全文获取类型
收费全文 | 10300篇 |
免费 | 1030篇 |
国内免费 | 772篇 |
专业分类
电工技术 | 712篇 |
综合类 | 813篇 |
化学工业 | 2382篇 |
金属工艺 | 2305篇 |
机械仪表 | 466篇 |
建筑科学 | 328篇 |
矿业工程 | 220篇 |
能源动力 | 351篇 |
轻工业 | 449篇 |
水利工程 | 94篇 |
石油天然气 | 171篇 |
武器工业 | 48篇 |
无线电 | 704篇 |
一般工业技术 | 2079篇 |
冶金工业 | 384篇 |
原子能技术 | 123篇 |
自动化技术 | 473篇 |
出版年
2024年 | 29篇 |
2023年 | 305篇 |
2022年 | 274篇 |
2021年 | 396篇 |
2020年 | 478篇 |
2019年 | 429篇 |
2018年 | 381篇 |
2017年 | 493篇 |
2016年 | 480篇 |
2015年 | 532篇 |
2014年 | 568篇 |
2013年 | 702篇 |
2012年 | 747篇 |
2011年 | 798篇 |
2010年 | 547篇 |
2009年 | 626篇 |
2008年 | 478篇 |
2007年 | 613篇 |
2006年 | 585篇 |
2005年 | 451篇 |
2004年 | 414篇 |
2003年 | 335篇 |
2002年 | 276篇 |
2001年 | 232篇 |
2000年 | 176篇 |
1999年 | 129篇 |
1998年 | 115篇 |
1997年 | 96篇 |
1996年 | 65篇 |
1995年 | 64篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 33篇 |
1991年 | 28篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1964年 | 3篇 |
1962年 | 2篇 |
1959年 | 3篇 |
1957年 | 2篇 |
1956年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A study on the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide batteries 下载免费PDF全文
Masoud Sabzi Saeid Mersagh Dezfuli 《International Journal of Applied Ceramic Technology》2018,15(6):1446-1458
In this study, the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide batteries have been investigated. For this purpose, firstly four silver oxide electrodes containing 5, 10, 15, and 20 wt% carbon powder were produced by powder metallurgy method. For the next step, all four silver oxide electrodes were sintered at 500°C for 10 minutes. Afterward and in order to investigate the microstructure, phase and elemental analysis of the electrodes were carried out using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X‐ray Diffraction (XRD), and Energy Dispersive Spectroscopy (EDS), respectively. Moreover, in order to investigate the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide, electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) and electric discharge test in 1.4 wt%KOH electrolyte were carried out respectively. The microstructural observations revealed that increasing carbon content in the silver oxide electrodes results in increasing the apparent porosities in these electrodes. Investigating the phase and elemental analysis results showed that by increasing the content of carbon in the silver oxide electrode, the amount of Ag2O and AgO phases in this electrode reduces and also the extent of pure silver formation increases. Investigations on the results of electrochemical tests showed that increasing carbon content results in the reduction of corrosion resistance in silver oxide electrodes. Moreover, the results of electric discharge test revealed that the silver oxide electrode containing 10wt% carbon yields the highest energy efficiency in the zinc‐silver oxide batteries. 相似文献
992.
993.
为了实现不锈钢微细电解定域加工,提出激光掩膜表面改性微细电解复合加工技术。研发了激光掩膜微细电解复合加工装置,并进行样件加工试验。首先,采用光纤激光在304不锈钢表面扫描加热进行打标图案,利用X射线光电子能谱分析(XPS)对不锈钢表面激光打标图案进行分析,发现激光在不锈钢表面打标时被空气氧化生成铁、铬等氧化物,生成的打标图案具有耐腐蚀性,形成保护性掩膜。然后进行电解加工,由于掩膜图案在电解过程中起到保护作用,选择合适的电解加工参数,在不锈钢表面能加工复杂的微结构。最后利用SEM、光学轮廓仪来观测微结构形貌、粗糙度等。研究结果表明:利用激光表面改性,结合微细电解加工能实现304不锈钢微结构的快速加工,该工艺在微细加工领域具有很好的发展前景。 相似文献
994.
Metal–Organic Framework Derived Narrow Bandgap Cobalt Carbide Sensitized Titanium Dioxide Nanocage for Superior Photo‐Electrochemical Water Oxidation Performance 下载免费PDF全文
Despite recent progress in photo‐electrochemical (PEC) water oxidation systems for TiO2‐based photoanodes, PEC performance improvement is still seriously hampered due to poor carrier transport efficiency and sluggish surface water oxidation kinetics of pristine TiO2. Herein, for the first time a brand new metal–organic framework (MOF)‐derived Co3C nanosheet with narrow bandgap energy is demonstrated, to effectively sensitize TiO2 hollow cages as a heterostructure photoanode for PEC water oxidation. It is found that MOF‐derived Co3C nanosheet with narrow bandgap characteristic can simultaneously accelerate the surface water oxidation kinetics and extend the light harvesting range of pristine TiO2. Meanwhile, a uniquely matched type‐II heterojunction constructed between MOF‐derived Co3C and TiO2 results in an evidently spontaneous e?/h+ separation. MOF‐derived Co3C/TiO2 heterostructure photoanodes bring about drastically improved PEC water oxidation performance. Specifically, MOF‐derived Co3C‐3/TiO2 photoanode with an optimized content of Co3C achieves the highest photocurrent density and charge separation efficiency of 2.6 mA cm?2 and 92.6% at 1.23 V versus reversible hydrogen electrode, corresponding to 201% and 152% improvement compared with pristine TiO2 nanocages. The ingeniously prepared MOF‐derived Co3C carbide with narrow bandgap energy as a cocatalyst paves new way to construct potentially high performance solar‐energy conversion system. 相似文献
995.
