全文获取类型
收费全文 | 2912篇 |
免费 | 191篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 86篇 |
综合类 | 4篇 |
化学工业 | 699篇 |
金属工艺 | 61篇 |
机械仪表 | 98篇 |
建筑科学 | 101篇 |
矿业工程 | 8篇 |
能源动力 | 118篇 |
轻工业 | 485篇 |
水利工程 | 14篇 |
石油天然气 | 13篇 |
无线电 | 178篇 |
一般工业技术 | 761篇 |
冶金工业 | 24篇 |
原子能技术 | 9篇 |
自动化技术 | 445篇 |
出版年
2023年 | 21篇 |
2022年 | 11篇 |
2021年 | 59篇 |
2020年 | 55篇 |
2019年 | 66篇 |
2018年 | 115篇 |
2017年 | 108篇 |
2016年 | 140篇 |
2015年 | 99篇 |
2014年 | 144篇 |
2013年 | 325篇 |
2012年 | 205篇 |
2011年 | 216篇 |
2010年 | 180篇 |
2009年 | 126篇 |
2008年 | 135篇 |
2007年 | 118篇 |
2006年 | 94篇 |
2005年 | 52篇 |
2004年 | 32篇 |
2003年 | 48篇 |
2002年 | 38篇 |
2001年 | 31篇 |
2000年 | 37篇 |
1999年 | 30篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 23篇 |
1991年 | 20篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1985年 | 32篇 |
1984年 | 34篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 36篇 |
1980年 | 32篇 |
1979年 | 25篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 14篇 |
1972年 | 14篇 |
排序方式: 共有3104条查询结果,搜索用时 0 毫秒
911.
We introduce wavelet packet correlation filter classifiers. Correlation filters are traditionally designed in the image domain by minimization of some criterion function of the image training set. Instead, we perform classification in wavelet spaces that have training set representations that provide better solutions to the optimization problem in the filter design. We propose a pruning algorithm to find these wavelet spaces by using a correlation energy cost function, and we describe a match score fusion algorithm for applying the filters trained across the packet tree. The proposed classification algorithm is suitable for any object-recognition task. We present results by implementing a biometric recognition system that uses the NIST 24 fingerprint database, and show that applying correlation filters in the wavelet domain results in considerable improvement of the standard correlation filter algorithm. 相似文献
912.
The effects of trinitrotoluene (TNT) dynamic adsorption on granular activated carbon produced by 'Miloje Zakic', Serbia, are presented. The main task was to determine the conditions for TNT dynamic adsorption in order to remove the dissolved TNT from wastewater. The effects of temperature, concentration and flow rate in the chromatographic system were examined. Flow rates between 1 and 4 dm(3)/h were used. The heights of activated carbon in the columns were 70 and 135 mm while the diameter was 12 mm. The experiments were conducted at different temperatures (10-60 degrees C) and TNT influent concentrations ranging from 32.76 to 171 mg/dm(3) were used. The adsorption capacity of the activated carbon increased with increasing temperature, but it decreased with increasing input concentration and flow rate. The results obtained indicate that the influence of temperature is greater than was expected and the bed height and the amount of GAC used could be significantly lowered by increasing the temperature. The possibility of desorbing TNT from saturated activated carbon was also investigated. The amount of TNT adsorbed per mass unit of adsorbent was calculated using a model that optimally agreed with the experimental data. 相似文献
913.
