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   5344篇
  免费   408篇
  国内免费   3篇
电工技术   15篇
综合类   1篇
化学工业   1896篇
金属工艺   38篇
机械仪表   104篇
建筑科学   200篇
矿业工程   10篇
能源动力   132篇
轻工业   1754篇
水利工程   48篇
石油天然气   37篇
无线电   185篇
一般工业技术   641篇
冶金工业   129篇
原子能技术   7篇
自动化技术   558篇
  2024年   17篇
  2023年   90篇
  2022年   347篇
  2021年   390篇
  2020年   207篇
  2019年   230篇
  2018年   228篇
  2017年   229篇
  2016年   265篇
  2015年   194篇
  2014年   285篇
  2013年   424篇
  2012年   397篇
  2011年   427篇
  2010年   316篇
  2009年   311篇
  2008年   266篇
  2007年   236篇
  2006年   169篇
  2005年   130篇
  2004年   111篇
  2003年   85篇
  2002年   76篇
  2001年   40篇
  2000年   45篇
  1999年   46篇
  1998年   31篇
  1997年   21篇
  1996年   18篇
  1995年   11篇
  1994年   13篇
  1993年   12篇
  1992年   9篇
  1991年   4篇
  1990年   3篇
  1989年   17篇
  1988年   7篇
  1987年   11篇
  1986年   4篇
  1985年   6篇
  1984年   6篇
  1983年   2篇
  1982年   4篇
  1981年   1篇
  1980年   6篇
  1978年   4篇
  1977年   1篇
  1976年   1篇
  1973年   2篇
排序方式: 共有5755条查询结果,搜索用时 15 毫秒
991.
The purpose of this study was to determine whether 2 forms of attentional inhibition, inhibition of return (IOR) and inhibitory tagging, are differentially affected by the aging process. The authors tested 24 younger adults (mean age = 22 years) and 24 older adults (mean age = 69 years) on a combined IOR and Stroop task (Vivas & Fuentes, 2001). As predicted, younger adults' performance was consistent with inhibitory tagging of objects at inhibited locations. Although older adults demonstrated intact IOR, there was no evidence of inhibitory tagging. The results suggest that age deficits in inhibition are selective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
993.
There are many chemometric applications, such as spectroscopy, where the objective is to explain a scalar response from a functional variable (the spectrum) whose observations are functions of wavelengths rather than vectors. In this paper, PLS regression is considered for estimating the linear model when the predictor is a functional random variable. Due to the infinite dimension of the space to which the predictor observations belong, they are usually approximated by curves/functions within a finite dimensional space spanned by a basis of functions. We show that PLS regression with a functional predictor is equivalent to finite multivariate PLS regression using expansion basis coefficients as the predictor, in the sense that, at each step of the PLS iteration, the same prediction is obtained. In addition, from the linear model estimated using the basis coefficients, we derive the expression of the PLS estimate of the regression coefficient function from the model with a functional predictor. The results provided by this functional PLS approach are compared with those given by functional PCR and discrete PLS and PCR using different sets of simulated and spectrometric data.  相似文献   
994.
On-line monitoring of a model reaction was performed by employing two pulsed mid-infrared Fabry-Pérot quantum cascade lasers (QCL). The emission maxima of the QCLs were located at 1393 and 1080 cm(-1). An optical system of parabolic mirrors and a ZnSe beam splitter combined the two laser beams and allowed a transmission cell to be probed with both QCLs simultaneously. The reaction mixture was pumped continuously through a cell that had an optical path of 48 microm. This dual QCL system allowed fast absorption measurements of the reaction mixture at two distinct wavenumbers. The reaction under study was the oxidation of sulfite to sulfate with hydrogen peroxide acting as oxidant. On-line measurements of the chemical reaction allowed direct, real-time monitoring of sulfate formation and hydrogen peroxide depletion.  相似文献   
995.
996.
