全文获取类型
收费全文 | 285904篇 |
免费 | 7060篇 |
国内免费 | 2831篇 |
专业分类
电工技术 | 6827篇 |
技术理论 | 6篇 |
综合类 | 2696篇 |
化学工业 | 46455篇 |
金属工艺 | 12501篇 |
机械仪表 | 9263篇 |
建筑科学 | 8688篇 |
矿业工程 | 2431篇 |
能源动力 | 6351篇 |
轻工业 | 27655篇 |
水利工程 | 3358篇 |
石油天然气 | 7258篇 |
武器工业 | 450篇 |
无线电 | 30631篇 |
一般工业技术 | 52416篇 |
冶金工业 | 48363篇 |
原子能技术 | 5965篇 |
自动化技术 | 24481篇 |
出版年
2022年 | 2345篇 |
2021年 | 3680篇 |
2020年 | 2621篇 |
2019年 | 2866篇 |
2018年 | 4161篇 |
2017年 | 4333篇 |
2016年 | 4521篇 |
2015年 | 3858篇 |
2014年 | 5843篇 |
2013年 | 12899篇 |
2012年 | 9276篇 |
2011年 | 11939篇 |
2010年 | 9583篇 |
2009年 | 10042篇 |
2008年 | 10782篇 |
2007年 | 10796篇 |
2006年 | 9641篇 |
2005年 | 8548篇 |
2004年 | 7385篇 |
2003年 | 6841篇 |
2002年 | 6771篇 |
2001年 | 6794篇 |
2000年 | 6420篇 |
1999年 | 6488篇 |
1998年 | 13424篇 |
1997年 | 9987篇 |
1996年 | 7765篇 |
1995年 | 5929篇 |
1994年 | 5420篇 |
1993年 | 5204篇 |
1992年 | 4145篇 |
1991年 | 3920篇 |
1990年 | 3946篇 |
1989年 | 3869篇 |
1988年 | 3623篇 |
1987年 | 3085篇 |
1986年 | 3093篇 |
1985年 | 3439篇 |
1984年 | 3352篇 |
1983年 | 3088篇 |
1982年 | 2707篇 |
1981年 | 2914篇 |
1980年 | 2652篇 |
1979年 | 2847篇 |
1978年 | 2740篇 |
1977年 | 2842篇 |
1976年 | 3697篇 |
1975年 | 2458篇 |
1974年 | 2290篇 |
1973年 | 2320篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Mineralization of Para-Chlorobenzoic Acid in Water by Cobalt-Incorporated MCM-41 Catalyzed Ozonation
Cobalt-incorporated MCM-41(Co-MCM-41) was used as a heterogeneous catalyst for the ozonation of para-chlorobenzoic acid (p-CBA) in aqueous solution. Cobalt oxide supported on MCM-41(Co/MCM-41) was synthesized for comparison. Their textural properties were elucidated by various characterization techniques to understand the relationship between surface texture and catalytic activity. TOC removal at 60 min reached 91% with Co-MCM-41, 83% with Co/MCM-41 and only 52% with ozone alone, respectively. Observations from diffuse reflection spectroscopy demonstrated that different metal phases were formed in these cobalt-modified molecular sieves samples. Radical scavenger experiments indicated the formation of hydroxyl radicals that were responsible for the effective degradation of p-CBA. An integrated approach to the catalytic mechanism was proposed by considering the variation of pH in the course of ozonation as well as its subsequent influence on the dissociation of targeted compounds and surface charge of the catalyst. In the reusability experiments, the reused Co-MCM-41 was able to regain the same catalytic capability as the fresh one within 5 cycles. X-ray photoelectron spectroscopy results indicated that a part of Co2+ was oxidized to Co3+ after oxidation reaction. 相似文献
72.
73.
74.
High Temperature - The temperature dependences of the viscosity of liquid Fe90B x Si(10 − x) alloys are studied in the mode of heating and subsequent cooling. The temperature dependences of... 相似文献
75.
Russian Engineering Research - Formulas are derived for the most important parameters of channel extrusion. 相似文献
76.
A conceptualization of intended learning outcomes supporting self‐regulated learners in indicating learning paths
下载免费PDF全文
![点击此处可从《Journal of Computer Assisted Learning》网站下载免费的PDF全文](/ch/ext_images/free.gif)
P. Tangworakitthaworn L. Gilbert G.B. Wills 《Journal of Computer Assisted Learning》2015,31(5):393-404
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs. 相似文献
77.
78.
79.
80.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)