全文获取类型
收费全文 | 136368篇 |
免费 | 13702篇 |
国内免费 | 7644篇 |
专业分类
电工技术 | 9736篇 |
技术理论 | 9篇 |
综合类 | 11937篇 |
化学工业 | 20690篇 |
金属工艺 | 7894篇 |
机械仪表 | 8684篇 |
建筑科学 | 10373篇 |
矿业工程 | 3969篇 |
能源动力 | 3901篇 |
轻工业 | 10521篇 |
水利工程 | 3048篇 |
石油天然气 | 6107篇 |
武器工业 | 1337篇 |
无线电 | 16302篇 |
一般工业技术 | 14818篇 |
冶金工业 | 5826篇 |
原子能技术 | 1866篇 |
自动化技术 | 20696篇 |
出版年
2024年 | 578篇 |
2023年 | 2053篇 |
2022年 | 4181篇 |
2021年 | 5610篇 |
2020年 | 4311篇 |
2019年 | 3471篇 |
2018年 | 3902篇 |
2017年 | 4331篇 |
2016年 | 4121篇 |
2015年 | 5747篇 |
2014年 | 7253篇 |
2013年 | 8643篇 |
2012年 | 9948篇 |
2011年 | 10634篇 |
2010年 | 9544篇 |
2009年 | 9167篇 |
2008年 | 8988篇 |
2007年 | 8420篇 |
2006年 | 8096篇 |
2005年 | 6738篇 |
2004年 | 5102篇 |
2003年 | 4247篇 |
2002年 | 4672篇 |
2001年 | 3975篇 |
2000年 | 2998篇 |
1999年 | 2352篇 |
1998年 | 1626篇 |
1997年 | 1337篇 |
1996年 | 1277篇 |
1995年 | 1012篇 |
1994年 | 784篇 |
1993年 | 575篇 |
1992年 | 473篇 |
1991年 | 323篇 |
1990年 | 274篇 |
1989年 | 187篇 |
1988年 | 178篇 |
1987年 | 121篇 |
1986年 | 65篇 |
1985年 | 81篇 |
1984年 | 55篇 |
1983年 | 43篇 |
1982年 | 32篇 |
1981年 | 29篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1977年 | 15篇 |
1976年 | 24篇 |
1959年 | 16篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
33.
34.
35.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献
36.
37.
Xuejing Lin Zhangxiao Peng Changqing Su 《International journal of molecular sciences》2015,16(5):10888-10906
Costunolide (CE) and dehydrocostuslactone (DE) are derived from many species of medicinal plants, such as Saussurea lappa Decne and Laurus nobilis L. They have been reported for their wide spectrum of biological effects, including anti-inflammatory, anticancer, antiviral, antimicrobial, antifungal, antioxidant, antidiabetic, antiulcer, and anthelmintic activities. In recent years, they have caused extensive interest in researchers due to their potential anti-cancer activities for various types of cancer, and their anti-cancer mechanisms, including causing cell cycle arrest, inducing apoptosis and differentiation, promoting the aggregation of microtubule protein, inhibiting the activity of telomerase, inhibiting metastasis and invasion, reversing multidrug resistance, restraining angiogenesis has been studied. This review will summarize anti-cancer activities and associated molecular mechanisms of these two compounds for the purpose of promoting their research and application. 相似文献
38.
39.
Choi Paul Santos Christian Ariane Kim Min-Kun Jung Hyunsook Hong Do-Young Koo Junemo 《Journal of Mechanical Science and Technology》2021,35(11):5007-5022
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations... 相似文献