Enhancing Ultrafast Lithium Ion Storage of Li4Ti5O12 by Tailored TiC/C Core/Shell Skeleton Plus Nitrogen Doping 下载免费PDF全文
Zhujun Yao Xinhui Xia Dong Xie Yadong Wang Cheng‐ao Zhou Sufu Liu Shengjue Deng Xiuli Wang Jiangping Tu 《Advanced functional materials》2018,28(31)
It is of great importance to reinforce electronic and ionic conductivity of Li4Ti5O12 electrodes to achieve fast reaction kinetics and good high‐power capability. Herein, for the first time, a dual strategy of combing N‐doped Li4Ti5O12 (N‐LTO) with highly conductive TiC/C skeleton to realize enhanced ultrafast Li ion storage is reported. Interlinked hydrothermal‐synthesized N‐LTO nanosheets are homogeneously decorated on the chemical vapor deposition (CVD) derived TiC/C nanowires forming binder‐free N‐LTO@TiC/C core–branch arrays. Positive advantages including large surface area, strong mechanical stability, and enhanced electronic/ionic conductivity are obtained in the designed integrated arrays and rooted upon synergistic TiC/C matrix and N doping. The above appealing features can effectively boost kinetic properties throughout the N‐LTO@TiC/C electrodes to realize outstanding high‐rate capability at different working temperatures (143 mAh g?1/10 C at 25 °C and 122 mAh g?1/50 C at 50 °C) and notable cycling stability with a capacity retention of 99.3% after 10 000 cycles at 10 C. Moreover, superior high‐rate cycling life is also demonstrated for the full cells with N‐LTO@TiC/C anode and LiFePO4 cathode. The dual strategy may provoke wide interests in fast energy storage areas and motivate the further performance improvement of power‐type lithium ion batteries (LIBs). 相似文献
996.
Investigating Energy Prosumer Behaviour in Crowd Energy Using an Interactive Model/Diorama 下载免费PDF全文
Smart living labs such as the one located in Fribourg (Switzerland) focus on improving wellbeing and furthering knowledge related to building the district of the future on a technical and social level. Therefore, smart living labs represent an experimental platform/space where sustainable production and consumption strategies can be tested in a protected environment. A significant change in the socioeconomic production and consumption sphere can be expected by the rise of the so-called energy prosumer. Accordingly, this article presents an interactive model for the experimental investigation of energy prosumer behavior. In this context, two potential experiments on investment and trade decisions are briefly outlined. Since (behavioral and economic) experiments are usually conducted under controlled conditions in experimental labs involving mainly undergraduate students, the presented interactive model is flexible and mobile, providing the advantage to conduct experiments nearly everywhere involving everyday citizens. 相似文献
997.
998.
Magnetic abrasive finishing (MAF) of alloy steel workpiece with unbounded magnetic abrasive particles (UMAPs) indicates that the surface finish in the range of nanometer can be achieved. Important controllable four process parameters have been identified which are as current to the electromagnet, machining gap, abrasive size (mesh number), and number of cycles. Experiments have been planned using design of experiments technique. Based upon the results of response surface methodology and analysis of variance (ANOVA), it is concluded that magnetic flux density that depends on current to the electromagnet and machining gap, is most influencing parameter followed by grain size and number of cycles. The surface roughness profile generated during the MAF process has been discussed. To understand the cutting mechanism of magnetic abrasive finishing process, scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the machined surfaces have been carried out. The correlation between surface finish and material removal has also been established. 相似文献
999.
Hiroshi Fujita 《Microscopy research and technique》1986,3(3):243-304
High voltage electron microscopy has shown numerous advantages for the study of natural science, including biology, but it is especially useful in materials science. The most important advantage for materials science is in-situ experiments on detailed processes of the same phenomena that occur in bulk materials. For such in-situ experiments, the specimens should be thicker than a few microns to observe the behavior of lattice effect. The maximum observable thickness of the specimens and other advantages markedly increase with increasing accelerating voltage, and since 1965, two 3 MV instruments have been installed. The present paper is mainly concerned with these 3 MV electron microscopes and their applications to new research fields. 相似文献
1000.
以棕榈油为原料,Pt/SAPO-11-mp为催化剂,在高压微型固定床反应器中一步加氢制生物航空煤油。在单因素实验的基础上,利用Box-Behnken中心组合实验设计响应面法考察了温度、压力、空速、氢油比(氢气与棕榈油体积的比,下同)对C8~C16烃的选择性影响。得到最优反应条件为:温度382.2℃,压力3.9 MPa,空速1.2 h–1,氢油比911.0。结合实际,在最优条件下重复3次验证实验,C8~C16烃的选择性为44.9%,C8~C16异构烷烃的选择性为27.9%。 相似文献