全文获取类型
收费全文 | 9481篇 |
免费 | 1326篇 |
国内免费 | 684篇 |
专业分类
电工技术 | 1802篇 |
综合类 | 901篇 |
化学工业 | 785篇 |
金属工艺 | 427篇 |
机械仪表 | 754篇 |
建筑科学 | 546篇 |
矿业工程 | 200篇 |
能源动力 | 268篇 |
轻工业 | 205篇 |
水利工程 | 90篇 |
石油天然气 | 233篇 |
武器工业 | 301篇 |
无线电 | 1826篇 |
一般工业技术 | 770篇 |
冶金工业 | 272篇 |
原子能技术 | 162篇 |
自动化技术 | 1949篇 |
出版年
2024年 | 30篇 |
2023年 | 92篇 |
2022年 | 219篇 |
2021年 | 211篇 |
2020年 | 291篇 |
2019年 | 249篇 |
2018年 | 263篇 |
2017年 | 330篇 |
2016年 | 384篇 |
2015年 | 441篇 |
2014年 | 610篇 |
2013年 | 596篇 |
2012年 | 723篇 |
2011年 | 741篇 |
2010年 | 611篇 |
2009年 | 544篇 |
2008年 | 558篇 |
2007年 | 649篇 |
2006年 | 601篇 |
2005年 | 517篇 |
2004年 | 403篇 |
2003年 | 381篇 |
2002年 | 321篇 |
2001年 | 336篇 |
2000年 | 274篇 |
1999年 | 240篇 |
1998年 | 145篇 |
1997年 | 170篇 |
1996年 | 110篇 |
1995年 | 99篇 |
1994年 | 88篇 |
1993年 | 40篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 39篇 |
1989年 | 24篇 |
1988年 | 19篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 9篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The supervision of a hybrid power plant, including solar panels, a gas microturbine and a storage unit operating under varying solar power profiles is considered. The Economic Supervisory Predictive controller assigns the power references to the controlled subsystems of the hybrid cell using a financial criterion. A prediction of the renewable sources power is embedded into the supervisor. Results deteriorate when the solar power is unsteady, owing to the inaccuracy of the predictions for a long-range horizon of 10 s. The receding horizon is switched between an upper and a lower value according to the amplitude of the solar power trend. Theoretical results show the relevance of horizon switching, according to a tradeoff between performance and prediction accuracy. Experimental results, obtained in a Hardware In the Loop (HIL) framework, show the relevance of the variable horizon approach. Power amplifiers allow us to simulate virtual components, such as a gas microturbine, and to blend their powers with that of real devices (storage unit, real solar panels). In this case, fuel savings, reaching 15%, obtained under unsteady operating conditions lead to a better overall performance of the hybrid cell. The overall savings obtained in the experiments amount to 12%. 相似文献
2.
Textured surface is commonly used to enhance the efficiency of silicon solar cells by reducing the overall reflectance and improving the light scattering. In this study, a comparison between isotropic and anisotropic etching methods was investigated. The deep funnel shaped structures with high aspect ratio are proposed for better light trapping with low reflectance in crystalline silicon solar cells. The anisotropic metal assisted chemical etching (MACE) was used to form the funnel shaped structures with various aspect ratios. The funnel shaped structures showed an average reflectance of 14.75% while it was 15.77% for the pillar shaped structures. The average reflectance was further reduced to 9.49% using deep funnel shaped structures with an aspect ratio of 1:1.18. The deep funnel shaped structures with high aspect ratios can be employed for high performance of crystalline silicon solar cells. 相似文献
3.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
4.
A flower‐shaped ultra‐wideband fractal antenna is presented. It comprises a fourth iterative flower‐shaped radiator, asymmetrical stub‐loaded feeding line, and coplanar quarter elliptical ground planes. A wide operating band of 12.12 GHz (4.58‐16.7 GHz) for S 11 ≤ ? 10 dB is achieved along with an overall antenna footprint of 15.7 × 11.4 mm2. In addition, other desirable characteristics, that is, omnidirectional radiation patterns, peak gain upto 5 dB, and fidelity factor more than 75% are achieved. A good agreement exists between the simulation and measured results. The obtained results illustrate that this antenna has wide operating range and compact dimensions than available structures. 相似文献
5.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献
6.
The topic of value creation through the recovery of returned products in closed loop supply chains is scattered across various bodies of literature. We undertake a systematic literature review of 144 articles in relevant green, reverse and closed loop supply chain literature to synchronize existing knowledge on value creation. Value manifestations of four types of value, namely economic, environmental, information and customer value, are identified. Value adding concepts from the forward- and reverse supply chain may leverage the process of value creation. They are classified into six subclasses, namely partnerships and collaboration, product design characteristics, service concepts, IT solutions, supply chain processes and organizational characteristics. We present a conceptual framework on a strategic level. In this way companies can create competitive advantages by closing the loop. The results of the literature analysis suggest avenues for future research on the operational and strategic level. 相似文献
7.
移动通信系统中功率控制研究 总被引:2,自引:0,他引:2
在阐述功率控制在移动通信系统中的发展过程的基础上,着重研究了WCDMA系统的功率控制,最后对功率控制未来的研究方向做了简要的分析。 相似文献
8.
2.4GHz动态CMOS分频器的设计 总被引:1,自引:0,他引:1
对现阶段的主流高速CMOS分频器进行分析和比较,在此基础上设计一种采用TSPC(truesingle phase clock)和E-TSPC(extended TSPC)技术的前置双模分频器电路.该分频器大大提高了工作频率,采用0.6μm CMOS工艺参数进行仿真的结果表明,在5V电源电压下,最高频率达到3GHz,功耗仅为8mW. 相似文献
9.
10.
本文基于矩阵方程解,提出了一种开环稳定系统反馈的设计方法,所设计的系统对任意传感器失效具有完整性。 相似文献