全文获取类型
收费全文 | 3772篇 |
免费 | 475篇 |
国内免费 | 294篇 |
专业分类
电工技术 | 234篇 |
综合类 | 402篇 |
化学工业 | 61篇 |
金属工艺 | 56篇 |
机械仪表 | 172篇 |
建筑科学 | 102篇 |
矿业工程 | 56篇 |
能源动力 | 89篇 |
轻工业 | 23篇 |
水利工程 | 69篇 |
石油天然气 | 31篇 |
武器工业 | 35篇 |
无线电 | 233篇 |
一般工业技术 | 214篇 |
冶金工业 | 161篇 |
原子能技术 | 8篇 |
自动化技术 | 2595篇 |
出版年
2023年 | 10篇 |
2022年 | 33篇 |
2021年 | 37篇 |
2020年 | 71篇 |
2019年 | 100篇 |
2018年 | 82篇 |
2017年 | 63篇 |
2016年 | 109篇 |
2015年 | 111篇 |
2014年 | 168篇 |
2013年 | 281篇 |
2012年 | 229篇 |
2011年 | 318篇 |
2010年 | 293篇 |
2009年 | 302篇 |
2008年 | 334篇 |
2007年 | 344篇 |
2006年 | 301篇 |
2005年 | 245篇 |
2004年 | 197篇 |
2003年 | 187篇 |
2002年 | 130篇 |
2001年 | 90篇 |
2000年 | 67篇 |
1999年 | 66篇 |
1998年 | 66篇 |
1997年 | 36篇 |
1996年 | 32篇 |
1995年 | 37篇 |
1994年 | 28篇 |
1993年 | 26篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 16篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有4541条查询结果,搜索用时 31 毫秒
1.
2.
热连轧生产中需频繁更换精轧机工作辊,而精轧机工作辊换辊操作极其复杂,故障率较高。为有效找出工作辊换辊故障中各个事件的因果关系,并进行逐一分析,以提高工作辊换辊的快速性和稳定性,采用了故障树分析法。介绍了故障树分析法的原理;以国内某钢厂1 780 mm热轧生产线精轧工作辊换辊为研究对象,建立了工作辊更换失效的故障树模型。通过对其进行定性、定量分析,确定了引起换辊故障的主要因素为升降轨道卡阻、入口导卫失效、出口导卫失效及弯辊缸不动作,并分析了其相应原因及提出了改进措施。采用改进措施后,彻底解决了工作辊换辊故障问题,提高了工作辊换辊的快速性和稳定性,保证了轧机正常的生产节奏。 相似文献
3.
4组鱼类DNA条形码引物的筛选与优化 总被引:1,自引:0,他引:1
目的通过对DNA条形码氧化酶亚基I基因(cytochrome oxidase subunit I,COI)的4组常用引物进行比较筛选,选择适于舟山鱼类鉴定的最佳引物。方法以舟山主产大黄鱼、小黄鱼、带鱼和乌贼样品DNA为模板,对4组常用DNA条形码引物进行PCR体系优化。通过比较PCR产物量、特异性、灵敏度和测序成功率,综合分析筛选最佳引物组。结果 4组引物均能扩增大黄鱼、小黄鱼和带鱼的DNA,对于乌贼DNA的扩增具有明显差异。COI优化引物具有易于扩增、测序简单等优势,更适于作为海产品鉴定的DNA条形码引物。结论本研究为舟山海产品的市场监管和实验室大量样品检测提供了技术参考。 相似文献
4.
Significant emergency measures should be taken until an emergency event occurs. It is understood that the emergency is characterized by limited time and information, harmfulness and uncertainty, and decision-makers are always critically bound by uncertainty and risk. This paper introduces many novel approaches to addressing the emergency situation of COVID-19 under spherical fuzzy environment. Fundamentally, the paper includes six main sections to achieve appropriate and accurate measures to address the situation of emergency decision-making. As the spherical fuzzy set (FS) is a generalized framework of fuzzy structure to handle more uncertainty and ambiguity in decision-making problems (DMPs). First, we discuss basic algebraic operational laws (AOLs) under spherical FS. In addition, elaborate on the deficiency of existing AOLs and present three cases to address the validity of the proposed novel AOLs under spherical fuzzy settings. Second, we present a list of Einstein aggregation operators (AgOp) based on the Einstein norm to aggregate uncertain information in DMPs. Thirdly, we are introducing two techniques to demonstrate the unknown weight of the criteria. Fourthly, we develop extended TOPSIS and Gray relational analysis approaches based on AgOp with unknown weight information of the criteria. In fifth, we design three algorithms to address the uncertainty and ambiguity information in emergency DMPs. Finally, the numerical case study of the novel carnivorous (COVID-19) situation is provided as an application for emergency decision-making based on the proposed three algorithms. Results explore the effectiveness of our proposed methodologies and provide accurate emergency measures to address the global uncertainty of COVID-19. 相似文献
5.
