全文获取类型
收费全文 | 217篇 |
免费 | 5篇 |
专业分类
化学 | 57篇 |
晶体学 | 1篇 |
力学 | 8篇 |
物理学 | 156篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2014年 | 4篇 |
2013年 | 13篇 |
2012年 | 16篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有222条查询结果,搜索用时 31 毫秒
31.
32.
33.
Measurements of microwave attenuation at room temperature and 4.2 K have been performed on some conductors commonly used in
receiver input circuits. The reduction in loss on cooling is substantial, particularly for copper and plated gold, both of
which showed a factor of 3 loss reduction. Copper passivated with benzotriazole shows the same loss as without passivation.
The residual resistivity ratio between room temperature and 4.2 K, deduced from the measurements using the classical skin
effect formula, was smaller than the measured DC value to a degree consistent with conduction in the extreme anomalous skin
effect regime at cryogenic temperatures. The measurements were made in the 5–10 GHz range. The materials tested were: aluminum
alloys 1100-T6 and 6061-O, C101 copper, benzotriazole treated C101 copper, and brass plated with electroformed copper, Pur-A-Gold
125-Au soft gold, and BDT200 bright gold. 相似文献
34.
35.
36.
Lolo M Pedreira S Vázquez BI Franco CM Cepeda A Fente CA 《Analytical and bioanalytical chemistry》2007,387(5):1933-1937
An efficiency extraction of fluoroquinolones in chicken muscle was achieved by pulverizing it in a freezer mill before treatment
with NaOH (10mM)/MeCN (1:1). The improvement of cryogenic grinding in the extraction was demonstrated for the same piece (whole
leg) of four chickens treated with enrofloxacin in equal doses. A confirmatory method based on high-performance liquid chromatography
tandem mass spectrometry (HPLC-MS/MS) was used to analyze the extracts. The chromatographic separation was achieved in 5min
with a Synergi Fusion-RP 80A (50 x 2mm, 4μm) column filled with a hybrid polymer. The HPLC was coupled with a detector based
in a quadrupole–linear ion trap Q-TRAP that allows a confirmatory detection according to the European legislation. The specificity
of the method was assessed by testing a number of representative blank muscle samples (n = 10) to verify the absence of potential interfering compounds. The limits of detection and quantitation were 2 and 5ng g-1 of quinolones in muscle samples, respectively. The chromatographic method was demonstrated to be linear for the range studied
(5–500ng g-1) with the P value for lack-of-fit in the ANOVA table greater or equal to 0.10 (calibration coefficient 0.9998 and 0.9996 for ciprofloxacin
and enrofloxacin, respectively). The mean intra-day relative standard deviation (RSD) (n = 6, c = 50ng g-1) was 6%; inter-day assay gave a RSD of 12%. The extraction and clean-up were carried out in one step with very satisfactory
recovery data (between 65 and 101%). 相似文献
37.
本文提出了一种利用红外光谱方法揭示晶态物质中分子的氢键结构的新方法。用KBr压片和氟油研磨法制备于红光谱测量的样品。测得的光谱有时基本相同,有时同明显的差别。对此现象一直没有一个十分满意的解释。我们用低温红外光谱法证明压力诱导晶格中氢键网络的微细变化是造成不同产法测得的光谱不同的原因。具有平面氢键结构的晶体不能有效地的御加于样品上的应力,易一城较低的外力作用下发生结构畸变,因此,用KBr压片和氟油 相似文献
38.
场效应器件低温特性与低噪声放大器 总被引:3,自引:0,他引:3
高温超导滤波器与低噪声放大器(LNA)组成的射频接收机前端设备具有高选择性、高灵敏度和极低的噪声,因而展现出广阔的应用前景.本文研究了场效应器件的低温物理特性和电学参数,研制了一种适用于高温超导微波接收系统的低温低噪声放大器,在60K工作温度下,具有很好的噪声特性.包括高电子迁移率场效应晶体管在内的元件参数均在60K温度下进行了实际测量.放大器的各项指标与设计值吻合,工作频段为800MHz~850MHz,增益大于18dB,输入输出驻波比小于1.2,噪声系数小于0.22dB. 相似文献
39.
40.