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   3067篇
  免费   317篇
  国内免费   138篇
电工技术   51篇
综合类   232篇
化学工业   1462篇
金属工艺   74篇
机械仪表   34篇
建筑科学   202篇
矿业工程   221篇
能源动力   27篇
轻工业   442篇
水利工程   85篇
石油天然气   228篇
武器工业   3篇
无线电   46篇
一般工业技术   279篇
冶金工业   84篇
原子能技术   42篇
自动化技术   10篇
  2024年   23篇
  2023年   60篇
  2022年   85篇
  2021年   99篇
  2020年   95篇
  2019年   108篇
  2018年   103篇
  2017年   129篇
  2016年   129篇
  2015年   111篇
  2014年   151篇
  2013年   190篇
  2012年   260篇
  2011年   211篇
  2010年   154篇
  2009年   167篇
  2008年   119篇
  2007年   180篇
  2006年   203篇
  2005年   135篇
  2004年   122篇
  2003年   107篇
  2002年   91篇
  2001年   80篇
  2000年   51篇
  1999年   53篇
  1998年   44篇
  1997年   48篇
  1996年   38篇
  1995年   35篇
  1994年   34篇
  1993年   17篇
  1992年   15篇
  1991年   11篇
  1990年   6篇
  1989年   7篇
  1988年   12篇
  1987年   5篇
  1986年   6篇
  1985年   7篇
  1984年   6篇
  1983年   4篇
  1982年   1篇
  1980年   1篇
  1978年   1篇
  1976年   2篇
  1975年   4篇
  1973年   1篇
  1951年   1篇
排序方式: 共有3522条查询结果,搜索用时 17 毫秒
1.
While perfluoroalkyl acids (PFAAs), also known as C8s, are used extensively in textile repellent coatings, concerns have arisen for their carcinogenicity and hazardous effects on the environment. In this study, a novel water-based, nonfluoro, and nanobrush textile repelling agent was prepared by conventional sol–gel chemistry using amorphous fumed silica and n-octyltriethoxysilane as the starting materials. Minimal interaction between the designed repelling agent and marketed water-based resins was confirmed using linear viscosity region (LVR) analysis and asymmetric-flow field-flow fractionation (AF4), suggesting the self-stratification potential of the repelling agent. More specifically, the repelling agent exhibited excellent compatibility and self-stratifying ability with a force-emulsified acrylic-based resin, affording a water contact angle of 104.3° when incorporated at 7% solid content. Performance tests carried out on thermoplastic polyurethane (TPU) revealed excellent adhesion (100/100) of a final formulation, and a significant increase in water contact angle from 80.1° to 103.8° after treatment. In addition, the fouling area after the removal of a submerged sample from a mixture of slurry, polymer, and oil decreased from 48 to 1% when the repelling agent was added. Moreover, the sludge-fouling property remained unchanged after 1000 cycles of abrasion. These findings demonstrate the potential of the described nonfluoro, nanobrush repelling agent as an environmentally safe alternative for use with commercial resins, in turn realizing a fully water-based hydrophobic coating. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48003.  相似文献   
2.
轻质滤料滤池的试验与研究   总被引:1,自引:0,他引:1  
轻质滤料滤池是以比水密度略小的滤料为滤床的滤池,通过以净水厂的原水和污水处理厂的二级处理出水为过滤试验对象,所取得的结果表明:下向流轻质滤料滤池对浊度和悬浮固体(SS)的去除率分别可以达到80%和45%,而滤床的水头损失不超过15cm。因此轻质滤料滤池可以以预过滤的形式配置在过滤处理的净水和污水的处理工艺中。  相似文献   
3.
The object of this study was to investigate the loss of hydrophobic polypeptides, which are important for foam quality and stability in finished beer. Loss of hydrophobic polypeptide due to fermenter foaming occurs during transfer of fermented wort since a gradient of hydrophobic polypeptides towards the surface is created during fermentation. Due to higher polyphenol levels in high gravity (20°Plato) wort, more hydrophobic polypeptides are lost due to cold break (cold trub) precipitation compared to low gravity (12°Plato) wort. Another important factor affecting the loss of hydrophobic polypeptides could be proteinase A activity during fermentation, especially in high gravity fermentation where the yeast is exposed the higher stress. During high gravity fermentation, where osmotic pressures are higher, ethanol levels become greater, and nitrogen‐carbohydrate ratios are lower, more proteinase A is released by the yeast. This release of proteinase A into fermenting wort could have implications for the foam stability of the finished product.  相似文献   
4.
