全文获取类型
收费全文 | 14509篇 |
免费 | 2159篇 |
国内免费 | 951篇 |
专业分类
电工技术 | 994篇 |
综合类 | 1267篇 |
化学工业 | 1559篇 |
金属工艺 | 1373篇 |
机械仪表 | 1682篇 |
建筑科学 | 573篇 |
矿业工程 | 297篇 |
能源动力 | 143篇 |
轻工业 | 1958篇 |
水利工程 | 131篇 |
石油天然气 | 444篇 |
武器工业 | 237篇 |
无线电 | 1778篇 |
一般工业技术 | 1728篇 |
冶金工业 | 399篇 |
原子能技术 | 82篇 |
自动化技术 | 2974篇 |
出版年
2024年 | 102篇 |
2023年 | 297篇 |
2022年 | 418篇 |
2021年 | 479篇 |
2020年 | 525篇 |
2019年 | 483篇 |
2018年 | 495篇 |
2017年 | 701篇 |
2016年 | 746篇 |
2015年 | 803篇 |
2014年 | 1014篇 |
2013年 | 1007篇 |
2012年 | 1335篇 |
2011年 | 1358篇 |
2010年 | 997篇 |
2009年 | 845篇 |
2008年 | 845篇 |
2007年 | 972篇 |
2006年 | 921篇 |
2005年 | 672篇 |
2004年 | 498篇 |
2003年 | 449篇 |
2002年 | 325篇 |
2001年 | 243篇 |
2000年 | 218篇 |
1999年 | 171篇 |
1998年 | 140篇 |
1997年 | 106篇 |
1996年 | 115篇 |
1995年 | 79篇 |
1994年 | 57篇 |
1993年 | 38篇 |
1992年 | 35篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1961年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
One of the most challenging issues in radio received signal strength (RSS)-based localization systems is the generation and distribution of a radio map with a coordinate system linked with spatial information in a large indoor space. This study proposes a novel spatial-tagged radio-mapping system (SRS) that effectively combines the heterogeneous properties of LiDAR and mobile phones to simultaneously perform both spatial and radio mappings. The SRS consists of synchronization, localization, and map building processes, and enables real-time spatial and radio mapping. In the synchronization process, the distance range, motion data, and radio signals obtained through the LiDAR and mobile phone are collected in nodal units according to the sensing time. In the localization process, a feature variance filter is used to control the number of features generated from LiDAR and estimate the positions at which the nodes are generated in real time according to the motion data and radio signals. In map building, the estimated positions of the nodes are used to extract spatial and radio maps by using a unified location coordinate system. To ensure mobility, the SRS is manufactured in the form of a backpack supporting LiDAR and a mobile phone; the usefulness of the system is experimentally verified. The experiments are performed in a large indoor shopping mall with a complex structure. The experimental results demonstrated that a common coordinate system could be used to build spatial and radio maps with high accuracy and efficiency in real time. In addition, the field applicability of the SRS to location-based services is experimentally verified by applying the constructed radio map to well-known fingerprinting algorithms using the heterogeneous mobile phones. 相似文献
2.
3.
Luca Pietrobon Lorenzo Fallarino Andreas Berger Andrey Chuvilin Flix Casanova Luis E. Hueso 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(47):6295-6301
Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials. 相似文献
4.
超声波强化原油破乳电脱盐技术的工业实践 总被引:9,自引:1,他引:8
报道了采用超声波强化原油破乳电脱盐技术的开发与工业应用.经过实验室开发确定的超声波强化原油破乳电脱盐专利技术--超声波-电场联合破乳脱盐组合技术采用顺逆流方式.该技术于2003年9月在齐鲁分公司完成工业应用试验后,超声波强化原油破乳设备直接投入生产运行,在不加入化学破乳剂的情况下,可使胜利混输原油(平均盐浓度为50 mg/L,平均水质量分数为0.5%~1.0%)脱后盐浓度低于3 mg/L,水质量分数小于0.3%. 相似文献
5.
陶瓷及陶瓷基复合材料微缺陷的超声检测 总被引:4,自引:0,他引:4
为研究陶瓷及陶瓷基复合材料微缺陷的超声检测能力,针对一些人工缺陷试样进行了超声检测试验。试验主要采用了纵波垂直入射法和泄漏瑞利波法。通过试验结果,比较了两种方法的检测能力。 相似文献
6.
文章通过对时差式超声波流量检测方法的分析,提出了基于过零检测技术及积分法的信号处理方法,避免了繁琐的信号处理,降低了整机功耗。结合工作时序的设计,提出了实现低功耗超声波液体流量检测的措施。 相似文献
7.
8.
The perceived locations of paired auditory images, simulating direct sounds and their echoes, have been recently studied in budgerigars (Melopsittacus undulatus; M. L. Dent & R. J. Dooling, 2003a, 2003b). In this article, the authors extend those experiments to include measurements of the precedence effect using a discrimination paradigm in two additional bird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). Although time courses of summing localization, localization dominance, and echo thresholds were similar across all species, budgerigars had slightly higher overall levels of discrimination. The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
10.