全文获取类型
收费全文 | 8455篇 |
免费 | 1088篇 |
国内免费 | 621篇 |
专业分类
电工技术 | 698篇 |
综合类 | 1054篇 |
化学工业 | 1209篇 |
金属工艺 | 142篇 |
机械仪表 | 594篇 |
建筑科学 | 331篇 |
矿业工程 | 104篇 |
能源动力 | 401篇 |
轻工业 | 237篇 |
水利工程 | 152篇 |
石油天然气 | 211篇 |
武器工业 | 108篇 |
无线电 | 1799篇 |
一般工业技术 | 900篇 |
冶金工业 | 203篇 |
原子能技术 | 104篇 |
自动化技术 | 1917篇 |
出版年
2024年 | 24篇 |
2023年 | 128篇 |
2022年 | 176篇 |
2021年 | 218篇 |
2020年 | 268篇 |
2019年 | 269篇 |
2018年 | 230篇 |
2017年 | 311篇 |
2016年 | 355篇 |
2015年 | 407篇 |
2014年 | 543篇 |
2013年 | 597篇 |
2012年 | 659篇 |
2011年 | 698篇 |
2010年 | 514篇 |
2009年 | 543篇 |
2008年 | 477篇 |
2007年 | 555篇 |
2006年 | 483篇 |
2005年 | 393篇 |
2004年 | 292篇 |
2003年 | 302篇 |
2002年 | 248篇 |
2001年 | 221篇 |
2000年 | 227篇 |
1999年 | 183篇 |
1998年 | 135篇 |
1997年 | 118篇 |
1996年 | 106篇 |
1995年 | 95篇 |
1994年 | 87篇 |
1993年 | 68篇 |
1992年 | 55篇 |
1991年 | 30篇 |
1990年 | 37篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1977年 | 3篇 |
1968年 | 1篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
介绍了新型TFT-LCD黑矩阵细线化研究。在原有工艺设备的基础上,突破设备局限和工艺瓶颈,通过引入相掩膜技术和背面曝光设备,达到进一步减小黑矩阵线宽的效果。实验测试结果显示:在普通掩膜板设计上应用相位移掩膜板技术,降低透光区边缘衍射和散射现象,使曝光后黑矩阵线宽降低1.0~1.5μm。在原有工艺基础上添加背面曝光工艺,使黑矩阵材料在显影后进行背面曝光预固化,改善黑矩阵图形形貌,进一步减小黑矩阵线宽达到0.3~0.5μm。通过新工艺和新设备的引入和应用,黑矩阵线宽整体降低1.5~2.0μm,达到5.0~5.5μm,可以满足目前高PPI(单位面积像素个数)产品对透过率和对比度要求。 相似文献
992.
目的:针对医院对检验信息管理系统的开发质量要求,研制解决方案,避免后期投入成本巨大浪费问题,实现因地制宜地保证系统上线。方法:采用标准的UML方法,编制了适合医院的检验管理信息系统,并完成了详细描述了其具体用例图(Use Case)、顺序图(Sequence Diagram)、类图(Class Diagram)。结果:设备的开机率提高了20%,标本控制时间明显缩短,故障响应时间为1分钟,在系统中及时报警提示。结论:完成了基于UML的LIS系统的设计,提高了设备的工作效能,收到了良好的效果。 相似文献
993.
994.
995.
为提高光学码分多址(CDMA)单用户的安全性,提出了基于单个偏振调制器(PolM)实现光码移键控(CSK)信号产生的方案,阐述了其工作原理并进行了仿真和实验验证。仿真结果表明,采用平衡检测器的CSK系统接收机灵敏度较开关键控(OOK)系统高4.1dBm;实验结果表明,采用单端接收的CSK系统最低误码率(BER)为1.15×10-8,引入光阈值器件后系统BER降低到4.02×10-11,即实现了背靠背无误码传输。基于速率级能量检测的窃听实验表明,CSK系统可以抵抗速率级能量检测的窃听者。 相似文献
996.
997.
998.
《Organic Electronics》2014,15(8):1815-1821
The alternating current (AC) responses of double-injection and double-insulated organic light-emitting diodes (OLEDs) were investigated and compared. To reveal the electroluminescent (EL) processes in these devices, the AC voltage and frequency dependence of the EL intensity and capacitive current were studied in the time domain with a focus on phase difference analysis. It was found that the voltage-dependent transit time and frequency-dependent carrier distribution were important for the AC-driven performance of the double-injection OLEDs. In contrast, although the double-insulated OLEDs shared some similarities with the double-injection OLEDs, they had some unique characteristics, which were the absence of resistive current and phase shift of EL profiles. It was revealed that the EL in the double-insulated OLEDs was driven by the displacement current generated by the ionization of the doped layers, which, however, formed space charge regions and undermined the EL emission. The space charge redistributed the electric field across the devices after the initiation of EL, making the EL maintain for a limited time interval. This effect was significant under low frequency and high AC voltage. Comparing the phase difference between both devices, it was indicated that the space charge effect was responsible for the observed EL phase shift and the asymmetric EL profiles at low frequency and high AC voltage in the double-insulated OLEDs. The proposed model was also of help to understand the EL saturation phenomena with AC frequency and voltage in those devices. 相似文献
999.
In this paper, we partly determine the cycle structure of two types of Nonlinear feedback shift registers (NFSRs). Based on these results, the cycle structure of a class of NFSRs with symmetric feedback functions can be completely characterized. Furthermore, an alternative proof of Kjeldsen's results is presented. Compared with the original proof based on abstract algebra theory, ours is straightforward and easy to understand. 相似文献
1000.
Adaptive modulation and decision feedback equalization for frequency‐selective MIMO channels 下载免费PDF全文
Mohamed Lassaad Ammari Kalthoum Zaouali Paul Fortier 《International Journal of Communication Systems》2014,27(11):3323-3338
In this paper, an adaptive modulation scheme for the multiple‐input multiple‐output (MIMO) frequency‐selective channels is investigated. We consider a scenario with precoded block‐based transceivers over spatially correlated Rayleigh multipath MIMO channels. To eliminate the inter‐block interference, the zero‐padding is used. The receiver is equipped with a MIMO minimum‐mean‐squared‐error decision feedback equalizer. The precoder aims to force each subchannel to have an identical signal‐to‐interference‐plus‐noise ratio (SINR). To adjust the constellation size, the unbiased mean square error at the equalizer output is sent back to the transmitter. To simplify our analysis, the feedback channel is considered as instantaneous and error free. We first derive the probability density function of the overall SINR for flat fading and frequency‐selective channels. On the basis of the probability density function of the upper bound of the SINR, we evaluate the system performance. We present accurate closed‐form expressions of the average spectral efficiency, the average bit error rate and the outage probability. The derived expressions are compared with Monte Carlo simulation results. Furthermore, we analyze the effect of the channel spatial correlation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献