全文获取类型
收费全文 | 280篇 |
免费 | 38篇 |
国内免费 | 30篇 |
专业分类
化学 | 184篇 |
力学 | 7篇 |
综合类 | 6篇 |
数学 | 11篇 |
物理学 | 23篇 |
无线电 | 117篇 |
出版年
2024年 | 4篇 |
2023年 | 30篇 |
2022年 | 27篇 |
2021年 | 34篇 |
2020年 | 32篇 |
2019年 | 28篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 19篇 |
2013年 | 12篇 |
2012年 | 13篇 |
2011年 | 9篇 |
2010年 | 9篇 |
2009年 | 2篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 15篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
排序方式: 共有348条查询结果,搜索用时 600 毫秒
1.
2.
3.
Sarkar M. Ang Chew Hoe Huang Jiayi Chen T.P. 《Electron Devices, IEEE Transactions on》2005,52(6):1200-1204
In a MOSFET, a nonuniform, graded vertical dopant profile in the polysilicon gate causes a potential drop at the polysilicon/oxide interface. In this paper, the effect of this potential drop on the gate leakage current has been evaluated for the first time. The extent of variations of this affected gate leakage current with gate oxide thickness, gate length, and gate and drain bias conditions have been assessed with device simulation for an nMOS at 0.13 /spl mu/m low-voltage process. The results provide a guideline to the severity of this effect from the point of view of device and circuit operation and standby power consumption. 相似文献
4.
In order to achieve "postponement of school without suspension of learning" during the prevention and control of new coronavirus pneumonia, the online teaching strategy was constructed based on Enterprise WeChat and Integrated Online Education Platform for the online teaching of Separation Science and Technology. The student-centered teaching methods were applied in online teaching process. 相似文献
5.
Comprehensive two-dimensional liquid chromatographic separation by means of a combination of ion-exchange chromatography (IEC)
and reversed-phase liquid chromatography (RPLC) has been realized and applied to the analysis of components of a traditional
Chinese medicine Flos Lonicera. In the first dimension the components of a Flos Lonicera extract is separated on strong anion-exchange (SAX) column according to the charge-exchange properties of the components.
In the second dimension the components are further fractionated by reversed-phase liquid chromatography (on ODS) on the basis
of their hydrophobicity. The RPLC effluent is desalted and split and the components are identified on-line by use of both
diode-array detection and mass spectrometry with atmospheric pressure chemical ionization (APCI–MS). In this way, the extract
of Flos Lonicera can be rapidly separated, desalted, and analyzed, with determination of molecular weight. More than 58 components of an extract
of Flos Lonicera were well resolved and six were tentatively identified from their UV and mass spectra. 相似文献
6.
Ningyi Chen Jiayi Xu Michael Reuman Xun Li Ronald K. Russell Zhihua Sui 《Tetrahedron letters》2006,47(33):5909-5913
Various substituents were introduced onto the methyl group in 4-methyl coumarins through lithiation, followed by reactions with a wide range of electrophiles. The presence of an alkoxy group on 6′-phenyl ring was found to be pivotal for the success of this reaction. This procedure provided a convenient synthetic pathway to elaborate the methyl group of 4-methylcoumarins. Application of this methodology was showcased with the synthesis of biologically important novel tetracyclic chromene ring systems (n = 1-3). 相似文献
7.
Jing Li Huayi Shi Runzhi Chen Xiaofeng Wu Jiayi Cheng Fenglin Dong Houyu Wang Yao He 《Chemical science》2021,12(3):896
Synthesis of programmable atom-like nanoparticles (PANs) with high valences and high yields remains a grand challenge. Here, a novel synthetic strategy of microfluidic galvanic displacement (μ-GD) coupled with microfluidic DNA nanoassembly is advanced for synthesis of single-stranded DNA encoder (SSE)-encoded PANs for reliable surface-enhanced Raman scattering (SERS) sensing. Notably, PANs with high valences (e.g., n-valence, n = 12) are synthesized with high yields (e.g., >80%) owing to the effective control of interfacial reactions sequentially occurring in the microfluidic system. On the basis of this, we present the first demonstration of a PAN-based automatic analytical platform, in which sensor construction, sample loading and on-line monitoring are carried out in the microfluidic system, thus guaranteeing reliable quantitative measurement. In the proof-of-concept demonstration, accurate determination of tetracycline (TET) in serum and milk samples with a high recovery close to 100% and a low relative standard deviation (RSD) less than 5.0% is achieved by using this integrated analytical platform.A novel synthetic strategy is presented for microfluidic preparation of programmable atom-like nanoparticles with high valences and high yields. 相似文献
8.
9.
10.