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   275182篇
  免费   21632篇
  国内免费   14078篇
电工技术   19282篇
技术理论   56篇
综合类   37576篇
化学工业   29123篇
金属工艺   9864篇
机械仪表   15168篇
建筑科学   38670篇
矿业工程   15283篇
能源动力   8404篇
轻工业   14735篇
水利工程   14400篇
石油天然气   11485篇
武器工业   2617篇
无线电   18517篇
一般工业技术   19545篇
冶金工业   15791篇
原子能技术   2655篇
自动化技术   37721篇
  2024年   865篇
  2023年   2637篇
  2022年   5070篇
  2021年   6139篇
  2020年   6488篇
  2019年   5454篇
  2018年   5095篇
  2017年   6232篇
  2016年   7373篇
  2015年   8361篇
  2014年   15453篇
  2013年   13965篇
  2012年   18238篇
  2011年   19506篇
  2010年   15516篇
  2009年   16095篇
  2008年   15133篇
  2007年   19709篇
  2006年   18667篇
  2005年   16370篇
  2004年   13986篇
  2003年   12517篇
  2002年   10260篇
  2001年   8756篇
  2000年   7350篇
  1999年   6001篇
  1998年   4524篇
  1997年   3993篇
  1996年   3656篇
  1995年   3100篇
  1994年   2741篇
  1993年   2064篇
  1992年   1822篇
  1991年   1359篇
  1990年   1184篇
  1989年   1042篇
  1988年   842篇
  1987年   572篇
  1986年   433篇
  1985年   357篇
  1984年   338篇
  1983年   248篇
  1982年   217篇
  1981年   168篇
  1980年   131篇
  1979年   112篇
  1978年   64篇
  1977年   72篇
  1976年   55篇
  1975年   57篇
排序方式: 共有10000条查询结果,搜索用时 0 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.
In the last few years, more and more complex microsphere models have been proposed to predict the mechanical response of various polymers. Similarly than for microplane models, they consist in deriving a one-dimensional force vs. stretch equation and to integrate it over the unit sphere to obtain a three-dimensional constitutive equation. In this context, the focus of authors is laid on the physics of the one-dimensional relationship, but in most of the case the influence of the integration method on the prediction is not investigated.Here we compare three numerical integration schemes: a classical Gaussian scheme, a method based on a regular geometric meshing of the sphere, and an approach based on spherical harmonics. Depending on the method, the number of integration points may vary from 4 to 983,040! Considering simple quantities, i.e. principal (large) strain invariants, it is shown that the integration method must be carefully chosen. Depending on the quantities retained to described the one-dimensional equation and the required error, the performances of the three methods are discussed. Consequences on stress–strain prediction are illustrated with a directional version of the classical Mooney–Rivlin hyperelastic model. Finally, the paper closes with some advices for the development of new microsphere constitutive equations.  相似文献   
6.
7.
8.
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