全文获取类型
收费全文 | 46496篇 |
免费 | 3944篇 |
国内免费 | 2273篇 |
专业分类
电工技术 | 3767篇 |
技术理论 | 3篇 |
综合类 | 5351篇 |
化学工业 | 5500篇 |
金属工艺 | 1790篇 |
机械仪表 | 2102篇 |
建筑科学 | 6501篇 |
矿业工程 | 2353篇 |
能源动力 | 1301篇 |
轻工业 | 3304篇 |
水利工程 | 1990篇 |
石油天然气 | 2226篇 |
武器工业 | 295篇 |
无线电 | 3973篇 |
一般工业技术 | 3716篇 |
冶金工业 | 2672篇 |
原子能技术 | 508篇 |
自动化技术 | 5361篇 |
出版年
2024年 | 183篇 |
2023年 | 610篇 |
2022年 | 1061篇 |
2021年 | 1262篇 |
2020年 | 1210篇 |
2019年 | 1046篇 |
2018年 | 978篇 |
2017年 | 1157篇 |
2016年 | 1315篇 |
2015年 | 1473篇 |
2014年 | 2510篇 |
2013年 | 2378篇 |
2012年 | 2996篇 |
2011年 | 3218篇 |
2010年 | 2527篇 |
2009年 | 2679篇 |
2008年 | 2540篇 |
2007年 | 3240篇 |
2006年 | 2976篇 |
2005年 | 2693篇 |
2004年 | 2241篇 |
2003年 | 2084篇 |
2002年 | 1755篇 |
2001年 | 1504篇 |
2000年 | 1281篇 |
1999年 | 1059篇 |
1998年 | 744篇 |
1997年 | 648篇 |
1996年 | 557篇 |
1995年 | 519篇 |
1994年 | 400篇 |
1993年 | 322篇 |
1992年 | 260篇 |
1991年 | 177篇 |
1990年 | 190篇 |
1989年 | 170篇 |
1988年 | 138篇 |
1987年 | 102篇 |
1986年 | 71篇 |
1985年 | 62篇 |
1984年 | 55篇 |
1983年 | 29篇 |
1982年 | 25篇 |
1981年 | 36篇 |
1980年 | 29篇 |
1979年 | 31篇 |
1977年 | 27篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
This paper is prepared in honour of Professor E.T. Brown for his outstanding contributions to rock mechanics and geotechnical engineering and also for his personal influence on the first author's research career in geomechanics and geotechnical engineering. As a result, we have picked a topic that reflects two key research areas in which Professor E.T. Brown has made seminal contributions over a long and distinguished career. These two areas are concerned with the application of the critical state concept to modelling geomaterials and the analysis of underground excavation or tunnelling in geomaterials.Partially due to Professor Brown's influence, the first author has also been conducting research in these two areas over many years. In particular, this paper aims to describe briefly the development of a unified critical state model for geomaterials together with an application to cavity contraction problems and tunnelling in soils. 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.
As the development of cloud computing and the convenience of wireless sensor netowrks, smart devices are widely used in daily life, but the security issues of the smart devices have not been well resolved. In this paper, we present a new NTRU-type public-key cryptosystem over the binary field. Specifically, the security of our scheme relies on the computational intractability of an unbalanced sparse polynomial ratio problem (DUSPR). Through theoretical analysis, we prove the correctness of our proposed cryptosystem. Furthermore, we implement our scheme using the NTL library, and conduct a group of experiments to evaluate the capabilities and consuming time of encryption and decryption. Our experiments result demonstrates that the NTRU-type public-key cryptosystem over the binary field is relatively practical and effective. 相似文献
5.
Measuring nonlinear optical response of a specific material in a mixture, not only leads to investigate the behavior of a particular component in various circumstances, but also can be a way to select suitable combination and optimum concentration of additives and therefore obtaining the maximum nonlinear optical signals. In this work, by using dual-arm Z-scan technique, the nonlinear refractive index of Disperse Red1 (DR1) organic dye molecules inside the core of prepared polymeric nanocapsules was measured among various materials which prepared nanocapsules were made of them. Then the measured value was compared with nonlinear refractive index of DR1 solved in dichloromethane. 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.
8.
文章中主要采用有机溶剂萃取法(OSE)对高浓度石油污染土壤进行修复,经过精馏操作,有效回收原油,建立脱附等温曲线,研究了石油污染物在土壤-有机溶剂两相间的迁移规律。 相似文献
9.
10.
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