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   309912篇
  免费   24673篇
  国内免费   16173篇
电工技术   20193篇
技术理论   54篇
综合类   39983篇
化学工业   36740篇
金属工艺   12788篇
机械仪表   17054篇
建筑科学   42632篇
矿业工程   16913篇
能源动力   9630篇
轻工业   16915篇
水利工程   15070篇
石油天然气   12529篇
武器工业   3283篇
无线电   20231篇
一般工业技术   25195篇
冶金工业   18157篇
原子能技术   3048篇
自动化技术   40343篇
  2024年   866篇
  2023年   2880篇
  2022年   5887篇
  2021年   7226篇
  2020年   7429篇
  2019年   6194篇
  2018年   5808篇
  2017年   7159篇
  2016年   8433篇
  2015年   9399篇
  2014年   17283篇
  2013年   15744篇
  2012年   20637篇
  2011年   22108篇
  2010年   17607篇
  2009年   18434篇
  2008年   17084篇
  2007年   22489篇
  2006年   21031篇
  2005年   18478篇
  2004年   15663篇
  2003年   14168篇
  2002年   11678篇
  2001年   9809篇
  2000年   8295篇
  1999年   6696篇
  1998年   5066篇
  1997年   4401篇
  1996年   4052篇
  1995年   3395篇
  1994年   3038篇
  1993年   2262篇
  1992年   1929篇
  1991年   1419篇
  1990年   1236篇
  1989年   1096篇
  1988年   863篇
  1987年   580篇
  1986年   432篇
  1985年   380篇
  1984年   342篇
  1983年   259篇
  1982年   229篇
  1981年   175篇
  1980年   143篇
  1979年   118篇
  1978年   68篇
  1977年   77篇
  1976年   60篇
  1975年   60篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
61.
来水利 《云南化工》2019,(7):180-181
有机化学是化学化工、材料、制药、食品等多个专业的基础课程,在其教学过程中,教师可以根据课程的内容及特点,分别以有机化学发展中的重大历史事件、有机化物的性质及有机反应为引导,开展学生的思想品德教育,加强课程思政建设。  相似文献   
62.
63.
To improve the convertibility of reconfigurable manufacturing system (RMS), the concept of delayed reconfigurable manufacturing system (D-RMS) was proposed. RMS and D-RMS are both constructed around part family. However, D-RMS may suffer from ultra-long system problem with unacceptable idle machines using generic RMS part families. Besides, considering the complex basic system structure of D-RMS, machine selection of D-RMS should be addressed, including dedicated machine, flexible machine, and reconfigurable machine. Therefore, a system design method for D-RMS based on part family grouping and machine selection is proposed. Firstly, a part family grouping method is proposed for D-RMS that groups the parts with more former common operations into the same part family. The concept of longest relative position common operation subsequence (LPCS) is proposed. The similarity coefficient among the parts is calculated based on LPCS. The reciprocal value of the operation position of LPCS is adopted as the characteristic value. The average linkage clustering (ALC) algorithm is used to cluster the parts. Secondly, a machine selection method is proposed to complete the system design of D-RMS, including machine selection rules and the dividing point decision model. Finally, a case study is given to implement and verify the proposed system design method for D-RMS. The results show that the proposed system design method is effective, which can group parts with more former common operations into the same part family and select appropriate machine types.  相似文献   
64.
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。  相似文献   
65.
66.
67.
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype.  相似文献   
68.
69.
A small handful of recent studies have addressed a phenomenon known as “phantom vibration syndrome”. This refers to when phone users perceive their device to vibrate, indicating that a call or text is incoming, when in fact the phone did not vibrate at all. Though these studies show that most users do not find phantom vibration hallucinations to be very bothersome, they also find that a large majority of users experience this phenomenon. This paper explores what the striking prevalence of phantom vibration syndrome means for our contemporary relationships with technology. I begin with a review of the theories purporting to explain these data, which largely rely on particular understandings of the brain. Next I develop an alternative theory of phantom vibration syndrome based on insights from the philosophical tradition of phenomenology. This account considers the ways users develop bodily and perceptual habits regarding how the phone is understood and used. By critically contrasting these different theories, we can refine our questions about what the high prevalence of phantom vibration syndrome implies about our contemporary technological situation.  相似文献   
70.
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