全文获取类型
收费全文 | 5389篇 |
免费 | 474篇 |
国内免费 | 201篇 |
专业分类
电工技术 | 10篇 |
综合类 | 328篇 |
化学工业 | 3388篇 |
金属工艺 | 112篇 |
机械仪表 | 42篇 |
建筑科学 | 58篇 |
矿业工程 | 92篇 |
能源动力 | 51篇 |
轻工业 | 456篇 |
水利工程 | 26篇 |
石油天然气 | 1002篇 |
武器工业 | 19篇 |
无线电 | 67篇 |
一般工业技术 | 349篇 |
冶金工业 | 48篇 |
原子能技术 | 4篇 |
自动化技术 | 12篇 |
出版年
2024年 | 6篇 |
2023年 | 56篇 |
2022年 | 76篇 |
2021年 | 87篇 |
2020年 | 104篇 |
2019年 | 139篇 |
2018年 | 124篇 |
2017年 | 163篇 |
2016年 | 196篇 |
2015年 | 172篇 |
2014年 | 266篇 |
2013年 | 310篇 |
2012年 | 380篇 |
2011年 | 345篇 |
2010年 | 291篇 |
2009年 | 281篇 |
2008年 | 242篇 |
2007年 | 366篇 |
2006年 | 366篇 |
2005年 | 339篇 |
2004年 | 286篇 |
2003年 | 273篇 |
2002年 | 258篇 |
2001年 | 182篇 |
2000年 | 172篇 |
1999年 | 137篇 |
1998年 | 115篇 |
1997年 | 61篇 |
1996年 | 61篇 |
1995年 | 51篇 |
1994年 | 36篇 |
1993年 | 26篇 |
1992年 | 37篇 |
1991年 | 11篇 |
1990年 | 17篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1984年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有6064条查询结果,搜索用时 15 毫秒
21.
22.
Marcel Richter Yuriy Zakrevskyy Michael Eisele Nino Lomadze Svetlana Santer Regine v. Klitzing 《Polymer》2014
The contraction/swelling transition of anionic PNIPAM-co-AAA particles can be manipulated by light using interactions with cationic azobenzene-containing surfactant. In this study the influence of pH-buffers and their concentrations, the charge density (AAA content) in microgel particles as well as the spacer length of the surfactant on the complex formation between the microgel and surfactant is investigated. It is shown that the presence of pH buffer can lead to complete blocking of the interactions in such complexes and the resulting microgel contraction/swelling response. There is a clear competition between the buffer ions and the surfactant molecules interacting with microgel particles. When working in pure water solutions with fixed concentration (charge density) of microgel, the contraction/swelling of the particles is controlled only by relative concentration (charge ratio) of the surfactant and AAA groups of the microgel. Furthermore, the particle contraction is more efficient for shorter spacer length of the surfactant. The onset point of the contraction process is not affected by the surfactant hydrophobicity. This work provides new insight into the interaction between microgel particles and photo-sensitive surfactants, which offers high potential in new sensor systems. 相似文献
23.
Highly monodisperse polystyrene nanoparticles with mean diameters of less than 100 nm are synthesized via aqueous emulsion polymerization using an amphoteric initiator (VA-057) in the presence of sub-millimolar concentrations of anionic surfactant. Since the net charge on the initiator is almost zero at neutral pH, the resultant latex particle size is mainly determined by surfactant adsorption. Polymerizations were performed in the presence of a range of anionic surfactants with differing critical micelle concentrations (CMC) by varying the concentrations of surfactant, initiator and monomer, and also the ionic strength. Sodium dodecyl benzene sulfonate (SDBS), sodium hexadecyl sulfate (SHS), and sodium octadecyl sulfate (SOS) have relatively low CMCs and so enable formation of highly monodisperse nanoparticles at relatively low (sub-millimolar) surfactant concentrations, CS (i.e. below the CMC in each case). Empirically, it was found that the particle number, Np, and coefficient of variation of the particle size, CV, were strongly dependent on the CS/CMC ratio: Np increased almost in proportion with the square of this ratio, while the CV exhibited a minimum at approximately CS/CMC = 0.20. Higher ionic strength reduced the particle size, which is consistent with the above relationship because the addition of salt lowers the CMCs of ionic surfactants. Polymer latex particles produced using such formulations form highly regular, close-packed colloidal arrays. 相似文献
24.
Knowledge of the wetting characteristic of mineral surfaces is very important in enhancing the efficiency of separation of valuable minerals from gangue using froth flotation or oil agglomeration. In this paper a capillary rise technique was used to characterize the glass beads surface modified with cationic surfactant. The glass microspheres were used as model particles with a spherical shape and smooth surface to eliminate the roughness effect. The value of the contact angle for water was found to be 21.5 for unmodified beads, and 61.8, 89.7, 68.4 for 0.1, 1.0, 10 mg/gsolid of CTAB, and 39.8, 68.6, 87.9 for 0.1, 1.0, 10 mg/gsolid of DDAHCl, respectively. Data revealed that the adsorption of surfactant onto glass beads decreased the value of the electron donor component, γ-, which defines the hydrophobicity of the surface. Also, the property of the surface was investigated by flotation and oil agglomeration experiments. It was observed that particles with low value of contact angle for water and high for 1-bromonaphthalene and low value of γ- were floated with a recovery equal to 91.1 and 83.1% for CTAB and DDAHCl, respectively, and effectively agglomerated. This indicates that the capillary rise method can be successfully used to predict the wetting properties of solid particles in mineral processing. 相似文献
25.
26.
针对AP-P4/SDBS聚表二元体系,选用不同浓度配方的聚表体系,在石英砂上展开静态吸附和动态滞留实验,研究聚表体系中各组分的吸附规律,考察了浓度、温度、矿化度对组分的吸附影响。结果表明,聚表二元体系中各组分在石英砂上的吸附符合Langmuir吸附模式,其中,SDBS表现为双分子层吸附、AP-P4表现为单分子层吸附特质。AP-P4与SDBS存在竞争吸附关系,SDBS的吸附量是AP-P4的20多倍。温度和矿化度升高,SDBS的吸附量增大。聚表二元体系中SDBS的动态滞留量小于其静态吸附量,而AP-P4的动态滞留量大于其静态吸附量。 相似文献
27.
以测试表面活性剂溶液在固体表面铺展能力的方法,研究了温度、湿度和外加电解质浓度对新型双尾三硅氧烷表面活性剂1 L溶液在石蜡等低能固体表面的铺展性能的影响,结果表明:测试铺展性能也能大致求出表面活性剂1L的临界润湿浓度(CWC);1L溶液的铺展能力是随着温度和湿度的升高而增强的;较低的外加电解质浓度有助于提高1L溶液的铺展性能。实验说明,表面活性剂1L作为润湿剂或铺展剂使用时可以选择在较高的温度和(或)湿度下使用,以及(或者)通过添加适量的电解质的方法来提升其铺展能力,而且使用的浓度应该要在其CWC以上。 相似文献
28.
29.
介绍了表面活性剂的基本性质、作用、分类及其化学结构与物理性质的关系,系统地介绍了表面活性剂在电镀和电镀废水处理中的应用,并说明了表面活性剂未来的应用及发展前景。 相似文献
30.