全文获取类型
收费全文 | 1820874篇 |
免费 | 48091篇 |
国内免费 | 17238篇 |
专业分类
电工技术 | 49296篇 |
技术理论 | 31篇 |
综合类 | 23340篇 |
化学工业 | 315746篇 |
金属工艺 | 79990篇 |
机械仪表 | 61817篇 |
建筑科学 | 69117篇 |
矿业工程 | 20875篇 |
能源动力 | 57631篇 |
轻工业 | 134356篇 |
水利工程 | 20294篇 |
石油天然气 | 56295篇 |
武器工业 | 2376篇 |
无线电 | 225848篇 |
一般工业技术 | 320996篇 |
冶金工业 | 207010篇 |
原子能技术 | 36850篇 |
自动化技术 | 204335篇 |
出版年
2022年 | 14090篇 |
2021年 | 25972篇 |
2020年 | 19729篇 |
2019年 | 21212篇 |
2018年 | 24590篇 |
2017年 | 24984篇 |
2016年 | 29253篇 |
2015年 | 28079篇 |
2014年 | 41766篇 |
2013年 | 103107篇 |
2012年 | 53988篇 |
2011年 | 68823篇 |
2010年 | 59676篇 |
2009年 | 66634篇 |
2008年 | 61430篇 |
2007年 | 58390篇 |
2006年 | 60890篇 |
2005年 | 54169篇 |
2004年 | 50890篇 |
2003年 | 49580篇 |
2002年 | 47842篇 |
2001年 | 44378篇 |
2000年 | 43241篇 |
1999年 | 44185篇 |
1998年 | 60951篇 |
1997年 | 50386篇 |
1996年 | 43995篇 |
1995年 | 36993篇 |
1994年 | 33928篇 |
1993年 | 32795篇 |
1992年 | 28572篇 |
1991年 | 25197篇 |
1990年 | 25113篇 |
1989年 | 23985篇 |
1988年 | 22326篇 |
1987年 | 20365篇 |
1986年 | 19560篇 |
1985年 | 22754篇 |
1984年 | 22642篇 |
1983年 | 20546篇 |
1982年 | 19561篇 |
1981年 | 19691篇 |
1980年 | 18031篇 |
1979年 | 18370篇 |
1978年 | 17665篇 |
1977年 | 17819篇 |
1976年 | 19453篇 |
1975年 | 15841篇 |
1974年 | 15342篇 |
1973年 | 15462篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
High‐performance thermosets with tailored properties derived from methacrylated eugenol and epoxy‐based vinyl ester 下载免费PDF全文
Yuehong Zhang Yuzhan Li Vijay Kumar Thakur Zhenhua Gao Jiyou Gu Michael R Kessler 《Polymer International》2018,67(5):544-549
A renewable chemical, eugenol, is methacrylated to produce methacrylated eugenol (ME) employing the Steglich esterification reaction without any solvent. The resulting ME is used as a low‐viscosity co‐monomer to replace styrene in a commercial epoxy‐based vinyl ester resin (VE). The volatility and viscosity of ME and styrene are compared. The effect of ME loading and temperature on the viscosity of the VE–ME resin is investigated. Moreover, the thermomechanical properties, curing extent and thermal stability of the fully cured VE–ME thermosets are systematically examined. The results indicate that ME is a monomer with low volatility and low viscosity, and therefore the incorporation of ME monomer in VE resins allows significant reduction of viscosity. Moreover, the viscosity of the VE–ME resin can be tailored by adjusting the ME loadings and processing temperature to meet commercial liquid molding technology requirements. The glass transition temperatures of VE–ME thermosets range from 139 to 199 °C. In addition, more than 95% of the monomer is incorporated and fixed in the crosslinked network structure of VE–ME thermosets. Overall, the developed ME monomer exhibits promising potential for replacing styrene as an effective low‐viscosity co‐monomer. The VE–ME resins show great advantages for use in polymer matrices for high‐performance fiber‐reinforced composites. This work is of great significance to the vinyl ester industry by providing detailed experimental support. © 2018 Society of Chemical Industry 相似文献
992.
993.
ABSTRACTImproving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)2 particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%. 相似文献
994.
S.K. Vimala Bharathi M. Maria Leena J.A. Moses C. Anandharamakrishnan 《International Journal of Food Science & Technology》2020,55(3):1238-1245
The usage of cling wraps is emerging as an easy and cost-effective approach to protect fresh-cut fruits and vegetables from dust, whilst improving visual appeal on retail counters. This study focused on developing an alternate, protein-based packaging material as a food grade cling wrap for food packaging applications. Zein-based cling wraps were produced, and their physical and mechanical characteristics were evaluated and compared with conventionally used chitosan biopolymer films and commercial synthetic polymer films. Antioxidant potential of the prepared films was studied, and the effectiveness of the developed films as anti-browning cling wraps was evaluated using studies conducted on fresh-cut apple slices at ambient conditions. Anti-browning effects were in par with polymeric counterparts; however, zein cling wraps could better prevent weight loss in apple slices. Zein-based films can be adopted as biodegradable food grade cling wraps as an alternative to chitosan and synthetic polymeric materials. 相似文献
995.
996.
997.
998.
999.
1000.
Amer Ibrahim Al-Omari Ibrahim M. Almanjahie Amal S. Hassan Heba F. Nagy 《计算机、材料和连续体(英文)》2020,64(2):835-857
In reliability analysis, the stress-strength model is often used to describe the life of
a component which has a random strength (X) and is subjected to a random stress (Y). In this
paper, we considered the problem of estimating the reliability R=P [Y<X] when the
distributions of both stress and strength are independent and follow exponentiated Pareto
distribution. The maximum likelihood estimator of the stress strength reliability is calculated
under simple random sample, ranked set sampling and median ranked set sampling methods.
Four different reliability estimators under median ranked set sampling are derived. Two
estimators are obtained when both strength and stress have an odd or an even set size. The
two other estimators are obtained when the strength has an odd size and the stress has an
even set size and vice versa. The performances of the suggested estimators are compared
with their competitors under simple random sample via a simulation study. The simulation
study revealed that the stress strength reliability estimates based on ranked set sampling and
median ranked set sampling are more efficient than their competitors via simple random
sample. In general, the stress strength reliability estimates based on median ranked set
sampling are smaller than the corresponding estimates under ranked set sampling and simple
random sample methods. 相似文献