全文获取类型
收费全文 | 285632篇 |
免费 | 4051篇 |
国内免费 | 1305篇 |
专业分类
电工技术 | 4922篇 |
综合类 | 526篇 |
化学工业 | 41996篇 |
金属工艺 | 11253篇 |
机械仪表 | 8734篇 |
建筑科学 | 6734篇 |
矿业工程 | 1589篇 |
能源动力 | 7306篇 |
轻工业 | 23864篇 |
水利工程 | 3144篇 |
石油天然气 | 5818篇 |
武器工业 | 45篇 |
无线电 | 33993篇 |
一般工业技术 | 57652篇 |
冶金工业 | 51681篇 |
原子能技术 | 7547篇 |
自动化技术 | 24184篇 |
出版年
2021年 | 2525篇 |
2020年 | 1872篇 |
2019年 | 2323篇 |
2018年 | 3908篇 |
2017年 | 4003篇 |
2016年 | 4271篇 |
2015年 | 2742篇 |
2014年 | 4670篇 |
2013年 | 12619篇 |
2012年 | 7578篇 |
2011年 | 10315篇 |
2010年 | 7930篇 |
2009年 | 9203篇 |
2008年 | 9487篇 |
2007年 | 9467篇 |
2006年 | 8099篇 |
2005年 | 7467篇 |
2004年 | 7370篇 |
2003年 | 7132篇 |
2002年 | 6868篇 |
2001年 | 6953篇 |
2000年 | 6589篇 |
1999年 | 6862篇 |
1998年 | 16589篇 |
1997年 | 11788篇 |
1996年 | 9053篇 |
1995年 | 6925篇 |
1994年 | 6065篇 |
1993年 | 6119篇 |
1992年 | 4422篇 |
1991年 | 4202篇 |
1990年 | 4095篇 |
1989年 | 4076篇 |
1988年 | 3771篇 |
1987年 | 3403篇 |
1986年 | 3410篇 |
1985年 | 3758篇 |
1984年 | 3479篇 |
1983年 | 3240篇 |
1982年 | 3038篇 |
1981年 | 3053篇 |
1980年 | 3044篇 |
1979年 | 2842篇 |
1978年 | 2875篇 |
1977年 | 3153篇 |
1976年 | 4122篇 |
1975年 | 2423篇 |
1974年 | 2386篇 |
1973年 | 2402篇 |
1972年 | 2022篇 |
排序方式: 共有10000条查询结果,搜索用时 126 毫秒
81.
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
82.
83.
84.
85.
86.
87.
Rodríguez-Pérez Ángel Mariano Pérez-Calañas Cinta Pulido-Calvo Inmaculada 《Water Resources Management》2021,35(6):1977-1990
Water Resources Management - This paper aims to evaluate the possibility of using non-utilized hydraulic energy in urban water distribution systems. For this purpose, the viability and possible... 相似文献
88.
Wireless Personal Communications - Cloud computing is a growing technology where lot of heterogeneous resources are available and large amount of requests are submitted by the customers... 相似文献
89.
Maria A. Ospina Monica Pizarro Thierry Tran Julien Ricci John Belalcazar Jorge L. Luna Luis F. Londoño Sandra Salazar Hernan Ceballos Dominique Dufour Luis A. Becerra Lopez-Lavalle 《International Journal of Food Science & Technology》2021,56(3):1343-1353
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes. 相似文献
90.
Influence of Wheel Blunting on the Machining Precision in CNC Plunge Grinding: Digital Twin Analysis
Akintseva A. V. Pereverzev P. P. Prokhorov A. V. Omel’chenko S. V. 《Russian Engineering Research》2022,42(7):726-730
Russian Engineering Research - The machining precision in grinding a flexible shaft by sharp and blunt wheels is compared for a CNC system with a specified cycle of radial supply velocities. To... 相似文献