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   1924篇
  免费   182篇
  国内免费   1篇
电工技术   14篇
综合类   1篇
化学工业   428篇
金属工艺   21篇
机械仪表   32篇
建筑科学   69篇
矿业工程   2篇
能源动力   87篇
轻工业   345篇
水利工程   15篇
石油天然气   8篇
无线电   170篇
一般工业技术   368篇
冶金工业   61篇
原子能技术   10篇
自动化技术   476篇
  2024年   6篇
  2023年   24篇
  2022年   80篇
  2021年   99篇
  2020年   56篇
  2019年   92篇
  2018年   111篇
  2017年   85篇
  2016年   94篇
  2015年   72篇
  2014年   116篇
  2013年   159篇
  2012年   149篇
  2011年   184篇
  2010年   116篇
  2009年   98篇
  2008年   97篇
  2007年   83篇
  2006年   79篇
  2005年   55篇
  2004年   54篇
  2003年   39篇
  2002年   32篇
  2001年   13篇
  2000年   13篇
  1999年   16篇
  1998年   19篇
  1997年   16篇
  1996年   4篇
  1995年   10篇
  1994年   10篇
  1993年   4篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1975年   1篇
  1974年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有2107条查询结果,搜索用时 15 毫秒
221.
The authors report 3 experiments that examine a new mechanism by which overt head movements can affect attitude change. In each experiment, participants were induced to either nod or to shake their heads while listening to a persuasive message. When the message arguments were strong, nodding produced more persuasion than shaking. When the arguments were weak, the reverse occurred. These effects were most pronounced when elaboration was high. These findings are consistent with the "self-validation" hypothesis that postulates that head movements either enhance (nodding) or undermine (shaking) confidence in one's thoughts about the message. In a 4th experiment, the authors extended this result to another overt behavior (writing with the dominant or nondominant hand) and a different attitude domain (self-esteem). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
222.
Abstract:   We show how intervention analysis can be used in conjunction with dynamic performance modeling to analyze the effect of maintenance activities on the performance of infrastructure facilities. Specifically, we consider state-space specifications of autoregressive moving averages with exogenous inputs models to develop deterioration and inspection models for infrastructure facilities, and intervention analysis to estimate transitory and permanent effects of maintenance, for example, performance jumps or deterioration rate changes. To illustrate the methodology, we analyze the effectiveness of an overlay on a flexible pavement section from the AASHO Road Test. The results show the effect of the overlay on improvements both on surface distress, that is, rutting and slope variance, as well as on the pavement's underlying serviceability. The results also provide evidence that the overlay changes the pavement's response to traffic, that is, the overlay causes a reduction in the rate at which traffic damages the pavement .  相似文献   
223.
Software-defined radio (SDR) is a revolution in radio design due to the ability to create radios that can self-adapt on the fly. In SDR devices, all of the signal processing is implemented in the digital domain, mainly on DSP blocks or by DSP software. By simply downloading a new program, a SDR device is able to interoperate with different wireless protocols, incorporate new services, and upgrade to new standards. Therefore, massively parallel signal processing at higher frequencies are needed to implement a realistic SDR. Thus, FPGAs have been used extensively for implementing essential functions in SDR architectures at lower frequencies. In this paper, we explore the design of a digital FM receiver using the approach of an All-Digital Phase Locked-Loop (ADPLL). The circuit is designed in VHDL, then synthesized and simulated using LeonardoSpectrum Level 3 and ModelSim SE 6, respectively. It operates at a frequency up to 150 MHz and occupies the area of roughly 15 K logic gates.  相似文献   
224.
An integrated method for symbolical derivation of Eqs and numerical computations using dual numbers for analysis of spatial mechanisms is presented in this paper. The formulation is based on 3×3 dual transformation matrices and derived symbolically using the Mathematica TM software package. Based on the solution procedure presented in this paper, a software library of functions for displacement analysis of spatial mechanisms has been developed. Functions in this software library can be readily used in theC H language environment, where dual number is treated as a first-class object. Displacement analysis of the RCRCR spatial mechanisms is used as an example to illustrate the solution procedure and programming details.  相似文献   
225.
