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   277709篇
  免费   22778篇
  国内免费   14806篇
电工技术   17768篇
技术理论   52篇
综合类   37121篇
化学工业   30249篇
金属工艺   11174篇
机械仪表   16000篇
建筑科学   38092篇
矿业工程   15065篇
能源动力   8075篇
轻工业   15472篇
水利工程   14067篇
石油天然气   11961篇
武器工业   2688篇
无线电   21173篇
一般工业技术   21126篇
冶金工业   16052篇
原子能技术   3165篇
自动化技术   35993篇
  2024年   938篇
  2023年   2999篇
  2022年   5513篇
  2021年   6597篇
  2020年   6948篇
  2019年   5811篇
  2018年   5510篇
  2017年   6675篇
  2016年   7829篇
  2015年   8654篇
  2014年   15608篇
  2013年   14191篇
  2012年   18467篇
  2011年   19520篇
  2010年   15513篇
  2009年   16151篇
  2008年   15085篇
  2007年   19696篇
  2006年   18600篇
  2005年   16220篇
  2004年   13863篇
  2003年   12479篇
  2002年   10296篇
  2001年   8668篇
  2000年   7377篇
  1999年   6020篇
  1998年   4560篇
  1997年   4035篇
  1996年   3731篇
  1995年   3112篇
  1994年   2799篇
  1993年   2104篇
  1992年   1866篇
  1991年   1385篇
  1990年   1205篇
  1989年   1061篇
  1988年   840篇
  1987年   580篇
  1986年   441篇
  1985年   362篇
  1984年   346篇
  1983年   250篇
  1982年   217篇
  1981年   170篇
  1980年   138篇
  1979年   113篇
  1978年   65篇
  1977年   73篇
  1976年   56篇
  1975年   57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.
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   
9.
10.
Electrical resistivity, Seebeck coefficient, specific heat and thermal conductivity measurements on the Ti50−xNi50+x (x = 0.0–1.6 at.%) shape memory alloys are performed to investigate their thermal and transport properties. In this study, anomalous features are observed in both cooling and heating cycles in all measured physical properties of the slightly Ni-rich TiNi alloys (x ≤ 1.0), corresponds to the transformation between the B19′ martensite and B2 austenite phases. Besides, the transition temperature is found to decrease gradually with increasing Ni content, and the driving force for the transition is also found to diminish slowly with the addition of excess Ni, as revealed by specific heat measurements. While the signature of martensitic transformation vanishes for the Ni-rich TiNi alloys with x ≥ 1.3, the characteristics of strain glass transition start to appear. The Seebeck coefficients of these TiNi alloys were found to be positive, suggesting the hole-type carriers dominate the thermoelectric transport. From the high-temperature Seebeck coefficients, the estimated value of Fermi energy ranges from ∼1.5 eV (Ti48.4Ni51.6) to ∼2.1 eV (Ti50Ni50), indicating the metallic nature of these alloys. In addition, the thermal conductivity of the slightly Ni-rich TiNi alloys with x ≤ 1.0 shows a distinct anomalous feature at the B19′ → B2 transition, likely due to the variation in lattice thermal conductivity.  相似文献   
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