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   288514篇
  免费   23787篇
  国内免费   14469篇
电工技术   17619篇
技术理论   51篇
综合类   37860篇
化学工业   34106篇
金属工艺   14982篇
机械仪表   15904篇
建筑科学   38856篇
矿业工程   15847篇
能源动力   8909篇
轻工业   15737篇
水利工程   14202篇
石油天然气   11897篇
武器工业   2685篇
无线电   19139篇
一般工业技术   23401篇
冶金工业   18416篇
原子能技术   2894篇
自动化技术   34265篇
  2024年   956篇
  2023年   3293篇
  2022年   5537篇
  2021年   6809篇
  2020年   7289篇
  2019年   6241篇
  2018年   5724篇
  2017年   6872篇
  2016年   7967篇
  2015年   8805篇
  2014年   15935篇
  2013年   14758篇
  2012年   18910篇
  2011年   20049篇
  2010年   15885篇
  2009年   16639篇
  2008年   15492篇
  2007年   20337篇
  2006年   19407篇
  2005年   17028篇
  2004年   14428篇
  2003年   13209篇
  2002年   10841篇
  2001年   9153篇
  2000年   7797篇
  1999年   6322篇
  1998年   4845篇
  1997年   4177篇
  1996年   3850篇
  1995年   3242篇
  1994年   2893篇
  1993年   2171篇
  1992年   1908篇
  1991年   1414篇
  1990年   1240篇
  1989年   1092篇
  1988年   855篇
  1987年   588篇
  1986年   441篇
  1985年   371篇
  1984年   348篇
  1983年   258篇
  1982年   225篇
  1981年   169篇
  1980年   134篇
  1979年   114篇
  1978年   64篇
  1977年   74篇
  1976年   55篇
  1975年   60篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) X¯ scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA X¯ scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA X¯ scheme.  相似文献   
2.
In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals.  相似文献   
3.
高素质人才培养是我国可持续发展战略、科教兴国战略以及人才强国战略等多项发展战略的一项基础性工程。本文针对中医药类院校程序设计类课程实践教学模式单一等教学实际,以“学科竞赛”为平台,“赛教结合”为理念,以《C语言程序设计》为例,从现存问题、赛教结合模式的引入、建立实施及其评价机制4个方面展开阐述,旨在提高学生学习积极性和能力。  相似文献   
4.
本文以云杉八齿小蠹Ips typographus Linnaeus为例,经标本选取,观察虫体整体形态,绘制整体结构草图,电子显微镜观察局部、得到局部数字图像,分别建立虫体每一部分的高精度细节。把模型每部分拼装在一起组成整体模型,构建出了云杉八齿小蠹三维虚拟昆虫数字化模型。  相似文献   
5.
6.
7.
8.
We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope.  相似文献   
9.
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   
10.
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