Businesses in knowledge intensive industries must appropriately engage with their customers in order to produce goods and services that are desired and valued in the marketplace. Engagement with customers calls for exchanging information and knowledge with customers and fostering exchanges between customers. Recent developments in the area of information and communication technologies (ICTs) have radically increased the variety of opportunities for improving customer engagement. In this paper, we will examine the use of ICTs to build Business Customer Communities (BCCs) to help an organization foster knowledge exchanges between its professional and institutional customers. We define BCCs as groups of business customers, which are deliberately enabled by a firm and share a long-term need to exchange work related knowledge through online and offline interaction. The objectives of this study are (1) to describe BCCs and outline their attributes and features, and (2) to contribute to the understanding of challenges associated with the enabling of BCC formation and how firms can overcome these challenges. As such, a contribution is made to the discussion of knowing in practice in customer communities, which rely in large part on ICT.  相似文献   
226.
The effects of enzyme‐active full‐fat (EAFFSF), heat‐treated full‐fat (HTFFSF) and enzyme‐active defatted (EADSF) soy flours and commercial soy protein isolates (SPIs) on mixing properties and extensibility of dough, gluten formation, gas production and retention properties of dough and bread quality were studied. The soy products utilised in this study presented values of urease activity, nitrogen solubility index (NSI) and enthalpies of protein denaturation according to their previous heat processing. Soy products interfered in gluten formation, weakened dough strength and decreased dough gas retention capacity. Bread quality was negatively affected by soy product addition. The negative effects were exacerbated by an increase in soy/wheat ratio. Soybean protein state was identified as an important factor in determining dough and bread properties. Copyright © 2005 Society of Chemical Industry  相似文献   
227.
Regarding micro components and systems, experimental work for characterizing materials’ properties as well as components’ and systems’ behaviors have to be supplemented by numerical analyses. These analyses should cover component and system issues. On a component level, macroscopic approaches are extended by methods allowing consideration of the influence of components’ grain structures including possible defects. On a system level, the high tolerances accepted for the individual components due to production inaccuracy and their effects on the expected load distribution capability of the system are taken into account. This paper presents approaches for simulation of micro components and systems using the finite element method and multi body simulation. Methods to overcome the abovementioned issues will be shown, as well as the effects of grain structure on the stress distribution in the individual components.  相似文献   
228.
A real-time polymerase chain reaction assay using primers targeting the porcine-specific mitochondrial 12S rRNA gene and universal eukaryotic primers amplifying a conserved fragment of the nuclear 18S rRNA gene has been developed for the detection and quantification of porcine DNA in food and feedstuffs. The 18S rRNA primers were used as endogenous control for the total content of PCR-amplifiable DNA in the sample. The assay was tested on DNA extracted from raw and heat-treated binary mixtures of porcine tissues in a plant matrix, and on DNA extracted from reference feedstuff samples. Analysis of experimental mixtures demonstrated the suitability of the assay for the detection and quantification of porcine DNA in mixtures containing as little as 0.1%.  相似文献   
229.
230.
The curing reaction of an epoxy–phenolic resin under different conditions was monitored using rheological measurements. The evolution of viscoelastic properties, such as storage modulus, G′, and loss modulus, G″, was recorded. Several experiments were performed to confidently compare the rheological data obtained under varied curing conditions of temperature, catalyst concentration, and reactive ratios. The values of G′ measured at the end of the reactions (at maximum conversion) were independent of the frequency and temperature of the tests in the range of high temperatures investigated. The overall curing process was described by a second‐order phenomenological rheokinetic equation based on the model of Kamal. The effects of the epoxy‐to‐phenolic ratio as well as the curing temperature and the catalyst concentration were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4430–4439, 2006  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