全文获取类型
收费全文 | 102894篇 |
免费 | 1345篇 |
国内免费 | 1230篇 |
专业分类
电工技术 | 1924篇 |
综合类 | 138篇 |
化学工业 | 10489篇 |
金属工艺 | 5456篇 |
机械仪表 | 3186篇 |
建筑科学 | 2033篇 |
矿业工程 | 159篇 |
能源动力 | 2959篇 |
轻工业 | 6061篇 |
水利工程 | 704篇 |
石油天然气 | 668篇 |
武器工业 | 15篇 |
无线电 | 15950篇 |
一般工业技术 | 21757篇 |
冶金工业 | 25245篇 |
原子能技术 | 1382篇 |
自动化技术 | 7343篇 |
出版年
2022年 | 452篇 |
2021年 | 698篇 |
2020年 | 522篇 |
2019年 | 676篇 |
2018年 | 1130篇 |
2017年 | 1093篇 |
2016年 | 1173篇 |
2015年 | 924篇 |
2014年 | 1489篇 |
2013年 | 4667篇 |
2012年 | 2569篇 |
2011年 | 3840篇 |
2010年 | 3097篇 |
2009年 | 3719篇 |
2008年 | 3894篇 |
2007年 | 4079篇 |
2006年 | 3689篇 |
2005年 | 3325篇 |
2004年 | 3177篇 |
2003年 | 3024篇 |
2002年 | 2670篇 |
2001年 | 2970篇 |
2000年 | 2718篇 |
1999年 | 3076篇 |
1998年 | 9437篇 |
1997年 | 6153篇 |
1996年 | 4762篇 |
1995年 | 3163篇 |
1994年 | 2788篇 |
1993年 | 2724篇 |
1992年 | 1630篇 |
1991年 | 1595篇 |
1990年 | 1519篇 |
1989年 | 1322篇 |
1988年 | 1173篇 |
1987年 | 861篇 |
1986年 | 887篇 |
1985年 | 916篇 |
1984年 | 803篇 |
1983年 | 698篇 |
1982年 | 699篇 |
1981年 | 681篇 |
1980年 | 567篇 |
1979年 | 476篇 |
1978年 | 414篇 |
1977年 | 533篇 |
1976年 | 958篇 |
1975年 | 299篇 |
1974年 | 276篇 |
1973年 | 256篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
The Frizzled genes encode receptors for WNTs, secreted glycoproteins implicated in development as well as in carcinogenesis. In this paper, we report molecular cloning of Hfz6, the human homologue of Mfz6. Nucleotide sequence analysis showed that the Hfz6 gene encodes the 706 amino-acid protein with seven transmembrane domains, a cystein-rich domain in the N-terminal extracellular region, two N-linked glycosylation sites, and two cystein residues in the second and third extracellular loops. Hfz6 mRNA 4.4-kb in size was detected in various normal adult and fetal tissues, and a larger amount of Hfz6 mRNA was detected in both fetal lung and fetal kidney. The Hfz6 gene has been mapped to human chromosome 8q22.3-q23.1. In conclusion, we have cloned Hfz6, which encodes a seven-transmembrane receptor with the cystein-rich domain in the N-terminal extracellular region, but without the Ser/Thr-X-Val motif in the C-terminus. 相似文献
35.
36.
37.
38.
Development of a recurrent Sigma-Pi neural network rainfall forecasting system in Hong Kong 总被引:1,自引:1,他引:0
At the moment, weather forecasting is still an art — the experience and intuition of forecasters play a significant role in determining the quality of forecasting. This paper describes the development of a new approach to rainfall forecasting using neural networks. It deals with the extraction of information from radar images and an evaluation of past rain gauge records to provide shortterm rainfall forecasting. All of the meteorological data were provided by the Royal Observatory of Hong Kong (ROHK). Preprocessing procedures were essential for this neural network rainfall forecasting. The forecast of the rainfall was performed every half an hour so that a storm warning signal can be delivered to the public in advance. The network architecture is based on a recurrent Sigma-Pi network. The results are very promising, and this neural-based rainfall forecasting system is capable of providing a rain storm warning signal to the Hong Kong public one hour ahead. 相似文献
39.
PURPOSE: To report the disappearance of traumatic macular hole in three eyes of three patients. METHODS: Clinical data of the patients were reviewed. RESULTS: The three patients were relatively young, ranging in age from 12 to 18 years old. In one eye of each patient, a small traumatic macular hole was observed at the first visit. Visual acuities ranged from 20/100 to 20/40. The macular holes resolved spontaneously 3 to 4 months after the trauma, and final visual acuity improved to 20/20 in all patients. CONCLUSION: Small traumatic macular holes in young patients can resolve spontaneously, and this can be associated with good visual recovery. 相似文献
40.
Phase contrast magnetic resonance imaging (MRI) can provide in vivo myocardial velocity field measurements. These data allow densely spaced material points to be tracked throughout the whole heart cycle using, for example, the Fourier tracking algorithm. To process the tracking results for myocardial deformation and strain quantification, we developed a method that is based on fitting the tracking results to an appropriate local deformation model. We further analyzed the accuracy and precision of the method and provided performance predictions for several local models. In order to validate the method and the theoretical performance analysis, we conducted controlled computer simulations and a phantom study. The results agreed well with expectations. Human heart data were also acquired and analyzed, and provided encouraging results. At the signal-to-noise ratio (SNR) level and spatial resolution expected in clinical settings, the study predicts strain quantification accuracy and precision that may allow the technique to become a practical and powerful noninvasive approach for the study of cardiac function, although clinically acceptable data acquisition strategies for three-dimensional (3-D) data are still a challenge. 相似文献