全文获取类型
收费全文 | 5724篇 |
免费 | 185篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 57篇 |
综合类 | 5篇 |
化学工业 | 1037篇 |
金属工艺 | 116篇 |
机械仪表 | 75篇 |
建筑科学 | 217篇 |
矿业工程 | 4篇 |
能源动力 | 89篇 |
轻工业 | 534篇 |
水利工程 | 31篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 377篇 |
一般工业技术 | 906篇 |
冶金工业 | 1954篇 |
原子能技术 | 58篇 |
自动化技术 | 443篇 |
出版年
2022年 | 32篇 |
2021年 | 63篇 |
2020年 | 46篇 |
2019年 | 51篇 |
2018年 | 75篇 |
2017年 | 75篇 |
2016年 | 100篇 |
2015年 | 100篇 |
2014年 | 113篇 |
2013年 | 162篇 |
2012年 | 159篇 |
2011年 | 190篇 |
2010年 | 182篇 |
2009年 | 147篇 |
2008年 | 179篇 |
2007年 | 147篇 |
2006年 | 157篇 |
2005年 | 112篇 |
2004年 | 117篇 |
2003年 | 128篇 |
2002年 | 108篇 |
2001年 | 126篇 |
2000年 | 111篇 |
1999年 | 150篇 |
1998年 | 596篇 |
1997年 | 374篇 |
1996年 | 267篇 |
1995年 | 147篇 |
1994年 | 132篇 |
1993年 | 146篇 |
1992年 | 64篇 |
1991年 | 52篇 |
1990年 | 69篇 |
1989年 | 66篇 |
1988年 | 46篇 |
1987年 | 49篇 |
1986年 | 48篇 |
1985年 | 41篇 |
1984年 | 37篇 |
1983年 | 42篇 |
1982年 | 48篇 |
1981年 | 53篇 |
1980年 | 44篇 |
1979年 | 45篇 |
1978年 | 41篇 |
1977年 | 108篇 |
1976年 | 166篇 |
1975年 | 39篇 |
1972年 | 26篇 |
1970年 | 27篇 |
排序方式: 共有5910条查询结果,搜索用时 93 毫秒
951.
952.
953.
Adriana Andrade Carvalho Daiane Finger Christiane Schinieder Machado Eduardo Morgado Schmidt Patrícia Marçal da Costa Ana Paula Negreiros Nunes Alves Thamires Maria Fontenele Morais Maria Goretti Rodrigues de Queiroz Sueli Pércio Quináia Marcos Roberto da Rosa Julio Murilo Trevas dos Santos Cláudia Pessoa Manoel Odorico de Moraes Letícia Veras Costa-Lotufo Alexandra Christine Helena Frankland Sawaya Marcos Nogueira Eberlin Yohandra Reyes Torres 《Food chemistry》2011
The present study aimed to evaluate in vivo and in vitro the antitumoural activity of a propolis extract obtained with edible vegetable oil and its fractions and also to investigate its chemical composition by LC–MS and LC–MS/MS. To evaluate the toxicological aspects related to the propolis extract treatment, hematological, biochemical, histopathological and morphological analyses of treated animals were performed. All propolis extracts showed an in vivo antitumour activity in the experimental model with a moderate toxicity effect at experimental exposure levels. The oil extract was as effective as the ethanolic extract at inhibiting tumour growth. In vitro assays showed that the whole oil extract produced better inhibition of tumour cells than its fractions. LC–MS and LC–MS/MS identified four phenolic acids and three flavonoids. The anticancer potential of the oil extract of propolis has been demonstrated and the edible vegetable oil was shown as an attractive alternative solvent to extract bioactive natural propolis components. 相似文献
954.
F.T. Röhrle A.P. Moloney A. Black M.T. Osorio T. Sweeney O. Schmidt F.J. Monahan 《Food chemistry》2011
These studies investigated the potential application of analysis of stereoisomers of α-tocopherol to discriminate between beef from animals raised at pasture or fed concentrates containing synthetic vitamin E. Muscle α-tocopherol levels were affected (P < 0.05) by diet with mean values of 2.63, 1.14, 2.43 and 1.77 μg g−1 muscle for beef from animals receiving pasture only (P), a barley-based concentrate with synthetic vitamin E (C), winter silage followed by summer pasture (SiP) and winter silage followed by summer pasture with concentrate (SiPC), respectively. Stereoisomeric analysis of α-tocopherol permitted discrimination between beef from the P/SiP, C and SiPC animals. In a comparison of Irish and non-Irish beef, Brazilian beef had higher (P < 0.05) α-tocopherol (8.13 μg g−1) than beef from Austria, England, France, Germany, the U.S. and Ireland (mean 2.51 μg g−1). Stereoisomeric analysis of α-tocopherol in non-Irish beef revealed supplementation with synthetic vitamin E in all samples, including the samples marketed as pasture-fed beef. 相似文献
955.
