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   4796篇
  免费   458篇
  国内免费   206篇
电工技术   26篇
综合类   271篇
化学工业   1435篇
金属工艺   78篇
机械仪表   74篇
建筑科学   146篇
矿业工程   289篇
能源动力   146篇
轻工业   1350篇
水利工程   16篇
石油天然气   849篇
武器工业   9篇
无线电   93篇
一般工业技术   154篇
冶金工业   379篇
原子能技术   18篇
自动化技术   127篇
  2024年   16篇
  2023年   66篇
  2022年   169篇
  2021年   232篇
  2020年   180篇
  2019年   170篇
  2018年   156篇
  2017年   167篇
  2016年   196篇
  2015年   189篇
  2014年   256篇
  2013年   352篇
  2012年   393篇
  2011年   388篇
  2010年   278篇
  2009年   252篇
  2008年   200篇
  2007年   313篇
  2006年   277篇
  2005年   193篇
  2004年   148篇
  2003年   140篇
  2002年   128篇
  2001年   103篇
  2000年   129篇
  1999年   86篇
  1998年   63篇
  1997年   63篇
  1996年   35篇
  1995年   25篇
  1994年   25篇
  1993年   22篇
  1992年   12篇
  1991年   9篇
  1990年   1篇
  1989年   3篇
  1988年   6篇
  1987年   5篇
  1986年   1篇
  1985年   2篇
  1984年   6篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1951年   1篇
排序方式: 共有5460条查询结果,搜索用时 93 毫秒
61.
将煅烧后的电解锰渣作为单一的实验原料,采用烧结法,制备微晶玻璃,通过正交实验对锰渣微晶玻璃的热处理方案及性能进行探讨。实验通过DSC、XRD、SEM等方法对样品的性能进行表征,并测试了样品的体积密度、抗弯强度等性能。结果显示:不同的热处理条件下的锰渣微晶玻璃的主晶相均为透辉石(含铁),次晶相为普通辉石相。在800℃/0.5 h+980℃/1 h的热处理条件下得到的锰渣微晶玻璃的综合性能最优,其抗弯强度为106.82 MPa;体积密度为2.68 g/cm^3;维氏硬度为4.43 GPa;耐酸度为0.71%;耐碱度为0.07%。此外,锰渣微晶玻璃用作建筑材料,有非常大的应用潜力。  相似文献   
62.
An efficient analytical method was developed and validated using a modified QuEChERS method and LC-MS/MS for the detection and quantification of neonicotinoid insecticide residues in rice whole grain and rice straw. The samples were extracted using acetonitrile and cleaned up by dispersive solid-phase extraction. Validation based on five fortification levels showed good recoveries of neonicotinoids ranging from 75% to 116 % and 60% to 105 % for rice whole grain and straw, respectively. The precision ranged between 3% and 17 %, and 2% and 10 % for grain and straw, respectively. The limit of detection was from 0.007 to 0.0084 mg kg?1 and 0.005 to 0.15 mg kg?1 and the limit of quantification was in the range of 0.024–0.028 mg kg?1 and 0.016–0.051 mg kg?1 for rice whole grain and rice straw, respectively. Monitoring of farm gate samples indicated that, out of 24 samples, 1 rice whole grain sample was contaminated with thiamethoxam residues (0.07 mg kg?1).  相似文献   
63.
This work presents the influence of dispersants on coal-water slurry (CWS), which was prepared from the solid residue of plasma pyrolysis of coal. The effects of dispersant type, solid concentration, dispersant content, and temperature on the rheological properties of CWS are examined. A suitable empirical model regarding the relation between viscosity and temperature is proposed. Through the sedimentation experiment of CWS, dispersants are found to significantly promote the stability of CWS.  相似文献   
64.
