全文获取类型
收费全文 | 89211篇 |
免费 | 11428篇 |
国内免费 | 6679篇 |
专业分类
电工技术 | 7659篇 |
技术理论 | 3篇 |
综合类 | 8749篇 |
化学工业 | 12001篇 |
金属工艺 | 5415篇 |
机械仪表 | 6088篇 |
建筑科学 | 7413篇 |
矿业工程 | 3299篇 |
能源动力 | 2602篇 |
轻工业 | 10025篇 |
水利工程 | 2729篇 |
石油天然气 | 3625篇 |
武器工业 | 1073篇 |
无线电 | 10296篇 |
一般工业技术 | 8169篇 |
冶金工业 | 3331篇 |
原子能技术 | 1177篇 |
自动化技术 | 13664篇 |
出版年
2024年 | 683篇 |
2023年 | 2079篇 |
2022年 | 4189篇 |
2021年 | 5291篇 |
2020年 | 3735篇 |
2019年 | 2765篇 |
2018年 | 2976篇 |
2017年 | 3237篇 |
2016年 | 2868篇 |
2015年 | 4396篇 |
2014年 | 5336篇 |
2013年 | 5912篇 |
2012年 | 7285篇 |
2011年 | 7516篇 |
2010年 | 6677篇 |
2009年 | 6389篇 |
2008年 | 6300篇 |
2007年 | 5946篇 |
2006年 | 5047篇 |
2005年 | 4082篇 |
2004年 | 2948篇 |
2003年 | 2400篇 |
2002年 | 2514篇 |
2001年 | 2213篇 |
2000年 | 1473篇 |
1999年 | 841篇 |
1998年 | 409篇 |
1997年 | 350篇 |
1996年 | 275篇 |
1995年 | 238篇 |
1994年 | 201篇 |
1993年 | 159篇 |
1992年 | 115篇 |
1991年 | 85篇 |
1990年 | 65篇 |
1989年 | 49篇 |
1988年 | 42篇 |
1987年 | 33篇 |
1986年 | 28篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 40篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1959年 | 11篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
3.
目的:解决当前饮料瓶盖检测系统功能单一、体积偏大、颜色识别率低的问题。方法:提出一种基于ARM处理器的小型饮料瓶盖颜色识别系统设计方案,通过仿真软件HyperLynx的LineSim工具设计四层PCB板,设置传输线参数并进行阻抗匹配仿真分析;利用编译软件Jupyter Notebook实现阈值设置、目标轮廓检测、目标框出等功能。结果:在强、弱光条件下,识别系统对红、绿、蓝3种颜色瓶盖的识别率达到92.7%。结论:与傅里叶描述子相比,该识别系统识别准确率和精度更高,同时系统也具有人脸识别功能,适用于各种智能应用场景。 相似文献
4.
为满足不同规格晶体探测器对分割校准晶体条响应事件位置数据的需求,开发了一种以禁忌搜索算法为核心,结合UDP数据帧、二维高斯模型及光导折射率的位置信息分割校准方法。实验结果表明,本方法在溢出率为5%时,峰谷比可达1218,空间分辨率达17 mm,晶体条响应位置识别准确度高达99%,滤除了引发伪峰的噪声,避免了过分割问题。在面对多种规格晶体阵列的位置谱时,本方法能依照阵列规格将晶体条区域的响应自动校准编号并输出晶体位置查找表,实现响应事件的精确校准。 相似文献
5.
6.
Shilin Du Yichen Dong Feiqiang Guo Beile Tian Songbo Mao Lin Qian Chengyun Xin 《International Journal of Hydrogen Energy》2021,46(27):14138-14147
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications. 相似文献
7.
8.
Sun Xiaohao Miao Linchang Wang Hengxing Chen Runfa Guo Xin 《Bulletin of Engineering Geology and the Environment》2021,80(6):4957-4966
Bulletin of Engineering Geology and the Environment - Bio-cementation is currently applied to solidify sandy soils, but only few studies use it to cement loess soil particles. In this study, the... 相似文献
9.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献
10.
Yuzhu Su Junpu Wang Xin Li Qiqi Tang Jing Yang Li Lei Yi Tian Zhiwei Wang Duanwei He 《Ceramics International》2021,47(15):21077-21082
The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al2O3, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression. 相似文献