全文获取类型
收费全文 | 52300篇 |
免费 | 6449篇 |
国内免费 | 4356篇 |
专业分类
电工技术 | 5211篇 |
技术理论 | 1篇 |
综合类 | 5634篇 |
化学工业 | 6241篇 |
金属工艺 | 3949篇 |
机械仪表 | 3970篇 |
建筑科学 | 4183篇 |
矿业工程 | 2068篇 |
能源动力 | 1573篇 |
轻工业 | 5245篇 |
水利工程 | 1898篇 |
石油天然气 | 1886篇 |
武器工业 | 880篇 |
无线电 | 5275篇 |
一般工业技术 | 4521篇 |
冶金工业 | 2035篇 |
原子能技术 | 1067篇 |
自动化技术 | 7468篇 |
出版年
2024年 | 314篇 |
2023年 | 879篇 |
2022年 | 2239篇 |
2021年 | 2839篇 |
2020年 | 1989篇 |
2019年 | 1337篇 |
2018年 | 1387篇 |
2017年 | 1603篇 |
2016年 | 1463篇 |
2015年 | 2356篇 |
2014年 | 2855篇 |
2013年 | 3535篇 |
2012年 | 4480篇 |
2011年 | 4539篇 |
2010年 | 4345篇 |
2009年 | 4148篇 |
2008年 | 4256篇 |
2007年 | 4253篇 |
2006年 | 3522篇 |
2005年 | 2831篇 |
2004年 | 2112篇 |
2003年 | 1391篇 |
2002年 | 1247篇 |
2001年 | 1240篇 |
2000年 | 973篇 |
1999年 | 395篇 |
1998年 | 106篇 |
1997年 | 79篇 |
1996年 | 61篇 |
1995年 | 52篇 |
1994年 | 43篇 |
1993年 | 31篇 |
1992年 | 29篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 24篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 2篇 |
1959年 | 9篇 |
1956年 | 2篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
1.
2.
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
3.
4.
5.
6.
Chengxiao Zhao Zupeng Chen Run Shi Xiaofei Yang Tierui Zhang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(28):1907296
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed. 相似文献
7.
Wang Yunfei Zheng Wang Zhang Xiaofei Shen Jinqing 《Multidimensional Systems and Signal Processing》2020,31(3):907-926
Multidimensional Systems and Signal Processing - Generalized coprime structure decomposes the interleaved subarrays in the conventional coprime array by introducing a displacement and the resulting... 相似文献
8.
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
9.
Dongdong Ji Zheng Liu Bailing Jiang Xiaofei Luo 《International Journal of Hydrogen Energy》2021,46(27):13960-13970
The evaluation of cell's weatherability is of practical interest. To further improve the soluble lead flow battery's weatherability, physiochemical properties of electrolytes containing fluoborate, perchlorate, methanesulfonate and trifluoromethanesulfonate are investigated from ?60 to 50 °C. Activities of CF3SO3H and HClO4 are poor in trifluoromethanesulfonate and perchlorate solutions due to common anion effect. The solubility of lead salt can be improved by increasing temperature, but worsened by increasing acid's content. With the temperature increasing, the conductivity is enhanced, and the viscosity is lowered for four solutions. The same results have been found by increasing acid's content except for CF3SO3H. The high energy efficiency can be achieved for cells over ?40–0 °C using fluoborate and perchlorate solutions, 73.2% at ?40 °C and 78.1% at ?30 °C respectively. Over the temperature range of 20–50 °C, the cells with methanesulfonate and trifluoromethanesulfonate solutions have good performance, 77.4% and 73.7% at 50 °C respectively. 相似文献
10.