全文获取类型
收费全文 | 4095篇 |
免费 | 142篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 88篇 |
综合类 | 73篇 |
化学工业 | 607篇 |
金属工艺 | 66篇 |
机械仪表 | 78篇 |
建筑科学 | 165篇 |
矿业工程 | 10篇 |
能源动力 | 46篇 |
轻工业 | 1892篇 |
水利工程 | 28篇 |
石油天然气 | 44篇 |
武器工业 | 5篇 |
无线电 | 231篇 |
一般工业技术 | 541篇 |
冶金工业 | 143篇 |
原子能技术 | 16篇 |
自动化技术 | 237篇 |
出版年
2023年 | 34篇 |
2022年 | 73篇 |
2021年 | 102篇 |
2020年 | 77篇 |
2019年 | 46篇 |
2018年 | 75篇 |
2017年 | 58篇 |
2016年 | 63篇 |
2015年 | 65篇 |
2014年 | 93篇 |
2013年 | 119篇 |
2012年 | 113篇 |
2011年 | 141篇 |
2010年 | 114篇 |
2009年 | 97篇 |
2008年 | 112篇 |
2007年 | 93篇 |
2006年 | 100篇 |
2005年 | 59篇 |
2004年 | 83篇 |
2003年 | 77篇 |
2002年 | 81篇 |
2001年 | 52篇 |
2000年 | 46篇 |
1999年 | 48篇 |
1998年 | 74篇 |
1997年 | 41篇 |
1996年 | 50篇 |
1995年 | 44篇 |
1994年 | 55篇 |
1993年 | 34篇 |
1921年 | 34篇 |
1919年 | 35篇 |
1917年 | 48篇 |
1916年 | 78篇 |
1915年 | 88篇 |
1914年 | 54篇 |
1913年 | 61篇 |
1912年 | 82篇 |
1911年 | 84篇 |
1910年 | 94篇 |
1909年 | 97篇 |
1908年 | 102篇 |
1907年 | 101篇 |
1906年 | 94篇 |
1905年 | 118篇 |
1904年 | 150篇 |
1903年 | 94篇 |
1902年 | 65篇 |
1901年 | 74篇 |
排序方式: 共有4270条查询结果,搜索用时 15 毫秒
31.
图20是数字摄像机信号处理的典型例子。图20(a)为一般DSP摄像机系统图,图20(b)是SONY公司DVW-700P的功能方块图,图20(c)为日立公司SK-2600P、SK-2800PW的功能方块图。 相似文献
32.
Linh Mai Jae-Young Lee Van-Su Pham Giwan Yoon 《Microwave and Wireless Components Letters, IEEE》2007,17(12):867-869
In this letter, we present the design and fabrication of a novel ZnO-based film bulk acoustic wave resonator (FBAR) microwave devices. The novel FBAR devices employ a new-type of Bragg reflector with very thin chromium (Cr) layer formed between SiO2 and W films. The Cr layer seems to enhance the adhesion between SiO2 and W layers. The novel FBAR devices show good return losses (S11) and high Q-factors at the frequency range of 2.7-3.0 GHz. This approach will be very helpful for mobile worldwide interoperability for microwave access applications. 相似文献
33.
Hsu‐Yang Kung Sumalee Chaisit Nguyen Thi Mai Phuong 《International Journal of Communication Systems》2015,28(4):625-644
An indoor localization technology is increasingly critical as location‐aware applications evolve. Researchers have proposed several indoor localization technologies. Because most of the proposed indoor localization technologies simply involve using the received signal strength indicator value of radio‐frequency identification (RFID) for indoor localization, radio‐frequency interference, and environmental factors often limit the accuracy of localization results. Therefore, this study proposes an accurate RFID localization based on the neural network (ARL‐N2), a passive RFID indoor localization scheme for identifying tag positions in a room, combining a location identification based on dynamic active RFID calibration algorithm with a backpropagation neural network (BPN). The proposed scheme composed of two phases: in the training phase, an appropriate BPN architecture is constructed using the training data derived from the coordinates of reference tags and the coordinates obtained using the localization algorithm. By contrast, the online phase involves calculating the tracking tag coordinates and using these values as BPN inputs, thereby enhancing the estimated location. A performance evaluation of the ARL‐N2 schemes confirms its high localization accuracy. The proposed method can be used to locate critical objects in difficult‐to‐find areas by creating minimal errors and applying and economical technique. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
34.
