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   3631篇
  免费   340篇
  国内免费   82篇
电工技术   125篇
综合类   184篇
化学工业   1499篇
金属工艺   74篇
机械仪表   85篇
建筑科学   521篇
矿业工程   70篇
能源动力   194篇
轻工业   148篇
水利工程   22篇
石油天然气   466篇
无线电   221篇
一般工业技术   238篇
冶金工业   135篇
原子能技术   18篇
自动化技术   53篇
  2024年   25篇
  2023年   94篇
  2022年   220篇
  2021年   282篇
  2020年   156篇
  2019年   125篇
  2018年   101篇
  2017年   96篇
  2016年   143篇
  2015年   130篇
  2014年   192篇
  2013年   187篇
  2012年   233篇
  2011年   230篇
  2010年   158篇
  2009年   209篇
  2008年   155篇
  2007年   181篇
  2006年   168篇
  2005年   151篇
  2004年   120篇
  2003年   125篇
  2002年   93篇
  2001年   103篇
  2000年   83篇
  1999年   65篇
  1998年   43篇
  1997年   26篇
  1996年   29篇
  1995年   26篇
  1994年   19篇
  1993年   18篇
  1992年   14篇
  1991年   15篇
  1990年   4篇
  1989年   8篇
  1988年   4篇
  1987年   7篇
  1985年   3篇
  1984年   3篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1977年   1篇
  1951年   2篇
排序方式: 共有4053条查询结果,搜索用时 15 毫秒
41.
In this paper, the ethylene adsorption capacities of the nano-sized carbon hollow spheres (CNB) and active carbon (AC), the Pd (PdCl2) impregnated CNB or AC (Pd/CNB, Pd/AC) and heat treatment under various conditions, were studied at different ethylene concentrations from 64 to 1060 ppm. The results indicated that AC had a good ethylene adsorption capacity at high ethylene concentration. Pd impregnation decreased the ethylene adsorption capacity of AC. Heat treatment and H2 activation could increase the ethylene adsorption capacity, but also lowered than AC itself. CNB had lower ethylene adsorption capacity than AC, but heat treatment and H2 activation could increase its ethylene adsorption capacity markedly. With activating condition from heat treatment in N2 at 300 °C to activation in H2/N2 at 100 °C, to activation in H2 at 200 °C, and to activation in H2 at 300 °C, the ethylene adsorption capacity of Pd/CNB was increased regularly. At low ethylene concentration, viz., 64 ppm, the ethylene adsorption quantities (q a) by Pd/CNB activated in H2 at 200 or 300 °C were higher than any other adsorbents. So, activated in H2 atmosphere at higher than 100 °C, Pd/CNB is particularly advantaged for adsorbing low concentration of ethylene. Amongst all the adsorbents used, Pd/CNB activated in H2 atmosphere at 300 °C for 2 h has the highest ethylene adsorption capacity at lower concentration than 125 ppm. In addition, all the CNB, Pd/CNB, AC, and Pd/AC samples can be easily regenerated in airflow for more than 3 h.  相似文献   
42.
介绍流动床离子交换装置回收催化剂的生产工艺,从交换装置的选择到运行,分析了流动床的优点、影响因素以及生产中应注意的问题和要求。  相似文献   
43.
44.
45.
废橡胶再生技术研究进展   总被引:12,自引:0,他引:12  
综述了废橡胶再生利用的技术和方法,介绍了废橡胶的物理再生、化学再生的再行剂和微生物再生方法及进展,并对化学再生助剂、植物再生剂和生物再生助剂的再生效果进行了系统评述。  相似文献   
46.
阐述了离子膜法烧碱系统中螯合树脂塔的工艺设计和生产中已出现和可能出现的问题,并介绍了解决问题的方法。  相似文献   
47.
ABSTRACT

This study explores an electrochemical adsorption method on the regeneration of aqueous drilling fluid waste. Response surface analysis was applied to investigating the electrochemical factors on the adsorption performance. The response surface polynomial model optimized the preferred electrochemical adsorption conditions with adsorption time of 20 min, spacing electrodes of 5 cm, adsorption concentration of 5% and NaCl concentration of 2 g/L. The model calculated electrochemical adsorption amount of drilling fluid showed only 1.3% deviation from the experimental results. Thus, the model could provide effective support for the device design and application of drilling fluid electrochemical adsorption process.  相似文献   
48.
In this study, we explored a new ion exchange material synthesized by radical polymerization of styrene and 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid by using 2,2′‐azo‐isobutyronitrile (1 mol %) and divinylbenzene (0.5 mol %) as initiator and crosslinking reagents, respectively. The resin was obtained from a large excess (90%) of styrene in the feed. The yield was 72.3%. The resin was completely insoluble in water and characterized by elemental analysis, FTIR spectroscopy, scanning electron microscopy, and thermal analysis. The metal ion retention capability was investigated for Ag(I), Hg(II), Cd(II), Zn(II), Pb(II), and Cr(III). The effect of pH, time, and resin/metal ion mol ratio on the metal ion retention was studied. Selectivity of the resins from a mixture of metal ions and the maximum retention capacity at optimum pH were also determined. The recovery of the resin by using 1 and 4 M HClO4 and HNO3 demonstrated that it is possible to recover the resin above 80%. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1230–1235, 2003  相似文献   
49.
闫健  王亚军 《中国氯碱》2006,(11):19-21
介绍了盐水二次精制的工艺流程、操作方法以及树脂塔的再生原理和注意问题。通过加强对盐水二次精制生产条件和螯舍树脂再生过程的控制,提高了树脂性能,保证了螯合能力的发挥,生产的合格精制盐水满足了离子膜电解生产的要求。  相似文献   
50.
A micro-envioment for nerve cells and tissue growth were designed and constructed via surface modification of poly(L-lactide-co-glycolide)(PLGA) with chitosan and hydroxyapatite(HA). The poly(L-lactide-co-glycolide)/chitosan/hydroxyapatite (PLGA/chitosan/HA) conduits were manufactured by a combined solvent casting and particulate leaching technique. The conduits were highly porous with an interconnected pore structure and 76.5% porosity. Micropores with 50–100 micrometer diameter were formed in the conduits. In vivo application of PLGA/chitosan/HA conduits for reconstruction of 10 mm sciatic nerve defect was assessed by the walking track analysis, the quantifying of the wet weight of tibialis anterior muscle and the histological assessment. The conduits in host rats in vivo can not only be an effective in promoting regenerating of nerves but can also lead to favorable nerve functional recovery. Funded by the National Natural Science Foundation of China(No.50774096)  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