全文获取类型
收费全文 | 169420篇 |
免费 | 1405篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 2568篇 |
综合类 | 121篇 |
化学工业 | 26880篇 |
金属工艺 | 9498篇 |
机械仪表 | 5752篇 |
建筑科学 | 3051篇 |
矿业工程 | 1888篇 |
能源动力 | 2757篇 |
轻工业 | 8909篇 |
水利工程 | 2752篇 |
石油天然气 | 8697篇 |
武器工业 | 12篇 |
无线电 | 14598篇 |
一般工业技术 | 38479篇 |
冶金工业 | 27840篇 |
原子能技术 | 6974篇 |
自动化技术 | 10254篇 |
出版年
2019年 | 1641篇 |
2018年 | 3043篇 |
2017年 | 3161篇 |
2016年 | 3437篇 |
2015年 | 1708篇 |
2014年 | 3012篇 |
2013年 | 6418篇 |
2012年 | 4380篇 |
2011年 | 5482篇 |
2010年 | 4477篇 |
2009年 | 4932篇 |
2008年 | 4981篇 |
2007年 | 4894篇 |
2006年 | 4154篇 |
2005年 | 3828篇 |
2004年 | 3640篇 |
2003年 | 3524篇 |
2002年 | 3458篇 |
2001年 | 3469篇 |
2000年 | 3365篇 |
1999年 | 3214篇 |
1998年 | 7030篇 |
1997年 | 5155篇 |
1996年 | 3831篇 |
1995年 | 2923篇 |
1994年 | 2598篇 |
1993年 | 2726篇 |
1992年 | 2258篇 |
1991年 | 2308篇 |
1990年 | 2416篇 |
1989年 | 2321篇 |
1988年 | 2322篇 |
1987年 | 2193篇 |
1986年 | 2248篇 |
1985年 | 2294篇 |
1984年 | 2207篇 |
1983年 | 2136篇 |
1982年 | 1982篇 |
1981年 | 2196篇 |
1980年 | 2055篇 |
1979年 | 2272篇 |
1978年 | 2431篇 |
1977年 | 2432篇 |
1976年 | 3095篇 |
1975年 | 2244篇 |
1974年 | 2308篇 |
1973年 | 2342篇 |
1972年 | 2156篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Kobrakov K. I. Kurnetsov D. N. Ruchkina A. G. Sharpar N. M. 《Theoretical Foundations of Chemical Engineering》2020,54(5):1052-1056
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the... 相似文献
23.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation... 相似文献
24.
Dorofeyev V. Yu. Sviridova A. N. Svistun L. I. 《Russian Journal of Non-Ferrous Metals》2020,61(3):354-361
Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of... 相似文献
25.
26.
27.
28.
Susan Sabra Khalid Mahmood Malik Muhammad Afzal Vian Sabeeh Ahmad Charaf Eddine 《Expert Systems》2020,37(1):e12388
Clinical narratives such as progress summaries, lab reports, surgical reports, and other narrative texts contain key biomarkers about a patient's health. Evidence-based preventive medicine needs accurate semantic and sentiment analysis to extract and classify medical features as the input to appropriate machine learning classifiers. However, the traditional approach of using single classifiers is limited by the need for dimensionality reduction techniques, statistical feature correlation, a faster learning rate, and the lack of consideration of the semantic relations among features. Hence, extracting semantic and sentiment-based features from clinical text and combining multiple classifiers to create an ensemble intelligent system overcomes many limitations and provides a more robust prediction outcome. The selection of an appropriate approach and its interparameter dependency becomes key for the success of the ensemble method. This paper proposes a hybrid knowledge and ensemble learning framework for prediction of venous thromboembolism (VTE) diagnosis consisting of the following components: a VTE ontology, semantic extraction and sentiment assessment of risk factor framework, and an ensemble classifier. Therefore, a component-based analysis approach was adopted for evaluation using a data set of 250 clinical narratives where knowledge and ensemble achieved the following results with and without semantic extraction and sentiment assessment of risk factor, respectively: a precision of 81.8% and 62.9%, a recall of 81.8% and 57.6%, an F measure of 81.8% and 53.8%, and a receiving operating characteristic of 80.1% and 58.5% in identifying cases of VTE. 相似文献
29.
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which... 相似文献
30.
Strength of Materials - The statistical analysis performed on the defectiveness of rails in the Kiev subway railway shows that the main cause of the occurrence of most defects is the contact... 相似文献