全文获取类型
收费全文 | 259959篇 |
免费 | 22548篇 |
国内免费 | 12951篇 |
专业分类
电工技术 | 16441篇 |
技术理论 | 21篇 |
综合类 | 18449篇 |
化学工业 | 41352篇 |
金属工艺 | 15164篇 |
机械仪表 | 16661篇 |
建筑科学 | 20620篇 |
矿业工程 | 7821篇 |
能源动力 | 7405篇 |
轻工业 | 17478篇 |
水利工程 | 5111篇 |
石油天然气 | 14114篇 |
武器工业 | 2340篇 |
无线电 | 31644篇 |
一般工业技术 | 29793篇 |
冶金工业 | 11772篇 |
原子能技术 | 3303篇 |
自动化技术 | 35969篇 |
出版年
2024年 | 927篇 |
2023年 | 3715篇 |
2022年 | 6631篇 |
2021年 | 9868篇 |
2020年 | 7313篇 |
2019年 | 6180篇 |
2018年 | 6951篇 |
2017年 | 7857篇 |
2016年 | 7059篇 |
2015年 | 9912篇 |
2014年 | 12686篇 |
2013年 | 15452篇 |
2012年 | 17256篇 |
2011年 | 18759篇 |
2010年 | 16917篇 |
2009年 | 16353篇 |
2008年 | 16278篇 |
2007年 | 15440篇 |
2006年 | 15350篇 |
2005年 | 13018篇 |
2004年 | 9248篇 |
2003年 | 8063篇 |
2002年 | 7817篇 |
2001年 | 6935篇 |
2000年 | 6345篇 |
1999年 | 6272篇 |
1998年 | 4781篇 |
1997年 | 4159篇 |
1996年 | 3752篇 |
1995年 | 3127篇 |
1994年 | 2479篇 |
1993年 | 1931篇 |
1992年 | 1477篇 |
1991年 | 1141篇 |
1990年 | 906篇 |
1989年 | 756篇 |
1988年 | 583篇 |
1987年 | 415篇 |
1986年 | 305篇 |
1985年 | 216篇 |
1984年 | 132篇 |
1983年 | 119篇 |
1982年 | 133篇 |
1981年 | 92篇 |
1980年 | 77篇 |
1979年 | 42篇 |
1978年 | 29篇 |
1977年 | 39篇 |
1976年 | 43篇 |
1959年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
Pengfei Liang Jie Zhu Di Wu Hui Peng Xiaolian Chao Zupei Yang 《Journal of the American Ceramic Society》2021,104(6):2702-2710
Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO2-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag+/Nb5+ co-doped (Ag1/4Nb3/4)xTi1−xO2 (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 103 and 1.6 × 104 at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics. 相似文献
2.
3.
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
6.
Yuhang Xing Ruyi Li Lu Xue Mianhong Chen Xuli Lu Zhihao Duan Wei Zhou Jihua Li 《International Journal of Food Science & Technology》2022,57(8):5268-5279
Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W1/O/W2 emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL−1. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W1/O/W2 emulsions. Subsequently, the MGF-loaded W1/O/W2 emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W1/O/W2 emulsions were investigated. The MGF-loaded W1/O/W2 emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W1/O/W2 emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W1/O/W2 emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin. 相似文献
7.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
9.
Qian Wu Xiangmei Liu Bo Li Lei Tan Yong Han Zhaoyang Li Yanqin Liang Zhenduo Cui Shengli Zhu Shuilin Wu Yufeng Zheng 《材料科学技术学报》2021,67(8):70-79
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection. 相似文献
10.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. 相似文献