全文获取类型
收费全文 | 208747篇 |
免费 | 20922篇 |
国内免费 | 14891篇 |
专业分类
电工技术 | 33012篇 |
技术理论 | 8篇 |
综合类 | 21513篇 |
化学工业 | 11964篇 |
金属工艺 | 8274篇 |
机械仪表 | 19927篇 |
建筑科学 | 19978篇 |
矿业工程 | 8528篇 |
能源动力 | 5821篇 |
轻工业 | 5332篇 |
水利工程 | 7008篇 |
石油天然气 | 6859篇 |
武器工业 | 3510篇 |
无线电 | 16078篇 |
一般工业技术 | 12324篇 |
冶金工业 | 8366篇 |
原子能技术 | 1374篇 |
自动化技术 | 54684篇 |
出版年
2024年 | 346篇 |
2023年 | 2453篇 |
2022年 | 4147篇 |
2021年 | 5070篇 |
2020年 | 5961篇 |
2019年 | 4717篇 |
2018年 | 4379篇 |
2017年 | 6222篇 |
2016年 | 7069篇 |
2015年 | 7739篇 |
2014年 | 13913篇 |
2013年 | 12275篇 |
2012年 | 15778篇 |
2011年 | 16582篇 |
2010年 | 12658篇 |
2009年 | 12931篇 |
2008年 | 12873篇 |
2007年 | 15789篇 |
2006年 | 14065篇 |
2005年 | 12180篇 |
2004年 | 10019篇 |
2003年 | 8774篇 |
2002年 | 7040篇 |
2001年 | 5898篇 |
2000年 | 5053篇 |
1999年 | 3974篇 |
1998年 | 3052篇 |
1997年 | 2655篇 |
1996年 | 2142篇 |
1995年 | 1829篇 |
1994年 | 1555篇 |
1993年 | 1126篇 |
1992年 | 894篇 |
1991年 | 685篇 |
1990年 | 533篇 |
1989年 | 492篇 |
1988年 | 335篇 |
1987年 | 188篇 |
1986年 | 132篇 |
1985年 | 131篇 |
1984年 | 184篇 |
1983年 | 136篇 |
1982年 | 132篇 |
1981年 | 84篇 |
1980年 | 68篇 |
1979年 | 80篇 |
1978年 | 50篇 |
1977年 | 51篇 |
1964年 | 13篇 |
1959年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
随着煤矿产业的持续发展,矿井生产的自动化要求也不断提升,将PLC可编程技术应用到矿井电气自动化控制系统中,对于提升矿井综合效益意义重大。以此为着手点,以矿井提升机为对象,在分析PLC技术在提升机电气自动控制系统中应用的基础上,对电气设备单片机选型开展分析,同时总结了矿井提升机电气自动化控制系统的改造要求,希望能够为其他矿井相似工程的开展提供借鉴与参考。 相似文献
72.
针对以英飞凌TC275单片机为平台的整车控制器,进行控制器局域网络标定协议(controller area network calibration protocol,CCP)底层驱动程序的开发。依据CCP的需求开发了英飞凌TC275的控制器局域网络(controller area network,CAN)模块、系统定时器(system timer,STM)模块和FLASH模块的底层驱动程序,实现CCP标定系统的通信连接、数据上传、数据下载、数据存储等功能。为验证系统的性能,进行整车控制器的实际测试,测试结果表明:所开发的基于TC275单片机的CCP底层驱动程序能够实现CCP的功能要求。 相似文献
73.
TETSUYA OJIRO HIDEKI HONDA KAZUHIRO TSURUTA TSUYOSHI HANAMOTO 《Electrical Engineering in Japan》2018,203(2):39-46
At present, many industrial carrier devices utilize linear motor sliders. However, a heavier load requires a linear motor (which is an example of a direct drive device) to get higher power, compared with a rotary motor with a ball screw slider (which is an example of an indirect drive device). In order to obtain higher power at a lower cost, a linear slider with multiple motors can be utilized, for example, a gantry type linear motor slider. Moving the gantry type slider requires two linear motors that are set up in parallel to enable synchronization control. Some conventional synchronization control methods have been proposed for the parallel twin linear slider; however, a large‐scaled gantry type linear motor slider has two unique problems: mechanical distortion caused by the limitations of installation environment and coupling caused by joints with low stiffness. This paper proposes a control model to solve these problems, and an identification method of each parameter. Furthermore, the effectiveness of the control model is verified by comparison with simulation results and experimental results. 相似文献
74.
75.
