全文获取类型
收费全文 | 3280篇 |
免费 | 233篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 62篇 |
综合类 | 1篇 |
化学工业 | 853篇 |
金属工艺 | 86篇 |
机械仪表 | 72篇 |
建筑科学 | 82篇 |
矿业工程 | 10篇 |
能源动力 | 111篇 |
轻工业 | 494篇 |
水利工程 | 33篇 |
石油天然气 | 14篇 |
无线电 | 264篇 |
一般工业技术 | 533篇 |
冶金工业 | 482篇 |
原子能技术 | 23篇 |
自动化技术 | 397篇 |
出版年
2024年 | 7篇 |
2023年 | 36篇 |
2022年 | 92篇 |
2021年 | 147篇 |
2020年 | 107篇 |
2019年 | 112篇 |
2018年 | 134篇 |
2017年 | 137篇 |
2016年 | 146篇 |
2015年 | 95篇 |
2014年 | 104篇 |
2013年 | 241篇 |
2012年 | 186篇 |
2011年 | 210篇 |
2010年 | 172篇 |
2009年 | 168篇 |
2008年 | 157篇 |
2007年 | 122篇 |
2006年 | 101篇 |
2005年 | 63篇 |
2004年 | 65篇 |
2003年 | 72篇 |
2002年 | 53篇 |
2001年 | 46篇 |
2000年 | 43篇 |
1999年 | 40篇 |
1998年 | 132篇 |
1997年 | 121篇 |
1996年 | 70篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 38篇 |
1992年 | 15篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 20篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1973年 | 3篇 |
排序方式: 共有3517条查询结果,搜索用时 0 毫秒
41.
Magossi Maiara S. Maraldi Vitor A. Magossi Mariana S. DA Costa Fabíola M. Alves Kamilla Franco Fernanda D. S. DO Carmo Devaney R. 《SILICON》2021,13(7):2243-2255
Silicon - This study describes the preparation and characterization of 3-chloropropyl silica gel with 4-amino-5-(4pyridyl)-4H-1,2,4-triazole-3-thiol (SGA) for copper adsorption in different media.... 相似文献
42.
Rafael S. Pinto João P. Serra João C. Barbosa Renato Gonçalves Maria M. Silva Senentxu Lanceros-Méndez Carlos M. Costa 《大分子材料与工程》2021,306(11):2100372
Considering the high levels of materials used in the fields of electronics and energy storage systems, it is increasingly necessary to take into consideration environmental impact. Thus, it is important to develop devices based on environmentally friendlier materials and/or processes, such as additive manufacturing techniques. In this work, poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) are prepared by direct-ink-writing (DIW) by varying solvent evaporation temperature and fill density percentage. Different morphologies for both polymers are obtained, including dense films and porous membranes, as well as different electroactive β-phase content, thermal and mechanical properties. The dielectric constant and piezoelectric d33 coefficient for dense films reaches up to 16 at 1 kHz and 4 pC N−1, respectively for PVDF-HFP with a fill density of 80 and a solvent evaporation temperature of 50 °C. Porous structures are developed for battery separator membranes in lithium-ion batteries, with a highest ionic conductivity value of 3.8 mS cm−1 for the PVDF-HFP sample prepared with a fill density of 100 and a solvent evaporation temperature of 25 °C, the sample showing an excellent cycling performance. It is demonstrated that electroactive films and membranes can be prepared by direct-ink writing suitable for sensors/actuators and energy storage systems. 相似文献
43.
Tiago Santos Celso S. F. Gomes Luc Hennetier Vítor A. F. Costa Luís C. Costa 《International Journal of Applied Ceramic Technology》2021,18(5):1801-1813
Industrial competition and environmental concerns lead to the exploration of alternative and energy-efficient technologies for ceramic materials processing. The main objective of this work was to present microwave heating as a viable option for stoneware processing. Stoneware functional properties are presented and discussed, with emphasis on impact strength, water absorption, porosity, and color. Microstructure analyses show that microwave- and gas-fired samples have higher densifications than electrically fired samples. A relevant finding for processing conditions is that microwave firing requires temperatures approximately 100°C lower than those required by conventional firing. Microwave-fired samples’ rupture energies are approximately twice (0.57 ± 0.06 (J)) those of the reference samples (0.26 ± 0.03 (J)), and their water absorptions are approximately one-half (1.5% at 1170°C and 0.8% at 1190°C) of those of the reference samples (2.0%), whereas the water absorption of electrically fired samples at 1180°C has been estimated to be 7.5%. Color analysis also evidences a shift to lower microwave firing temperatures, what is attributed to the enhanced transformations promoted by microwave heating when comparing with the transformations promoted by conventional (gas or electric) heating. 相似文献
44.