On the Structure of Linear and Cyclic Codes over a Finite Chain Ring   总被引:9,自引:0,他引:9  
We generalise structure theorems of Calderbank and Sloane for linear and cyclic codes over ℤ pa to a finite chain ring. Our results are more detailed and do not use non-trivial results from Commutative Algebra. Received: January 25, 1999; revised version: November 17, 1999  相似文献   
997.
Fullerene reactivity in an oxygen plasma was measured and compared with those determined under the same conditions for a comprehensive set of 50 carbon materials. The possible reasons for the high plasma reactivity of the fullerene sample in an oxygen plasma are discussed.  相似文献   
998.
Twenty-five early-onset relapsing-remitting multiple sclerosis patients (12 women and 13 men) with mild disability were compared with 25 matched controls in a dichotic listening (DL) test under nonforced and forced attentional-shift conditions. Patients showed left ear impairment and no left ear advantage in the forced-left condition. Four corpus callosum (CC) regions were measured in patients on a rnidsaggital magnetic resonance imaging scan. The right ear score was negatively correlated whereas the left ear score was positively correlated with CC regions (significant only for the nonforced condition). Moreover, in men, the correlations with DL scores were linked mainly to the splenium and posterior isthmus, and in women, they were stronger for anterior isthmus and posterior body. An inverse correlation between months of disease evolution and CC area was found only in women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
The web benchmarking systems broadly used in the construction industry (CI) are designed to provide results based on key performance indicators (KPIs). No insights concerning organization overall performance and improvements targets are available. This research aims to fulfill this gap using data envelopment analysis (DEA) as a method to complement the information provided by a set of KPIs. The methodology proposed is useful to all organizations involved in benchmarking routines. To enable a more realistic assessment of CI companies, two types of DEA models were used, one allows factor weights to vary freely and the other includes weight restrictions. These models assign an efficiency score to each organization, identifying efficient organizations and providing performance improvements targets for the others. To enable suggesting targets for all organizations, expert opinion was used to specify virtual units which were included in the efficiency assessment to define a practical frontier located beyond the productivity levels of the original DEA frontier. Based on a sample of 20 Portuguese leading contractors, the Portuguese web benchmarking system for CI, icBench, was used to demonstrate the advantages of integrating the DEA method with KPIs benchmark scores.  相似文献   
1000.
Quantifying the quality of urban storm water is an important prerequisite to the effective management of urban runoff, which is recognized as the major nonpoint source of pollution in urban areas. Although data on urban storm-water quality are widely available, they are often based on relatively limited data sets, usually containing few samples per event and/or few events per catchment. This paper reports on a large scale monitoring of the key storm-water pollutants found in urban discharges during both wet and dry weather from seven urban catchments in South Eastern Australia. The catchments are all separately sewered (with wholly piped systems) with varying sizes and land uses. Using the same monitoring technique, between 16 and 52 pollutographs were captured at each site for total suspended solid (TSS), total phosphorus, and total nitrogen (TN), while event mean concentrations (EMCs) of heavy metals and major ions, as well as species of N and P, were recorded at a subset of sites. It was found that EMCs of TSS were around 50% less than have been typically reported in earlier literature. During wet weather, nutrients were similar to previously reported, as were most metals concentrations. However, zinc concentrations were significantly higher than previously reported. EMCs of TSS were higher during storm flows than in baseflow, while TN concentrations were consistently higher during baseflow. EMCs of all pollutants monitored were poor with simple hydrological parameters (e.g., event rainfall depth); however, event pollution loads correlated very well with the rainfall intensity to a power, summed over the event duration. It was not possible to distinguish an impact of land use on pollutant concentrations. The first-flush effect was found not to be significant at all sites except the smallest catchment with the simplest drainage layout (the roof of a large building). All these findings have significant implication for treatment strategies with the significantly lower than previously observed TSS requiring consideration in future modeling and treatment design.  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