全文获取类型
收费全文 | 292489篇 |
免费 | 35613篇 |
国内免费 | 11238篇 |
专业分类
电工技术 | 16289篇 |
技术理论 | 16篇 |
综合类 | 16932篇 |
化学工业 | 58461篇 |
金属工艺 | 15360篇 |
机械仪表 | 17866篇 |
建筑科学 | 22796篇 |
矿业工程 | 8307篇 |
能源动力 | 8440篇 |
轻工业 | 23544篇 |
水利工程 | 5009篇 |
石油天然气 | 16686篇 |
武器工业 | 2156篇 |
无线电 | 34515篇 |
一般工业技术 | 40181篇 |
冶金工业 | 12969篇 |
原子能技术 | 2961篇 |
自动化技术 | 36852篇 |
出版年
2024年 | 1173篇 |
2023年 | 4363篇 |
2022年 | 7779篇 |
2021年 | 10886篇 |
2020年 | 9439篇 |
2019年 | 9518篇 |
2018年 | 10137篇 |
2017年 | 11500篇 |
2016年 | 10958篇 |
2015年 | 14043篇 |
2014年 | 16362篇 |
2013年 | 19787篇 |
2012年 | 19233篇 |
2011年 | 20058篇 |
2010年 | 18053篇 |
2009年 | 17164篇 |
2008年 | 16211篇 |
2007年 | 15325篇 |
2006年 | 15518篇 |
2005年 | 13467篇 |
2004年 | 9493篇 |
2003年 | 8700篇 |
2002年 | 8409篇 |
2001年 | 7574篇 |
2000年 | 7268篇 |
1999年 | 7145篇 |
1998年 | 5377篇 |
1997年 | 4548篇 |
1996年 | 4260篇 |
1995年 | 3644篇 |
1994年 | 2928篇 |
1993年 | 2064篇 |
1992年 | 1708篇 |
1991年 | 1267篇 |
1990年 | 960篇 |
1989年 | 803篇 |
1988年 | 663篇 |
1987年 | 441篇 |
1986年 | 338篇 |
1985年 | 192篇 |
1984年 | 139篇 |
1983年 | 109篇 |
1982年 | 111篇 |
1981年 | 74篇 |
1980年 | 64篇 |
1979年 | 35篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1970年 | 6篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 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.
Wireless Networks - Geolocation is important for many emerging applications such as disaster management and recommendation system. In this paper, we propose a multilayer recognition model (MRM) to... 相似文献
4.
Sinan Zhang Yadonga Zhao Xueshuang Yao Zhenhong Zheng Chuyao Zheng Zhuo Jiang 《International Journal of Food Science & Technology》2022,57(7):4245-4253
Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing. 相似文献
5.
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
6.
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
7.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
8.
Applied Composite Materials - In this paper, the low-velocity impact deformation behavior of biaxial warp-knitted flexible composite was investigated. A simplified finite element model (FEM) of the... 相似文献
9.
10.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献