全文获取类型
收费全文 | 1693篇 |
免费 | 45篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 28篇 |
化学工业 | 293篇 |
金属工艺 | 78篇 |
机械仪表 | 30篇 |
建筑科学 | 24篇 |
能源动力 | 74篇 |
轻工业 | 38篇 |
水利工程 | 5篇 |
石油天然气 | 7篇 |
无线电 | 252篇 |
一般工业技术 | 374篇 |
冶金工业 | 287篇 |
原子能技术 | 13篇 |
自动化技术 | 242篇 |
出版年
2023年 | 15篇 |
2022年 | 20篇 |
2021年 | 36篇 |
2020年 | 37篇 |
2019年 | 31篇 |
2018年 | 51篇 |
2017年 | 32篇 |
2016年 | 42篇 |
2015年 | 36篇 |
2014年 | 29篇 |
2013年 | 102篇 |
2012年 | 64篇 |
2011年 | 90篇 |
2010年 | 55篇 |
2009年 | 69篇 |
2008年 | 84篇 |
2007年 | 85篇 |
2006年 | 53篇 |
2005年 | 49篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 29篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 30篇 |
1998年 | 59篇 |
1997年 | 57篇 |
1996年 | 39篇 |
1995年 | 38篇 |
1994年 | 38篇 |
1993年 | 35篇 |
1992年 | 18篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 22篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1975年 | 6篇 |
1974年 | 12篇 |
排序方式: 共有1745条查询结果,搜索用时 15 毫秒
1.
Cognitive load varies the attention level, which has serious consequences in complex dynamic situations. Assessment of uncertainty in cognitive load during multiple object tracking task is necessary, as it is used to improve the cognitive capabilities. The present research work investigates the uncertainty in cognitive load of multiple object tracking task using electroencephalograph (EEG) on 25 football players. A d2 test of neuropsychological measure of attention was employed before starting the experiment. Each player participated in four levels of the task with variation in the cognitive load, which varies in terms of the targets from 2 to 5. Percentage changes in the power spectral density were estimated for the cognitive levels. Results show that the percentage changes were much more in high cognitive load than in low cognitive load. Significant changes (p < 0.05) were observed in level 1 (− 11.07 to 1.91%), level 2 (− 3.13 to − 14.51%), level 3 (− 6.33 to − 19.46%) and level 4 (− 8.10 to − 20.88%). Variation in the EEG data in terms of the combined uncertainty corresponds very well with low to high cognitive loads. The fourth level of the task with high cognitive load has more uncertainty than the low cognitive load levels. The results are useful for assessing the cognitive state of the player, which is valuable for the design of the effective training model. 相似文献
2.
Maurya Ranjan Kumar Kaur Rajvinder Kumar Ramesh Agarwal Ajay 《Microsystem Technologies》2019,25(10):3933-3941
Microsystem Technologies - This paper reports the development of a novel electronic micro-viscometer capable of measuring viscosity of different Newtonian fluids using less than 100 µl which... 相似文献
3.
Singh Dalip Saini Ajay Dhayal Veena Agarwal Dinesh Chandra 《Protection of Metals and Physical Chemistry of Surfaces》2019,55(4):682-688
Protection of Metals and Physical Chemistry of Surfaces - Dense alumina coatings were fabricated over aluminum alloy via dip coating method using oxime-modified aluminum(III) isopropoxide as a... 相似文献
4.
Chenhui Ding Marion Breunig Jana Timm Roland Marschall Jürgen Senker Seema Agarwal 《Advanced functional materials》2021,31(49):2106507
Covalent organic frameworks (COFs) show advantageous characteristics, such as an ordered pore structure and a large surface area for gas storage and separation, energy storage, catalysis, and molecular separation. However, COFs usually exist as difficult-to-process powders, and preparing continuous, robust, flexible, foldable, and rollable COF membranes is still a challenge. Herein, such COF membranes with fiber morphology for the first time prepared via a newly introduced template-assisted framework process are reported. This method uses electrospun porous polymer membranes as a sacrificial large dimension template for making self-standing COF membranes. The porous COF fiber membranes, besides having high crystallinity, also show a large surface area (1153 m2 g−1), good mechanical stability, excellent thermal stability, and flexibility. This study opens up the possibility of preparation of large dimension COF membranes and their derivatives in a simple way and hence shows promise in technical applications in separation, catalysis, and energy in the future. 相似文献
5.
Tanvi Bhasin Ashish Agarwal Sujata Sanghi R.K. Kotnala Jyoti Shah Manisha Yadav Muskaan Tuteja 《Ceramics International》2018,44(7):7629-7636
Multiferroic composites of spinel ferrite and ferroelectric xCoFe2O4 – (1-x)Na0.5Bi0.5TiO3 (with x = 0.10,0.30,0.50) were efficiently prepared by standard solid state reaction mechanism. X-ray diffractometer was used to analyze crystal structure of the prepared composites. The observed XRD patterns of the composites comprise peaks of both the phases i.e. ferrite and ferroelectric, with no sign of secondary peaks. Rietveld refinement of XRD data further confirms the coexistence of these two phases with cubic (Fd3m) and rhombohedral (R3c) symmetry corresponding to ferrite and ferroelectric phase respectively. The 3-dimensional overview of crystal structure of pure CoFe2O4 and Na0.5Bi0.5TiO3 and of composite 0.50CoFe2O4?0.50Na0.5Bi0.5TiO3 is generated by using refined parameters. The dielectric constant (ε´) and dielectric loss (tanδ) values were recorded as a function of frequency ranging from 100?Hz to 7?MHz and at different temperatures. Both ε´ and tanδ follow dispersion pattern at lower frequencies while show frequency independent behavior at higher frequencies. The magnetic evaluation carried by analyzing M-H hysteresis loop reveals the ferrimagnetic characteristics of these composites. The highest value of magnetic moment is 1.12μB observed for composite 0.50CoFe2O4 – 0.50Na0.5Bi0.5TiO3. Magnetoelectric (ME) voltage coefficient (α) was also demonstrated to observe the interaction between ferrite and ferroelectric phases. The highest value of α (72.72μV/Oe cm) is obtained for low ferrite composition 0.10CoFe2O4 – 0.90Na0.5Bi0.5TiO3, which suggests the dependence of magnetoelectric response on the resistivity of the composites. 相似文献
6.
7.
8.
9.
10.
Mingxuan Lu Prabhakar V. Gulgunje Pedro J. Arias-Monje Jeffrey Luo Jyotsna Ramachandran Yudhisthira Sahoo Sandip Agarwal Satish Kumar 《Polymer Engineering and Science》2020,60(9):2143-2151
Bi-component, polyacrylonitrile (PAN)/carbon nanotube (CNT) fibers were processed, at different core-sheath area ratios, by gel spinning. A percolated CNT network at 10 wt% CNT in the sheath enhanced electrical conductivity as compared to the neat PAN fiber, while PAN polymer in the core contributed to the good mechanical properties. Fibers with relatively thin sheath allowed overall CNT loading as low as 3.7 wt% to be made with good electrical conductivity, and PAN stabilization by Joule heating was demonstrated. Such fibers with combined good mechanical properties and electrical conductivity can also potentially be used for electrical heating of fabrics, for making smart textiles, and for electromagnetic interference shielding. 相似文献