全文获取类型
收费全文 | 2467篇 |
免费 | 37篇 |
国内免费 | 39篇 |
专业分类
电工技术 | 37篇 |
综合类 | 138篇 |
化学工业 | 683篇 |
金属工艺 | 292篇 |
机械仪表 | 129篇 |
建筑科学 | 168篇 |
矿业工程 | 54篇 |
能源动力 | 30篇 |
轻工业 | 335篇 |
水利工程 | 15篇 |
石油天然气 | 157篇 |
武器工业 | 7篇 |
无线电 | 80篇 |
一般工业技术 | 143篇 |
冶金工业 | 105篇 |
原子能技术 | 20篇 |
自动化技术 | 150篇 |
出版年
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 23篇 |
2020年 | 43篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 24篇 |
2016年 | 25篇 |
2015年 | 56篇 |
2014年 | 67篇 |
2013年 | 88篇 |
2012年 | 112篇 |
2011年 | 168篇 |
2010年 | 77篇 |
2009年 | 104篇 |
2008年 | 81篇 |
2007年 | 153篇 |
2006年 | 138篇 |
2005年 | 128篇 |
2004年 | 117篇 |
2003年 | 142篇 |
2002年 | 118篇 |
2001年 | 130篇 |
2000年 | 105篇 |
1999年 | 107篇 |
1998年 | 97篇 |
1997年 | 83篇 |
1996年 | 70篇 |
1995年 | 86篇 |
1994年 | 77篇 |
1993年 | 31篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2543条查询结果,搜索用时 15 毫秒
41.
含钪铝合金的研究进展 总被引:20,自引:0,他引:20
钪是优化铝合金性能最为有效的合金元素,含钪铝合金强度高,塑性好,焊接性能,耐腐蚀性能等优良,是舰船、航空航天、核能等国防军工尖端领域用新一代铝合金结构材料,通过对Al-Mg-Sc和Al-Zn-Mg-Sc合金的研究状况分析,综述了钪与铝及铝合金的作用关系和对性能的改善作用。并提出我国含钪铝合金的研究方向。 相似文献
42.
43.
总结了双联熔炼工艺中灰铸铁熔炼材料的要求和特点,并针对使用过程中容易出现的问题进行了分析,同时分析了熔炼材料对铸件性能可能造成的影响,为合理选用熔炼材料提供了依据。 相似文献
44.
针对水稻空壳率的自动化检测问题,采用机器视觉技术,设计一种实验设备,利用稻谷的透光性,使用普通可见光照射,对获得的图像进行分析处理,并比较采用灰度特征以及YUV颜色模型两种方法进行统计的结果,表明该设备和相关图像处理算法完全可以胜任空壳率的自动统计工作,为后续发展实际的应用设备奠定基础。 相似文献
45.
Neng Li Shuai Huang Guodong Zhang Renyao Qin Wei Liu Huaping Xiong Gongqi Shi Jon Blackburn 《材料科学技术学报》2019,35(2):242-269
Recent efforts and advances in additive manufacturing (AM) on different types of new materials are presented and reviewed. Special attention is paid to the material design of cladding layers, the choice of feedstock materials, the metallurgical behavior and synthesis principle during the AM process, and the resulted microstructures and properties, as well as the relationship between these factors. Thereafter, the trend of development in the future is forecasted, including: Effects of the particles size and size distribution of powders; Approaches for producing fine microstructures; Opportunities for creating new materials by AM; Wide applications in reconditioning of damaged components; Challenges for deep understanding and applications of the AMed new materials. The idea of “Develop Materials” or “Create Materials” by AM is highlighted, but a series of scientific, technological and engineering problems remain to be solved in future. 相似文献
46.
提出一种多重查询调度算法——连续读取特性(CRP)调度算法,该算法应用连续读取特性,使查询的数据可以重组出某些连续关系,从而使之具有连续读取特性,解决了现有算法中有部分系统资源闲置的问题,提高查询速度。仿真实验结果表明,CRP调度算法的系统利用率和系统性能均优于其他算法。 相似文献
47.
We present two formalisations of the Business Process Modelling Notation (BPMN). In particular, we introduce a semantic model for BPMN in the process algebra CSP; we then study an augmentation of this model in which we introduce relative timing information, allowing one to specify timing constraints on concurrent activities. By exploiting CSP refinement, we are able to show some relationships between the timed and the untimed models. We then describe a novel empirical studies’ model, and the transformation to BPMN, allowing one to apply our formal semantics for analysing different kinds of workflows. To provide a better facility for describing behaviour specification about a BPMN diagram, we also present a pattern-based approach using which a workflow designer could specify properties which could otherwise be difficult to express. Our approach is specifically designed to allow behavioural properties of BPMN diagrams to be mechanically verified via automatic model checking as provided by the FDR tool. We use two examples to illustrate our approach. 相似文献
48.
Previously we provided two formal behavioural semantics for the Business Process Modelling Notation (BPMN) in the process algebra CSP. By exploiting CSP’s refinement orderings, developers may formally compare their BPMN models. However, BPMN is not a specification language, and it is difficult and sometimes impossible to use it to construct behavioural properties against which other BPMN models may be verified. This paper considers a pattern-based approach to expressing behavioural properties. We describe a property specification language PL for capturing a generalisation of Dwyer et al.’s Property Specification Patterns, and present a translation from PL into a bounded, positive fragment of linear temporal logic, which can then be automatically translated into CSP for simple refinement checking. We present a detailed example studying the behavioural properties of an airline ticket reservation business process. Using the same example we also describe some recent results on expressing behavioural compatibility within our semantic models. These results lead to a compositional approach for ensuring deadlock freedom of interacting business processes. 相似文献
49.
Kunsoo Han Robert J. Kauffman Barrie R. Nault 《Information Technology and Management》2008,9(3):181-200
Implementation and maintenance of interorganizational systems (IOS) require investments by all the participating firms. Compared
with intraorganizational systems, however, there are additional uncertainties and risks. This is because the benefits of IOS
investment depend not only on a firm’s own decisions, but also on those of its business partners. Without appropriate levels
of investment by all the firms participating in an IOS, they cannot reap the full benefits. Drawing upon the literature in
institutional economics, we examine IOS ownership as a means to induce value-maximizing noncontractible investments. We model
the impact of two factors derived from the theory of incomplete contracts and transaction cost economics: relative importance
of investments and specificity of investments. We apply the model to a vendor-managed inventory system (VMI) in a supply chain
setting. We show that when the specificity of investments is high, this is a more critical determinant of optimal ownership
structure than the relative importance of investments. As technologies used in IOS become increasingly redeployable and reusable,
and less specific, the relative importance of investments becomes a dominant factor. We also show that the bargaining mechanism—or
the agreed upon approach to splitting the incremental payoffs—that is used affects the relationship between these factors
in determining the optimal ownership structure of an IOS.
相似文献
Barrie R. NaultEmail: |
50.
We consider the edit distance with moves on the class of words and the class of ordered trees. We first exhibit a simple tester
for the class of regular languages on words and generalize it to the class of ranked and unranked regular trees. We also show
that this distance problem is
-complete on ordered trees.
A preliminary version of this paper appeared in Proceedings of 31st International Colloquium on Automata, Languages and Programming, volume 3142 of Lecture Notes in Computer Science, pages 932–944, Springer, 2005. Work supported by ACI Sécurité Informatique: VERA of the French Ministry of research. 相似文献