全文获取类型
收费全文 | 60935篇 |
免费 | 3704篇 |
国内免费 | 1059篇 |
专业分类
电工技术 | 1796篇 |
技术理论 | 4篇 |
综合类 | 1596篇 |
化学工业 | 12202篇 |
金属工艺 | 2115篇 |
机械仪表 | 2336篇 |
建筑科学 | 3431篇 |
矿业工程 | 910篇 |
能源动力 | 2037篇 |
轻工业 | 4741篇 |
水利工程 | 631篇 |
石油天然气 | 1059篇 |
武器工业 | 147篇 |
无线电 | 7392篇 |
一般工业技术 | 9996篇 |
冶金工业 | 5645篇 |
原子能技术 | 577篇 |
自动化技术 | 9083篇 |
出版年
2023年 | 601篇 |
2022年 | 1227篇 |
2021年 | 1847篇 |
2020年 | 1297篇 |
2019年 | 1199篇 |
2018年 | 1504篇 |
2017年 | 1474篇 |
2016年 | 1515篇 |
2015年 | 1678篇 |
2014年 | 2260篇 |
2013年 | 3812篇 |
2012年 | 3322篇 |
2011年 | 4162篇 |
2010年 | 3135篇 |
2009年 | 3120篇 |
2008年 | 3353篇 |
2007年 | 2982篇 |
2006年 | 2626篇 |
2005年 | 2234篇 |
2004年 | 1970篇 |
2003年 | 1985篇 |
2002年 | 2149篇 |
2001年 | 1634篇 |
2000年 | 1268篇 |
1999年 | 1182篇 |
1998年 | 1471篇 |
1997年 | 1114篇 |
1996年 | 967篇 |
1995年 | 810篇 |
1994年 | 721篇 |
1993年 | 652篇 |
1992年 | 511篇 |
1991年 | 447篇 |
1990年 | 445篇 |
1989年 | 441篇 |
1988年 | 367篇 |
1987年 | 335篇 |
1986年 | 312篇 |
1985年 | 374篇 |
1984年 | 333篇 |
1983年 | 261篇 |
1982年 | 246篇 |
1981年 | 259篇 |
1980年 | 211篇 |
1979年 | 199篇 |
1978年 | 207篇 |
1977年 | 194篇 |
1976年 | 220篇 |
1975年 | 167篇 |
1974年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Chen Wen-Kuo Chang Jing-Rong Chen Long-Sheng Hsu Rui-Yang 《Multimedia Tools and Applications》2022,81(6):8317-8347
Multimedia Tools and Applications - With the advancement of technology and the spread of the COVID19 epidemic, learning can no longer only be done through face-to-face teaching. Numerous digital... 相似文献
3.
4.
Jincheng Yu Yabin Chang Ewa Jakubczyk Bing Wang Feridoon Azough Robert Dorey Robert Freer 《Journal of the European Ceramic Society》2021,41(9):4859-4869
Ca3Co4O9 is a promising p-type thermoelectric oxide material having intrinsically low thermal conductivity. With low cost and opportunities for automatic large scale production, thick film technologies offer considerable potential for a new generation of micro-sized thermoelectric coolers or generators. Here, based on the chemical composition optimized by traditional solid state reaction for bulk samples, we present a viable approach to modulating the electrical transport properties of screen-printed calcium cobaltite thick films through control of the microstructural evolution by optimized heat-treatment. XRD and TEM analysis confirmed the formation of high-quality calcium cobaltite grains. By creating 2.0 at% cobalt deficiency in Ca2.7Bi0.3Co4O9+δ, the pressureless sintered ceramics reached the highest power factor of 98.0 μWm?1 K-2 at 823 K, through enhancement of electrical conductivity by reduction of poorly conducting secondary phases. Subsequently, textured thick films of Ca2.7Bi0.3Co3.92O9+δ were efficiently tailored by controlling the sintering temperature and holding time. Optimized Ca2.7Bi0.3Co3.92O9+δ thick films sintered at 1203 K for 8 h exhibited the maximum power factor of 55.5 μWm?1 K-2 at 673 K through microstructure control. 相似文献
5.
Karimi Bayan Chang Yu-Cheng Pekola Jukka P. 《Journal of Low Temperature Physics》2022,207(3-4):220-225
We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.
相似文献6.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
7.
8.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
9.
Aleksandar Miletić Peter Panjan Miha Čekada Lazar Kovačević Pal Terek Janez Kovač Goran Dražič Branko Škorić 《Ceramics International》2021,47(2):2022-2033
With the goal to produce a hard and tough coating intended for tribological applications, CrAlN/TiSiN nanolayer coating was prepared by alternative deposition of CrAlN and TiSiN layers. In the first part of the article, a detailed study of phase composition, microstructure, and layer structure of CrAlN/TiSiN coating is presented. In the second part, its mechanical properties, fracture and tribological behavior are compared to the nanocomposite TiSiN coating. An industrial magnetron sputtering unit was used for coating deposition. X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used for compositional and microstructural analysis. Mechanical properties and fracture behavior were studied by instrumented indentation and focused ion beam techniques. Tribological properties were evaluated by ball-on-disk test in a linear reciprocal mode. A complex layer structure was found in the nanolayer coating. The TiSiN layers were epitaxially stabilized inside the coating which led to formation of dislocations at interfaces, to introduction of disturbances in the coating growth, and as a result, to development of fine-grained columnar microstructure. Indentation load required for the onset of fracture was twice lower for the nanolayer CrAlN/TiSiN, compared to the nanocomposite TiSiN coating. This agrees very well with their mechanical properties, with H3/E2 being twice higher for the TiSiN coating. However, the nanolayer coating experienced less severe damage, which had a strong impact on tribological behavior. A magnitude of order lower wear rate and four times lower steady state friction coefficient were found for the nanolayer coating. 相似文献
10.
基于柴油产品质量升级的需求,中国石化大连石油化工研究院(FRIPP)开发了FHIDW加氢改质技术及配套FF-46加氢精制催化剂、FC-14B加氢改质催化剂和FDW-3临氢降凝催化剂.该技术及催化剂级配体系在格尔木炼油厂0.8 Mt·a-1加氢改质装置上的工业应用情况表明,级配催化剂体系对原料适应性强,装置运转平稳,操作灵活性高,催化剂失活速率慢,产品分布合理且质量优异,在降低柴油产品凝点的同时可以明显改善其密度和十六烷值,解决了改造前装置生产重柴油密度偏低的问题,为炼油厂生产符合国V质量标准的柴油提供了技术保障. 相似文献