全文获取类型
收费全文 | 289628篇 |
免费 | 5031篇 |
国内免费 | 932篇 |
专业分类
电工技术 | 5495篇 |
综合类 | 558篇 |
化学工业 | 43110篇 |
金属工艺 | 10999篇 |
机械仪表 | 9137篇 |
建筑科学 | 7141篇 |
矿业工程 | 1174篇 |
能源动力 | 7414篇 |
轻工业 | 27071篇 |
水利工程 | 2798篇 |
石油天然气 | 4062篇 |
武器工业 | 75篇 |
无线电 | 36819篇 |
一般工业技术 | 54730篇 |
冶金工业 | 52177篇 |
原子能技术 | 5670篇 |
自动化技术 | 27161篇 |
出版年
2021年 | 2944篇 |
2020年 | 2139篇 |
2019年 | 2737篇 |
2018年 | 4308篇 |
2017年 | 4416篇 |
2016年 | 4617篇 |
2015年 | 2998篇 |
2014年 | 5065篇 |
2013年 | 13052篇 |
2012年 | 7945篇 |
2011年 | 10670篇 |
2010年 | 8319篇 |
2009年 | 9198篇 |
2008年 | 9804篇 |
2007年 | 9579篇 |
2006年 | 8581篇 |
2005年 | 7935篇 |
2004年 | 7734篇 |
2003年 | 7525篇 |
2002年 | 7146篇 |
2001年 | 7134篇 |
2000年 | 6701篇 |
1999年 | 6741篇 |
1998年 | 16031篇 |
1997年 | 11468篇 |
1996年 | 8974篇 |
1995年 | 6990篇 |
1994年 | 6163篇 |
1993年 | 6089篇 |
1992年 | 4778篇 |
1991年 | 4488篇 |
1990年 | 4262篇 |
1989年 | 3968篇 |
1988年 | 3826篇 |
1987年 | 3333篇 |
1986年 | 3235篇 |
1985年 | 3807篇 |
1984年 | 3536篇 |
1983年 | 3151篇 |
1982年 | 3002篇 |
1981年 | 3101篇 |
1980年 | 2910篇 |
1979年 | 2776篇 |
1978年 | 2611篇 |
1977年 | 3114篇 |
1976年 | 3822篇 |
1975年 | 2435篇 |
1974年 | 2392篇 |
1973年 | 2406篇 |
1972年 | 1895篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献
12.
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
13.
Optimization and Engineering - 相似文献
14.
15.
Gordenchuk A. D. Kudryashova O. S. 《Theoretical Foundations of Chemical Engineering》2019,53(4):591-595
Theoretical Foundations of Chemical Engineering - Calcium formate is widely used in construction, tanning, and textile manufacture and as an E238 biological additive in cosmetology and the food... 相似文献
16.
Virginija Sacevičienė Milda Jucienė Vaida Dobilaitė Valentina Krylova Skirma Žalenkienė Nijolė Dukštienė Raimondas Bliūdžius 《应用聚合物科学杂志》2019,136(21):47523
The aim of this work was to investigate the physical and mechanical performance of architectural polyester (PES)–poly(vinyl chloride) (PVC) membranes exposed to different artificial aging conditions. Two commercially available architectural membranes were chosen as research objects. The durability of the PES/PVC fabrics was evaluated by the loss in mechanical performance, scanning electron microscopy, and X-ray diffraction analysis in order to understand the effect of the degradation agents on the surface of the membranes. The mechanical performance of the PES/PVC membranes was unchanged. Scanning electron microscopy images of the tested materials showed initial cracks after aging. The X-ray fluorescence analysis showed that at the time of aging, the amount of Cl and Si decreased slightly, while Ti decreased by half, and Ca by volume increased twice. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47523. 相似文献
17.
John D. Rodney S. Deepapriya M. Cyril Robinson C. Justin Raj Suresh Perumal Byung Chul Kim S. Krishnan S. Jerome Das 《International Journal of Hydrogen Energy》2021,46(54):27585-27596
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting. 相似文献
18.
Blagoveshchenskii D. I. Kozlovskii V. N. Vasin S. A. 《Russian Engineering Research》2021,41(12):1255-1259
Russian Engineering Research - Digital tools for managing improvements in automobile production are developed. An operative tool provides warnings regarding the operational quality of the vehicles... 相似文献
19.
Currently, the efficient detection of fingerprints is essential for the crime investigations. Revealing fingerprints is commonly achieved with fluorescent organic compounds but they are not efficient for fingerprint detection on porous or reflective surfaces. In order to solve the problem of collecting fingerprints on porous/reflective surfaces, inorganic phosphors have been employed, since they have characteristics of variable color emission, afterglow, high chemical stability and nano-size, which allow the fingerprint detection on any porous or non-porous surfaces. Due to these last properties, this review presents a summary about the use of phosphorescent and fluorescent phosphors for the detection of latent fingerprints. First, we discussed the main physical and chemical characteristics of the fingerprints which permit their detection and collection from any surface. After this, we presented the main morphological, structural and luminescent properties of the phosphorescent and fluorescent phosphors that allow their use for fingerprint detection. Later, we demonstrated with pictures of fingerprints (with and without light emission from the phosphors deposited on them) that both, phosphorescent and fluorescent phosphors can be used to visualize fingerprints with high resolution and high contrast without interference of the background surface, which is ideal for its collection and registration in the Automated Fingerprint Identification System (AFIS). We believe that this review could be useful to understand how to select an appropriate phosphorescent or fluorescent material for fingerprint detection depending on the type of surface (porous or non-porous, reflective or not reflective) where the fingerprint is deposited. 相似文献
20.
Automation and Remote Control - We consider multicriteria minimax optimization problems with criteria in the form of the maxima of functionals given by the induced norms of linear operators taking... 相似文献