全文获取类型
收费全文 | 397890篇 |
免费 | 32579篇 |
国内免费 | 17415篇 |
专业分类
电工技术 | 23315篇 |
技术理论 | 50篇 |
综合类 | 28156篇 |
化学工业 | 66402篇 |
金属工艺 | 23152篇 |
机械仪表 | 25151篇 |
建筑科学 | 30749篇 |
矿业工程 | 13062篇 |
能源动力 | 10966篇 |
轻工业 | 26581篇 |
水利工程 | 7434篇 |
石油天然气 | 25871篇 |
武器工业 | 3198篇 |
无线电 | 43663篇 |
一般工业技术 | 44373篇 |
冶金工业 | 20609篇 |
原子能技术 | 4188篇 |
自动化技术 | 50964篇 |
出版年
2024年 | 1647篇 |
2023年 | 6211篇 |
2022年 | 11023篇 |
2021年 | 15397篇 |
2020年 | 11724篇 |
2019年 | 9520篇 |
2018年 | 11006篇 |
2017年 | 12436篇 |
2016年 | 11372篇 |
2015年 | 15502篇 |
2014年 | 19625篇 |
2013年 | 23540篇 |
2012年 | 25501篇 |
2011年 | 28110篇 |
2010年 | 24794篇 |
2009年 | 23506篇 |
2008年 | 23081篇 |
2007年 | 22016篇 |
2006年 | 22280篇 |
2005年 | 19588篇 |
2004年 | 13324篇 |
2003年 | 11855篇 |
2002年 | 11074篇 |
2001年 | 9843篇 |
2000年 | 9780篇 |
1999年 | 10398篇 |
1998年 | 8043篇 |
1997年 | 6870篇 |
1996年 | 6479篇 |
1995年 | 5298篇 |
1994年 | 4324篇 |
1993年 | 2921篇 |
1992年 | 2320篇 |
1991年 | 1743篇 |
1990年 | 1387篇 |
1989年 | 1118篇 |
1988年 | 926篇 |
1987年 | 576篇 |
1986年 | 467篇 |
1985年 | 288篇 |
1984年 | 231篇 |
1983年 | 187篇 |
1982年 | 150篇 |
1981年 | 89篇 |
1980年 | 104篇 |
1979年 | 49篇 |
1978年 | 18篇 |
1977年 | 25篇 |
1976年 | 34篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Feng Wenran Li Zhen Chen Yingying Chen Jinyang Lang Haoze Wan Jianghong Gao Yan Dong Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in... 相似文献
2.
Zhao Jiandong Lei Wei Li Zijian Zhao Dongfeng Han Mingmin Hou Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding... 相似文献
3.
5.
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
8.
Peng Wang Yan Li Yujiao Qu Baowei Wang Jingxin Sun Chunwei Miao Ming Huang He Huang Congxiang Zhang 《International Journal of Food Science & Technology》2022,57(6):3428-3439
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP. 相似文献
9.
Xin Li Yurui Wang Minxuan Xu Yueqin Shi Hemiao Wang Xin Yang Haoting Ying Qi Zhang 《应用聚合物科学杂志》2021,138(19):50406
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field. 相似文献
10.
Peiying Wang Juanli Zhao Yun Fan Wei Zhang Yuanyuan Cui Liangmiao Zhang Bin Liu Hongqiang Nian Yiran Li 《Ceramics International》2021,47(11):15023-15029
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity. 相似文献