基于微机电系统(MEMS)技术的薄膜体声波谐振器(FBAR)在无线通讯领域取得了巨大的成功后,由于其具备厚度薄,体积小,与IC兼容及谐振频率和灵敏度都远高于传统的微质量传感器(如石英晶体微天平)等优势,逐渐在微生物分子检测方面崭露头角.由于微生物分子大都生存于液体环境,而纵波模式下FBAR微质量传感器在液体环境中声波损耗大,其品质因数Q值只有3.53.因此,该文在分析了纵波模式下FBAR微质量传感器在气相和液相环境中的特性后,针对液相环境中传感器Q值较低问题,设计了一种具有微通道的FBAR微质量传感器,使其Q值达到30.85,增加了近9倍,从而提升了纵波模式下FBAR微质量传感器对液体中微生物分子检测的性能. 相似文献
35.
本文介绍了广州电视台8讯道数字转播车音频系统的改造,通过对系统的选择、构成、路由、备份、监听、扩展以及测量结果的介绍,提出了利用DolbyE技术对转播车拾取的环绕声信号进行编码记录的方案。 相似文献
36.
针对3G业务发展的特点,通过对几种主流传送技术的对比,提出了引入MSTP+设备的必要性,介绍了该设备的主要特点并提出相应的传送网组网演进模式。 相似文献
37.
Ming-Shen Jian Jun-Hong Shen Kuan-Wei Lee Yi-Chen Jhou Chien-Tang Mai 《电子科技学刊:英文版》2016,14(4):362-369
This paper develops cloud based software computing as a service (SCaaS) in the hybrid evolution algorithm with feedback assistance to solve the data optimal NP-complete problems such as travel salesman problems and job shop scheduling problems. Suitable steps, methods, or procedures of the genetic algorithm can be adopted from various evolution procedures or methods of the genetic algorithms based on the fitness evaluation results and survival ratio of different crossover methods in the current generation. The proposed system can dynamically emphasize the corresponding methods or procedures for the better performance in optimal solution searching. In addition, according to the proposed XML format, system users can upload only the coding of chromosomes without implementing the genetic algorithm program. Furthermore, by using the feedback assistance, the convergence time of the optimal solution can be enhanced. 相似文献
38.
This paper presents a comprehensive cross-layer framework on the performance of transmission control protocol (TCP) over a free-space optical (FSO) link, which employs automatic repeat request (ARQ) and adaptive modulation and coding (AMC) schemes. Not similar to conventional works in the literature of FSO, we conduct a Markov error model to accurately capture effects of burst errors caused by atmospheric turbulence on cross-layer operations. From the framework, we quantify the impacts of different parameters/settings of ARQ, AMC, and the FSO link on TCP throughput performance. We also discuss several optimization aspects for TCP performance. 相似文献
39.
40.
Yikun Su Weirui Yu Liming Liao Xinbo Xiong Huanwen Chen Lingzhi Hu Tongjia Lei Jinlai Zhao Dong Chen Wenjie Mai 《Advanced functional materials》2023,33(42):2303976
Photo-electrochemical (PEC) water splitting is a promising method for converting solar energy into clean energy, but the mechanism of improving PEC efficiency through the interfacial contact and defect strategy remains highly controversial. Herein, reduced graphene oxide (rGO) and oxygen vacancies are introduced into α-Fe2O3 nanorod (NR) arrays using a simple spin-coating method and acid treatment. The resultant oxygen vacancy–α-Fe2O3/rGO-integrated system exhibits a higher photocurrent, four times than the pristine α-Fe2O3. It is well evidenced that the electronic interface interaction between α-Fe2O3 and rGO is boosted with the oxygen vacancies, facilitating electron transfer from α-Fe2O3 to rGO. Moreover, the oxygen vacancies not only create interband states in α-Fe2O3 that can trap photogenerated holes and thus facilitate charge separation but significantly also strengthen the adsorption of oxidative intermediates and reduce the energy barrier of rate-determining step during oxygen evolution reaction (OER). This study demonstrates an rGO–oxygen vacancy synergistic interfacial contact and defect modification approach to design semiconducting photocatalysts for high-efficiency solar energy capture and conversion. The generated principle is expected to be extendable to another material system. 相似文献