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   11443篇
  免费   887篇
  国内免费   434篇
电工技术   652篇
技术理论   1篇
综合类   780篇
化学工业   1907篇
金属工艺   871篇
机械仪表   758篇
建筑科学   796篇
矿业工程   263篇
能源动力   314篇
轻工业   577篇
水利工程   207篇
石油天然气   822篇
武器工业   105篇
无线电   1126篇
一般工业技术   1411篇
冶金工业   713篇
原子能技术   115篇
自动化技术   1346篇
  2024年   54篇
  2023年   173篇
  2022年   262篇
  2021年   374篇
  2020年   299篇
  2019年   272篇
  2018年   312篇
  2017年   335篇
  2016年   317篇
  2015年   404篇
  2014年   493篇
  2013年   684篇
  2012年   645篇
  2011年   768篇
  2010年   688篇
  2009年   671篇
  2008年   709篇
  2007年   689篇
  2006年   647篇
  2005年   586篇
  2004年   374篇
  2003年   295篇
  2002年   337篇
  2001年   291篇
  2000年   300篇
  1999年   347篇
  1998年   276篇
  1997年   241篇
  1996年   194篇
  1995年   168篇
  1994年   121篇
  1993年   112篇
  1992年   78篇
  1991年   59篇
  1990年   48篇
  1989年   48篇
  1988年   25篇
  1987年   18篇
  1986年   18篇
  1985年   5篇
  1984年   7篇
  1983年   4篇
  1982年   6篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   1篇
  1976年   1篇
  1974年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
国内外无机颜料工业的现状及发展趋势   总被引:1,自引:0,他引:1  
曲颖 《中国涂料》2005,20(10):7-12
阐述了国内外无机颜料的生产及需求现状,预测了无机颜料工业的发展趋势、产品发展方向,提出了发展我国无机颜料工业的策略。  相似文献   
82.
扼要介绍了某选厂碎磨试验研究的情况.并根据研究结论,提出了该厂技术改造应当采用的流程与设备方案,以提高产品合格粒级产率。  相似文献   
83.
本文就十余年来我国在冶金学领域使用国际单位制所遇到的问题,特别是关于热量和压力单位等问题,提出一些不同的意见;期望在冶金领域中使用国际单位更加顺利,又不要影响数据的精确性.  相似文献   
84.
透辉石瓷砖的研制   总被引:1,自引:0,他引:1  
用透辉石新型节能陶瓷原料生产瓷砖的工艺技术关键与开拓应用。  相似文献   
85.
The flame‐retardant and smoke‐suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were investigated in a comparison with alumina trihydrate, magnesium hydroxide, and Sb2O3 through the limiting oxygen index test and smoke density test. The flame‐retardant mechanisms were studied through the char yield test, SEM, quantitative analysis, thermogravimetry and differential thermal analysis. The thermal degradation in air of flexible PVC treated with the above compounds was studied by thermal analysis from ambient temperature to 800°C. The results showed that tin compounds such as ZHS and ZS could be used as a highly effective flame retardant for flexible PVC, and it appears that the tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1469–1475, 2005  相似文献   
86.
利用ANSYS软件,模拟了振动诱导单螺杆挤出机熔体输送段中非牛顿幂律流体的三维脉动流场,得到了三维脉动流场的瞬时速度分布及螺槽中物料的流动轨迹。结果表明,在脉动流场作用下,非牛顿流体的瞬时速度响应与在驱动壁面上所施加的正弦形式的脉动驱动形式不同,横螺槽方向的环流中心位置受幂律指数影响,且发生周期性改变。振动的引入使得在相同的时间内,物料的流动路程增加,且可增大物料的平均停留时间,有利于改善混合效果。  相似文献   
87.
Mesoporous silica materials with ordered hexagonal and parallel-arranged pore channel have been synthesized using cetyl trimethylammonium bromide as a template and Na2SO4 as counterions. Their ordered mesostructures were characterized by infrared spectroscopy, X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. The effects of Na2SO4 concentration on variations of morphology, specific surface area, and pore size were discussed; the results show that a high concentration of Na2SO4 induces the formation of crystal threads with a "tubules-within-tubule" structure, and also leads to mesoporous silica materials with spherical, fabaceous, sheet-like, or prismatic shapes. The results also show that a high concentration of Na2SO4 can make the pore size decrease, but cannot change pore wall thickness, demonstrating the stability of the hexagonal-shaped pores.  相似文献   
88.
The supermolecular structure of photocross-linked polyethylene (XLPE) has been studied by small-angle light scattering (SALS). The data show that the spherulitic structure of XLPE gradually deteriorates with increasing degree of cross-linking and increasing irradiation temperature from well-developed spherulites to rodlike aggregates and disordered lamellar structures. A photocross-linked sample of PE has lower crystallinity, smaller crystallites, and smaller spherulites than does the original sample. At high degrees of cross-linking, the SALS patterns show little or no spherulitic structure. Results with photocross-linked polyethylene demonstrate that the overall effect of cross-linking on the morphological structure is similar to that of an increase in molecular weight of the polymer. © 1993 John Wiley & Sons, Inc.  相似文献   
89.
Photoinitiated crosslinking of EVA in the presence of benzophenone (BP) as photoinitiator and triallyl isocyanurate (TAIC) as crosslinker and characterization of the related properties have been studied by gel determination, heat extension, DSC, DMTA, TGA, and mechanical measurements. The photoinitiated crosslinking efficiency of the EVA‐BP‐TAIC system and various factors affecting the crosslinking process, such as photoinitiator and crosslinker and their concentrations, irradiation temperature, and irradiation atmosphere were studied in detail and optimized by comparison of gel contents. The results show that the EVA samples with a thickness of 1 mm are readily crosslinked to a gel content of above 80% with 5 s UV‐irradiation under optimum conditions. The data from the heat extension and DSC show that the crosslinking density of photocrosslinked EVA increase and their crystallinities decrease with increasing the UV‐irradiation time. At the same time, photocrosslinking of EVA leads to a lowering of the melt temperature and a decrease of heat of fusion. The DMTA results show that photocrosslinking increases the amorphous phase and storage modulus of the crosslinked EVA, but does not change the glass transition temperature. The data from TGA and mechanical tests give evidence that the thermal stability and mechanical properties of photocrosslinked EVA samples are much better than those of the uncrosslinked EVA. POLYM. ENG. SCI., 47:1761–1767, 2007. © 2007 Society of Plastics Engineers  相似文献   
90.
The effect of preparation method on MnO x –CeO2 mixed oxide catalysts for methane combustion at low temperature was investigated by means of BET, XRD, XPS, H2-TPR techniques and methane oxidation reaction. The catalysts were prepared by the conventional coprecipitation, plasma and modified coprecipitation methods, respectively. It was found that the catalyst prepared by modified coprecipitation was the most active, over which methane conversion reached 90% at a temperature as low as 390 °C. The XRD results showed the preparation methods had no effect on the solid solution structure of MnO x –CeO2 catalysts. More Mn4+ and richer lattice oxygen were found on the surface of the modified coprecipitation prepared catalyst with the help of XPS analysis, and its reduction and BET surface area were remarkably promoted. These factors could be responsible for its higher activity for methane combustion at low temperature.  相似文献   
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