H. R. Ossareh 《International journal of control》2020,93(1):113-125
ABSTRACTIn this paper, we consider the problem of constraint management in Linear Periodic (LP) systems using Reference Governors (RG). First, we introduce the periodic-invariant maximal output admissible sets for LP systems. We extend the earlier results in the literature to Lyapunov stable LP systems with output constraints, which arise in RG applications. We show that, while the invariant sets for these systems may not be finitely determined, a finitely-determined inner approximation, which is periodically invariant, can be obtained by constraint tightening. We then analyze the geometric and algebraic relationship between these sets and show that these sets are related via simple transformations, implying that it suffices to compute only one of them for real-time applications. This greatly reduces the memory burden of RG (or other similar constraint management strategies), at the expense of an increase in processing requirements. We present a thorough analysis of this trade-off. In the second part of this paper, we present two RG formulations, and discuss their properties and algorithms for their computation. Numerical simulations demonstrate the efficacy of the approach. 相似文献
6.
7.
针对水利工程施工进度的多准则群决策问题,提出了一种新的模糊灰色多准则决策模型。该模型基于模糊集理论、灰色关联分析和折衷解的理论方法,将各决策属性和决策者权重的语言变量转化为梯形模糊数;采用改进的 GRA-VIKOR方法对模糊信息群体决策问题进行求解,并对各决策者的群体效益值和个体遗憾值进行聚合;通过折衷解对施工进度方案进行排序,获得最优方案。该模型有效地避免了信息的扭曲和丢失,确保了决策信息的完备性。通过在某水利工程施工进度方案优选的案例分析与计算,证明了该模型的有效性和实用性。 相似文献
8.
9.
Cryptocurrencies have brought many innovations and discussions to economic life. Digital assets, which are very popular by investors, are frequently used for many purposes such as store of value, exchange, and speculation. It creates a research area that intentions cryptocurrency experts prioritize in crypto investments. In this paper, therefore, the fuzzy Full Consistency Method-Bonferroni (FUCOM-F’B) model is conducted to determine the priorities of drivers for investing in cryptocurrencies. The selected twenty-three drivers are classified based on five aspects, including functionality, financial, legal infrastructure, technology, and security. Based on the findings, “strong electronic encryption” and “use of digital signature” are the most significant drivers for preferring a cryptocurrency. A validation check is performed to verify the reliability, usefulness, and stability of the proposed approach. Further, the introduced approach allows taking the ambiguities and subjectivity into account which exist in the decision-making procedure. The suggested framework can be a helpful decision support tool for regulators, policymakers, practitioners, and cryptocurrency investors. 相似文献
10.
中国云南省的电源结构以水电为主,水电消纳问题异常突出,且云南水电外送的受端调峰压力巨大.为充分挖掘云南电网"西电东送"通道潜力,最大限度消纳云南水电,同时响应多电网的调峰需求,文中构建了兼顾多电网调峰与水电消纳的跨流域梯级水电站调度的混合整数线性规划模型.模型采用目标权重法将多电网调峰问题转化成单目标问题,并通过调整各电网余荷距平绝对值的平均值权重,使得目标兼顾了多电网的调峰需求与水电消纳.同时,通过引入特殊顺序集约束,对最小持续时间约束提出了一种简易的线性化方法,此方法可应用于其他同类型的约束中.最后,以澜沧江干流与金沙江干流的18座水电站为例,验证了模型的可行性与有效性,结果表明所提方法可满足多电网调峰与水电消纳的需求. 相似文献