全文获取类型
收费全文 | 27118篇 |
免费 | 3242篇 |
国内免费 | 1497篇 |
专业分类
电工技术 | 3553篇 |
技术理论 | 1篇 |
综合类 | 2369篇 |
化学工业 | 3639篇 |
金属工艺 | 986篇 |
机械仪表 | 3676篇 |
建筑科学 | 377篇 |
矿业工程 | 1018篇 |
能源动力 | 890篇 |
轻工业 | 2493篇 |
水利工程 | 222篇 |
石油天然气 | 542篇 |
武器工业 | 434篇 |
无线电 | 3144篇 |
一般工业技术 | 2533篇 |
冶金工业 | 962篇 |
原子能技术 | 284篇 |
自动化技术 | 4734篇 |
出版年
2024年 | 121篇 |
2023年 | 488篇 |
2022年 | 770篇 |
2021年 | 888篇 |
2020年 | 912篇 |
2019年 | 726篇 |
2018年 | 649篇 |
2017年 | 831篇 |
2016年 | 952篇 |
2015年 | 1026篇 |
2014年 | 1526篇 |
2013年 | 1441篇 |
2012年 | 2033篇 |
2011年 | 2174篇 |
2010年 | 1647篇 |
2009年 | 1669篇 |
2008年 | 1558篇 |
2007年 | 2053篇 |
2006年 | 1914篇 |
2005年 | 1529篇 |
2004年 | 1318篇 |
2003年 | 1116篇 |
2002年 | 866篇 |
2001年 | 741篇 |
2000年 | 577篇 |
1999年 | 520篇 |
1998年 | 351篇 |
1997年 | 305篇 |
1996年 | 248篇 |
1995年 | 212篇 |
1994年 | 168篇 |
1993年 | 129篇 |
1992年 | 92篇 |
1991年 | 86篇 |
1990年 | 55篇 |
1989年 | 36篇 |
1988年 | 34篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1977年 | 3篇 |
1966年 | 3篇 |
1961年 | 3篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
蓝牙技术是一种短距离无线通信技术,具有低成本、低功耗、灵活、快速、抗干扰能力强等特点,目的是取代终端的连接电缆.为提高部队的作战效能,采用蓝牙技术和计算机测量与控制技术,研制了机载火控故障诊断系统;该系统在实际应用中取得了良好效果,并具有诊断结果准确、自动化程度高、工作稳定可靠、操作简便、易于转移和维护等优点,为技术人员进行机载火控系统的性能检测与故障诊断提供了便利. 相似文献
52.
Javier Roca-Pardiñas Carmen Cadarso-Suárez María J. Lado 《Computational statistics & data analysis》2008,52(4):1958-1970
In many applications, the joint effect of two continuous covariates on the target binary response may vary across groups defined by levels of a given factor. A testing procedure that would enable this type of surface-by-factor interactions to be detected has been designed. To accomplish this goal, a logistic generalized additive model (GAM) with bivariate continuous interactions varying across groups defined by levels of a factor is considered. A local scoring algorithm based on local linear kernel smoothers was implemented to estimate the proposed logistic GAM. Bootstrap resampling techniques were used for the purpose of testing for factor-by-surface interactions. Given the high computational cost involved, binning techniques were used to speed up computation in the estimation and testing processes. The adequacy of the bootstrap-based test was assessed by means of a simulation study. If a factor-by-surface interaction is detected in the model, it is then established that the use of the odds-ratio curves is very useful in obtaining a direct interpretation of the fitted model. The benefits of using this methodology when analyzing real data are illustrated by applying the technique to the outputs produced by a computerized system dedicated to the early detection of breast cancer. 相似文献
53.
This research investigates the utility of passive microwave remote sensing instruments to accurately determine snow water equivalent (SWE) over large spatial extents. Three existing Special Sensor Microwave Imager (SSM/I) snow water equivalent algorithms produced by Chang, Tait and Goodison were evaluated for their ability to determine snow water equivalent in a snowpack containing substantial depth hoar, large faceted snow crystals. The Kuparuk River Watershed (8140 km2) test site on the North Slope of Alaska was chosen for its snowpack containing a think depth hoar layer and long history of ground truth data. A new regional snow water equivalent algorithm was developed to determine if it could produce better results than the existing algorithms in an area known to contain significant depth hoar. The four algorithms were tested to see how well they could determine snow water equivalent: (1) on a per pixel basis, (2) across swath-averaged spatial bands of approximately 850 km2, and (3) on a watershed scale. The algorithms were evaluated to see if they captured the annual spatial distribution in snow water equivalent over the watershed. Results show that the algorithms developed by Chang and from this research are generally within 3 cm of the spatially averaged snow water equivalents over the entire watershed. The algorithms produced by Chang, Tait, and in this research were able to predict the basin-wide ground measured snow water equivalent value within a percent error range from −32.4% to 24.4% in the years with a typical snowpack. None of the algorithms produce accurate results on a pixel-by-pixel scale, with errors ranging from −26% to 308%. 相似文献
54.
55.
56.
Reviews the book, L'insomnie: Traitement comportemental by Robert Ladouceur and Yves Gros-Louis (1984). The work offers a prospect broader than the medical vision which traditionally dominates the treatment of insomnia. More specifically, the work is articulated around two chapters. The first locates the relative source data of insomnia, and provides the criteria for a precise diagnosis, establishing a clear distinction between primary insomnia and secondary insomnia, and methods generally utilized to measure sleep. As for the second chapter, it is centered on the behavioral methods of treatment of insomnia. According to the authors, any treatment must be preceded by factual information on insomnia, to facilitate the application of the chosen method. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
58.
介绍了500W宽频带功率负载的设计及实验结果,并将研究成果扩展到10~1000W范围。负载主要技术指标:输入阻抗50Ω,频带宽度0~1000MHz,电压驻波比≤1.1.表面最高温升△t≤100℃。 相似文献
59.
60.
通过对 HL- 1M装置真空运行模式、真空运行参数、氦辉光放电清洗和硅化壁处理手段等的规范化 ,显著地改善了装置的真空壁出气、本底杂质浓度、托卡马克放电杂质出气比和再循环 ,成功地实现了高参数放电、长脉冲放电和装置暴露大气后快速恢复放电 ,并成功地为演证低混杂电流驱动、离子回旋共振加热、电子回旋共振加热、中性束注入、弹丸注入和分子束注入实验和升级等离子体运行等提供了良好的真空壁条件。描述了 HL- 1M装置真空系统、壁出气和再循环控制、质谱诊断和程序脉冲送气等方面的主要实验成果 ,并为 HL- 2 A装置的真空系统研制和运行提供了有益的参考 相似文献