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   745898篇
  免费   10618篇
  国内免费   1905篇
电工技术   13521篇
综合类   640篇
化学工业   115784篇
金属工艺   29451篇
机械仪表   23733篇
建筑科学   17553篇
矿业工程   4734篇
能源动力   20377篇
轻工业   64017篇
水利工程   8402篇
石油天然气   16558篇
武器工业   44篇
无线电   83753篇
一般工业技术   148651篇
冶金工业   130933篇
原子能技术   16877篇
自动化技术   63393篇
  2021年   6691篇
  2020年   5025篇
  2019年   6407篇
  2018年   10959篇
  2017年   11155篇
  2016年   11878篇
  2015年   7584篇
  2014年   12769篇
  2013年   34875篇
  2012年   20354篇
  2011年   27859篇
  2010年   22305篇
  2009年   24784篇
  2008年   25484篇
  2007年   25174篇
  2006年   22053篇
  2005年   20023篇
  2004年   19095篇
  2003年   18699篇
  2002年   17890篇
  2001年   17787篇
  2000年   16796篇
  1999年   16990篇
  1998年   39346篇
  1997年   28253篇
  1996年   21896篇
  1995年   16791篇
  1994年   15037篇
  1993年   14737篇
  1992年   11251篇
  1991年   10767篇
  1990年   10599篇
  1989年   10234篇
  1988年   9881篇
  1987年   8682篇
  1986年   8401篇
  1985年   9747篇
  1984年   8846篇
  1983年   8377篇
  1982年   7568篇
  1981年   7713篇
  1980年   7276篇
  1979年   7312篇
  1978年   7105篇
  1977年   7898篇
  1976年   9889篇
  1975年   6330篇
  1974年   6056篇
  1973年   6187篇
  1972年   5165篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
112.
Sustainable and efficient food supply chain has become an essential component of one’s life. The model proposed in this paper is deeply linked to people's quality of life as a result of which there is a large incentive to fulfil customer demands through it. This proposed model can enhance food quality by making the best possible food quality accessible to customers, construct a sustainable logistics system considering its environmental impact and ensure the customer demand to be fulfilled as fast as possible. In this paper, an extended model is examined that builds a unified planning problem for efficient food logistics operations where four important objectives are viewed: minimising the total expense of the system, maximising the average food quality along with the minimisation of the amount of CO2 emissions in transportation along with production and total weighted delivery lead time minimisation. A four objective mixed integer linear programming model for intelligent food logistics system is developed in the paper. The optimisation of the formulated mathematical model is proposed using a modified multi-objective particle swarm optimisation algorithm with multiple social structures: MO-GLNPSO (Multi-Objective Global Local Near-Neighbour Particle Swarm Optimisation). Computational results of a case study on a given dataset as well as on multiple small, medium and large-scale datasets followed by sensitivity analysis show the potency and effectiveness of the introduced method. Lastly, there has been a scope for future study displayed which would lead to the further progress of these types of models.  相似文献   
113.
114.
The Journal of Supercomputing - Infrastructure-as-a-service container-based virtualization is gaining interest as a platform for running distributed applications. With increasing scale of cloud...  相似文献   
115.
Theoretical Foundations of Chemical Engineering - A set of measures to establish the technology for manufacturing highly active sources of γ radiation with an active part from...  相似文献   
116.
Puzanov  A. S.  Obolenskiy  S. V.  Kozlov  V. A. 《Semiconductors》2020,54(8):946-950
Semiconductors - On the basis of the Monte Carlo algorithm, a method for calculating the energy spectrum of hot nonequilibrium electrons and holes in the track of a primary recoil atom after being...  相似文献   
117.
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation.  相似文献   
118.
119.
120.
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