全文获取类型
收费全文 | 1576篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 180篇 |
金属工艺 | 9篇 |
机械仪表 | 21篇 |
建筑科学 | 38篇 |
矿业工程 | 1篇 |
能源动力 | 13篇 |
轻工业 | 114篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
无线电 | 122篇 |
一般工业技术 | 127篇 |
冶金工业 | 794篇 |
原子能技术 | 14篇 |
自动化技术 | 132篇 |
出版年
2021年 | 8篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 20篇 |
2013年 | 61篇 |
2012年 | 32篇 |
2011年 | 43篇 |
2010年 | 29篇 |
2009年 | 26篇 |
2008年 | 44篇 |
2007年 | 34篇 |
2006年 | 24篇 |
2005年 | 34篇 |
2004年 | 28篇 |
2003年 | 36篇 |
2002年 | 24篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 43篇 |
1998年 | 170篇 |
1997年 | 116篇 |
1996年 | 94篇 |
1995年 | 75篇 |
1994年 | 62篇 |
1993年 | 46篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 27篇 |
1989年 | 33篇 |
1988年 | 30篇 |
1987年 | 35篇 |
1986年 | 21篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 18篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 28篇 |
1976年 | 61篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1968年 | 6篇 |
1967年 | 6篇 |
1966年 | 7篇 |
排序方式: 共有1597条查询结果,搜索用时 15 毫秒
1.
Mohsen Ghazel George H Freeman Edward R Vrscay 《IEEE transactions on image processing》2006,15(9):2669-2675
The essence of fractal image denoising is to predict the fractal code of a noiseless image from its noisy observation. From the predicted fractal code, one can generate an estimate of the original image. We show how well fractal-wavelet denoising predicts parent wavelet subtress of the noiseless image. The performance of various fractal-wavelet denoising schemes (e.g., fixed partitioning, quadtree partitioning) is compared to that of some standard wavelet thresholding methods. We also examine the use of cycle spinning in fractal-based image denoising for the purpose enhancing the denoised estimates. Our experimental results show that these fractal-based image denoising methods are quite competitive with standard wavelet thresholding methods for image denoising. Finally, we compare the performance of the pixel- and wavelet-based fractal denoising schemes. 相似文献
2.
Steeves G.M. Elezzabi A.Y. Teshima R. Said R.A. Freeman M.R. 《Quantum Electronics, IEEE Journal of》1998,34(8):1415-1418
A lumped element circuit model for the operation of a junction mixing scanning tunneling microscope (JM-STM) is presented. Fits from this model show excellent agreement with experimental results in the picosecond time regime. The tip sample capacitance employed in the model was calculated to be 33 fF, using the method of images. By varying the capacitance, various tip/sample geometries can be investigated. Testing the response of the model tunnel junction, for faster electrical pulses, suggests how the JM-STM can be pushed into the femtosecond time regime 相似文献
3.
4.
The purpose of the study was to identify psychiatric symptoms, neurological impairments, and situational factors associated with the emergence of violence and with its persistence. Psychiatric symptoms were assessed in newly admitted physically assaultive psychiatric patients and nonviolent controls. Patients were than evaluated for 4 weeks to determine the persistence or resolution of these physical assaults. Patients who showed marked resolution of assaults were classified as transiently violent (n = 41), and those who remained assaultive throughout were categorized as persistently violent (n = 34). At the end of 4 weeks, all patients received a comprehensive psychiatric and neurological assessment. Physical assaults were associated initially with prominent positive psychotic symptoms. Both transiently and persistently violent patients were more psychotic than the nonviolent controls; however transiently violent patients showed better resolution of these symptoms over the 4 weeks. They also evidenced less frontal lobe impairment on the neurological examination than the persistently violent patients. The two violent groups differed in their susceptibility to environmental influences: the surrounding ward agitation fostered physical assaults in transiently but not in persistently violent patients. This differentiation between transiently and persistently violent patients has major implications for the comprehensive treatment of violent behavior. 相似文献
5.
6.
7.
8.
Sellars M.P. Greaves S.D. Porter J. Crosby D.B. Freeman B.R. 《Electronics letters》2003,39(7):624-625
A precoding technique for pre-equalising contention bursts in a slotted-ALOHA access request scheme, for use in single-carrier broadband fixed wireless access (FWA) networks is presented. Multipath channel distortion is compensated for at the transmitter, so that the contention burst arrives undistorted at the receiver. 相似文献
9.
A non-invasive headspace analysis method to measure rate and amount of oxygen uptake in oxygen-scavenging polymers is presented. Oxygen uptake data for metal-catalyzed poly(1,4-butadiene) at 30 °C are provided to illustrate the method. These data were obtained by measuring oxygen headspace concentration above the scavenging polymer with an OxySense® 200T non-invasive oxygen sensor, and, for comparison, oxygen uptake was measured with an analytical balance. Excellent agreement was observed between these two independent experiments. 相似文献
10.
BACKGROUND: The matrix metalloproteinases (MMPs) MMP2 and MMP9 play a significant role in epidermal detachment, inflammation and re-epithelialization. We have evaluated their activity in toxic epidermal necrolysis (TEN). DESIGN: The level and pattern of activity of MMP2 and MMP9 were investigated by measuring the degradation of 3H-labelled gelatin and by zymography in blister fluid from six TEN patients and compared the results with three other blistering conditions: bullous pemphigoid (n = 6), second-degree burn (n = 13) or suction blister (n = 3). RESULTS: A higher amount of MMP2 was found in TEN blister fluid with the constant presence of a significantly larger proportion of the activated forms of MMP2, a particular feature of TEN, than the other blistering diseases studied. CONCLUSION: This study emphasizes the potential role of MMP2 in the specific inflammatory reaction and reparation process in TEN skin. 相似文献