全文获取类型
收费全文 | 3829篇 |
免费 | 275篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 53篇 |
综合类 | 12篇 |
化学工业 | 1112篇 |
金属工艺 | 103篇 |
机械仪表 | 134篇 |
建筑科学 | 118篇 |
矿业工程 | 6篇 |
能源动力 | 313篇 |
轻工业 | 420篇 |
水利工程 | 62篇 |
石油天然气 | 34篇 |
武器工业 | 1篇 |
无线电 | 331篇 |
一般工业技术 | 744篇 |
冶金工业 | 88篇 |
原子能技术 | 39篇 |
自动化技术 | 554篇 |
出版年
2024年 | 15篇 |
2023年 | 87篇 |
2022年 | 149篇 |
2021年 | 283篇 |
2020年 | 187篇 |
2019年 | 250篇 |
2018年 | 248篇 |
2017年 | 257篇 |
2016年 | 237篇 |
2015年 | 183篇 |
2014年 | 231篇 |
2013年 | 404篇 |
2012年 | 274篇 |
2011年 | 337篇 |
2010年 | 190篇 |
2009年 | 154篇 |
2008年 | 110篇 |
2007年 | 77篇 |
2006年 | 62篇 |
2005年 | 32篇 |
2004年 | 26篇 |
2003年 | 33篇 |
2002年 | 26篇 |
2001年 | 22篇 |
2000年 | 26篇 |
1999年 | 14篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1978年 | 4篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有4124条查询结果,搜索用时 31 毫秒
1.
The methanol‐to‐olefins reaction (MTO) was studied in a small‐scale fluidized‐bed reactor over synthesized silicoaluminophosphate (SAPO‐34) catalysts. Mesoporous nanocrystalline SAPO‐34 molecular sieves were synthesized hydrothermally by ultrasonic and microwave‐assisted aging processes in the presence of hexadecyltrimethylammonium bromide (CTAB) and tetradecyldimethyl(3‐trimethoxysilylpropyl)ammonium chloride (TPOAC) as surfactant agents. The Box‐Behnken experimental design method was applied to determine the optimum operating parameters of this process conducted in the fluidized‐bed reactor. The optimum conditions in terms of reaction temperature, ratio of inlet gas velocity to minimum fluidizing velocity, and MeOH weight fraction were evaluated. 相似文献
2.
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
3.
4.
Hamzehzadeh Seyedhashem Mazinani Sayyed Majid 《Wireless Personal Communications》2019,107(4):1995-2017
Wireless Personal Communications - One of the main concerns at the time of production or share of information on social networking sites for scientific research and business analysis is privacy.... 相似文献
5.
Khalid Tauqeer Khan Abdul Nasir Ali Mazhar Adeel Adil ur Rehman Khan Atta Shuja Junaid 《Multimedia Tools and Applications》2019,78(17):24595-24615
Multimedia Tools and Applications - The world is facing many problems including that of traffic congestion. To highlight the issue of traffic congestion worldwide specially in urban areas and to... 相似文献
6.
7.
Abdul Rahman Mohtasebzadeh Longfei Ye Thomas M. Crawford 《International journal of molecular sciences》2015,16(8):19769-19779
We study magnetic-field directed self-assembly of magnetic nanoparticles onto templates recorded on perpendicular magnetic recording media, and quantify feature width and height as a function of assembly time. Feature widths are determined from Scanning Electron Microscope (SEM) images, while heights are obtained with Atomic Force Microscopy (AFM). For short assembly times, widths were ~150 nm, while heights were ~14 nm, a single nanoparticle on average with a 10:1 aspect ratio. For long assembly times, widths approach 550 nm, while the average height grows to 3 nanoparticles, ~35 nm; a 16:1 aspect ratio. We perform magnetometry on these self-assembled structures and observe the slope of the magnetic moment vs. field curve increases with time. This increase suggests magnetic nanoparticle interactions evolve from nanoparticle–nanoparticle interactions to cluster–cluster interactions as opposed to feature–feature interactions. We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media. If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials. 相似文献
8.
9.
In the present work, inter-diffusion of nickel and titanium and formation of Ni-Ti intermetallic compounds on Ti-6Al-4V substrate have been studied. Initially, nickel was electrodeposited on the alloy using a modified Watts bath solution at a current density of 2 A dm?2 for 1?h. The coated specimens were then heat treated for different durations at 750, 800 and 850 °C under argon atmosphere. The effects of temperature and time on the characteristics, hardness and wear resistance of intermetallic phases were investigated. The results showed that a multilayer structure was formed after heat treatment, an outer layer of residual nickel, an area of intermetallic layers with different compositions followed by a solid solution of Ni-Ti. It was also observed that an increase in time or temperature at first led to the formation of thicker intermetallic layers; however, after passing a critical point, the intermetallic layers seem to dissolve into the substrate. Furthermore, the wear rates of the diffusion treated samples were four times lower compared to Ti-6Al-4V alloy when sliding against AISI 52100 hardened steel. 相似文献
10.