全文获取类型
收费全文 | 315678篇 |
免费 | 27554篇 |
国内免费 | 14611篇 |
专业分类
电工技术 | 19175篇 |
技术理论 | 20篇 |
综合类 | 21939篇 |
化学工业 | 52136篇 |
金属工艺 | 18325篇 |
机械仪表 | 19966篇 |
建筑科学 | 24644篇 |
矿业工程 | 9351篇 |
能源动力 | 8612篇 |
轻工业 | 23570篇 |
水利工程 | 6494篇 |
石油天然气 | 19470篇 |
武器工业 | 2615篇 |
无线电 | 34175篇 |
一般工业技术 | 37684篇 |
冶金工业 | 15000篇 |
原子能技术 | 4177篇 |
自动化技术 | 40490篇 |
出版年
2024年 | 1273篇 |
2023年 | 4859篇 |
2022年 | 9714篇 |
2021年 | 13138篇 |
2020年 | 10088篇 |
2019年 | 7985篇 |
2018年 | 8939篇 |
2017年 | 10218篇 |
2016年 | 9058篇 |
2015年 | 12818篇 |
2014年 | 15907篇 |
2013年 | 18917篇 |
2012年 | 20802篇 |
2011年 | 22240篇 |
2010年 | 19461篇 |
2009年 | 18303篇 |
2008年 | 17932篇 |
2007年 | 16966篇 |
2006年 | 16851篇 |
2005年 | 14327篇 |
2004年 | 9896篇 |
2003年 | 9000篇 |
2002年 | 8876篇 |
2001年 | 7903篇 |
2000年 | 7027篇 |
1999年 | 7119篇 |
1998年 | 5528篇 |
1997年 | 4655篇 |
1996年 | 4419篇 |
1995年 | 3657篇 |
1994年 | 2984篇 |
1993年 | 2110篇 |
1992年 | 1812篇 |
1991年 | 1411篇 |
1990年 | 1118篇 |
1989年 | 1029篇 |
1988年 | 830篇 |
1987年 | 620篇 |
1986年 | 539篇 |
1985年 | 428篇 |
1984年 | 392篇 |
1983年 | 357篇 |
1982年 | 369篇 |
1980年 | 332篇 |
1978年 | 361篇 |
1977年 | 335篇 |
1976年 | 347篇 |
1974年 | 394篇 |
1973年 | 374篇 |
1972年 | 357篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
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
2.
Mobile Networks and Applications - Inverse kinematics is an important basic theory in walking control of biped robot. This study focuses on the parameter setting using the improved algorithm in... 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.
Ya Gu Quanmin Zhu Hassan Nouri 《International Journal of Adaptive Control and Signal Processing》2022,36(1):138-154
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results. 相似文献
6.
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
7.
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
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.
基于电信运营商数字化转型,系统性地提出了数据驱动的云网发展规划体系,以及六大关键数字化能力构建,设计和实现了一种云网规划数字化平台,该平台可用于实现目标网络精细规划、边缘计算精准预测等场景,并探讨了数字孪生在规划领域的应用前景,对运营商推进云网融合战略、推进高质量发展具有指导和参考意义。 相似文献