Decomposition of phenol by hybrid gas/liquid electrical discharge reactors with zeolite catalysts 总被引:5,自引:0,他引:5
Application of hybrid gas/liquid electrical discharge reactors and a liquid phase direct electrical discharge reactor for degradation of phenol in the presence and absence of zeolites have been investigated. Hybrid gas/liquid electrical discharges involve simultaneous high voltage electrical discharges in water and in the gas phase above the water surface leading to the additional OH radicals in the liquid phase and ozone formation in the gas phase with subsequent dissolution into the liquid. The role of applied zeolites, namely NH4ZSM5, FeZSM5 and HY, were also studied. Phenol degradation and production of primary phenol by-products, catechol and hydroquinone, during the treatment were monitored by HPLC measurements. The highest phenol removal results, 89.4-93.6%, were achieved by electrical discharge in combination with FeZSM5 in all three configurations of corona reactors. These results indicate that the Fenton reaction has significant influence on overall phenol removal efficiency in the electrical discharge/FeZSM5 system due to the additional OH radical formation from hydrogen peroxide generated by the water phase discharge. 相似文献
914.
In a school with floor moisture problems, the personnel had complaints consistent with the sick-building syndrome (SBS). Interventive measures including the laying of a ventilated floor were undertaken to eliminate the emissions. To examine if the intervention resulted in positive health effects, 34 personnel and 336 pupils were interviewed just before the intervention and also 7 months after. Also were interviewed 21 personnel and 224 pupils at an adjacent school serving as a control. Compared with the control school, the problem school showed more complaints, more general symptoms and more symptoms from the eyes, airways and skin, both among the personnel and the pupils. In the post-intervention examinations, the excess of symptoms among the personnel had almost disappeared. Among the pupils, the frequency of eye irritation was reduced but a general improvement of the other symptoms was not as obvious. However, after adjustment for a recent common cold, atopy and stress among the pupils, only one symptom ("stuffy nose") remained significantly elevated. In conclusion, the intervention was followed by positive health effects, supporting the hypothesis that emissions from building material had contributed to the excess of symptoms. A recent common cold was highly related to the symptoms and should be considered in future SBS studies. 相似文献
915.
Location of Staphylococcus aureus within the experimentally infected bovine udder and the expression of capsular polysaccharide type 5 in situ 总被引:2,自引:0,他引:2
The objective of this study was to locate Staphylococcus aureus in the bovine udder and to investigate the expression of capsular polysaccharide type 5 (CP5) in situ in both the early and chronic stages of experimental intramammary S. aureus infections. Bovine udder tissue was obtained in early and chronic stages of intramammary infection; i.e., 24 to 96 h and 122 d after experimental intramammary infection with S. aureus Newbould 305. The presence and location of S. aureus was investigated by Gram staining of tissue sections. The expression of CP5 by S. aureus in situ was investigated by immunochemical staining of tissue sections with specific antibodies against CP5. Both in the early and chronic stages of infection, S. aureus was located within the lumen of alveoli or lactiferous ducts, in association with the epithelium, and within phagocytic cells. The staphylococci were mainly observed in clusters and often in the presence of polymorphonuclear neutrophils. Expression of CP5 by S. aureus was observed both in the early and chronic stages of infection. In general, CP5-positive S. aureus were located in alveoli and in association with the mammary epithelium. In the chronic infection, CP5-positive S. aureus were also located deep in the interstitial tissue. These results indicate that--both in early and chronic stages of experimental S. aureus mastitis--colonization of the mammary epithelia and invasion into the interstitial tissue occurs and that CP5 is expressed by S. aureus Newbould 305 in situ. The invasion of S. aureus in the interstitial tissue and the expression of CP5 probably help the bacteria to withstand the host defense mechanisms. 相似文献
916.
917.
Vladislav B. Tadić 《Machine Learning》2006,63(2):107-133
The mean-square asymptotic behavior of temporal-difference learning algorithms with constant step-sizes and linear function
approximation is analyzed in this paper. The analysis is carried out for the case of discounted cost function associated with
a Markov chain with a finite dimensional state-space. Under mild conditions, an upper bound for the asymptotic mean-square
error of these algorithms is determined as a function of the step-size. Moreover, under the same assumptions, it is also shown
that this bound is linear in the step size. The main results of the paper are illustrated with examples related to M/G/1 queues and nonlinear AR models with Markov switching.
Editor: Robert Schapire 相似文献
918.
919.
920.