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   6284篇
  免费   488篇
  国内免费   238篇
电工技术   14篇
综合类   385篇
化学工业   3871篇
金属工艺   126篇
机械仪表   52篇
建筑科学   81篇
矿业工程   115篇
能源动力   60篇
轻工业   496篇
水利工程   28篇
石油天然气   1204篇
武器工业   20篇
无线电   74篇
一般工业技术   396篇
冶金工业   60篇
原子能技术   10篇
自动化技术   18篇
  2024年   9篇
  2023年   61篇
  2022年   103篇
  2021年   107篇
  2020年   126篇
  2019年   155篇
  2018年   144篇
  2017年   194篇
  2016年   236篇
  2015年   210篇
  2014年   321篇
  2013年   357篇
  2012年   460篇
  2011年   424篇
  2010年   333篇
  2009年   350篇
  2008年   288篇
  2007年   418篇
  2006年   419篇
  2005年   372篇
  2004年   311篇
  2003年   298篇
  2002年   277篇
  2001年   200篇
  2000年   193篇
  1999年   150篇
  1998年   138篇
  1997年   67篇
  1996年   64篇
  1995年   57篇
  1994年   40篇
  1993年   27篇
  1992年   39篇
  1991年   13篇
  1990年   19篇
  1989年   6篇
  1988年   4篇
  1987年   8篇
  1986年   3篇
  1984年   4篇
  1980年   1篇
  1951年   4篇
排序方式: 共有7010条查询结果,搜索用时 15 毫秒
21.
综述了助剂、添加剂和表面活性剂的发展概况和投资热点。  相似文献   
22.
介绍了控制烷基磺酸钠型砂的混砂工艺、配制要点及保存使用等控制要点,并就实际生产中可能出现的一些问题作了探讨,提出了解决的办法。  相似文献   
23.
摘要:研究以阳离子表面活性剂HDTMA改性天然斜发沸石,制得HDTMA改性沸石,进而研究HDTMA改性沸石对废水中Cr(VI)的吸附特征。结果表明:HDTMAL改性沸石对cr(VI)吸附符合Langmuir等温式和拟二级动力学方程,饱和吸附量为10.99mg/g,吸附主要为化学吸附,但温度、pH值和干扰离-~HDTMA沸石吸附cr(VI)具有明显影响。  相似文献   
24.
Objective: To investigate the modulation of the wettability of excipients by different types of surfactants and its impacts on the disintegration of tablets and drug release.

Materials and methods: The critical micelle concentration (CMC) of surfactants, including sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), dodecyl trimethyl ammonium bromide (DTAB), cetyltrimethyl ammonium bromide (CTAB) and polysorbate (Tween-20 and Tween-80), was obtained using the platinum ring method. Contact angles of surfactant solutions on the excipient compacts and double-distilled water on the mixture of surfactant and the other excipient (magnesium stearate (MgSt) or sodium alginate (SA)) were measured by the sessile drop technique. Besides, surface free energy of excipients was calculated by the Owens method. Finally, the disintegration of tablets and in vitro dissolution testing were performed according to the method described in USP.

Results and discussion: The wettability of excipients could be enhanced to different extent with low concentration of surfactant solutions and maintained stable basically after CMC. For MgSt (hydrophobic excipient), the shorter the hydrophobic chain (C12, including SDS and DTAB), the better the wettability with the addition of surfactant in the formulation, leading to the shorter disintegration time of tablets and higher drug release rate. In contrast, the wettability of SA (hydrophilic excipient) was reduced by adding surfactant, resulting in the longer disintegration time of tablets and lower release rate.

Conclusion: The modulation of the wetting of pharmaceutical excipients by surfactant had changed the disintegration time of tablets and drug release rate to a greater extent.  相似文献   

25.
Polypyrrole (PPR)–carbon nanotube (CNT) films were prepared by an electrodeposition method, combining PPR electropolymerization and anaphoresis of CNT. PPR polymerization experiments showed advantages of a dopant from the catechol family for the deposition of PPR films at reduced electrode potentials. The method allowed the formation of adherent films on stainless steel substrates. The amphiphilic molecules with steroid-like structures, such as carbenoxolone disodium salt, glycyrrhizic acid, ammonium salt, and sodium taurodeoxycholate, were used for dispersion and charging of CNT. The new dispersing agents showed outstanding dispersion ability. In addition to dispersing properties, electrodeposition experiments revealed film-forming properties of carbenoxolone and ability to form pure carbenoxolone or carbenoxolone–CNT films. The PPR–CNT films formed using carbenoxolone disodium salt, glycyrrhizic acid ammonium salt, and sodium taurodeoxycholate showed diverse microstructural features. The dispersion and deposition mechanisms were discussed.  相似文献   
26.
In this work, the effects of the presence of surfactants in the liquid phase and the hydrodynamic regime of the bubble flow on the oxygen transfer rate were investigated in an electroflotation process in batch mode. The volumetric mass transfer coefficient KLα and the oxygenation capacity were evaluated to improve the performances of the electroflotation process in terms of oxygenation. In order to evaluate the liquid-side mass transfer coefficient KLα the volumetric mass transfer coefficient KLα was dissociated into KL and the specific interracial area (a) since the last one was obtained from the gas hold-up and the bubble diameter. The effect of Reynolds number which define the hydrodynamic of the bubble flow has been also studied. Models of KLa and KL have been established to show the effects of the hydrodynamic parameters and liquid phase characteristics on the oxygen transfer rate.  相似文献   
27.
Turbulence transport of surfactant solution flow during drag reduction degeneration is investigated experimentally in a two-dimensional channel.Particle Image Velocimetry (P1V) system is used to take t...  相似文献   
28.
Life-cycle inventories were compiled to characterize natural resource requirements and environmental emissions associated with the sourcing and production of selected, detergent-grade surfactants and surfactant feedstocks. Petrochemical surfactant types examined were linear alkylbenzene sulfonate, alcohol sulfate (AS), alcohol ethoxylate (AE) and alcohol ethoxylate sulfate (AES). Oleochemical surfactants derived from palm oil, palm kernel oil and inedible tallow were AS, AE, AES and (for palm oil and tallow) methyl ester sulfonate. It was determined that natural resource requirements were primarily related to the source of feedstock and secondarily to surfactant type. Likewise, the composition and mass of atmospheric, aqueous and solid emissions were principally determined by feedstock source. Energy requirements varied as a function of both feedstock and surfactant type. The inventories do not support fundamental shifts in surfactant usage or feedstock sourcing on the basis of environmental concerns, as no single surfactant or feedstock was identified as superior across all resource and emissions criteria examined. The data provide baselines for evaluating opportunities for resource optimization, pollution prevention and waste minimization within each production technology surveyed.  相似文献   
29.
烷基糖苷—新型世界级表面活性剂   总被引:42,自引:0,他引:42  
本文综述了烷基糖苷的合成方法、物化性能及应用性能。  相似文献   
30.
介孔氧化硅薄膜在膜分离、传感器件、异相催化、低介电常数微电子绝缘片的应用方面具有潜在应用价值。首先简要介绍了介孔薄膜的制备途径,然后重点综述了介孔氧化硅薄膜的研究进展。  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