Preparation of clean coal by flotation following ultra fine liberation   总被引:1,自引:0,他引:1  
This paper reports the results of current fundamental research at the Department of Process Engineering, University of Miskolc on the processing of clean coal from Mecsek bituminous coal, Southern Hungary. The theoretical possibility of the separation of different petrographic components was proven experimentally and their liberation degree was determined based on the petrographic composition, flotation kinetic study of isolated components (groups of components), scanning electron microscopy and microprobe analyses. The mill with stirred ball media was chosen for the ultra-fine liberation of the coal components. It was revealed that along with the liberation of coal components, their surface oxidation and spontaneous agglomeration, entrapping the mineral impurities take place in ultra-fine grinding. This paper discusses the interfacial phenomena occurring in the ultra-fine grinding process and their influence on the flotation. The concept for the advanced preparation of clean coal was developed, tested and proved. The main steps of this concept are the ultra-fine liberation in the stirred-media mill, the de-agglomeration of flocs spontaneously formed during the ultra-fine grinding and the induced (hydrophobic) flocculation with the following two-step flotation in a flotation column.  相似文献   
5.
6.
一种两性离子聚合物的合成性能及应用分析   总被引:2,自引:0,他引:2  
本文合成了一种两性离子聚合物:丙烯酰胺—二甲基二烯丙基氯化铵—丙烯酸共聚物(PADA),讨论了三种单体的投料比对产物的组成影响。对它的结构进行了红外表征,就其絮凝、粘土防膨、抗温、抗盐性能进行了研究。结果表明:PADA具有好的防膨能力和良好的抗温抗盐性能,并有絮凝能力。  相似文献   
7.
溶胶-凝胶法制备疏水型SiO-2气凝胶   总被引:2,自引:0,他引:2  
以正硅酸乙酯 (TEOS)为硅源 ,用三甲基氯硅烷 (TMCS)为疏水试剂 ,通过溶胶 凝胶法在室温下制备出疏水型SiO2 气凝胶。用傅立叶变温红外 (FT IR)、扫描电镜 (SEM)、透射电镜 (TEM)和吸水性能对疏水型SiO2气凝胶的结构和性能进行了研究  相似文献   
8.
一种有机硫类絮凝剂DTC的合成及性能评价   总被引:1,自引:0,他引:1  
李丽  刘伟 《油田化学》2007,24(1):48-52
讨论了由有机伯胺或仲胺和CS2合成二硫代氨基甲酸盐DTC的反应及副反应,简介了合成工艺。根据红外光谱确认了由三乙烯四胺合成的二硫代氨基甲酸盐(以下简称DTC)的结构。以含原油350 mg/L、含悬浮固体55.1 mg/L,含Fe^2+10.0 mg/L的模拟污水为实验水样,考察了该DTC的絮凝性能,在40℃、pH=6-7、沉降时间30分钟条件下DTC的适宜加量为20 mg/L,此时污水含油量为9.0 mg/L;使用DTC的适宜pH范围在4-8,pH=6为最佳值,适宜温度范围为10-45℃,温度高于45℃时DTC可发生热分解;DTC的除油效果随污水中Fe^2+浓度增大而改善。在含油89.1 mg/L、含悬浮固体55.1 mg/L、含Fe^2+13.2 mg/L的油田污水中,DTC的除油率最高,远高于常用絮凝剂PFS,PAC,CPAM,HPAM和PAM。当污水中不含Fe^2+时,DTC无絮凝除油效果。讨论了DTC在Fe^2+参与下的絮凝过程。图5表1参8。  相似文献   
9.
应用 p H电位滴定法研究了配合物 Zn( Aa) 2 [Aa-=L- val(缬氨酸根 ) ,L- phe(苯丙氨酸根 ) ,L- trp(色氨酸根 ) ,L- tyr(酪氨酸根 ) ]在水和 2 0 %、40 %及 60 %二氧六环 /水溶液中的稳定性 [t=2 5℃ ,c=0 .1 mol/L Na Cl O4]。配合物 Zn( Aa) 2 相对于母体配合物 Zn( Aa) + 稳定性用Δlog K=log KZn( Aa)Zn( Aa) 2 - log KZn Zn( Aa) 表示。结果表明 :与 L-丙氨酸 ( L- ala)配合物 Zn( L- ala) 2 相比 ,所有这些氨基酸配合物 Zn( Aa) 2 均具有相对较大的 Δlog K值 ,表明这些配合物分子内存在着额外的稳定化作用。这种稳定性化作用可能主要归因于配合物分子内氨基酸侧链之间的疏水作用 ,并且这种作用随着氨基酸侧链结构及溶剂极性变化而变化  相似文献   
10.
Thermodynamic parameters have been determined for the interaction of methyl orange and poly(vinylpyrrolidone) in aqueous solutions containing tris, tris and hydrochloric acid, or water only. Enthalpy changes were determined by use of a flow microcalorimeter. Free energy changes were calculated from the results of equilbrium dialysis studies. The results are interpreted in terms of the behaviour of poly(vinylpyrrolidone) in these systems. Analysis of data shows that the hydrophobic interactions in the systems are in the order: tris > wateronly > tris-HC1.  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