全文获取类型
收费全文 | 187篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 25篇 |
综合类 | 3篇 |
化学工业 | 51篇 |
金属工艺 | 3篇 |
机械仪表 | 5篇 |
建筑科学 | 2篇 |
能源动力 | 8篇 |
轻工业 | 30篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 8篇 |
一般工业技术 | 27篇 |
冶金工业 | 1篇 |
原子能技术 | 4篇 |
自动化技术 | 25篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 9篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1924年 | 1篇 |
1919年 | 1篇 |
1918年 | 1篇 |
1915年 | 1篇 |
1911年 | 1篇 |
1907年 | 1篇 |
1906年 | 1篇 |
1904年 | 1篇 |
排序方式: 共有198条查询结果,搜索用时 15 毫秒
191.
Gunther Reißig 《Electrical Engineering (Archiv fur Elektrotechnik)》2007,90(2):143-146
We investigate the performance of a combination of sophisticated local symmetric ordering methods with a simple symmetrization
step on a test set of Jacobians obtained from modified nodal equations. It is demonstrated that using such ordering heuristics
as a replacement for Markowitz’ algorithm may accelerate circuit simulation significantly. 相似文献
192.
Females of the lichen moth, Miltochrista calamina (Arctiidae, Lithosiinae), were previously shown to produce 5-methylheptadecan-7-ol (1) as a sex pheromone. In field tests, males were attracted only by the (5R,7R)-isomer of the four stereoisomers that were prepared by separation from two mixtures of diastereoisomers. A new route to (5R,7R)-1 starting from (S)-propylene oxide was developed utilizing the SN2 reaction of an optically active secondary tosylate and the Jacobsen hydrolytic kinetic resolution of an epoxide intermediate as key steps. Enantioselective HPLC analysis of the product and the antipode synthesized from (R)-propylene oxide confirmed their high enantiomeric excess (> 99 %). Using this stereospecific synthesis, six analogues with the same configuration as (5R,7R)-1 but with different alkyl chain(s) connected to the stereogenic centers were prepared in order to obtain GC/MS data and to examine the ability of M. calamina males to discriminate between them. The mass spectra of the synthetic analogues revealed characteristic fragment ions derived by cleavage around the methyl group in addition to that at the hydroxyl group. In field trapping tests, five out of the six compounds were attractive to male M. calamina moths, indicating that the males distinguished the configurations of methyl and hydroxyl groups but were less able to perceive differences in the lengths of the two alkyl chains in the pheromone. 相似文献
193.
194.
The 885 nm direct pumping directly into the 4F3/2 emitting level of Nd3+ is applied on an Nd:Lu0.15Y0.85VO4 crystal. The maximum output power of 2.8 W for continuous wave (CW) operation is obtained. For Q-switched operation, the maximum average output power is 1.2 W with pulse repetition of 23.69 kHz and pulse width of 35 ns at the pump power of 27.9 W. The high-quality fundamental transverse mode can be observed owing to the reduction of thermal effect for Nd:Lu0.15Y0.85VO4 crystal by 885 nm direct pumping. 相似文献
195.
语青合成(Text-to-speech)技术在近年来不断进步,已经逐渐从桌面软件走向芯片级应用.本文结合了人们对朗读设备的需要以及新型的TTS语音合成技术,设计了一款朗读同步显示系统. 相似文献
196.
A 1D1V hybrid Vlasov-fluid model was developed for this study to elucidate discharge current oscillations of Hall thrusters (HTs). The Vlasov equation for ions velocity distribution function with ionization source term is solved using a constrained interpolation profile conservative semi-Lagrangian method. The fourth-order weighted essentially non-oscillatory (4th WENO) limiter is applied to the first derivative value to minimize numerical oscillation in the discharge oscillation analyses. The fourth-order accuracy is verified through a 1D scalar test case. Nonoscillatory and high-resolution features of the Vlasov model are confirmed by simulating the test cases of the Vlasov–Poisson system and by comparing the results with a particle-in-cell (PIC) method. A 1D1V HT simulation is performed through the hybrid Vlasov model. The ionization oscillation is analyzed. The oscillation amplitude and plasma density are compared with those obtained from a hybrid PIC method. The comparison indicates that the hybrid Vlasov-fluid model yields noiseless results and that the steady-state waveform is calculable in a short time period. 相似文献
197.
Rei Itsukushima 《河流研究与利用》2023,39(6):1136-1147
Dams have contributed to population growth and technological innovation by reducing the risk of flooding and allowing humans to cultivate productive alluvial soils on river floodplains. However, in countries where many dams have already been constructed, many problems have been observed, such as river environment degradation, aging of the embankments, and inadequate dam performance. As the social and natural environment surrounding dams is becoming more complex and diverse, it is necessary to understand the current overall status of dams and the history of their construction such that we may consider how social capital and dams are related to human society and the natural environment. In this study, the relationship of basic information of dams and the social background in which the dams exist was examined for Japan, where dam construction began in earnest in the late 1800s and became a driving force for economic development. The situations surrounding dams are drastically changing, as maintenance and management costs increase due to the aging of dams and water demand varies due to changes in the industrial structure of a region. Simultaneously, there are instances where dams are expected to reduce damage, such as in the presence of more severe and frequent droughts and floods caused by climate change. It is therefore necessary to remove or restructure dams while considering numerous complex and diverse factors, such as the local social conditions, potential future changes, and environmental impact of rivers. 相似文献
198.
Dr. Hayama Tsutsumi Prof. Yohei Katsuyama Dr. Takeaki Tezuka Dr. Rei Miyano Dr. Yuki Inahashi Dr. Yoko Takahashi Dr. Takuji Nakashima Prof. Yasuo Ohnishi 《Chembiochem : a European journal of chemical biology》2022,23(3):e202100517
Indolizidine alkaloids, which have versatile bioactivities, are produced by various organisms. Although the biosynthesis of some indolizidine alkaloids has been studied, the enzymatic machinery for their biosynthesis in Streptomyces remains elusive. Here, we report the identification and analysis of the biosynthetic gene cluster for iminimycin, an indolizidine alkaloid with a 6-5-3 tricyclic system containing an iminium cation from Streptomyces griseus. The gene cluster has 22 genes, including four genes encoding polyketide synthases (PKSs), which consist of eight modules in total. In vitro analysis of the first module revealed that its acyltransferase domain selects malonyl-CoA, although predicted to select methylmalonyl-CoA. Inactivation of seven tailoring enzyme-encoding genes and structural elucidation of four compounds accumulated in mutants provided important insights into iminimycin biosynthesis, although some of these compounds appeared to be shunt products. This study expands our knowledge of the biosynthetic machinery of indolizidine alkaloids and the enzymatic chemistry of PKS. 相似文献