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   10338篇
  免费   1125篇
  国内免费   395篇
电工技术   171篇
综合类   616篇
化学工业   4744篇
金属工艺   527篇
机械仪表   116篇
建筑科学   179篇
矿业工程   400篇
能源动力   128篇
轻工业   2199篇
水利工程   35篇
石油天然气   486篇
武器工业   12篇
无线电   295篇
一般工业技术   1041篇
冶金工业   580篇
原子能技术   289篇
自动化技术   40篇
  2024年   37篇
  2023年   156篇
  2022年   265篇
  2021年   359篇
  2020年   387篇
  2019年   347篇
  2018年   314篇
  2017年   376篇
  2016年   409篇
  2015年   372篇
  2014年   575篇
  2013年   719篇
  2012年   817篇
  2011年   762篇
  2010年   523篇
  2009年   509篇
  2008年   448篇
  2007年   587篇
  2006年   595篇
  2005年   493篇
  2004年   434篇
  2003年   363篇
  2002年   347篇
  2001年   294篇
  2000年   261篇
  1999年   229篇
  1998年   158篇
  1997年   133篇
  1996年   105篇
  1995年   85篇
  1994年   74篇
  1993年   66篇
  1992年   53篇
  1991年   43篇
  1990年   30篇
  1989年   24篇
  1988年   18篇
  1987年   9篇
  1986年   9篇
  1985年   17篇
  1984年   10篇
  1983年   11篇
  1982年   10篇
  1981年   3篇
  1980年   9篇
  1979年   4篇
  1976年   2篇
  1961年   1篇
  1959年   4篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
31.
一种制备插层和无定形高岭土的新方法   总被引:1,自引:0,他引:1  
利用甲醇钠强烈的夺氢作用 ,介绍了一种制备插层和无定形高岭土的方法。利用XRD为主要检测手段研究了甲醇钠的质量分数、反应温度等因素对反应的影响。结果表明 :在反应温度较低、质量分数较低的甲醇钠溶液中 ,高岭土容易被插层而膨胀 ,反之高岭土的层状结构被破坏而无定形化。红外光谱分析进一步证明了插层和无定形高岭土结构的变化  相似文献   
32.
Ionic interactions in the two systems NaCl-HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid) and NaCl-MOPSO (3-(N-Morpholino)-2-hydroxypropanesulfonic acid) have been studied in terms of their mutual influence on the respective activity coefficients of each component. Activity coefficients for each component of the two systems and for corresponding buffers are calculated from emf measurements of solutions containing NaCl, the aminosulfonic acid, and its conjugate base in a NalSE/solution/AgCl-Ag cell at 5, 15, 25, and 37 °C.  相似文献   
33.
硫化钠在黑白钨加温精选中的应用研究   总被引:3,自引:0,他引:3  
陈文胜 《中国钨业》2002,17(3):26-28,32
介绍了柿竹园黑白钨混合粗精矿加温精选中 ,添加硫化钠与水玻璃混合剂比单一添加水玻璃能更有效地使白钨矿与萤石等含钙矿物及脉石矿物分离。论述了硫化钠在加温精选中的作用效果并探讨了其作用机理  相似文献   
34.
SiO2粉末浮选除铁研究   总被引:3,自引:0,他引:3  
进行了石英粉末浮选除铁净化试验,结果表明,用六偏磷酸钠作分散剂及浮选调整剂,胺作捕收剂,可获得较为理想的浮选指标。  相似文献   
35.
