全文获取类型
收费全文 | 7280篇 |
免费 | 1407篇 |
国内免费 | 815篇 |
专业分类
电工技术 | 323篇 |
综合类 | 803篇 |
化学工业 | 272篇 |
金属工艺 | 231篇 |
机械仪表 | 555篇 |
建筑科学 | 458篇 |
矿业工程 | 111篇 |
能源动力 | 84篇 |
轻工业 | 65篇 |
水利工程 | 251篇 |
石油天然气 | 189篇 |
武器工业 | 585篇 |
无线电 | 1346篇 |
一般工业技术 | 1081篇 |
冶金工业 | 98篇 |
原子能技术 | 55篇 |
自动化技术 | 2995篇 |
出版年
2024年 | 83篇 |
2023年 | 242篇 |
2022年 | 317篇 |
2021年 | 294篇 |
2020年 | 290篇 |
2019年 | 314篇 |
2018年 | 286篇 |
2017年 | 396篇 |
2016年 | 432篇 |
2015年 | 463篇 |
2014年 | 628篇 |
2013年 | 556篇 |
2012年 | 710篇 |
2011年 | 731篇 |
2010年 | 575篇 |
2009年 | 478篇 |
2008年 | 450篇 |
2007年 | 456篇 |
2006年 | 379篇 |
2005年 | 307篇 |
2004年 | 236篇 |
2003年 | 176篇 |
2002年 | 148篇 |
2001年 | 109篇 |
2000年 | 113篇 |
1999年 | 69篇 |
1998年 | 51篇 |
1997年 | 39篇 |
1996年 | 63篇 |
1995年 | 27篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1979年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有9502条查询结果,搜索用时 15 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.
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
3.
本文在深入研究水声通信信道特性及多载波关键技术的基础上,设计并研制了基于M FSK的高速自适应多载波水声通信系统,并进行了湖上实验。理论分析、仿真及湖上试验结果表明:基于M FSK的多载波水声通信系统,多径抑制有效,对同步的精确度要求不高,性能稳健,更适合于恶劣水声通信环境下、中距离(10~30km)较高数据率多载波通信系统,易于工程实现,具有良好的应用前景。 相似文献
4.
水下航行体专用光纤的特性 总被引:2,自引:1,他引:1
高继和 《光纤与电缆及其应用技术》2003,(1):41-43
着重论述水下航行体线控专用光纤的特殊性及其应用特点.并对其发展作了展望。 相似文献
5.
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
6.
激光水下成像技术及其进展 总被引:6,自引:0,他引:6
介绍了近年发展起来的三种主要的激光水下成像方法,即常规水下激光成像、高分辨率水下激光三维成像和偏振激光成像,分析了它们各自的工作原理、特点以及各自的发展状况。 相似文献
7.
8.
海洋管线具有复杂的工程结构,在恶劣的海洋环境中,承受着比陆地管线更为复杂的载荷。为了保证管线安全工作,需对其进行准确的应力分析。本文应用有限元法对恒定水深拖拉铺管的管线内力、应力及位移进行了计算,并将结果与已有的计算结果进行对比,进一步分析了各种海洋环境因素对管线弯曲效应的影响,取得了有一定实用性的成果,可供海洋拖拉铺管施工时参考。 相似文献
9.
本文针对背景噪声为冲击噪声的情况,提出了一种新的近场源二维参数估计方法.本方法利用协变异(或协变异系数)构造矩阵,并通过求根的方法估计近场源的方向角和距离参数.该算法可以抑制冲击噪声对估计性能的影响,同时具有无需谱峰搜索的优点.仿真实验证明了该算法的有效性. 相似文献
10.
Catherine Mongenet 《International journal of parallel programming》1997,25(6):497-524
This paper introduces results on placement and communications minimization for systems of affine recurrence equations. We show how to classify the dependences according to the number and nature of communications they may result in. We give both communication-free conditions and conditions for an efficient use of broadcast or neighbor-to-neighbor communication primitives. Since the dependences of a problem can generally not be all communication-free, we finally introduce a heuristic to globally minimize the communications based on the classification of dependences. 相似文献