James D. McCambridge Myles A. Steiner Blair L. Unger Keith A. Emery Eric L. Christensen Mark W. Wanlass Allen L. Gray Laszlo Takacs Roger Buelow Timothy A. McCollum James W. Ashmead Greg R. Schmidt Alex W. Haas John R. Wilcox James Van Meter Jeffery L. Gray Duncan T. Moore Allen M. Barnett Richard J. Schwartz 《Progress in Photovoltaics: Research and Applications》2011,19(3):352-360
We have designed, fabricated, and tested a small, integrated photovoltaic module comprised of two separately‐contacted, high efficiency, multijunction solar cells and non‐imaging optics that both concentrate and spectrally split the incoming light. This hybrid design allows us to individually optimize the tandem cells and optical elements. The system has a measured module efficiency, including optical and packaging losses but not power combination losses, of 38.5 ± 1.9% under the AM1.5 direct terrestrial spectrum. The internal optics concentrate the light by a factor of approximately 20. We find excellent agreement between the modeled and measured performance. This is the highest confirmed conversion efficiency demonstrated for a photovoltaic module. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
956.
957.
Benjamin Bock Anne Schmidt Edyta Sniezek Steffen Dudczig Gert Schmidt Jacek Szczerba Christos G. Aneziris 《Ceramics International》2019,45(4):4499-4508
Since solid, non-metallic inclusions influence considerably the quality of casted steel products, carbon-bonded alumina foam filters are used in secondary metallurgical treatments to remove these particles from steel melts. In order to attain a significant improvement of the filtration process, five different carbonaceous spinel compounds from the Fe-/Mg-/Mn-Al-O systems are applied on carbon-bonded alumina filters in this study and investigated with regard of their filtration efficiency. However, these spinel compounds decompose partially during sintering at 1400?°C under reducing atmosphere, wherefore the resulting coatings contain not only spinel compounds, but also oxidic and metallic components. The subsequent interaction with molten steel leads to the development of multicrystal structures on the filter surface, which stem from interfacial reactions between coating materials, molten steel, and inclusions. As a result of this procedure, a reduction of almost 60% alumina inclusions is measured with the aid of an automatic SEM, whereby spinel compounds from the Fe-Mn-Al-O system achieve highest filtration efficiencies. 相似文献
958.
959.
Alejandro M. Alcaraz Johanna Eva Maria Schmidt Paolo Colombo Carlos Martinez 《Journal of the European Ceramic Society》2021,41(6):3314-3320
Stop flow lithography (SFL) combines aspects of microfluidic and photolithography to continuously fabricate particles with uniform planar shapes as dictated by a mask. In this work we aim to expand the palette of materials suitable for SFL processing by investigating the use of UV-crosslinkable preceramic polymers to make ceramic particles. A commercially available methacrylated-polysiloxane was used as the preceramic polymer and was mixed with 2.5 wt% Irgacure 651 photoinitiator. A simple SFL system was assembled to continuously fabricate UV-crosslinked preceramic polymer particles in the shape of hexagons, triangles, and gears with diameters ranging from 100 to 200 μm and thicknesses of 74 μm +/- 4 μm. Particles were harvested from the excess preceramic solution, cleaned and then pyrolyzed at 1000 °C to transform them into silicon oxycarbide ceramic particles. Particle shape was maintained during pyrolysis despite a ~80 % linear shrinkage due to the removal of acryl and methyl side groups, as confirmed via FTIR. After pyrolysis the outer diameters of the SiOC particles ranged from 20 to 40 μm with thicknesses of 10 μm–12 μm. Pyrolyzed particles were successfully recovered and dispersed in water. This work demonstrates a robust path for the fabrication of ceramic particles with specific shapes from preceramic polymers via SFL. 相似文献
960.
Carolin Spatz Nico Langhof Jens Schmidt Walter Krenkel 《Journal of the European Ceramic Society》2018,38(8):2954-2960
Steel materials suffer extensive creep by the application at temperatures of about 700?°C and pressures about 350?bar in a power plant environment. The presented concept overwraps a steel pipe with a ceramic matrix composite (CMC) jacket in order to support the steel pipe and provide high temperature strength. Finite Element simulations show the influence of the wall thickness of CMC jacket and the coefficient of thermal expansion (CTE) on circumferential stresses within the hybrid metal ceramic pipe. Suitable fiber and matrix materials were studied, composites fabricated and mechanical properties determined. Finally, a prototype was designed in order to confirm the feasibility of the concept. The lifetime of a pure steel pipe was increased by more than four-fold by the additional CMC jacket. 相似文献