全文获取类型
收费全文 | 129785篇 |
免费 | 14344篇 |
国内免费 | 9363篇 |
专业分类
电工技术 | 10746篇 |
技术理论 | 3篇 |
综合类 | 11793篇 |
化学工业 | 17348篇 |
金属工艺 | 8513篇 |
机械仪表 | 9286篇 |
建筑科学 | 10752篇 |
矿业工程 | 4564篇 |
能源动力 | 3911篇 |
轻工业 | 10654篇 |
水利工程 | 3855篇 |
石油天然气 | 5738篇 |
武器工业 | 1639篇 |
无线电 | 15224篇 |
一般工业技术 | 12725篇 |
冶金工业 | 4987篇 |
原子能技术 | 2157篇 |
自动化技术 | 19597篇 |
出版年
2024年 | 547篇 |
2023年 | 1836篇 |
2022年 | 3951篇 |
2021年 | 5504篇 |
2020年 | 4007篇 |
2019年 | 3157篇 |
2018年 | 3441篇 |
2017年 | 3904篇 |
2016年 | 3678篇 |
2015年 | 5601篇 |
2014年 | 7188篇 |
2013年 | 8389篇 |
2012年 | 10178篇 |
2011年 | 11056篇 |
2010年 | 10326篇 |
2009年 | 9895篇 |
2008年 | 10062篇 |
2007年 | 9784篇 |
2006年 | 8805篇 |
2005年 | 7016篇 |
2004年 | 5088篇 |
2003年 | 3963篇 |
2002年 | 3822篇 |
2001年 | 3377篇 |
2000年 | 2597篇 |
1999年 | 1668篇 |
1998年 | 920篇 |
1997年 | 777篇 |
1996年 | 638篇 |
1995年 | 526篇 |
1994年 | 410篇 |
1993年 | 315篇 |
1992年 | 213篇 |
1991年 | 172篇 |
1990年 | 130篇 |
1989年 | 124篇 |
1988年 | 71篇 |
1987年 | 59篇 |
1986年 | 55篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 32篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 31篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1959年 | 26篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
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
5.
大气波导干扰是特定气象条件下发生的时分双工(time-division duplex,TDD)系统内干扰,是TDD移动通信系统大规模组网面临的顽疾。在总结分析大气波导干扰成因和分类等的基础上,对大气波导干扰进行建模和表征,验证了海量干扰源在时域和频域的功率集总特征,并结合大量4G/5G现网实测数据给出了典型条件下内陆波导和海面波导的量化干扰信号传播模型,对于干扰的预测和预防具有重要意义。基于干扰特征,给出了TDD系统预防大气波导干扰的帧结构与组网的4项设计原则,5G现网数据表明干扰控制方案有效,上行干扰下降10 dB以上,相关原则对于6G系统的设计也具有指导意义。 相似文献
6.
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
7.
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
8.
9.
Jia Dai Xiang Cheng Xiaofeng Li Zhisheng Wang Yufeng Wang Jing Zheng Jun Liu Jiawei Chen Changjin Wu Jinyao Tang 《Advanced functional materials》2021,31(48):2106204
Synthetic active matters are perfect model systems for non-equilibrium thermodynamics and of great potential for novel biomedical and environmental applications. However, most applications are limited by the complicated and low-yield preparation, while a scalable synthesis for highly functional microswimmers is highly desired. In this paper, an all-solution synthesis method is developed where the gold-loaded titania-silica nanotree can be produced as a multi-functional self-propulsion microswimmer. By applying light, heat, and electric field, the Janus nanotree demonstrated multi-mode self-propulsion, including photochemical self-electrophoresis by UV and visible light radiation, thermophoresis by near-infrared light radiation, and induced-charge electrophoresis under AC electric field. Due to the scalable synthesis, the Janus nanotree is further demonstrated as a high-efficiency, low-cost, active adsorbent for water decontamination, where the toxic mercury ions can be reclaimed with enhanced efficiency. 相似文献
10.
Chunsheng Wang Yishuang Wang Mingqiang Chen Defang Liang Zhonglian Yang Wen Cheng Zhiyuan Tang Jun Wang Han Zhang 《International Journal of Hydrogen Energy》2021,46(7):5852-5874
Given the continuing issues of environment and energy, methane dry reforming for syngas production have sparked interest among researchers, but struggled with the process immaturity owing to catalyst deactivation. This review summarizes the recent advances in the development of efficient and stable catalysts with strong resistance to coking and metal sintering, including the application of novel materials, the assessment of advanced characterizations and the compatibility to improved reaction system. One feasible option is the crystalline oxide catalysts (perovskite, pyrochlore, spinel and LDHs), which feature a fine metal dispersion and surface confinement effect via a metal exsolution strategy and exhibit superior reactivity and stability. Some new materials (h-BN, clays and MOFs) also extend the option because of their unique morphology and microstructure. It also is elaborated that progresses were achieved in advanced characterizations application, leading to success in the establishment of reaction mechanisms and attributions to the formed robust catalysts. In addition, the perspective described the upgrade of reaction system to a higher reaction efficiency and milder reaction conditions. The combination of efficient reaction systems and robust catalysts paves a way for a scaling-up application of the process. 相似文献