ABSTRACT:  The aim of this study was to determine the effect of adding 3.3% sodium lactate (SL), 0.25% calcium lactate (CL), and 1.65% SL along with 0.125% CL (SL+CL) on the physicochemical properties, cooking characteristics, and microbiological quality of microwave-cooked chicken patties compared to control (no added lactates). The addition of lactates did not affect the proximate composition of cooked chicken patties. The pH of CL- or SL+CL-containing patties was significantly ( P < 0.05) reduced compared to control or SL patties. The SL-containing patties had lower ( P < 0.05) a w values compared to control or CL patties. The CL- or SL+CL-containing patties had lower denatured myoglobin and higher ( P < 0.05) cooking yield, surface redness (CIE a *), and chroma values. However, addition of CL alone resulted in higher total expressible fluid, indicating lower water-holding capacity. The CL-containing patties exhibited lower Warner–Bratzler shear force values and higher ( P < 0.05) penetrometer reading compared to the SL-containing patties, indicating soft texture. Thiobarbituric acid (TBA) values were significantly ( P < 0.05) reduced in all lactate-containing patties compared to control up to the 7th day of refrigerated storage under aerobic conditions. No difference ( P > 0.05) was observed in aerobic plate counts between control and lactate-added patties during 28-d storage.  相似文献   
36.
Investigation of the effects of varying air velocity, slice thickness, and pre-treatment with sodium chloride solutions and surface active agents on drying potato slices indicated that the drying occurred entirely in the falling rate period and was controlled by the mechanism of liquid diffusion. The rate of drying, and therefore the diffusion coefficients, increased with the addition of sodium chloride and surface active agents. Diffusion coefficients were also influenced by air velocity and slice thickness, suggesting that the rate of drying of potato slices is controlled by a combination of internal and external resistances.  相似文献   
37.
The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0°C and the concentration of CO2 was < 1 ppm or 350 ppm. Different amounts of sodium chloride (0–70 μg/cm2) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X‐ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl‐induced corrosion is inhibited by ambient concentrations of CO2. Exposure in the absence of CO2 gives rise to heavy pitting, with brucite, Mg(OH)2, being the dominant corrosion product. In the presence of CO2 a layer of hydrated magnesium hydroxy carbonate, Mg5(CO3)4(OH)2 · 5 H2O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments.  相似文献   
38.
Mortars of blast furnace slag blended with a geothermal silica waste at various replacement levels of 0%, 5%, 10%, 15%, and 20% were cured for up to 90 days. The binder was activated by 6 wt% Na2O equivalent of sodium hydroxide. Lime was added as an activating agent and also to promote pozzolanic reaction with the silica. It was found that the presence of the silica waste increased the reactivity of the cementitious materials, as measured by means of nonevaporable water. The compressive strength was increased in the presence of the silica, except at the highest replacement level of 20%, the optimum silica replacement was that of 5%–10%. The microstructures of blended slag showed less porosity than those of neat slag mortars. The lime was completely consumed after 90 days of hydration.  相似文献   
39.
Polysaccharide was isolated from Cordia abyssinica and its effect, at differing concentrations, on its emulsifying ability was determined. Emulsions of vegetable oil containing up to 1% of the polysaccharide in phosphate pH 7.4 buffer, were prepared by using a hand piston homogenizer. Emulsification was assessed by diluting samples of the emulsions in sodium dodecyl sulphate and measuring absorbance at 500 nm. Addition of increasing concentrations of the polysaccharide up to 1% enhanced emulsification and emulsion stability. Above 1% concentration the polysaccharide solutions were too viscous for making emulsions conveniently. At a constant concentration of the polysaccharide, addition of up to a 1% concentration of salt enhanced emulsion formation. Further addition of salt above 1% resulted in no further changes in emulsifying ability, but the stability of the emulsions formed decreased on increasing the concentration of salt above 1%. The effect of pH on emulsifying ability was investigated by preparing emulsions using buffers of different pH, from pH 3 to pH 13. The polysaccharide had poor emulsifying ability below pH 7. Emulsifying ability increased with pH between pH 7 and 11. At pH above 11 there was a decrease in emulsifying ability.  相似文献   
40.
本介绍了将氰化钠镀锌溶液转换为氯化钾镀锌溶液的镀锌工艺过程,从工艺、健康、环保、成本等方面进行阐述。  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