全文获取类型
收费全文 | 27659篇 |
免费 | 2540篇 |
国内免费 | 1370篇 |
专业分类
电工技术 | 1750篇 |
技术理论 | 4篇 |
综合类 | 2186篇 |
化学工业 | 4782篇 |
金属工艺 | 1461篇 |
机械仪表 | 1599篇 |
建筑科学 | 1946篇 |
矿业工程 | 758篇 |
能源动力 | 668篇 |
轻工业 | 2624篇 |
水利工程 | 530篇 |
石油天然气 | 1393篇 |
武器工业 | 228篇 |
无线电 | 2844篇 |
一般工业技术 | 3266篇 |
冶金工业 | 1381篇 |
原子能技术 | 421篇 |
自动化技术 | 3728篇 |
出版年
2024年 | 111篇 |
2023年 | 448篇 |
2022年 | 751篇 |
2021年 | 985篇 |
2020年 | 789篇 |
2019年 | 678篇 |
2018年 | 758篇 |
2017年 | 872篇 |
2016年 | 799篇 |
2015年 | 1076篇 |
2014年 | 1443篇 |
2013年 | 1706篇 |
2012年 | 1790篇 |
2011年 | 2061篇 |
2010年 | 1787篇 |
2009年 | 1737篇 |
2008年 | 1818篇 |
2007年 | 1728篇 |
2006年 | 1627篇 |
2005年 | 1381篇 |
2004年 | 1026篇 |
2003年 | 925篇 |
2002年 | 1019篇 |
2001年 | 833篇 |
2000年 | 635篇 |
1999年 | 532篇 |
1998年 | 380篇 |
1997年 | 329篇 |
1996年 | 319篇 |
1995年 | 268篇 |
1994年 | 234篇 |
1993年 | 135篇 |
1992年 | 137篇 |
1991年 | 83篇 |
1990年 | 55篇 |
1989年 | 61篇 |
1988年 | 49篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 30篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1976年 | 13篇 |
1967年 | 4篇 |
1963年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Junjie Li Mei Liang Wanjing Cheng Shuhao Wang 《International Journal of Hydrogen Energy》2021,46(14):9553-9566
Electric vehicles (EVs) are considered a promising alternative to conventional vehicles (CVs) to alleviate the oil crisis and reduce urban air pollution and carbon emissions. Consumers usually focus on the tangible cost when choosing an EV or CV but overlook the time cost for restricting purchase or driving and the environmental cost from gas emissions, falling to have a comprehensive understanding of the economic competitiveness of CVs and EVs. In this study, a life cycle cost model for vehicles is conducted to express traffic and environmental policies in monetary terms, which are called intangible cost and external cost, respectively. Battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs), and CVs are compared in four first-tier, four new first-tier, and 4 s-tier and below cities in China. The comparison shows that BEVs and FCEVs in most cities are incomparable with CVs in terms of tangible cost. However, the prominent traffic and environmental policies in first-tier cities, especially in Beijing and Shanghai, greatly increase the intangible and external costs of CVs, making consumers more inclined to purchase BEVs and FCEVs. The main policy benefits of BEVs and FCEVs come from three aspects: government subsidies, purchase and driving restrictions, and environmental taxes. With the predictable reduction in government subsidies, traffic and environmental policies present important factors influencing the competitiveness of BEVs and FCEVs. In first-tier cities, BEVs and FCEVs already have a competitive foundation for large-scale promotion. In new first-tier and second-tier and below cities, stricter traffic and environmental policies need to be formulated to offset the negative impact of the reduction in government subsidies on the competitiveness of BEVs and FCEVs. Additionally, a sensitivity analysis reveals that increasing the mileage and reducing fuel prices can significantly improve the competitiveness of BEVs and FCEVs, respectively. 相似文献
2.
Xuejie Li Yaqing Wen Jian Zhang Dongyun Ma Jie Zhang Yanxia An Xiaoyan Song Xiujuan Ren Weifeng Zhang 《International Journal of Food Science & Technology》2022,57(3):1544-1553
The effects of non-thermal plasma (NTP) on the physicochemical properties of wheat flour and the quality of fresh wet noodles ( FWN) were investigated. The results showed that NTP effectively decreased the total plate count (TPC), yeast and mould count (YMC) and Bacillus spp. in wheat flour. Wet gluten contents and the stability time reached the maximum when treated for 20 s. The viscosity of starch increased significantly after treatment due to the increased of damaged starch. The contents of secondary structure were altered to some extent, which was because that the ordered network structure of gluten protein broken. Furthermore, compared with the control, texture properties of FWN were enhanced significantly at 20 s, and the darkening rate of FWN was greatly inhibited due to the low polyphenol oxidase (PPO) activity. Consequently, the most suitable treatment was 500 W for 20 s, providing a basis for the application of NTP in flour products. 相似文献
3.
以寺河矿南区回风大巷为工程背景,在分析巷道地质条件的基础上,通过理论计算分析了锚杆及锚索的主要支护参数,并确定了锚杆及锚索的型号;结合以往的生产实践经验,确定了巷道联合支护方案.实践表明,巷道支护方案合理,可以满足安全生产要求. 相似文献
4.
Polymer Bulletin - Preparation of konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride) (KGM-g-PTMAAC) was carried out using KGM as polysaccharide matrix and TMAAC as cationic... 相似文献
5.
Zhongkai Zhao Yohanes A. Situmorang Ping An Nichaboon Chaihad Jing Wang Xiaogang Hao Guangwen Xu Abuliti Abudula Guoqing Guan 《化学工程与技术》2020,43(4):625-640
In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils. 相似文献
6.
Zhang Keguo Cao Yang An Jianlin Wang Keyi 《Journal of Mechanical Science and Technology》2021,35(12):5405-5413
Journal of Mechanical Science and Technology - The flow stress increases with the increase in strain rate. This phenomenon is the strain rate effect of plastic deformation. Hopkinson experiment... 相似文献
7.
ABSTRACT Contact tracing is widely considered as an effective procedure in the fight against epidemic diseases. However, one of the challenges for technology based contact tracing is the high number of false positives, questioning its trust-worthiness and efficiency amongst the wider population for mass adoption. To this end, this paper proposes a novel, yet practical smartphone-based contact tracing approach, employing WiFi and acoustic sound for relative distance estimate, in addition to the air pressure and the magnetic field for ambient environment matching. We present a model combining six smartphone sensors, prioritising some of them when certain conditions are met. We empirically verified our approach in various realistic environments to demonstrate an achievement of up to 95% fewer false positives, and 62% more accurate than Bluetooth-only system. To the best of our knowledge, this paper was one of the first work to propose a combination of smartphone sensors for contact tracing. 相似文献
8.
9.
10.