全文获取类型
收费全文 | 518812篇 |
免费 | 15492篇 |
国内免费 | 6242篇 |
专业分类
电工技术 | 14588篇 |
技术理论 | 7篇 |
综合类 | 7896篇 |
化学工业 | 79927篇 |
金属工艺 | 22739篇 |
机械仪表 | 20725篇 |
建筑科学 | 17934篇 |
矿业工程 | 5585篇 |
能源动力 | 14942篇 |
轻工业 | 36042篇 |
水利工程 | 6348篇 |
石油天然气 | 15160篇 |
武器工业 | 893篇 |
无线电 | 62343篇 |
一般工业技术 | 96664篇 |
冶金工业 | 80236篇 |
原子能技术 | 10447篇 |
自动化技术 | 48070篇 |
出版年
2023年 | 2806篇 |
2022年 | 6049篇 |
2021年 | 8705篇 |
2020年 | 6635篇 |
2019年 | 6899篇 |
2018年 | 9825篇 |
2017年 | 10352篇 |
2016年 | 10176篇 |
2015年 | 8960篇 |
2014年 | 12779篇 |
2013年 | 26664篇 |
2012年 | 18734篇 |
2011年 | 23109篇 |
2010年 | 19002篇 |
2009年 | 20215篇 |
2008年 | 20356篇 |
2007年 | 19784篇 |
2006年 | 18654篇 |
2005年 | 16550篇 |
2004年 | 14174篇 |
2003年 | 13618篇 |
2002年 | 12848篇 |
2001年 | 12470篇 |
2000年 | 12021篇 |
1999年 | 12621篇 |
1998年 | 26880篇 |
1997年 | 18921篇 |
1996年 | 14846篇 |
1995年 | 11301篇 |
1994年 | 9806篇 |
1993年 | 9405篇 |
1992年 | 6902篇 |
1991年 | 6360篇 |
1990年 | 6162篇 |
1989年 | 5741篇 |
1988年 | 5392篇 |
1987年 | 4658篇 |
1986年 | 4465篇 |
1985年 | 4909篇 |
1984年 | 4486篇 |
1983年 | 4042篇 |
1982年 | 3716篇 |
1981年 | 3769篇 |
1980年 | 3464篇 |
1979年 | 3336篇 |
1978年 | 3337篇 |
1977年 | 3750篇 |
1976年 | 4847篇 |
1975年 | 2850篇 |
1973年 | 2730篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献
122.
L. S. Belevskii M. A. Levantsevich R. R. Dema L. V. Deryabina T. V. Usataya O. R. Latypov 《Russian Engineering Research》2020,40(5):390-395
The machining of metal surfaces and the application of functional coatings by means of a flexible tool (a rotating wire brush) is considered. Frictional cladding may be applied on metal-cutting machines by means of simple attachments or manual angle grinders. 相似文献
123.
124.
125.
High Temperature - The influence of heating from 260 to 400 K on the structure and mechanism of the formation of a molecular water film adsorbed on the walls of a plane fracture with the width of... 相似文献
126.
127.
128.
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
129.
ABSTRACT This study investigates the effects of strain, strain rates, and forming directions (RD-rolling direction, TD-transverse direction, and ND-normal direction) on adiabatic shear, via dynamic impact compression tests using the Split Hopkinson Pressure Bar (SHPB) apparatus. A modified Johnson-Cook (J-C) constitutive model is proposed, which used to analyse the influence of the constitutive parameters on the sensitivity of adiabatic shear, employing a finite element software. The different sensitivities of adiabatic shear under different directions are explained by combining microscopic analysis and results from mechanical responses. The results show that the sensitivity of adiabatic shear can be related to the time of stress collapse in the following trend: ND?>?TD?>?RD; the sensitivities of these constitutive parameters on adiabatic shear are calculated and compared. 相似文献
130.
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