全文获取类型
收费全文 | 23898篇 |
免费 | 644篇 |
国内免费 | 2353篇 |
专业分类
电工技术 | 1928篇 |
综合类 | 3357篇 |
化学工业 | 2283篇 |
金属工艺 | 2790篇 |
机械仪表 | 1047篇 |
建筑科学 | 1171篇 |
矿业工程 | 883篇 |
能源动力 | 375篇 |
轻工业 | 2339篇 |
水利工程 | 699篇 |
石油天然气 | 2560篇 |
武器工业 | 77篇 |
无线电 | 2031篇 |
一般工业技术 | 1630篇 |
冶金工业 | 538篇 |
原子能技术 | 653篇 |
自动化技术 | 2534篇 |
出版年
2020年 | 11篇 |
2017年 | 32篇 |
2016年 | 22篇 |
2015年 | 25篇 |
2014年 | 818篇 |
2013年 | 669篇 |
2012年 | 835篇 |
2011年 | 4247篇 |
2010年 | 1830篇 |
2009年 | 1146篇 |
2008年 | 996篇 |
2007年 | 559篇 |
2006年 | 714篇 |
2005年 | 903篇 |
2004年 | 3853篇 |
2003年 | 1930篇 |
2002年 | 1566篇 |
2001年 | 974篇 |
2000年 | 572篇 |
1999年 | 862篇 |
1998年 | 437篇 |
1997年 | 481篇 |
1996年 | 222篇 |
1995年 | 171篇 |
1994年 | 189篇 |
1993年 | 596篇 |
1992年 | 456篇 |
1991年 | 325篇 |
1990年 | 428篇 |
1989年 | 315篇 |
1988年 | 97篇 |
1987年 | 44篇 |
1986年 | 41篇 |
1985年 | 31篇 |
1984年 | 33篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 52篇 |
1979年 | 17篇 |
1975年 | 29篇 |
1974年 | 34篇 |
1973年 | 22篇 |
1972年 | 22篇 |
1971年 | 14篇 |
1970年 | 28篇 |
1969年 | 12篇 |
1968年 | 22篇 |
1966年 | 13篇 |
1963年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
61.
Applying the critical path method to manufacturing routing 总被引:1,自引:0,他引:1
Traditionally the critical path method (CPM) has been used primarily as an a'priori planning and scheduling device. Its applications have typically been limited to one-shot projects, usually with a long period of completion time. This paper proposes taking these ideas to continuous production systems, and to implement the CPM not just at the outset but throughout the process. The algorithm calls for repeatedly calculating the critical path through the production process and routing parts so as to remain off this path. Before the model is presented, some basic ideas are introduced from group technology (GT) and CPM. After the presentation of the model, two potential implementations with the usage of computer are proposed. 相似文献
62.
Lee C. Chang Ph.D. Associate Professor Director Jeri L. Edwards Senior Manager 《Computers & Industrial Engineering》1991,21(1-4):147-151
Image processing allows the automation of the business transaction, turning “paper factories” into “image factories.” This burgeoning new area of computerization needs new paradigms, theories, and methods to maximize its effectiveness at cutting time and costs. This paper investigates what this new area of computerization can gain from CIM technology. It examines the similarities between the processing of computer images in a paperless business environment and the processing of materials into products in the manufacturing plant. These similarities will allow us to apply mature, well-tested CIM techniques to emerging image factories. 相似文献
63.
Huai Wen-xin Wuhan University of Hydraulic & Electric Engineering Wuhan Hubei P.R.China Prof.Li Wei 《水动力学研究与进展(B辑)》1993,(3)
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion. 相似文献
64.