Parallel Multipopulation Differential Evolutionary Particle Swarm Optimization for Voltage and Reactive Power Control 下载免费PDF全文
This paper presents parallel multipopulation differential evolutionary particle swarm optimization (DEEPSO) for voltage and reactive power control (VQC). The problem can be formulated as a mixed integer nonlinear optimization problem and various evolutionary computation techniques have been applied to the problem including PSO, differential evolution (DE), and DEEPSO. Since VQC is one of the online controls, speed‐up of computation is required. Moreover, there is still room for improvement in solution quality. This paper applies parallel multipopulation DEEPSO in order to speed up the calculation and improve solution quality. The proposed method is applied to IEEE 30, 57, and 118 bus systems. The results indicate that the proposed method can realize fast computation and minimize more active power losses than the conventional evolutionary computation techniques. 相似文献
76.
在双离心机的线加速度计动态校准中,三参数余弦算法贯穿在幅频特性、相频特性以及幅值线性度的整个测试中。本文详细描述了三参数余弦算法的概念和推导过程,以及在双离心机线加速度计动态校准数据处理过程中三参数余弦算法的程序实现;介绍了在幅频特性和相频特性中关于采集点的选取方式,降低由于采集点选择方式不同对数据拟合精度造成的影响。选取某型线加速度计为例,利用双离心机进行动态校准,对采集得到的数据点进行曲线拟合并得到测试结果,验证了所编写的三参数余弦算法程序的可行性。 相似文献
77.
78.
河南地区大部分煤矿所采煤层均属于三软煤层,煤层透气性差,瓦斯治理困难。现阶段河南区域煤与瓦斯突出矿井主要采用穿层钻孔及开采保护层作为区域防突措施,而低瓦斯矿井或临突矿井(低瓦斯矿井与煤与瓦斯突出矿井相邻)存在高瓦斯区时,仅仅用风排瓦斯很难达到治理效果,近些年煤矿发生瓦斯事故多数为低瓦斯矿井,所以低瓦斯矿井和临突矿井存在高瓦斯区域的工作面回采期间瓦斯治理尤为重要。根据采场“竖三带”和“横三区”理论,利用钻孔抽放效果考察法和工作突出预测指标法研究了采场围岩动压分布特征。在此基础上,通过优化动压区抽放钻孔设计,提高了瓦斯抽放效果。瓦斯抽放量提高了1.8倍,有效降低了工作面生产期间的风排瓦斯量,提高了生产效率,保证了矿井安全生产。 相似文献
79.
Wenyuan Zhou Chasity P. Hankinson Prof. Dr. Alexander Deiters 《Chembiochem : a European journal of chemical biology》2020,21(13):1832-1836
We have developed a new tool for the optical control of cellular ATP concentrations with a photocaged adenylate kinase (Adk). The photocaged Adk is generated by substituting a catalytically essential lysine with a hydroxycoumarin-protected lysine through site-specific unnatural amino acid mutagenesis in both E. coli and mammalian cells. Caging of the critical lysine residue offers complete suppression of Adk's phosphotransferase activity and rapid restoration of its function both in vitro and in vivo upon optical stimulation. Light-activated Adk renders faster rescue of cell growth than chemically inducible expression of wild-type Adk in E. coli as well as rapid ATP depletion in mammalian cells. Thus, caging Adk provides a new tool for direct conditional perturbation of cellular ATP concentrations thereby enabling the investigation of ATP-coupled physiological events in temporally dynamic contexts. 相似文献
80.
Lokesh Kulhari Kanad Ray Ankit Paptan Nikhil Suri Pramod K Khanna 《International Journal of Applied Ceramic Technology》2020,17(3):1430-1439
Low temperature co-fired ceramic (LTCC) micro-hotplates show wide applications in gas sensors and micro-fluidic devices. It is easily structured in three-dimensional structures. This paper presents the low power consumption micro-hotplates which were developed with PTC (positive temperature coefficient) temperature sensor and inter-digitated electrodes. The paper presents two different structures for micro-hotplate with platinum as a heating element. The PTC temperature sensor using two different materials viz. PdAg and platinum paste are developed with micro-hotplates. The simulation has been achieved through COMSOL for LTCC and alumina micro-hotplates. The temperature variation with power consumption has been measured for the developed LTCC micro-hotplates. The change in resistance of PTC temperature sensors was measured with micro-hotplate temperature. The aim of this study was to place a temperature sensor with the gas sensor module to measure and control the temperature of micro-hotplate. A SnO2 sensing layer is coated on LTCC micro-hotplate using screen printing and characterized for the sensing of carbon monoxide gas (CO). This study will be beneficial for designing hotplates based on LTCC technology with low power consumption and better stability of temperature for gas-sensing applications. 相似文献