全文获取类型
收费全文 | 109145篇 |
免费 | 10000篇 |
国内免费 | 5142篇 |
专业分类
电工技术 | 6700篇 |
技术理论 | 11篇 |
综合类 | 7485篇 |
化学工业 | 18377篇 |
金属工艺 | 6268篇 |
机械仪表 | 7117篇 |
建筑科学 | 8028篇 |
矿业工程 | 2880篇 |
能源动力 | 3237篇 |
轻工业 | 7451篇 |
水利工程 | 1957篇 |
石油天然气 | 5723篇 |
武器工业 | 917篇 |
无线电 | 13444篇 |
一般工业技术 | 14075篇 |
冶金工业 | 4856篇 |
原子能技术 | 1426篇 |
自动化技术 | 14335篇 |
出版年
2024年 | 492篇 |
2023年 | 1773篇 |
2022年 | 3181篇 |
2021年 | 4482篇 |
2020年 | 3308篇 |
2019年 | 2838篇 |
2018年 | 3146篇 |
2017年 | 3566篇 |
2016年 | 3415篇 |
2015年 | 4500篇 |
2014年 | 5591篇 |
2013年 | 6772篇 |
2012年 | 7165篇 |
2011年 | 7804篇 |
2010年 | 6860篇 |
2009年 | 6388篇 |
2008年 | 6385篇 |
2007年 | 5951篇 |
2006年 | 5858篇 |
2005年 | 5024篇 |
2004年 | 3641篇 |
2003年 | 3342篇 |
2002年 | 3601篇 |
2001年 | 3041篇 |
2000年 | 2674篇 |
1999年 | 2468篇 |
1998年 | 2019篇 |
1997年 | 1693篇 |
1996年 | 1554篇 |
1995年 | 1283篇 |
1994年 | 1076篇 |
1993年 | 769篇 |
1992年 | 589篇 |
1991年 | 458篇 |
1990年 | 356篇 |
1989年 | 289篇 |
1988年 | 241篇 |
1987年 | 146篇 |
1986年 | 126篇 |
1985年 | 84篇 |
1984年 | 68篇 |
1983年 | 57篇 |
1982年 | 49篇 |
1981年 | 36篇 |
1980年 | 26篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
采用直流磁控溅射和后退火氧化工艺在p型GaAs单晶衬底上成功制备了n-VO_2/pGaAs异质结,研究了不同退火温度和退火时间对VO_2/GaAs异质结性能的影响,并分析其结晶取向、化学组分、膜层质量以及光电特性。结果表明,在退火时间2 h和退火温度693 K下能得到相变性能最佳的VO_2薄膜,相变前后电阻变化约2个数量级。VO_2/GaAs异质结在308 K、318 K和328 K温度下具有较好的整流特性,对应温度下的阈值跳变电压分别为6.9 V、6.6 V和6.2 V,该结果为基于VO_2相变特性的异质结光电器件的设计与应用提供了可行性。 相似文献
2.
了解我国儿童家长的家庭食品安全知识知晓情况及其影响因素,对开展精准食品安全宣教,减少家庭食源性疾病具有积极意义。本研究在7个城市的13 923名3~12岁儿童家长中开展问卷调查,收集基本信息、家庭食品安全知识知晓情况及需求。家长家庭食品安全知识平均得分为18.6分(总分29分),及格率为68.7%。易错知识点包括熟食室温存储时间、食品保质期、易引起中毒的食物以及食品贮存环境等。多因素logistics回归分析显示:家长家庭食品安全知识及格率受地区、文化程度、职业、家长类型、是否关注食品安全、孩子是否讲过食品安全知识以及是否阅读孩子带回来资料的影响。家长最关心的前三位内容为滥用食品添加剂(84.9%)、卫生状况不合格(82.9%)、农药/药物残留(82.7%)。受家长信任的信息来源主要为电视/广播/广告(76.1%)、书籍/报纸/期刊(70.4%)、微博/微信等新媒体(57.7%)。家长的家庭食品安全知识仍存在短板,需利用传统媒体和新媒体结合的方式以及小手牵大手形式开展精准专题宣传,并特别关注文化程度低,从事食品行业的家长以及孩子父亲和保姆。 相似文献
3.
4.
Hong Sae Jin Park Nam Il Hwang Dae Keun Yi Tae Gyu Eum Hyang Lan 《Food science and biotechnology》2022,31(6):669-679
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex... 相似文献
5.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
6.
Xiao-juan Li Yi-xiang Xu Xiang Li Zhi-jiang Jin Jin-yuan Qian 《International Journal of Hydrogen Energy》2021,46(7):5537-5547
Ambient condition, especially the wind condition, is an important factor to determine the behavior of hydrogen diffusion during hydrogen release. However, only few studies aim at the quantitative study of the hydrogen diffusion in a wind-exist condition. And very little researches aiming at the variable wind condition have been done. In this paper, the hydrogen diffusion in different wind condition which including the constant wind velocity and the variable wind velocity is investigated numerically. When considering the variable wind velocity, the UDF (user defined function) is compiled. Characteristics of the FGC (flammable gas cloud) and the HMF (hydrogen mass fraction) are analyzed in different wind condition and comparisons are made with the no-wind condition. Results indicate that the constant wind velocity and the variable wind velocity have totally different effect for the determination of hydrogen diffusion. Comparisons between the constant wind velocity and the variable wind velocity indicate that the variable wind velocity may cause a more dangerous situation since there has a larger FGC volume. More importantly, the wind condition has a non-negligible effect when considering the HMF along the radial direction. As the wind velocity increases, the distribution of the HMF along the radial direction is not Gaussian anymore when the distance between the release hole and the observation line exceeds to a critical value. This work can be a supplement of the research on the hydrogen release and diffusion and a valuable reference for the researchers. 相似文献
7.
随着经济的发展,消防救援队伍承担的任务越来越繁重.重大灾害事故的发生,对消防战勤保障方面提出了更高的要求.文章主要从消防战勤保障的主要任务职能、消防战勤的任务分类以及消防战勤保障体系建设存在的问题与建议等几个方面进行了详细的阐述,以期消防战勤保障得到更好的发展. 相似文献
8.
5G-oriented Virtual Augmented Reality Scene Construction and Business Information Flow Demonstration
Mobile Networks and Applications - Aiming at the problems of large data volume, long calculation time, and information feedback speed in traditional virtual augmented reality-based scenes, this... 相似文献
9.
10.
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