首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1100篇
  免费   40篇
  国内免费   1篇
电工技术   24篇
综合类   12篇
化学工业   342篇
金属工艺   13篇
机械仪表   31篇
建筑科学   84篇
矿业工程   7篇
能源动力   25篇
轻工业   109篇
水利工程   3篇
石油天然气   1篇
无线电   58篇
一般工业技术   200篇
冶金工业   97篇
原子能技术   12篇
自动化技术   123篇
  2022年   14篇
  2021年   24篇
  2020年   10篇
  2019年   16篇
  2018年   9篇
  2017年   16篇
  2016年   23篇
  2015年   30篇
  2014年   39篇
  2013年   59篇
  2012年   52篇
  2011年   62篇
  2010年   44篇
  2009年   42篇
  2008年   49篇
  2007年   35篇
  2006年   35篇
  2005年   32篇
  2004年   36篇
  2003年   23篇
  2002年   34篇
  2001年   20篇
  2000年   19篇
  1999年   26篇
  1998年   23篇
  1997年   15篇
  1996年   19篇
  1995年   13篇
  1994年   15篇
  1993年   16篇
  1992年   25篇
  1991年   17篇
  1990年   7篇
  1989年   20篇
  1988年   8篇
  1987年   20篇
  1986年   11篇
  1985年   10篇
  1984年   7篇
  1983年   13篇
  1982年   12篇
  1981年   19篇
  1980年   11篇
  1979年   16篇
  1978年   8篇
  1977年   9篇
  1976年   13篇
  1975年   14篇
  1974年   13篇
  1973年   7篇
排序方式: 共有1141条查询结果,搜索用时 859 毫秒
1.
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   
2.
The biorelevant PyFALGEA oligopeptide ligand, which is selective towards the epidermal growth factor receptor (EGFR), has been successfully employed as a substrate in magnetic resonance signal amplification by reversible exchange (SABRE) experiments. It is demonstrated that PyFALGEA and the iridium catalyst IMes form a PyFALGEA:IMes molecular complex. The interaction between PyFALGEA:IMes and H2 results in a ternary SABRE complex. Selective 1D EXSY experiments reveal that this complex is labile, which is an essential condition for successful hyperpolarization by SABRE. Polarization transfer from parahydrogen to PyFALGEA is observed leading to significant enhancement of the 1H NMR signals of PyFALGEA. Different iridium catalysts and peptides are inspected to discuss the influence of their molecular structures on the efficiency of hyperpolarization. It is observed that PyFALGEA oligopeptide hyperpolarization is more efficient when an iridium catalyst with a sterically less demanding NHC ligand system such as IMesBn is employed. Experiments with shorter analogues of PyFALGEA, that is, PyLGEA and PyEA, show that the bulky phenylalanine from the PyFALGEA oligopeptide causes steric hindrance in the SABRE complex, which hampers hyperpolarization with IMes. Finally, a single-scan 1H NMR SABRE experiment of PyFALGEA with IMesBn revealed a unique pattern of NMR lines in the hydride region, which can be treated as a fingerprint of this important oligopeptide.  相似文献   
3.
4.
Semantic Web Mining: State of the art and future directions   总被引:2,自引:0,他引:2  
Semantic Web Mining aims at combining the two fast-developing research areas Semantic Web and Web Mining. This survey analyzes the convergence of trends from both areas: More and more researchers are working on improving the results of Web Mining by exploiting semantic structures in the Web, and they make use of Web Mining techniques for building the Semantic Web. Last but not least, these techniques can be used for mining the Semantic Web itself.The Semantic Web is the second-generation WWW, enriched by machine-processable information which supports the user in his tasks. Given the enormous size even of today’s Web, it is impossible to manually enrich all of these resources. Therefore, automated schemes for learning the relevant information are increasingly being used. Web Mining aims at discovering insights about the meaning of Web resources and their usage. Given the primarily syntactical nature of the data being mined, the discovery of meaning is impossible based on these data only. Therefore, formalizations of the semantics of Web sites and navigation behavior are becoming more and more common. Furthermore, mining the Semantic Web itself is another upcoming application. We argue that the two areas Web Mining and Semantic Web need each other to fulfill their goals, but that the full potential of this convergence is not yet realized. This paper gives an overview of where the two areas meet today, and sketches ways of how a closer integration could be profitable.  相似文献   
5.
At very high temperatures loaded metallic structures undergo creep deformations. The generated creep strains are connected with stress relaxations, stress redistributions and/or progressive deformations.In mainly load controlled situations the behaviour of the material can be described by a nonlinear viscous flow law (Norton power law).A stress-deformation analysis of complex structures can be carried out by finite element codes in which the mentioned constitutive equation is implemented. The code PERMAS-VISCOUS was used to analyse the stress state of a notched tension bar and the deformation behaviour of a tube under external pressure undergoing a creep collapse. The relation to experimental findings is also given.  相似文献   
6.
7.
Full length and short model SSC (Superconducting Super Collider) 50 mm bore dipoles are being built and tested at Fermilab. The mechanical design of these magnets has been determined from experience with the construction of previous superconducting magnets. Construction experience includes coil fabrication, ground insulation, instrumentation, collaring, and yoke assembly. Fabrication techniques are explained, and construction problems and their solutions are reviewed. The relationship of short to long model construction is discussed  相似文献   
8.
Mechanism of Oxide Nucleation in Lithium Aluminosilicate Glass-Ceramics   总被引:1,自引:0,他引:1  
A commercial lithium aluminosilicate glass-ceramic material is investigated by high-resolution transmission electron microscopy after different heat treatments. Evidence is presented that epitaxy of β-quartz crystals on ZrTiO4-type crystallites is the critical step initiating silicate crystallization.  相似文献   
9.
Fiber Coating Concepts for Brittle-Matrix Composites   总被引:4,自引:0,他引:4  
The current interest in tough, high-temperature materials has motivated fiber coating development for brittle-matrix composites with brittle reinforcements. Such coatings are needed for controlled interface debonding and frictional sliding. The system investigated in this study was sapphire fiber-reinforced alumina. This system is thermochemically stable for severe use conditions, exhibits little thermal expansion mismatch, and utilizes the excellent strength and creep resistance of sapphire reinforcements. Porous oxide and refractory metal coatings which satisfy requirements for toughness improvement in these composites were identified by employing a variety of newly developed mechanical testing techniques for determining the interfacial fracture energies and sliding resistances.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号