全文获取类型
收费全文 | 72997篇 |
免费 | 7484篇 |
国内免费 | 4011篇 |
专业分类
电工技术 | 4279篇 |
技术理论 | 6篇 |
综合类 | 5244篇 |
化学工业 | 12049篇 |
金属工艺 | 4420篇 |
机械仪表 | 4618篇 |
建筑科学 | 5255篇 |
矿业工程 | 1977篇 |
能源动力 | 1926篇 |
轻工业 | 7046篇 |
水利工程 | 1495篇 |
石油天然气 | 3621篇 |
武器工业 | 613篇 |
无线电 | 8211篇 |
一般工业技术 | 8614篇 |
冶金工业 | 3332篇 |
原子能技术 | 831篇 |
自动化技术 | 10955篇 |
出版年
2024年 | 397篇 |
2023年 | 1286篇 |
2022年 | 2293篇 |
2021年 | 3025篇 |
2020年 | 2375篇 |
2019年 | 2037篇 |
2018年 | 2333篇 |
2017年 | 2479篇 |
2016年 | 2298篇 |
2015年 | 3120篇 |
2014年 | 3848篇 |
2013年 | 4834篇 |
2012年 | 5254篇 |
2011年 | 5756篇 |
2010年 | 5161篇 |
2009年 | 5046篇 |
2008年 | 4841篇 |
2007年 | 4563篇 |
2006年 | 4352篇 |
2005年 | 3645篇 |
2004年 | 2501篇 |
2003年 | 2034篇 |
2002年 | 1900篇 |
2001年 | 1570篇 |
2000年 | 1379篇 |
1999年 | 1290篇 |
1998年 | 933篇 |
1997年 | 728篇 |
1996年 | 663篇 |
1995年 | 534篇 |
1994年 | 449篇 |
1993年 | 339篇 |
1992年 | 264篇 |
1991年 | 198篇 |
1990年 | 149篇 |
1989年 | 102篇 |
1988年 | 104篇 |
1987年 | 76篇 |
1986年 | 55篇 |
1985年 | 45篇 |
1984年 | 39篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 11篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 15篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Hao Yin Chuang Lin Berton Sebastien Bo Li Geyong Min 《International Journal of Communication Systems》2005,18(8):711-729
Fast and accurate methods for predicting traffic properties and trend are essential for dynamic network resource management and congestion control. With the aim of performing online and feasible prediction of network traffic, this paper proposes a novel time series model, named adaptive autoregressive (AAR). This model is built upon an adaptive memory‐shortening technique and an adaptive‐order selection method originally developed by this study. Compared to the conventional one‐step ahead prediction using traditional Box–Jenkins time series models (e.g. AR, MA, ARMA, ARIMA and ARFIMA), performance results obtained from actual Internet traffic traces have demonstrated that the proposed AAR model is able to support online prediction of dynamic network traffic with reasonable accuracy and relatively low computation complexity. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
172.
Jae-Hee Han Su Hong Lee A.S. Berdinsky Yong Weon Kim Ji-Beom Yoo Chong-Yun Park Jin Ju Choi Taewon Jung In Taek Han Jong Min Kim 《Diamond and Related Materials》2005,14(11-12):1891
In this report, the FE characteristics of carbon nanotubes (CNTs) treated using both thermal annealing and mechanical coatings on the as-grown CNTs systematically studied. It was found that in the high temperature annealed samples, CNTs were attacked at its root during annealing due to a small amount of oxygen, and were pulled out of the substrate in places after FE measurements because of the contact resistance. However, for the mechanically coated samples both with spin on glass (SOG) and polymethyl methacrylate (PMMA), CNTs were found to be nearly intact after FE measurements and showed reliable FE characteristics over repeatable voltage scan. The reliability of CNTs during FE could be owing to the strong adhesion of CNTs to the substrate both by SOG and PMMA coatings. 相似文献
173.
KS Min AR Khan MK Kwon YJ Jung Z Yun Y Kiso 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(8):909-915
The performance of a laboratory‐scale anaerobic acidogenic fermenter fed with a mixture of blended kitchen food‐waste and primary sludge from a sewage treatment plant was investigated for the production of volatile fatty acids (VFA). The operating variables for acidogenic fermentation were kitchen food‐waste content (10 and 25 wt %), hydraulic retention time (HRT: 1, 3 and 5 days), temperature (ambient: 18 ± 2 °C, and mesophilic: 35 ± 2 °C) and pH (varied from 5.2 to 6.7). The experimental results indicated that effluent VFA concentrations and VFA production rates were higher at ambient temperature than at mesophilic conditions. The net amount of VFA with 10 wt % food‐waste increased up to 920 mg dm?3 with an increase of HRT, but contrasting results (a decrease of 2610 mg dm?3) were found due to the conversion of VFA into biogas in the case of 25 wt % food‐waste, which increased significantly at HRT of 3–5 days. In terms of biogas composition (CO2 and CH4), the organic matter was converted into CO2 through the oxidative pathway by facultative species at low temperature while mesophilic temperature and optimum pH (6.3–7.8) played a pivotal role in increasing rate of conversion of VFA into biogas by methanogenesis. Rates of VFA production and their conversion are dependent on the food‐waste content in the mixture. Yet, the higher concentration of food‐waste (25% compared with 10%) did not produce VFA proportionally due to the increased rate of conversion of VFA into gaseous products. The maximum VFA production rate (0.318 g VFAproduced g?1 VSfed day?1) was achieved in the 10 wt % food‐waste at ambient temperature and at a 5‐day HRT. Copyright © 2005 Society of Chemical Industry 相似文献
174.
历史中心区复兴中的地域性问题与对策 总被引:2,自引:0,他引:2
本文以上海思南路47~48街坊改造为例,探讨城市形态更新与居民外迁问题,并期待相关地域性社会对策的出现。 相似文献
175.
本文阐述了施工企业内部编制定额的必要性和成本分析平台的实用性,并根据多年的工作经验就建筑施工企业对施工成本的控制谈谈一自己的认识和看法. 相似文献
176.
177.
Lattice Distortion Analysis Directly from High Resolution Transmission Electron Microscopy Images—the LADIA Program Package 总被引:1,自引:0,他引:1
Direct strain mapping from high resolution transmission electron microscopy images is possible for coherent structures.At proper imaging conditions the intensity peaks in the image have a constant spatial relationship with the projected atom columns.This allows the determination of the geometry of the projected unit cell without comparison with image simulations.The fast procedure is particularly suited for the analysis of large areas.The software package LADIA is written in the PV-WAVE code and provides all necessary tools for image processing and analysis.Image iintensity peaks are determined by a cross-correlation technique,which avoids problems from noise in the low spatial frequency renage.The lower limit of strain that can be detected at a sampling rate of 44 pixels/nm is ≈2%. 相似文献
178.
179.
180.