somalu Andanastuti Muchtar Nurul Akidah Baharuddin Wan Nor Roslam Wan Isahak 《Ceramics International》2019,45(6):6605-6615
The performance of low-to-intermediate temperature (400–800?°C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O2-) conductors with proton (H+) conductors because H+ conductors have higher ionic conductivity and theoretical electrical efficiency than O2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H+ conductors. Cerate-based electrolytes have the highest H+ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped cerate–zirconate and hybrid-doped cerate–zirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application. 相似文献
6.
7.
8.
Mohan B. Ponnuchamy G. Mohan Muralikrishna Venkateswara Rao Mannava G. Srinivas Reddy 《Ceramics International》2018,44(13):15019-15023
Nanocrystalline nickel oxide (NiO) was prepared from nickel hydroxide by Spark plasma sintering (SPS) and the mechanisms involved in the densification of NiO were studied. Reverse precipitated nickel hydroxide powders were SPS processed at 400, 600 and 700?°C with 70?MPa pressure. Pure NiO with 12?nm crystallite size formed after 400?°C sintering process. However NiO grains had grown to 18 and 38?nm after 600 and 700?°C sintering respectively. NiO pellets prepared using 600 and 700?°C SPS sintering schedules had relative densities of 83% and 94% respectively. Two displacement rate regimes were observed during densification of NiO in both 600 and 700?°C sintering processes. Decomposition of nickel hydroxide and particle sliding of NiO led to first displacement rate maximum while inverse Hall-Petch based plastic deformation facilitated densification during the constant second displacement rate regime. No densification occurred during sintering holding times indicating the limited role that diffusion played during densification. 相似文献
9.
P. Sampath Brijesh Kakarla Raghava Reddy C. Venkata Reddy Nagaraj P. Shetti Raghavendra V. Kulkarni Anjanapura V. Raghu 《化学工程与技术》2020,43(7):1240-1248
Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency. 相似文献
10.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献