全文获取类型
收费全文 | 74754篇 |
免费 | 4953篇 |
国内免费 | 2777篇 |
专业分类
电工技术 | 4221篇 |
技术理论 | 39篇 |
综合类 | 14465篇 |
化学工业 | 5703篇 |
金属工艺 | 2184篇 |
机械仪表 | 4405篇 |
建筑科学 | 13290篇 |
矿业工程 | 3746篇 |
能源动力 | 1652篇 |
轻工业 | 3759篇 |
水利工程 | 4433篇 |
石油天然气 | 2651篇 |
武器工业 | 408篇 |
无线电 | 4924篇 |
一般工业技术 | 4557篇 |
冶金工业 | 3529篇 |
原子能技术 | 397篇 |
自动化技术 | 8121篇 |
出版年
2024年 | 185篇 |
2023年 | 504篇 |
2022年 | 1081篇 |
2021年 | 1303篇 |
2020年 | 1325篇 |
2019年 | 975篇 |
2018年 | 979篇 |
2017年 | 1415篇 |
2016年 | 1753篇 |
2015年 | 2261篇 |
2014年 | 5643篇 |
2013年 | 3835篇 |
2012年 | 5172篇 |
2011年 | 5754篇 |
2010年 | 4739篇 |
2009年 | 5138篇 |
2008年 | 4501篇 |
2007年 | 6048篇 |
2006年 | 5612篇 |
2005年 | 4671篇 |
2004年 | 3864篇 |
2003年 | 3226篇 |
2002年 | 2581篇 |
2001年 | 2184篇 |
2000年 | 1830篇 |
1999年 | 1303篇 |
1998年 | 789篇 |
1997年 | 621篇 |
1996年 | 585篇 |
1995年 | 491篇 |
1994年 | 425篇 |
1993年 | 325篇 |
1992年 | 293篇 |
1991年 | 174篇 |
1990年 | 168篇 |
1989年 | 173篇 |
1988年 | 128篇 |
1987年 | 78篇 |
1986年 | 78篇 |
1985年 | 40篇 |
1984年 | 40篇 |
1983年 | 28篇 |
1982年 | 14篇 |
1981年 | 40篇 |
1980年 | 21篇 |
1979年 | 19篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1975年 | 12篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
2.
3.
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
4.
Gerd J. Hahn 《国际生产研究杂志》2020,58(5):1425-1441
The Fourth Industrial Revolution – also known as Industry 4.0 (i4.0) – comprises the digitalisation of the industrial sector. This paper uses the theoretical lens of supply chain innovation (SCI) to investigate the implications of i4.0 on supply chain management. For these purposes, the method of structured content analysis is applied to more than 200 use cases of i4.0-enabled SCI introduced by both established and startup companies. i4.0-enabled SCI manifests along three dimensions: process, technology, and business architecture. The key findings of this study can be summarised as follows: first, i4.0-enabled SCI extends the initial focus on productivity improvements in SC processes towards scalability and flexibility. Second, extant i4.0 solutions rely mostly on analytics and smart things while omitting smart people technology and the human-centric approach associated with the i4.0 paradigm. Third, established companies adopt i4.0 merely to sustain their existing business architectures while startup companies radically change their operating models, relying heavily on data analytics and the platform economy. Consequently, established companies pursue a problem-driven, engineering-based approach to SCI while startup companies follow an ‘asset-light’, business-driven approach. Lastly, there are two distinct approaches to digitalising operational SC processes: platform-based crowdsourcing of standard processes and on-demand provision of customised services. 相似文献
5.
6.
This article reviews the four innovation governance approaches (the precautionary principle, responsible innovation, permissionless innovation, and the innovation principle), including definitions, important attributes, and weaknesses found in each approach, and when utilizing an affinity diagram as a tool of analysis, identifies their distinctive characteristics and common relationships. A discussion section summarizes the paper’s findings and offers insights into where there is common relationships for further possible convergence between two innovation governance approaches – responsible innovation and permissionless innovation – that conceptually share substantially more in common than they contrast with each other. For addressing this challenge, the study recommends the following policy proposals: embrace artificial intelligence/machine learning/data analytics for risk management and regulatory adaptability; consider “soft law”as an option to public regulation; and substitute corporate citizenship for corporate social responsibility. 相似文献
7.
张皓博 《重庆电力高等专科学校学报》2015,(3):5-6,17
以可编程控制器课程为例,介绍"任务驱动"教学法在教学过程中的具体应用,并探讨了实施过程中存在的问题与解决方法。 相似文献
8.
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
9.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献