全文获取类型
收费全文 | 134937篇 |
免费 | 17503篇 |
国内免费 | 9665篇 |
专业分类
电工技术 | 15585篇 |
技术理论 | 5篇 |
综合类 | 14852篇 |
化学工业 | 11004篇 |
金属工艺 | 8884篇 |
机械仪表 | 12713篇 |
建筑科学 | 8411篇 |
矿业工程 | 6226篇 |
能源动力 | 6715篇 |
轻工业 | 2678篇 |
水利工程 | 4551篇 |
石油天然气 | 6007篇 |
武器工业 | 3685篇 |
无线电 | 18322篇 |
一般工业技术 | 12078篇 |
冶金工业 | 3260篇 |
原子能技术 | 1799篇 |
自动化技术 | 25330篇 |
出版年
2024年 | 730篇 |
2023年 | 2179篇 |
2022年 | 3902篇 |
2021年 | 4402篇 |
2020年 | 4765篇 |
2019年 | 3665篇 |
2018年 | 3554篇 |
2017年 | 4691篇 |
2016年 | 5437篇 |
2015年 | 6072篇 |
2014年 | 9012篇 |
2013年 | 8775篇 |
2012年 | 10935篇 |
2011年 | 11808篇 |
2010年 | 8729篇 |
2009年 | 8738篇 |
2008年 | 8597篇 |
2007年 | 10343篇 |
2006年 | 8890篇 |
2005年 | 7430篇 |
2004年 | 6014篇 |
2003年 | 4748篇 |
2002年 | 3753篇 |
2001年 | 3016篇 |
2000年 | 2397篇 |
1999年 | 1906篇 |
1998年 | 1405篇 |
1997年 | 1181篇 |
1996年 | 1077篇 |
1995年 | 895篇 |
1994年 | 714篇 |
1993年 | 494篇 |
1992年 | 385篇 |
1991年 | 314篇 |
1990年 | 242篇 |
1989年 | 205篇 |
1988年 | 162篇 |
1987年 | 74篇 |
1986年 | 87篇 |
1985年 | 51篇 |
1984年 | 57篇 |
1983年 | 42篇 |
1982年 | 46篇 |
1981年 | 26篇 |
1980年 | 39篇 |
1979年 | 28篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1959年 | 26篇 |
1951年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
3.
以重庆市甄子岩29号危岩体为研究对象,基于现场调查和分析解剖,建立UDEC离散元数值计算模型,对其演化变形过程进行模拟分析。研究表明,在巨大的自重作用下,由于基座岩体岩质软,岩体较破碎,且基座外侧为直立的陡崖,具有完整的临空面,从而使基座岩体易发生压缩流变及剪切流变,进而使危岩体存在滑移垮塌的危险。 相似文献
4.
大型综合室内亲子乐园属于高大空间,设有游乐设施和游戏的特殊性使得对空间的舒适性要求一致,但是送风气流遇阻严重,室内存在较多气流死角,影响室内空气质量和儿童健康。因此其空调设计不仅需要考虑温度、风速的空间均匀度,还要考虑各点的空气龄和PMV-PPD指标。以天津某亲子乐园为研究对象,利用scSTREAM软件对适用于该房间的辐射供冷加新风、置换通风、混合通风三种空调方式的送风效果进行数值模拟分析,从流场的均匀性、人员的热舒适性等方面对模拟结果进行探讨,研究结果表明辐射供冷加新风方式的空间均匀性和PMV指标最佳,混合通风方式的空气龄最小。 相似文献
5.
现今国内的数字集群网络发展存在局限性、差异性,还远没有达到“网”状分布的程度,因此,共网数字集群发展空间巨大、前景广阔。通过列举共网数字集群系统在龙嘉国际机场和长春雷锋车队的成功应用案例,探讨了我国共网数字集群系统应用的可行性和必要性。 相似文献
6.
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
7.
8.
Numerical simulation, using SILVACO-TCAD, is carried out to explain experimentally observed effects of different types of deep levels on the capacitance–voltage characteristics of p-type Si-doped GaAs Schottky diodes grown on high index GaAs substrates. Two diodes were grown on (311)A and (211)A oriented GaAs substrates using Molecular Beam Epitaxy (MBE). Although, deep levels were observed in both structures, the measured capacitance–voltage characteristics show a negative differential capacitance (NDC) for the (311)A diodes, while the (211)A devices display a usual behaviour. The NDC is related to the nature and spatial distribution of the deep levels, which are characterized by the Deep Level Transient Spectroscopy (DLTS) technique. In the (311)A structure only majority deep levels (hole traps) were observed while both majority and minority deep levels were present in the (211)A diodes. The simulation, which calculates the capacitance–voltage characteristics in the absence and presence of different types of deep levels, agrees well with the experimentally observed behaviour. 相似文献
9.
ABSTRACT The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style. 相似文献
10.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献