Li Jian-zhong Niu Zheng-meng Chen Gang Tan Li-xing Shaanxi Institute of Mechanical Engineering Xi''''an P.R.China 《水动力学研究与进展(B辑)》1993,(4)
This paper will introduce experimental studies and numerical calculation onturbulent boundary layer of water flow along curved surface in our country in recent years.Onthe basis of the experimental studies,the effects of curvature and roughness on velocitydistribution and pressure distribution and the change of turbulent flow boundary layer onoverflow bucket concave surface is discussed.We proposed the empirical formula of velocity,pressure and the change of turbulent flow boundary layer on outlet bucket concave.According tothe momentum principle,we have deduced the momentum integral equation full water depthboundary layer and using the element as control unit inside the boundary layer on concavesurface of bucket.Combining with continuity equation,we have computed the boundary layerdevelopment on the bucket of a spillway.Compared with the field experimental data,thecalculation results are available.Under polar coordinates,a mathematical model for simulatingtime-averaged flow characteristics in concave surface of bucket is established.The turbulent flowfield on concave surface of bucket is calculated by SIMPLE method and this mathematicalmodel.The flow velocity field,pressure field,distribution of turbulent kinetic energy,distribution of turbulent energy dissipating rate and distribution of shear stress are available.Thecalculation value is consistent with measured test data. 相似文献
65.
The dye-sensitized TiO2 complex films were prepared by the dye coat onto TiO2 surfaces,and the sensitizing mechanism and adsorption properties of the dye-sensitized TiO2 complex films were inverstigated.The influence of the application conditions of dye adsorbed on TiO2 films on the amount of dye adsorption was discussed.Experimental results show that the concentration,the temperature of dye solutions and the dipping time of TiO2 films in the dye solutions have a significant influence on the amount of dye adsorption.Cell test indicates that the conversion efficiency of light to electricity increases with the amount of dye adsorption. 相似文献
66.
Xu You-heng Dong Li-yun Huang Dong-qun Fudan University Shanghai P. R. China 《水动力学研究与进展(B辑)》1998,(3)
In this paper,the oscillation amplitude of the free end of a group of threecylinders are studied.The three cylinders are erected at the vertices of an equilateral trian-gle,and three arrangements are made in this study.One of the three cylinders is served asa working cylinder which is mounted by a flexible cantilever and two accelerometers areattached on the free end in two directions.The results of the three-cylinder arrangementare compared with those of two cylinders in tandem/side-by-side arrangement in the samecondition.The experimental results show that the rear cylinder of a group of three cylin-ders is affected more seriously than that of the corresponding two cylinders in the contrastarrangement.The main direction of oscillation is changed.The transversal oscillation isstronger than the longitudinal oscillation in the three-cylinder arrangement.On the con-trary,the transversal oscillation is much weaker than the longitudinal oscillation in two-cylinder arrangement.The largest transversal oscillat 相似文献
67.
Zheng Wen Technological Faculty of Maintenance Engineering Guangzhou University Guangzhou P.R.China 《国际设备工程与管理》1997,(3)
VibrationMonitoringandDiagnosisofPipelinePumpsonOfshorePlatformsZhengWenTechnologicalFacultyofMaintenanceEngineringGuangzhou... 相似文献
68.
Shihong XU Pengshou XU Mingrong JI Xianming LIU Maosheng MA Jingsheng ZHU Yuheng ZHANG Structure Research Laboratory University of Science Technology of China Hefei ChinaZhenjia XU Institute of Semiconductor Academia Sinica Beijing China 《材料科学技术学报》1993,9(6):437-440
The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxidegrowth have been investigated by means of thermal desorption,work function,Auger electronspectroscopy and photoemission electron spectroscopy.The experimental data showed that therewas a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It wasfound that the presence of Na always caused an increase of the oxygen initial uptake whereas thepromotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A newmechanism of Na-promoted Si oxide growth is suggested in this paper. 相似文献
69.
本文叙述了智能网的业务管理系统所实现的3种功能:业务管理功能,网络管理功能和业务管理访问功能,还介绍了业务管理和网络管理之间的关系,SMS的集中式和分布式两种体系结构及业务管理功能的设计方法和进一步研究方向。 相似文献
70.