An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed, in which the electrolytic manganese residue(EMR) was initially calcined for cement buffering;then the generated SO_2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA) desulfurization; at last, the desulfurized slurry was introduced to the electrolytic manganese production(EMP). Results showed that 4.0 wt% coke addition reduced the sulfur of calcined EMR to 0.9%, thereby satisfying the cement-buffer requirement. Pilot-scale desulfurization showed that about 7.5 vol% of high SO_2 containing flue gas can be cleaned to less than 0.1 vol% through a five-stage countercurrent MOOA desulfurization. The desulfurized slurry had 42.44 g·L~(-) Mn~(2+) and 1.92 g·L~(-1) S_2 O_6~(2-), which was suitable for electrowinning after purification, and the purity of manganese product was 99.93%, satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7% of sulfur reutilization from the EMR and 94.1% was effectively used to the EMP. The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge, which promoted the cleaner production of EMP industry.  相似文献   
65.
随着新能源汽车行业进入黄金发展期,动力锂电池行业呈爆发式增长,碳酸锂的需求量也逐年递增,含锂氟化盐的使用造成大量含锂电解铝废渣产生,如果得到合理回收利用,将有利于缓解新能源产业带来的用锂压力。重点研究了以含锂电解铝废渣和浓硫酸为原料,通过酸浸取等一系列工艺,制备电池级碳酸锂,同时副产冰晶石,并从实验原理、实验方法、工艺关键点控制、产品质量、工艺特点等方面进行了深度剖析。本工艺具有良好的社会效益、经济效益和环保效益,易于推广应用。  相似文献   
66.
本文以湿法炼锌酸性浸出渣为研究对象,实验研究干燥温度、物料量、干燥时间对酸浸渣相对脱水率的影响,综合考虑干燥工艺的时效性、经济效益以及工艺效率,控制物料量为50g、干燥温度为90℃、干燥时间为80min时,酸浸渣相对脱水率可达到98.32%。实验研究对促进酸浸渣中有价金属的资源综合利用、改善环境等具有重要的指导意义。  相似文献   
67.
考察了2种进口渣油加氢催化剂(RM系列和ICR系列)在中化泉州石化有限公司330万t/a渣油加氢装置上的工业应用情况。结果表明:2种渣油加氢催化剂均具有良好的加氢活性;在原料性质和操作条件相近的条件下,与ICR系列催化剂相比,RM系列催化剂的脱硫、脱残炭性能较优,脱金属性能略差,且RM前部反应器床层压差上升速率较慢。  相似文献   
68.
云南省初中学业水平考试中,有关金属与盐溶液反应后的滤液滤渣问题一直是学生的难点。结合金属活动性顺序,利用"列表法"分析,可将复杂问题简单化,将反应后的滤液滤渣成分直观展示出来,有效提高学生做题的准确性,特别对理解能力较弱的同学帮助很大。  相似文献   
69.
In order to improve the thermal stability of condensed polynuclear aromatic(COPNA) resin synthesized from vacuum residue, 1,4-benzenedimethanol was added to cure COPNA resin. The curing mechanism was investigated by proton nuclear magnetic resonance spectrometry, solid carbon-13 nuclear magnetic resonance spectrometry and Fourier transform infrared spectroscopy. Microstructures of the uncured and the cured COPNA resins were studied by scanning electron microscopy and X-ray diffractometry. The thermal stability of COPNA resins before and after curing was tested by thermogravimetric analysis. The element composition of the cured COPNA resin heated at different temperatures was analyzed by an element analyzer. The results showed that the uncured COPNA resin reacted with the cross-linking agent during the curing process, and the curing mechanism was confirmed to be the electrophilic substitution reaction. Compared with the uncured COPNA resin, the cured COPNA resin had a smooth surface, well-ordered and streamlined sheet structure with more crystalline solids, better molecular arrangement and orientation. The weight loss process of the uncured and cured COPNA resins was divided into three stages. Carbon residue of the cured COPNA resin was 41.65% at 600 ℃, which was much higher than 25.02% of the uncured COPNA resin, which indicated that the cured COPNA resin had higher thermal stability.  相似文献   
70.
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