全文获取类型
收费全文 | 6805篇 |
免费 | 496篇 |
国内免费 | 814篇 |
专业分类
电工技术 | 99篇 |
综合类 | 896篇 |
化学工业 | 1432篇 |
金属工艺 | 424篇 |
机械仪表 | 595篇 |
建筑科学 | 77篇 |
矿业工程 | 68篇 |
能源动力 | 403篇 |
轻工业 | 286篇 |
水利工程 | 46篇 |
石油天然气 | 49篇 |
武器工业 | 25篇 |
无线电 | 1055篇 |
一般工业技术 | 1136篇 |
冶金工业 | 151篇 |
原子能技术 | 27篇 |
自动化技术 | 1346篇 |
出版年
2024年 | 19篇 |
2023年 | 172篇 |
2022年 | 198篇 |
2021年 | 240篇 |
2020年 | 311篇 |
2019年 | 198篇 |
2018年 | 135篇 |
2017年 | 246篇 |
2016年 | 262篇 |
2015年 | 240篇 |
2014年 | 518篇 |
2013年 | 622篇 |
2012年 | 712篇 |
2011年 | 857篇 |
2010年 | 654篇 |
2009年 | 593篇 |
2008年 | 460篇 |
2007年 | 562篇 |
2006年 | 436篇 |
2005年 | 170篇 |
2004年 | 44篇 |
2003年 | 59篇 |
2002年 | 66篇 |
2001年 | 45篇 |
2000年 | 38篇 |
1999年 | 36篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 39篇 |
1986年 | 29篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
排序方式: 共有8115条查询结果,搜索用时 15 毫秒
1.
2.
3.
Industrialized white organic light-emitting diodes (OLEDs) currently require host-guest doping, a complicated process necessitating precise control of the guest concentration to get high efficiency and stability. Two doping-free, hybrid white OLEDs with fluorescent blue, and phosphorescent green and red emissive layers (EMLs) are reported in this work. An ultra-thin red phosphorescent EML was situated in a blue-emitting electron transport layer (ETL), while the ultra-thin green phosphorescent EML was placed either in the ETL (Device 1), or the hole transport layer (HTL) (Device 2). Device 2 exhibits higher efficiency and more stable spectrum due to the enhanced utilization of excitons by ultra-thin green EML at the exciton generation zone within the HTL. Values of current efficiency (CE), power efficiency (PE), and CRI obtained for the optimized hybrid white OLEDs fabricated through a doping-free process were of 23.2 cd/A, 20.5 lm/W and 82 at 1000 cd/m2, respectively. 相似文献
4.
5.
Efficient and fully solution-processed blue organic light-emitting diodes (OLEDs) based on fluorescent small-molecule and methanol/water soluble conjugated polymer as electron-injection material are reported. The emitting layer is 3,6-bis(9,9,9′,9′-tetrakis (6-(9H-carbazol-9-yl)hexyl)-9H,9′H-[2,2′-bifluoren]-7-yl)dib-nzo[b, d]thiophene 5, 5-dioxide (OCSoC) with a blue-fluorescent small-molecule, and a methanol/water soluble polymer poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl-fluorene)] (PFN) acted as electron-injection layer (EIL). All the organic layers are spin-coated from solution. The multilayer device structure with emitting layer/electron-injection layer is achieved by solution-processed method without the dissolution problem between layers. The performances of the devices show that the maximum luminous efficiency of the multilayer device is increased about 43%, compared to the single-layer device. PFN acting as the EIL material plays a key role in the improvement of the device performance when used in solution-processed small-molecule OLEDs. 相似文献
6.
提出了基于压电技术的微操作系统的自动标定方法,采用混合式步进电机直接驱动的宏动平台,实现系统大行程宏动定位,安装在宏动平台上的压电陶瓷驱动的微动平台和精密光栅,实现亚微米级的分辨率和定位精度,通过以上两部分实现定位机构的全闭环反馈控制,采用显微视觉反馈获取微动台操作器在图像中的位置信息进行标定。实验结果表明:系统的动态和稳定性能良好,自动标定运算速度快,运行速度达到11 frame/s,实现了对系统的精确标定,标定精度达到0.1μm。 相似文献
7.
This paper proposed a novel hybrid probabilistic network, which is a good tradeoff between the model complexity and learnability
in practice. It relaxes the conditional independence assumptions of Naive Bayes while still permitting efficient inference
and learning. Experimental studies on a set of natural domains prove its clear advantages with respect to the generalization
ability. 相似文献
8.
Ming Yang Lei Wang Guanghua Li Lei Yang Zhan Shi Shouhua Feng 《Journal of Alloys and Compounds》2007,440(1-2):57-61
The hydrothermal reaction of 2,5-pyridinedicarboxylic acid (H2PDC), diethylene triamine and In(NO3)3·4.5H2O gave rise to a two-dimensional (2D) coordination polymer In(OH)(2,5-PDC). This compound crystallizes in the orthorhombic space group Iba2, with cell parameters, a = 12.656(3) Å, b = 20.114(4) Å, c = 6.2216(1) Å, V = 1583.9(5) Å3 and Z = 8. Its structure contains one-dimensional In–O–In–O– chains, which are further linked by 2,5-PDC ligands into a 2D supramolecular neutral framework. The adjacent 2D layers are parallel with each other and construct a three-dimensional framework via hydrogen bands. At room temperature, the compound exhibits intense photoluminescence. On the basis of the results of TG/DTA analyses, the structure is thermally stable up to 390 °C. 相似文献
9.
《Computer Networks》2007,51(3):699-711
We consider in this paper a WCDMA system with two types of calls: real time (RT) calls that have dedicated resources, and data non-real time (NRT) calls that are treated using a time-shared channel (such as the HDR or the HSDPA). We consider reservation of some resources for the NRT traffic and assume that this traffic is further assigned the resources left over from the RT traffic. The grade of service (GoS) of RT traffic is also controlled in order to allow for handling more RT calls during congestion periods, at the cost of degraded transmission rates. We consider both the downlink (with and without macrodiversity) as well as the uplink and study the blocking probabilities of RT traffic as well as the expected sojourn time of NRT traffic. We further study the conditional expected sojourn time of a data connection given its size and the state of the system. Finally, we extend our framework to handle handover calls. 相似文献
10.