全文获取类型
收费全文 | 24258篇 |
免费 | 938篇 |
国内免费 | 681篇 |
专业分类
电工技术 | 633篇 |
综合类 | 789篇 |
化学工业 | 6965篇 |
金属工艺 | 1789篇 |
机械仪表 | 1016篇 |
建筑科学 | 1311篇 |
矿业工程 | 254篇 |
能源动力 | 2638篇 |
轻工业 | 924篇 |
水利工程 | 206篇 |
石油天然气 | 687篇 |
武器工业 | 258篇 |
无线电 | 2383篇 |
一般工业技术 | 4157篇 |
冶金工业 | 653篇 |
原子能技术 | 497篇 |
自动化技术 | 717篇 |
出版年
2024年 | 36篇 |
2023年 | 412篇 |
2022年 | 592篇 |
2021年 | 644篇 |
2020年 | 682篇 |
2019年 | 624篇 |
2018年 | 608篇 |
2017年 | 738篇 |
2016年 | 702篇 |
2015年 | 816篇 |
2014年 | 1259篇 |
2013年 | 1879篇 |
2012年 | 1175篇 |
2011年 | 1963篇 |
2010年 | 1402篇 |
2009年 | 1469篇 |
2008年 | 1427篇 |
2007年 | 1384篇 |
2006年 | 1178篇 |
2005年 | 1078篇 |
2004年 | 960篇 |
2003年 | 776篇 |
2002年 | 668篇 |
2001年 | 477篇 |
2000年 | 444篇 |
1999年 | 408篇 |
1998年 | 393篇 |
1997年 | 315篇 |
1996年 | 266篇 |
1995年 | 229篇 |
1994年 | 183篇 |
1993年 | 135篇 |
1992年 | 105篇 |
1991年 | 92篇 |
1990年 | 73篇 |
1989年 | 71篇 |
1988年 | 51篇 |
1987年 | 30篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 15篇 |
1980年 | 6篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
In this work, the filiform corrosion behaviour of powder painted aluminium profiles was studied, and the coating barrier properties together with adhesion to the substrate were analysed. Samples coated with a traditional painting procedure (one powder layer application followed by curing), and other samples coated using a special cycle to obtain wood grain effect were compared using accelerated filiform corrosion tests. Moreover, in order to better understand the degradation mechanisms of painted metal substrates, thermal stresses were applied to accelerate the natural weathering. The effects of the thermal aging were analysed by electrochemical impedance spectroscopy. 相似文献
22.
23.
NUMERICAL ANALYSIS AND EXPERI- MENT OF UNSTEADY THERMAL FIELD OF ROTOR PLATE FOR EDDY CURRENT RETARDER 总被引:3,自引:0,他引:3
LIU Chengye HE Ren 《机械工程学报(英文版)》2008,21(4):71-75
The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder. 相似文献
24.
The influence of the substrate nature on the structure and morphology of ITO thin films grown by thermal evaporation in vacuum is investigated. The as-prepared metal films with Sn/In molar ratio of 0.1 were subsequently annealed for 2 h at 723 K in air (to obtain tin doped indium oxide), then annealed in vacuum at 523 K, followed by UV irradiation (to reduce the electrical resistivity). Irrespective of substrate nature, XRD data evidence a (222) preferential orientation in films. Substrate nature, annealing in vacuum and UV irradiation influence the structure, morphology, optical, electrical and surface wetting properties of the films' surface. 相似文献
25.
Influence of Ni Interlayers on the Mechanical Properties of Ti6Al4V/(WC-Co) Friction Welds 总被引:2,自引:0,他引:2
M. Shamanian M. Salehi A. Saatchi T. H. North 《Materials and Manufacturing Processes》2003,18(4):581-598
Ni interlayers were introduced prior to dissimilar friction welding of Ti6Al4V base material to three cemented carbide substrates. The fracture strength of Ti6Al4V/(WC-6 wt% Co) welds were poor and were markedly improved when 20-µm thick Ni interlayers were introduced prior to dissimilar friction welding. These results were only produced when the (WC-6 wt% Co) cermet was electroplated prior to friction welding. When the Ti6Al4V alloy was electroplated prior to friction welding, fractured WC particles and cracking were observed in the (WC-Co) carbide substrate. The fracture strengths of Ti6Al4V/(WC-11 wt% Co) and Ti6Al4V/(WC-24 wt% Co) welds were not improved when 20-µm thick Ni interlayers were introduced prior to friction welding. During mechanical testing, the Ni layer retained at the dissimilar joint interface created a region of weakness. 相似文献
26.
Fan Jing yu Wang Dao zeng Zhong Bao chang Shanghai Institute of Applied Mathematics Mechanics Shanghai University Shanghai China 《水动力学研究与进展(B辑)》2003,15(2)
1 . INTRODUCTIONUndertheinfluenceofnaturaltides,theinterac tionsbetweenflowfeaturesandpollutantlongitudinaldiffusionintidalriversareimportantforwaterenvi ronmentrectificationinestuarineregions.Thediffu sionandtransportofpollutantinnaturalriversfallin tom… 相似文献
27.
L.N. Koltunova 《Chemical Engineering Communications》1992,114(1):1-15
Methods of obtaining averaged diffusion equations are considered in case of non-uniform profile of the velocity in a channel. With the flow of Couette as an example, the comparison of exact and approximate solutions (obtained by means of perturbation method) has been carried out. The peculiarities of function of residence time distribution of liquid in the flows with non-uniform velocity field are noted. It is shown that the distribution function moments values including the zero and first moments values would depend on the degree of the velocity profile irregularity, on efficiency of radial mixing in a system as well as on the averaging method. The averaged diffusion equations which have been found by means of perturbation method are the most general of proposed ones at present in the appropriate literature. The Taylor's model and Goldstein's hyperbolic equations are included in said averaged equations as particular cases. The table of the numerical values of first three moments of RTD-function necessary for determining of the model parameters is given. The problems of application of the obtained averaged equation for calculating real chemical apparatuses, e.g. reactors, are discussed. 相似文献
28.
作者结合实例,论述了氨罐保冷改造的设计、选材及施工,给出了改造后两年的测试结果,并对测试结果进行了分析。 相似文献
29.
S. Scalat D. Banu D. Hawes J. Parish F. Haghighata D. Feldman 《Solar Energy Materials & Solar Cells》1996,44(1):49
Full scale thermal storage tests were conducted in a room lined with PCM wallboard having latent heat storage capacity. The results were compared with those obtained from tests conducted in a similar room lined with ordinary wallboard. The research showed that PCM wallboard can function efficiently as a thermal storage medium which can be applied to peak load shifting, improved use of waste and solar heat as well as more efficient operation of heating and cooling equipment. 相似文献
30.
Yilmaz Muslu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1991,51(4):449-460
A dispersed flow model previously developed to study substrate utilization in unsaturated media was experimentally verified and its practical application was considered. For this purpose, measurements were made using tap water and a synthetic feed solution. The importance of the change in fluid regime as regards to the simultaneous transport and reaction within biological filters were demonstrated. The effect of drop formation and the breakage of liquid jets inside the filters on substrate utilization was also shown. 相似文献