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   71810篇
  免费   7477篇
  国内免费   2718篇
电工技术   1073篇
技术理论   1篇
综合类   2821篇
化学工业   26428篇
金属工艺   10440篇
机械仪表   1447篇
建筑科学   1812篇
矿业工程   990篇
能源动力   1379篇
轻工业   9774篇
水利工程   315篇
石油天然气   1096篇
武器工业   341篇
无线电   2688篇
一般工业技术   16872篇
冶金工业   3352篇
原子能技术   262篇
自动化技术   914篇
  2024年   496篇
  2023年   1714篇
  2022年   2421篇
  2021年   3209篇
  2020年   3097篇
  2019年   2586篇
  2018年   2928篇
  2017年   3275篇
  2016年   3300篇
  2015年   3389篇
  2014年   4030篇
  2013年   5213篇
  2012年   4480篇
  2011年   5654篇
  2010年   3764篇
  2009年   4093篇
  2008年   3427篇
  2007年   3680篇
  2006年   3537篇
  2005年   2764篇
  2004年   2690篇
  2003年   2326篇
  2002年   1889篇
  2001年   1303篇
  2000年   1193篇
  1999年   919篇
  1998年   817篇
  1997年   707篇
  1996年   533篇
  1995年   494篇
  1994年   356篇
  1993年   263篇
  1992年   261篇
  1991年   196篇
  1990年   245篇
  1989年   239篇
  1988年   85篇
  1987年   59篇
  1986年   59篇
  1985年   68篇
  1984年   67篇
  1983年   33篇
  1982年   56篇
  1981年   8篇
  1980年   35篇
  1979年   6篇
  1978年   6篇
  1975年   6篇
  1974年   6篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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   
72.
液相添加剂对PTCR陶瓷电性能的影响   总被引:3,自引:2,他引:1  
液相添加剂AST(Al2O3+SiO2+TiO2)对BaTiO3陶瓷材料电性能的影响很大,随着Al2O3含量的增加,材料的电性能降低;SiO2、TiO2的物理特性对材料电性能影响较大;过量TiO2对材料PTC效应有重要影响,适当过量TiO2含量,可得到性能优良的PTCR陶瓷。  相似文献   
73.
氮化硅的性能及其聚合物材料   总被引:1,自引:0,他引:1  
叙述了氮化硅(Si3N4)的性能并制备了含Si3N4的聚合物材料,这种材料在医学上具有重要价值,对改变医学方面的概念、和对促进人类健康长寿具有重要意义。  相似文献   
74.
Y—TZP超细粉料性能的研究   总被引:5,自引:0,他引:5  
  相似文献   
75.
The water and oil uptake of mesquite and arabic gums in powdered form was studied at temperatures of 23, 35 and 45°C. A previously proposed equation to predict osmotic equilibrium was tested using the experimental data with both gums and a good statistical fit was obtained. Mesquite gum showed the highest water and oil absorption at all temperatures studied. Temperature dependence of the reciprocal of the S1 and WL were determined using an Arrhenius equation. The activation energy for water and oil absorption for gum arabic was 21.98 and 39.57 kJ mol−1, compared to that of mesquite gum having values of 15.79 and 46.16 kJ mol−1, respectively. A second order kinetic model was obtained for water and oil absorption for both gums.  相似文献   
76.
采用步进轧制工艺制备了Ti-6-22-22S合金Ф50mm棒材,对加工、热处理、组织与性能的关系进行了分析。结果表明:在两相区上部温度960℃轧制获得细网篮组织,棒材性能较好且数据均匀;热处理后,得到双态组织,强度.塑性达到优良组合,而片层状组织强度较高,但塑性稍低。  相似文献   
77.
The effect of annealing on microstructure,adhesive and frictional properties of GeSb 2 Te 4 films were experimentally studied.The GeSb 2 Te 4 films were prepared by radio frequency(RF)magnetron sputtering,and annealed at 200℃and 340℃under vacuum circumstance,respectively.The adhesion and friction experiments were mainly conducted with a lateral force microscope(LFM)for the GeSb 2 Te 4 thin films before and after annealing.Their morphology and phase structure were analyzed by using atomic force microscopy(AFM)and X-ray Diffraction(XRD)techniques,and the nanoindention was employed to evaluate their hardness values.Moreover,an electric force microscope(EFM)was used to measure the surface potential. It is found that the deposited GeSb 2 Te 4 thin film undergoes an amorphous-to-fcc and fcc-to-hex structure transition;the adhesion has a weaker dependence on the surface roughness,but a certain correlation with the surface potential of GeSb 2 Te 4 thin films.And the friction behavior of GeSb 2 Te 4 thin films follows their adhesion behavior under a lower applied load.However,such a relation is replaced by the mechanical behavior when the load is relatively higher.Moreover,the GeSb 2 Te 4 thin film annealed at 340℃presents a lubricative property.  相似文献   
78.
Carbon black composites (CBCs) have been prepared by pyrolyzing mixture of a carbon black with polyfurfuryl alcohol and then pretreated by oxidation with nitric acid, gasification with water steam or ammoxidation. The effects of the chemical character of the carrier surface, nature of the active metal phase and pH value of the impregnation solution on the catalytic activity towards the hydrodesulfurization (HDS) of thiophene of the CBC supported Mo (Co) catalysts were determined. It was stated that the catalytic properties of the CBC supported sulfides of Mo or Co and of Mo carbides are affected by the chemical character of the carrier surface. Generally, catalysts supported over basic surface CBC exhibit higher activity than those ones supported over CBC possessing acidic surface character. Co catalysts supported on acidic surface show lower activity (per mol of active metal) than Mo based ones supported on the same carrier. In the case of catalysts supported on basic CBC, Co exhibits distinctly higher activity than Mo. At the experimental conditions adopted for this study, CBC surface properties, active phase nature, and catalyst impregnation pH were found to exert a relatively small influence on both HDS and hydrogenation activities.  相似文献   
79.
M. Kwapi&#x  ska  I. Zbici&#x  ski 《Drying Technology》2005,23(8):1653-1665
The effect of drying and atomization conditions on the physical properties of powders for agglomerate-like materials and skin-forming material are studied in this article. A neural model is used for powder bulk and tapped density predictions.  相似文献   
80.
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