Manuel Belmonte Vitor A. Silva Antonio José Fernandes Florinda Costa Rui Silva 《Journal of the American Ceramic Society》2003,86(5):749-754
The efficiency of different surface pretreatments (four standard chemical etchings and four diamond powder abrasive procedures) on silicon nitride (Si3 N4 ) substrates for chemical vapor deposition (CVD) of diamond has been systematically investigated. Blank Si3 N4 samples were polished with colloidal silica (∼0.25 μm). Diamond nucleation and growth runs were conducted in a microwave plasma chemical vapor deposition apparatus for 10 min and 6 h, respectively. Superior results concerning nucleation density ( N d ∼ 1010 cm−2 after 10 min), film uniformity, and grain size (below 2 μm after 6 h) were obtained for the mechanically microflawed samples, revealing that chemical etchings (hot and cold strong acids, molten base or CF4 plasma) are not crucial for good CVD diamond quality on Si3 N4 . 相似文献
45.
P. Da Costa C. Potvin J.-M. Manoli M. Breysse G. Djega-Mariadassou 《Catalysis Letters》2003,86(1-3):133-138
Hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene on alumina-supported Mo2C has been studied. These catalysts are stable and active under deep HDS conditions (0-250 wt ppm S). However, although they are well known to have hydrogenation properties, they lead preferentially to a non-hydrogenated product of the HDS reaction: dimethylbiphenyl. For the same reaction, supported platinum and sulfided molybdenum oxide lead to the hydrogenated products dimethyldicyclohexyl and methylcyclohexyltoluene, respectively. The ranking of HDS activity is as follows: MoS2/Al2O3 < Mo2C/Al2O3 < Pt/SiO2. 相似文献
46.
Topics in Catalysis - A mathematical model has been developed to study the transient release of oxygen from a 1 wt% Pd/CeO2 catalyst in the 450–550 °C range based on alternate... 相似文献
47.
Black rice husk ash (BRHA) and white rice husk ash (WRHA) were incorporated into natural rubber (NR) using a laboratory‐size two‐roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI‐100 Curometer. The torque curves were obtained at 150, 160, 170, and 180°C. The overall rate and the apparent activation energy for the vulcanization process were calculated for each compound assuming that vulcanization follows first‐order kinetics. For comparison purposes, two commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N762), were also used. It was observed that addition of WRHA to NR compounds increased the cross‐linking rate and lowered the apparent activation energy more markedly than the other fillers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1194–1203, 2003 相似文献
48.
Francis Reny Costa 《Polymer》2005,46(12):4447-4453
Low density polyethylene (LDPE)/Mg-Al layered double hydroxide (LDH) nanocomposites have been synthesized with different compositions by melt-mixing technique using maleic anhydride grafted polyethylene as compatibilizer. LDH has been modified by sodium dodecylbenzene sulfonate using reconstruction method and characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The nanocomposites are characterized by different techniques such as, transmission electron microscopy (TEM), XRD and rheology. The TEM analysis shows a complex nature of particle dispersion in the polymer matrix with wide distribution of particles sizes and shapes. The rheological analysis showed significant changes in linear viscoelastic responses of the composites, even at very low concentration (2 phr) of LDH materials, in comparison to the pure polymer in low frequency regime in dynamic frequency sweep experiments. These changes are related to the LDHs-polymer chains interactions resulting in network-like structure. 相似文献
49.
The electrosynthesis of polypyrrole (PPy) has been achieved on aluminium in aqueous medium of tartaric acid by means of cyclic voltammetry, potentiostatic and galvanostatic techniques. Scanning electron microscopy (SEM) and X-ray microanalysis by energy spectroscopy dispersion (EDS) applying on surfaces show that the PPy coating is developed from the metal surface through the cracks of the initial Al2O3 layer.A mechanism involving the participation of the supporting electrolyte and the pyrrole (Py) in distinct active sites was proposed based on the linear sweep voltammetry. It is observed for all applied electrochemical techniques that the pyrrole concentration has to be higher than 0.1 M to allow the polypyrrole electrodeposition in acid medium.Scanning electron microscopy, secondary electrons (SE) and backscattering electrons (BE), shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. Moreover, EDS reveals a good homogeneity and compactness of the film achieved in galvanostatic method. The corrosion results in 3% NaCl medium show that the PPy coating decreases the corrosion behaviour of the aluminium. The bilayer Al2O3/PPy shows a capacitor with future applications. 相似文献
50.
Incorporation and oxidation of fatty acids (FA) were investigated in resident and thioglycolate-clicited (TG-elicited) rat
macrophages (Mϕ). Both cell types presented a time-dependent incorporation of [14C]-labeled palmitic acid (PA), oleic acid (OA), linoleic acid (LA), and arachidonic acid (AA) up to 6h. The total amount of
[14C]-FA incorporated by resident Mϕ after 6 h was: AA>PA=LA>OA. TG-elicited cells presented a 50% reduction in the incorporation
of LA, PA, and AA, whereas that of OA remained unchanged as compared to resident Mϕ. The FA were oxidized by resident Mϕ as
follows: LA>OA>PA>AA. TG elicitation promoted a reduction of 42% in LA oxidation and a marked increase in AA oxidation (280%).
The increased oxidation of AA in TG-elicited cells may account for the lower production of prostaglandins in Mϕ under these
conditions. The full significance of these findings for Mϕ function, however, remains to be examined. 相似文献