首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   386733篇
  免费   39693篇
  国内免费   13615篇
电工技术   19996篇
技术理论   58篇
综合类   21435篇
化学工业   75278篇
金属工艺   20051篇
机械仪表   23295篇
建筑科学   28813篇
矿业工程   11405篇
能源动力   11336篇
轻工业   27175篇
水利工程   6047篇
石油天然气   23925篇
武器工业   2760篇
无线电   44922篇
一般工业技术   51812篇
冶金工业   19617篇
原子能技术   3522篇
自动化技术   48594篇
  2024年   1164篇
  2023年   5324篇
  2022年   9370篇
  2021年   13431篇
  2020年   11381篇
  2019年   11006篇
  2018年   12307篇
  2017年   13815篇
  2016年   13238篇
  2015年   16512篇
  2014年   20346篇
  2013年   24839篇
  2012年   24029篇
  2011年   26261篇
  2010年   23004篇
  2009年   21990篇
  2008年   21123篇
  2007年   20418篇
  2006年   21016篇
  2005年   18492篇
  2004年   12442篇
  2003年   11248篇
  2002年   10401篇
  2001年   9517篇
  2000年   9669篇
  1999年   10595篇
  1998年   8521篇
  1997年   7101篇
  1996年   6662篇
  1995年   5584篇
  1994年   4517篇
  1993年   3230篇
  1992年   2615篇
  1991年   2039篇
  1990年   1562篇
  1989年   1273篇
  1988年   1050篇
  1987年   686篇
  1986年   546篇
  1985年   346篇
  1984年   248篇
  1983年   208篇
  1982年   210篇
  1981年   136篇
  1980年   142篇
  1979年   86篇
  1978年   45篇
  1977年   50篇
  1976年   68篇
  1975年   29篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
131.
This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis.  相似文献   
132.
王霄 《广东化工》2015,42(5):118-119,115
利用CAESARⅡ软件建立了某粉煤气化装置一级炉至二级炉设备及管道的整体模型,分析了管道应力及设备管口受力状况,并依此利用ANSYS软件对二级炉设备管口应力进行了详细分析.分析表明,管道支吊架调整后,管道及设备应力及应变符合规范要求.  相似文献   
133.
This study aimed at investigating the possible mechanisms of hepatic protective activity of Cichorium intybus L. (chicory) in acute liver injury. Pathological observation, reactive oxygen species (ROS) detection and measurements of biochemical indexes on mouse models proved hepatic protective effect of Cichorium intybus L. Identification of active compounds in Cichorium intybus L. was executed through several methods including ultra performance liquid chromatography/time of flight mass spectrometry (UPLC-TOF-MS). Similarity ensemble approach (SEA) docking, molecular modeling, molecular docking, and molecular dynamics (MD) simulation were applied in this study to explore possible mechanisms of the hepato-protective potential of Cichorium intybus L. We then analyzed the chemical composition of Cichorium intybus L., and found their key targets. Furthermore, in vitro cytological examination and western blot were used for validating the efficacy of the selected compounds. In silico analysis and western blot together demonstrated that selected compound 10 in Cichorium intybus L. targeted Akt-1 in hepatocytes. Besides, compound 13 targeted both caspase-1 and Akt-1. These small compounds may ameliorate liver injury by acting on their targets, which are related to apoptosis or autophagy. The conclusions above may shed light on the complex molecular mechanisms of Cichorium intybus L. acting on hepatocytes and ameliorating liver injury.  相似文献   
134.
135.
  Qing  Xu  Bin  Yu  Yang  Zhan  Wei  Zhao  Yu  Zheng  Jun  Ji  Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...  相似文献   
136.
137.
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage.  相似文献   
138.
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results.  相似文献   
139.
140.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号