全文获取类型
收费全文 | 13013篇 |
免费 | 1365篇 |
国内免费 | 782篇 |
专业分类
电工技术 | 531篇 |
技术理论 | 1篇 |
综合类 | 1250篇 |
化学工业 | 1973篇 |
金属工艺 | 246篇 |
机械仪表 | 1286篇 |
建筑科学 | 440篇 |
矿业工程 | 432篇 |
能源动力 | 311篇 |
轻工业 | 1487篇 |
水利工程 | 106篇 |
石油天然气 | 301篇 |
武器工业 | 93篇 |
无线电 | 847篇 |
一般工业技术 | 2373篇 |
冶金工业 | 257篇 |
原子能技术 | 73篇 |
自动化技术 | 3153篇 |
出版年
2024年 | 57篇 |
2023年 | 204篇 |
2022年 | 339篇 |
2021年 | 473篇 |
2020年 | 552篇 |
2019年 | 402篇 |
2018年 | 444篇 |
2017年 | 471篇 |
2016年 | 542篇 |
2015年 | 598篇 |
2014年 | 865篇 |
2013年 | 1195篇 |
2012年 | 952篇 |
2011年 | 940篇 |
2010年 | 668篇 |
2009年 | 756篇 |
2008年 | 675篇 |
2007年 | 814篇 |
2006年 | 746篇 |
2005年 | 652篇 |
2004年 | 609篇 |
2003年 | 474篇 |
2002年 | 365篇 |
2001年 | 279篇 |
2000年 | 219篇 |
1999年 | 175篇 |
1998年 | 116篇 |
1997年 | 96篇 |
1996年 | 76篇 |
1995年 | 67篇 |
1994年 | 56篇 |
1993年 | 49篇 |
1992年 | 50篇 |
1991年 | 39篇 |
1990年 | 35篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
ElectronmicroscopicobservationsandDNAchainfragmentationstudiesonapoptosisinbonetumorcelsinducedby153SmEDTMPZhuShouPeng,Xia... 相似文献
22.
双噁唑啉化合物对PBT的增粘作用 总被引:1,自引:0,他引:1
以2.2'-双(2-唑啉)和双(2-唑啉基)苯作扩链剂,用焙融挤出的方法,对聚对苯二甲酸丁二酯(PBT)进行扩链,考察扩链剂的用量、反应时间和反应温度对PBT的特性粘度及端羧基含量(CV)的影响。结果表明,当用2,2'-双(2-唑啉)作扩链剂时,PBT的特性粘度[η]从0.799提高到0.926dL/g,CV降至5eq/10 ̄6g以下;当用双(2- 唑啉基)苯作扩链剂,[η]从0.763增至0.925dL/g,CV降至10eq/10 ̄6g以下,达到了较满意的扩链效果。 相似文献
23.
事物未来的状态仅仅受事物现状的影响,而与过去的状态无关,也就是具有马尔可夫性。用马尔可夫链的理论与方法,对具有马尔可夫性产品的可靠性进行预测,既为产品的可靠性设计和产品售后服务的经济性分析提供了参考,也为马尔可夫模型的实际应用拓广了范围。通过实例说明在数学软件的帮助下这种预测方法的简单可行性。 相似文献
24.
从供应商受益角度研究国际供应链合作关系 总被引:11,自引:1,他引:10
首先指出从供应商受益角度对国际供应链合作关系进行研究的重要意义,接着对国际供应链合作关系的起源及其概念界定进行了综合分析;其次对国际供应链战略伙伴关系下的供应商受益进行了相关研究结论的综合,并对我国供应商参与国际供应链合作的实际受益进行分析,然后将两者进行了比较,最后综合全文探讨得出本文研究的结论。 相似文献
25.
针对战时装备供应链的特点,以远程精确打击、敌特后方袭扰和恶劣天气等三个因素为主要风险指标,运用修正的模糊信息熵权对TOPSIS法进行改进,提出了一种新的战时装备供应链风险评估方法。首先利用原始数据产生的模糊信息熵权进行客观赋权,并引入专家因素对权重进行主观修正,利用逼近理想解排序方法进行运算,最后通过实例计算与分析,验证该评估方法简便易行,结论合理,有效降低了指挥员决策的主观随意性。 相似文献
26.
The automated fare collection(AFC) system,also known as the transit smart card(SC) system,has gained more and more popularity among transit agencies worldwide.Compared with the conventional manual fare collection system,an AFC system has its inherent advantages in low labor cost and high efficiency for fare collection and transaction data archival.Although it is possible to collect highly valuable data from transit SC transactions,substantial efforts and methodologies are needed for extracting such data because most AFC systems are not initially designed for data collection.This is true especially for the Beijing AFC system,where a passenger’s boarding stop(origin) on a flat-rate bus is not recorded on the check-in scan.To extract passengers’ origin data from recorded SC transaction information,a Markov chain based Bayesian decision tree algorithm is developed in this study.Using the time invariance property of the Markov chain,the algorithm is further optimized and simplified to have a linear computational complexity.This algorithm is verified with transit vehicles equipped with global positioning system(GPS) data loggers.Our verification results demonstrated that the proposed algorithm is effective in extracting transit passengers’ origin information from SC transactions with a relatively high accuracy.Such transit origin data are highly valuable for transit system planning and route optimization. 相似文献
27.
Simulation is capable to cope with the uncertain and dynamic nature of industrial value chains. However, in-depth system expertise is inevitable for mapping objects and constraints from the real world to a virtual model. This knowledge-intensity leads to long development times of respective projects, which contradicts the need for timely decision support. Since more and more companies use industrial knowledge graphs and ontologies to foster their knowledge management, this paper proposes a framework on how to efficiently derive a simulation model from such semantic knowledge bases. As part of the approach, a novel Simulation Ontology provides a standardized meta-model for hybrid simulations. Its instantiation enables the user to come up with a fully parameterized formal simulation model. Newly developed Mapping Rules facilitate this process by providing guidance on how to turn knowledge from existing ontologies, which describe the system to be simulated, into instances of the Simulation Ontology. The framework is completed by a parsing procedure for an automated transformation of this conceptual model into an executable one. This novel modeling approach makes model development more efficient by reducing its complexity. It is validated in a use case implementation from semiconductor manufacturing, where cross-domain knowledge was required in order to model and simulate the impacts of the COVID-19 pandemic on a global supply chain network. 相似文献
28.
29.
J.H. Trienekens P.M. WognumA.J.M. Beulens J.G.A.J. van der Vorst 《Advanced Engineering Informatics》2012,26(1):55-65
Food supply chains are increasingly complex and dynamic due to (i) increasing product proliferation to serve ever diversifying and globalising markets as a form of mass customisation with resulting global flows of raw materials, ingredients and products, and (ii) the need to satisfy changing and variable consumer and governmental demands with respect to food safety, animal welfare, and environmental impact. Transparency in the food supply chain is essential to guarantee food quality and provenance to all users of food and food products. Intensified information exchange and integrated information systems involving all chain actors are needed to achieve transparency with respect to a multitude of food properties.In this paper, specific challenges of food supply chains are highlighted. Major elements are addressed that support transparency to consumers, the government and food companies, which are considered the claimants of transparency. Elements considered to be enablers of transparency are governance mechanisms, quality and safety standards and information exchange. The paper specifies these transparency claimants and enablers for food supply chains and identifies major information system functions and information technology applications needed to comply with transparency demands. It thereby provides a framework for transparency analysis in food supply chains. 相似文献
30.