全文获取类型
收费全文 | 76370篇 |
免费 | 8897篇 |
国内免费 | 6146篇 |
专业分类
电工技术 | 6934篇 |
综合类 | 7545篇 |
化学工业 | 9701篇 |
金属工艺 | 5514篇 |
机械仪表 | 5567篇 |
建筑科学 | 6106篇 |
矿业工程 | 2784篇 |
能源动力 | 2243篇 |
轻工业 | 7613篇 |
水利工程 | 2428篇 |
石油天然气 | 2972篇 |
武器工业 | 1184篇 |
无线电 | 8296篇 |
一般工业技术 | 7044篇 |
冶金工业 | 3002篇 |
原子能技术 | 1366篇 |
自动化技术 | 11114篇 |
出版年
2024年 | 487篇 |
2023年 | 1337篇 |
2022年 | 3063篇 |
2021年 | 3958篇 |
2020年 | 2844篇 |
2019年 | 1996篇 |
2018年 | 2079篇 |
2017年 | 2468篇 |
2016年 | 2224篇 |
2015年 | 3470篇 |
2014年 | 4185篇 |
2013年 | 4971篇 |
2012年 | 6340篇 |
2011年 | 6488篇 |
2010年 | 6168篇 |
2009年 | 5890篇 |
2008年 | 5888篇 |
2007年 | 5903篇 |
2006年 | 4976篇 |
2005年 | 4043篇 |
2004年 | 2953篇 |
2003年 | 2023篇 |
2002年 | 1862篇 |
2001年 | 1750篇 |
2000年 | 1469篇 |
1999年 | 781篇 |
1998年 | 330篇 |
1997年 | 321篇 |
1996年 | 231篇 |
1995年 | 186篇 |
1994年 | 157篇 |
1993年 | 106篇 |
1992年 | 93篇 |
1991年 | 58篇 |
1990年 | 66篇 |
1989年 | 61篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 21篇 |
1979年 | 14篇 |
1978年 | 4篇 |
1959年 | 17篇 |
1956年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
3.
以蚕丝蛋白为模板,在相对温和的条件下通过生物矿化的手段形成具有特殊形貌的α-GaOOH颗粒,并通过在不同温度下煅烧α-GaOOH得到α-Ga2O3和β-Ga2O3.采用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)和荧光分光光度计(PL)等手段研究了丝素蛋白多肽和矿化时间对颗粒的影响,对其生物矿化机理进行了初步探讨.结果表明,所制备的β-Ga2O3具有优良的发光特性,丝素蛋白多肽模板以无定形的结构与产物结合在一起,并且经过高温烧结后仍以碳膜的形式包覆在材料的表面.这种碳膜结构对于提高材料的生物学性能起着重要的作用. 相似文献
4.
5.
Changbai Long Ning Ji Li Yang Wenjie Zhou Kun Zheng Wei Ren Laijun Liu 《Journal of the European Ceramic Society》2021,41(6):3369-3378
With co-substitution of (Li0.5Sm0.5) at A site and W at B site, the electrical properties of modified Ca0.92(Li0.5Sm0.5)0.08Bi2Nb2-xWxO9 [(CLS)BN-xW, x = 0, 0.015 and 0.03] piezoceramics with ultrahigh Curie temperature (TC) of > 930 °C were enhanced dramatically. The increased resistivity induced by the co-substitution ensure them to be polarized under an enough high field. Combined with the increase of spontaneous ferroelectric polarization (PS), the significant enhancements in the piezoelectric, dielectric and ferroelectric properties can be obtained in the composition x = 0.015. Furthermore, the piezoelectric activity (d33) and bulk resistivity (ρb) of (CLS)BN-0.015 W can be further enhanced at an appropriate sintering temperature. This optimum composition sintered at 1170 °C shows ultrahigh TC of ~948 °C, d33 of ~17.3 pC/N and ρb of ~6.9 MΩ cm at 600 °C, which are comparable to those of the reported high-temperature Aurivillius piezoceramics with TC > 850 °C. 相似文献
6.
A novel CdS/CaFe2O4 (CS/CFO) heterogeneous p-n junction was created by thermal deposition of CaFe2O4 nanoparticles on CdS rods. The CS/CFO hetero-structured photocatalysts exhibited increasingly efficient visible light harvesting compared to the bare CdS. The CS/CFO composites also presented higher photocurrent and slower decay of photoluminescence, suggesting a better separation of the photo-generated electrons and holes. The photocatalytic H2 evolution quantity on the optimized CS/CFO composite from water in the presence of ethanol was up to 2200 μmol after 3-h visible light illumination, which is more than twice that of the pristine CdS. The chemical interaction between CdS and CaFe2O4 was confirmed by the shifts in the XPS peaks, which made it possible for the charge carriers to transfer across the p-n junction interface. This research highlights the importance of forming an interfacial p-n heterojunction between two semiconductors for efficient charge separation and improved photocatalytic performance. 相似文献
7.
8.
9.
Rui ZHAO Weikai LI Tian WANG Ke ZHAN Zheng YANG Ya YAN Bin ZHAO Junhe YANG 《材料科学前沿(英文版)》2020,14(2):188
Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m−1·K−1, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film. 相似文献
10.
针对基站柜式空调耗电量大的问题,创造性地使用基站分布式冷却的方式,达到精确送风,节能高效的目的.在应用实践中检验了分布式冷却系统实际节能量和应用效果,总结出分布式冷却系统应用场景和范围,为更大范围推广应用DCS分布式冷却系统提供实践依据. 相似文献