全文获取类型
收费全文 | 417547篇 |
免费 | 6650篇 |
国内免费 | 1585篇 |
专业分类
电工技术 | 8031篇 |
综合类 | 688篇 |
化学工业 | 62879篇 |
金属工艺 | 14541篇 |
机械仪表 | 12134篇 |
建筑科学 | 12089篇 |
矿业工程 | 1114篇 |
能源动力 | 11235篇 |
轻工业 | 44131篇 |
水利工程 | 3434篇 |
石油天然气 | 2111篇 |
武器工业 | 30篇 |
无线电 | 56028篇 |
一般工业技术 | 77265篇 |
冶金工业 | 75229篇 |
原子能技术 | 5629篇 |
自动化技术 | 39214篇 |
出版年
2021年 | 2858篇 |
2019年 | 2577篇 |
2018年 | 3991篇 |
2017年 | 4044篇 |
2016年 | 4299篇 |
2015年 | 3649篇 |
2014年 | 5993篇 |
2013年 | 19574篇 |
2012年 | 10499篇 |
2011年 | 15020篇 |
2010年 | 11568篇 |
2009年 | 13154篇 |
2008年 | 14211篇 |
2007年 | 14571篇 |
2006年 | 13066篇 |
2005年 | 12219篇 |
2004年 | 11739篇 |
2003年 | 11427篇 |
2002年 | 11063篇 |
2001年 | 11256篇 |
2000年 | 10414篇 |
1999年 | 10916篇 |
1998年 | 24118篇 |
1997年 | 17687篇 |
1996年 | 13991篇 |
1995年 | 11058篇 |
1994年 | 9838篇 |
1993年 | 9400篇 |
1992年 | 7174篇 |
1991年 | 6824篇 |
1990年 | 6426篇 |
1989年 | 6130篇 |
1988年 | 5876篇 |
1987年 | 4889篇 |
1986年 | 4843篇 |
1985年 | 5983篇 |
1984年 | 5604篇 |
1983年 | 4835篇 |
1982年 | 4501篇 |
1981年 | 4447篇 |
1980年 | 4209篇 |
1979年 | 4081篇 |
1978年 | 3772篇 |
1977年 | 4550篇 |
1976年 | 6100篇 |
1975年 | 3115篇 |
1974年 | 3012篇 |
1973年 | 2890篇 |
1972年 | 2319篇 |
1971年 | 2004篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
James E. Tyrrell Martyn G. Boutelle Alasdair J. Campbell 《Advanced functional materials》2021,31(1):2007086
Biological environments use ions in charge transport for information transmission. The properties of mixed electronic and ionic conductivity in organic materials make them ideal candidates to transduce physiological information into electronically processable signals. A device proven to be highly successful in measuring such information is the organic electrochemical transistor (OECT). Previous electrophysiological measurements performed using OECTs show superior signal-to-noise ratios than electrodes at low frequencies. Subsequent development has significantly improved critical performance parameters such as transconductance and response time. Here, interdigitated-electrode OECTs are fabricated on flexible substrates, with one such state-of-the-art device achieving a peak transconductance of 139 mS with a 138 µs response time. The devices are implemented into an array with interconnects suitable for micro-electrocorticographic application and eight architecture variations are compared. The two best-performing arrays are subject to the full electrophysiological spectrum using prerecorded signals. With frequency filtering, kHz-scale frequencies with 10 µV-scale voltages are resolved. This is supported by a novel quantification of the noise, which compares the gate voltage input and drain current output. These results demonstrate that high-performance OECTs can resolve the full electrophysiological spectrum and suggest that superior signal-to-noise ratios could be achieved in high frequency measurements of multiunit activity. 相似文献
84.
Freddy A. Bernal Dr. Marcel Kaiser Prof. Dr. Bernhard Wünsch Prof. Dr. Thomas J. Schmidt 《ChemMedChem》2020,15(1):68-78
Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model. 相似文献
85.
86.
87.
88.
89.
90.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process. 相似文献