全文获取类型
收费全文 | 175404篇 |
免费 | 15936篇 |
国内免费 | 8125篇 |
专业分类
电工技术 | 11191篇 |
技术理论 | 13篇 |
综合类 | 11575篇 |
化学工业 | 28179篇 |
金属工艺 | 9799篇 |
机械仪表 | 11216篇 |
建筑科学 | 13511篇 |
矿业工程 | 5317篇 |
能源动力 | 5260篇 |
轻工业 | 12136篇 |
水利工程 | 3235篇 |
石油天然气 | 10542篇 |
武器工业 | 1403篇 |
无线电 | 21247篇 |
一般工业技术 | 21074篇 |
冶金工业 | 8385篇 |
原子能技术 | 1913篇 |
自动化技术 | 23469篇 |
出版年
2024年 | 391篇 |
2023年 | 3207篇 |
2022年 | 5338篇 |
2021年 | 8034篇 |
2020年 | 6215篇 |
2019年 | 4920篇 |
2018年 | 5598篇 |
2017年 | 6217篇 |
2016年 | 5561篇 |
2015年 | 7478篇 |
2014年 | 9300篇 |
2013年 | 11166篇 |
2012年 | 12231篇 |
2011年 | 12868篇 |
2010年 | 10986篇 |
2009年 | 10365篇 |
2008年 | 9895篇 |
2007年 | 9115篇 |
2006年 | 9290篇 |
2005年 | 7959篇 |
2004年 | 5308篇 |
2003年 | 4465篇 |
2002年 | 4001篇 |
2001年 | 3600篇 |
2000年 | 3465篇 |
1999年 | 4069篇 |
1998年 | 3393篇 |
1997年 | 2870篇 |
1996年 | 2667篇 |
1995年 | 2187篇 |
1994年 | 1765篇 |
1993年 | 1277篇 |
1992年 | 1030篇 |
1991年 | 763篇 |
1990年 | 554篇 |
1989年 | 455篇 |
1988年 | 358篇 |
1987年 | 237篇 |
1986年 | 194篇 |
1985年 | 122篇 |
1984年 | 108篇 |
1983年 | 76篇 |
1982年 | 80篇 |
1981年 | 65篇 |
1980年 | 61篇 |
1979年 | 29篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1975年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Catalysis Letters - To explore the possibility of coreaction of selective catalytic reduction with NH3 (NH3-SCR) and CO oxidation (CO-O), bimetallic doping catalysts of Mn and Cu were synthesized... 相似文献
72.
以红花菜籽油中亚油酸为原料,偏铁酸钠为催化剂,在单因素试验的基础上,选取反应温度、反应时间、催化剂用量为考察因素,以异构化产物共轭亚油酸(CLA)转化率为响应值,通过响应面分析法对异构化反应进行优化,并建立相应的回归模型,试验结果表明,红花菜籽油中亚油酸异构化为CLA的最佳工艺为:反应温度195℃、反应时间4.7 h、催化剂用量0.6 g,在此条件下得到CLA转化率为92.90%,与预测值93.92%相比,误差为1.02%.然后再通过脲素包合纯化、经2%的H2SO4-CH3OH溶液甲酯化后,用气相色谱-质谱联用仪检测CLA含量为64.27%. 相似文献
73.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system. 相似文献
74.
Shu-Hung Yang Yi-Nan Lin Cheng-Ying Yang Ming-Kuen Chen Victor R. L. Shen Yu-Wei Lin 《电子科技学刊:英文版》2022,20(2):209-223
An increasing number of social media and networking platforms have been widely used. People usually post the online comments to share their own opinions on the networking platforms with social media. Business companies are increasingly seeking effective ways to mine what people think and feel regarding their products and services. How to correctly understand the online customers’ reviews becomes an important issue. This study aims to propose a method with the aspect-oriented Petri nets (AOPN) to improve the examination correctness without changing any process and program. We collect those comments from the online reviews with Scrapy tools, perform sentiment analysis using SnowNLP, and examine the analysis results to improve the correctness. In this paper, we apply our method for a case of the online movie comments. The experimental results have shown that AOPN is helpful for the sentiment analysis and verifying its correctness. 相似文献
75.
Miao Hu Xiaoqian Du Guannan Liu Shuang Zhang Haibo Wu Yang Li 《International Journal of Food Science & Technology》2022,57(7):3892-3902
The effects of soybean variety and germination time on structural changes, antinutritional factor content, antioxidant activity of germinated soybean, and on the functional properties of soymilk were comprehensively investigated. The results showed that the antioxidant activity increased with increasing germination time. The content of antinutritional factors decreased with increasing germination time. Soybean varieties with the lowest tannin and trypsin inhibitor content were DN690 and HJ1. Lipoxygenase activity and phytic acid content showed no significant differences among soybean varieties. The content of α-helices and β-turns in soybean protein decreased with increasing germination time, while the content of β-sheets was increased. Soybean protein was progressively broken down into smaller molecular peptides during the germination process. The digestion and content of soluble protein in soymilk increased with germination. In summary, we show that germination is an effective, cheap, and green method that improves the functional properties of soybean and soymilk. 相似文献
76.
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique... 相似文献
77.
78.
79.
80.
Weiyu Bi Panfeng Zhang Xiangrui Du Wei Lü Shitou Wang Tangying Yang Liping Ma Xiaochun Liu Haifeng Zhao Shaoran Ren 《Journal of surfactants and detergents》2022,25(3):387-398
Natural gas foam can be used for mobility control and channel blocking during natural gas injection for enhanced oil recovery, in which stable foams need to be used at high reservoir temperature, high pressure and high water salinity conditions in field applications. In this study, the performance of methane (CH4) foams stabilized by different types of surfactants was tested using a high pressure and high temperature foam meter for surfactant screening and selection, including anionic surfactant (sodium dodecyl sulfate), non-anionic surfactant (alkyl polyglycoside), zwitterionic surfactant (dodecyl dimethyl betaine) and cationic surfactant (dodecyl trimethyl ammonium chloride), and the results show that CH4-SDS foam has much better performance than that of the other three surfactants. The influences of gas types (CH4, N2, and CO2), surfactant concentration, temperature (up to 110°C), pressure (up to 12.0 MPa), and the presence of polymers as foam stabilizer on foam performance was also evaluated using SDS surfactant. The experimental results show that the stability of CH4 foam is better than that of CO2 foam, while N2 foam is the most stable, and CO2 foam has the largest foam volume, which can be attributed to the strong interactions between CO2 molecules with H2O. The foaming ability and foam stability increase with the increase of the SDS concentration up to 1.0 wt% (0.035 mol/L), but a further increase of the surfactant concentration has a negative effect. The high temperature can greatly reduce the stability of CH4-SDS foam, while the foaming ability and foam stability can be significantly enhanced at high pressure. The addition of a small amount of polyacrylamide as a foam stabilizer can significantly increase the viscosity of the bulk solution and improve the foam stability, and the higher the molecular weight of the polymer, the higher viscosity of the foam liquid film, the better foam performance. 相似文献