全文获取类型
收费全文 | 151398篇 |
免费 | 6466篇 |
国内免费 | 2395篇 |
专业分类
电工技术 | 3699篇 |
技术理论 | 5篇 |
综合类 | 5192篇 |
化学工业 | 25779篇 |
金属工艺 | 8216篇 |
机械仪表 | 6647篇 |
建筑科学 | 6448篇 |
矿业工程 | 2306篇 |
能源动力 | 3204篇 |
轻工业 | 10753篇 |
水利工程 | 2237篇 |
石油天然气 | 4147篇 |
武器工业 | 396篇 |
无线电 | 15439篇 |
一般工业技术 | 24741篇 |
冶金工业 | 7298篇 |
原子能技术 | 990篇 |
自动化技术 | 32762篇 |
出版年
2024年 | 232篇 |
2023年 | 995篇 |
2022年 | 2102篇 |
2021年 | 3371篇 |
2020年 | 2145篇 |
2019年 | 1925篇 |
2018年 | 16284篇 |
2017年 | 15446篇 |
2016年 | 11991篇 |
2015年 | 3224篇 |
2014年 | 3654篇 |
2013年 | 4451篇 |
2012年 | 7384篇 |
2011年 | 14020篇 |
2010年 | 12179篇 |
2009年 | 9119篇 |
2008年 | 10232篇 |
2007年 | 11137篇 |
2006年 | 3567篇 |
2005年 | 4059篇 |
2004年 | 3001篇 |
2003年 | 2807篇 |
2002年 | 2080篇 |
2001年 | 1266篇 |
2000年 | 1511篇 |
1999年 | 1700篇 |
1998年 | 1540篇 |
1997年 | 1369篇 |
1996年 | 1297篇 |
1995年 | 1055篇 |
1994年 | 815篇 |
1993年 | 586篇 |
1992年 | 466篇 |
1991年 | 374篇 |
1990年 | 296篇 |
1989年 | 241篇 |
1988年 | 229篇 |
1987年 | 149篇 |
1986年 | 138篇 |
1985年 | 114篇 |
1984年 | 109篇 |
1983年 | 78篇 |
1982年 | 88篇 |
1981年 | 93篇 |
1980年 | 93篇 |
1978年 | 64篇 |
1977年 | 134篇 |
1976年 | 268篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
41.
42.
Cheese fortification using saturated monoglyceride self‐assembly structures as carrier of omega‐3 fatty acids
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sonia Calligaris Alexandra Ignat Marialuisa Biasutti Nadia Innocente Maria Cristina Nicoli 《International Journal of Food Science & Technology》2015,50(9):2129-2134
The purpose of this research was to study the capacity of emulsions containing saturated monoglyceride self‐assembly structures to deliver omega‐3 fatty acids in fresh soft cheese. To this aim, fortified emulsions containing different ratios of milk, saturated monoglycerides (MGs) and cod liver oil were added to milk before cheese‐making. These emulsions were characterised by distinct microstructural features observed by polarised light microscopy and apparent viscosity values. The omega‐3 delivery performance of MG emulsions highlighted that this strategy allowed a good retention of the omega‐3‐rich oil in the curd (up to 75%). The fortified cheeses showed yield value and fat content higher than those of control samples. The enriched cheese showed hardness and cohesiveness obtained by texture profile analysis similar to those of the unfortified product. Only a slight decrease in gumminess was detected in fortified cheese. 相似文献
43.
Huizhu Cai Bingbing Chen Xiao Zhang Yuchen Deng Dequan Xiao Ding Ma Chuan Shi 《Nano Research》2021,14(1):122-130
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe3C/C and Fe2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH4/H2and pure NH3,respectively.By acid leaching of Fe2N/C sample,only single sites of FeN4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN4in ORR.A correlation was conducted between the concentration of FeⅡN4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin FeⅡN4 species as highly active sites for the ORR. 相似文献
44.
45.
46.
47.
Ting Liu Huimin Zhang Panfei Ma Aimin Chang Hui Jiang 《Journal of the American Ceramic Society》2019,102(8):4393-4398
Core–shell structures have been proposed to improve the electrical properties of negative-temperature coefficient (NTC) thermistor ceramics. In this work, Al2O3-modified Co1.5Mn1.2Ni0.3O4 NTC thermistor ceramics with adjustable electrical properties were prepared through citrate-chelation followed by conventional sintering. Co1.5Mn1.2Ni0.3O4 powder was coated with a thin Al2O3 shell layer to form a core–shell structure. Resistivity (ρ) increased rapidly with increasing thickness of the Al2O3 layer, and the thermal constant (B) varied moderately between 3706 and 3846 K. In particular, Co1.5Mn1.2Ni0.3O4@Al2O3 ceramic with 0.08 wt% Al2O3 showed the increase of ρ double, and the change in its B was less than 140 K. The Co1.5Mn1.2Ni0.3O4@Al2O3 NTC ceramics showed high stability, and their grain size was relatively uniform due to the protection offered by the shell. The aging coefficient of the ceramic was less than 0.2% after aging for 500 hours at 125°C. Taken together, the results indicate that as-prepared Co1.5Mn1.2Ni0.3O4@Al2O3 NTC ceramics with a core–shell structure may be promising candidates for application as wide-temperature NTC thermistor ceramics. 相似文献
48.
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of... 相似文献
50.
This paper presents an analytical solution to the non-uniform pressure on thick-walled cylinder. The formulation is based on the linear elasticity theory (plain strain) and stress function method. As an example, the proposed solution is used to model the stress distribution due to non-uniform steel reinforcement corrosion in concrete. The model is formulated considering different scenarios of corrosion pressure distribution. It is validated against the finite element model for different cases of non-uniform pressure distributions. The results show that the corrosion-induced cracks are likely to start just beyond the anodic zone. This is confirmed by the experimental tests on concrete cylinder exposed to non-uniform accelerated corrosion of steel reinforcement. The model can be effectively used to calculate the distribution of corrosion-induced stresses in concrete. 相似文献