全文获取类型
收费全文 | 566018篇 |
免费 | 7052篇 |
国内免费 | 1003篇 |
专业分类
电工技术 | 10511篇 |
综合类 | 467篇 |
化学工业 | 90101篇 |
金属工艺 | 23335篇 |
机械仪表 | 18497篇 |
建筑科学 | 12533篇 |
矿业工程 | 4313篇 |
能源动力 | 14429篇 |
轻工业 | 45760篇 |
水利工程 | 6941篇 |
石油天然气 | 14961篇 |
武器工业 | 39篇 |
无线电 | 60294篇 |
一般工业技术 | 116222篇 |
冶金工业 | 95565篇 |
原子能技术 | 14681篇 |
自动化技术 | 45424篇 |
出版年
2021年 | 5480篇 |
2019年 | 5268篇 |
2018年 | 9201篇 |
2017年 | 9408篇 |
2016年 | 9831篇 |
2015年 | 6025篇 |
2014年 | 10245篇 |
2013年 | 26100篇 |
2012年 | 15771篇 |
2011年 | 21088篇 |
2010年 | 16969篇 |
2009年 | 18820篇 |
2008年 | 19069篇 |
2007年 | 18765篇 |
2006年 | 16285篇 |
2005年 | 14742篇 |
2004年 | 14007篇 |
2003年 | 13694篇 |
2002年 | 13249篇 |
2001年 | 12851篇 |
2000年 | 12331篇 |
1999年 | 12013篇 |
1998年 | 27655篇 |
1997年 | 20043篇 |
1996年 | 15629篇 |
1995年 | 12007篇 |
1994年 | 10859篇 |
1993年 | 10614篇 |
1992年 | 8334篇 |
1991年 | 8102篇 |
1990年 | 7990篇 |
1989年 | 7763篇 |
1988年 | 7478篇 |
1987年 | 6749篇 |
1986年 | 6534篇 |
1985年 | 7391篇 |
1984年 | 6701篇 |
1983年 | 6439篇 |
1982年 | 5777篇 |
1981年 | 5897篇 |
1980年 | 5632篇 |
1979年 | 5733篇 |
1978年 | 5664篇 |
1977年 | 6180篇 |
1976年 | 7689篇 |
1975年 | 5109篇 |
1974年 | 4903篇 |
1973年 | 4980篇 |
1972年 | 4279篇 |
1971年 | 4038篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
135.
136.
Bochkareva N. I. Ivanov A. M. Klochkov A. V. Kogotkov V. S. Rebane Yu. T. Virko M. V. Shreter Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode... 相似文献
137.
Aleksandrov A. V. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(4):477-481
Power Technology and Engineering - The work done on the test site to ensure the operational safety of the powerhouse of the Zagorsk PSP-2 after its leveling is described. The controlled... 相似文献
138.
Mechanical durability of extruded fish feed must be optimized to lower economic losses as well as emission of organic matter to aquatic environments. The glass transition hypothesis for viscoelastic biopolymers is demonstrated and confirmed experimentally to be valid for extruded fish feed pellets. It is proposed and demonstrated that it is important to avoid early glass transition onset, to optimize the obtained mechanical durability. From the proposed glass transition hypothesis, immediate process relevance to the pre-drying transport mechanism is demonstrated. Furthermore, measured mechanical durability is found to range from 1.5 to 5.0% loss, for different combinations of drying parameters. 相似文献
139.
Wireless Personal Communications - In this paper, cooperative communication (CC) assisted cognitive wireless sensor network (CWSN) is presented for monitoring health and activity of an end-user in... 相似文献
140.
Angelico Mendy Nervana Metwali Sarah S. Perry Elizabeth A. Chrischilles Kai Wang Peter S. Thorne 《Indoor air》2020,30(1):88-97
Endotoxin exacerbates asthma. We designed the Louisa Environmental Intervention Project (LEIP) and assessed its effectiveness in reducing household endotoxin and improving asthma symptoms in rural Iowa children. Asthmatic school children (N = 104 from 89 homes) of Louisa and Keokuk counties in Iowa (aged 5-14 years) were recruited and block-randomized to receive extensive (education + professional cleaning) or educational interventions. Environmental sampling collection and respiratory survey administration were done at baseline and during three follow-up visits. Mixed-model analyses were used to assess the effect of the intervention on endotoxin levels and asthma symptoms in the main analysis and of endotoxin reduction on asthma symptoms in exploratory analysis. In the extensive intervention group, dust endotoxin load was significantly reduced in post-intervention visits. The extensive compared with the educational intervention was associated with significantly decreased dust endotoxin load in farm homes and less frequent nighttime asthma symptoms. In exploratory analysis, dust endotoxin load reduction from baseline was associated with lower total asthma symptoms score (Odds ratio: 0.52, 95% confidence interval: 0.29-0.92). In conclusion, the LEIP intervention reduced household dust endotoxin and improved asthma symptoms. However, endotoxin reductions were not sustained post-intervention by residents. 相似文献