全文获取类型
收费全文 | 8509篇 |
免费 | 1834篇 |
国内免费 | 667篇 |
专业分类
化学 | 2019篇 |
晶体学 | 56篇 |
力学 | 931篇 |
综合类 | 178篇 |
数学 | 1604篇 |
物理学 | 6222篇 |
出版年
2024年 | 29篇 |
2023年 | 92篇 |
2022年 | 242篇 |
2021年 | 242篇 |
2020年 | 238篇 |
2019年 | 203篇 |
2018年 | 215篇 |
2017年 | 341篇 |
2016年 | 401篇 |
2015年 | 362篇 |
2014年 | 565篇 |
2013年 | 716篇 |
2012年 | 533篇 |
2011年 | 672篇 |
2010年 | 494篇 |
2009年 | 573篇 |
2008年 | 586篇 |
2007年 | 551篇 |
2006年 | 503篇 |
2005年 | 434篇 |
2004年 | 386篇 |
2003年 | 385篇 |
2002年 | 310篇 |
2001年 | 276篇 |
2000年 | 253篇 |
1999年 | 210篇 |
1998年 | 171篇 |
1997年 | 163篇 |
1996年 | 133篇 |
1995年 | 98篇 |
1994年 | 81篇 |
1993年 | 76篇 |
1992年 | 71篇 |
1991年 | 47篇 |
1990年 | 44篇 |
1989年 | 57篇 |
1988年 | 41篇 |
1987年 | 31篇 |
1986年 | 22篇 |
1985年 | 28篇 |
1984年 | 30篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Hedberg C Dekker FJ Rusch M Renner S Wetzel S Vartak N Gerding-Reimers C Bon RS Bastiaens PI Waldmann H 《Angewandte Chemie (International ed. in English)》2011,50(42):9832-9837
A matter of common sense: A common recognition motif consisting of a negatively charged group five to six bonds away (red) from the (thio)ester functionality (green) and a positively charged tail group ten to twelve bonds away (blue) was identified in two native acyl protein thioesterase?1 (APT1) substrates. This similarity led to the design of potent inhibitors of the Ras-depalmitoylating enzyme APT1. 相似文献
992.
Beyond petrochemicals: the renewable chemicals industry 总被引:1,自引:0,他引:1
Vennestrøm PN Osmundsen CM Christensen CH Taarning E 《Angewandte Chemie (International ed. in English)》2011,50(45):10502-10509
993.
994.
Liu C Pan J Li S Zhao Y Wu LY Berkman CE Whorton AR Xian M 《Angewandte Chemie (International ed. in English)》2011,50(44):10327-10329
995.
The rhythmic movement is a spontaneous behavior due to the central pattern generator(CPG).At present,the CPG model only shows the spontaneous behavior,butdoes not refer to the instruction regulation role of the cerebral cortex.In this paper,a modified model based on the Matsuoka neural oscillator theory is presented to better show the regulation role of the cerebral cortex signal to the CPG neuronal network.The complex interaction between the in put signal and other parameters in the CPG networkis establish... 相似文献
996.
The aeroacoustic noise generated by a high speed, planar gas jet impinging on a flat plate is investigated experimentally. The jet used in this study is typical of those commonly found in industrial applications such as in various coating control and heat transfer processes. Normal jet impingement on the plate is found to generate strong acoustic tones over a wide range of impingement distances and jet velocities. The characteristics of these tones, as a function of the jet velocity and impingement distance, are quantified. Phase and amplitude measurements of the pressure fluctuations on the impingement plate indicate that the acoustic tones are generated by an antisymmetric instability mode of the jet oscillation. The effect of plate inclination in both the transverse and span-wise directions, with respect to the incident jet, is also studied. The jet-plate tone is found to be much more sensitive to changes in the span-wise plate inclination than to changes in the transverse inclination, but in both cases, a complete suppression of the tone is found to be possible. 相似文献
997.
Ulrich Soupremanien Stephane Le PersonMichel Favre-Marinet Yann Bultel 《Experimental Thermal and Fluid Science》2011,35(5):797-809
This article presents experiments conducted with two single rectangular mini-channels of same hydraulic diameter (1.4 mm) and different aspect ratios for conditions of horizontal boiling flow. The Forane® 365 HX used was subcooled (ΔTsub = 15 °C) for all the boiling curves presented in the paper. Local heat transfer coefficients were measured for heat flux ranging from 25 to 62 kW m−2 and mass flux from 200 kg m−2 s−1 to 400 kg m−2 s−1. The boiling flows were observed with two different cameras (depending on the flow velocity) through a visualization window. The flow patterns in the two channels were compared for similar conditions. The results show that the boiling heat transfer coefficient and the pressure drop values are different for the two single mini-channels. For low heat flux condition, the channel with lowest aspect ratio (H/W = 0.143) has a higher heat transfer coefficient. On the other hand, for high heat flux condition, the opposite situation occurs, namely the heat transfer coefficient becomes higher for the channel with highest aspect ratio (H/W = 0.43). This is probably due to the earlier onset of dryout in the channel with lowest aspect ratio. For the two cases of heating, the pressure drop for the two-phase flow remains lower for the channel with lowest aspect ratio. These results show that the aspect ratio plays a substantial role for boiling flows in rectangular channels. As for single-phase flows, the heat transfer characteristics are significantly influenced (even though the hydraulic diameter remains the same) by this parameter. 相似文献
998.
Experimental results about concrete under sulfate attack are summarized,which include the variation of mass density of samples and velocity of ultrasonic wave propagating in samples.The evolution damage is analyzed in terms of the experimental results,and close attention is paid to the effect of damage evolution on Poisson’s ratio.This study shows that Poisson’s ratio is significantly affected by the concentration of solution and water-cement ratio.Poisson’s ratio of concrete changes very little when the water-cement ratio is selected as 0.6 or 0.8,so that such change may be neglected.If water-cement is 0.4,however,the Poisson’s ratio of the sample significantly changes.When the concrete sample of 0.4 water-cement ratio is immersed in sodium sulfate solution of 8% concentration for 285 days,Poisson’s ratio increase 10.14% compared with its initial value.There exist a sensitive region and a non-sensitive region for the change rate of Poisson’s ratio with respect to corrosion time.The change rate of Poisson’s ratio monotonously decreases with corrosion time in the sensitive region;in the non-sensitive region,the change rate of Poisson’s ratio is almost equal to zero. 相似文献
999.
1000.
摩擦振动信号谐波小波包特征提取 总被引:2,自引:2,他引:0
在销-盘摩擦磨损试验机上进行了船用柴油机缸套-活塞环摩擦配副摩擦磨损试验,应用谐波小波包变换分析了不同磨损状态下的摩擦振动信号.结果表明:谐波小波包变换可提取微弱的摩擦振动特征.当磨损机制为轻微的黏着磨损时,摩擦振动信号的频谱以边频为主,没有明显的固有频率,平均幅值小;当磨损机制以磨粒磨损为主时,摩擦振动信号的频谱出现较大峰值的固有频率,但仍存在大量的边频,平均幅值变大;当磨损机制以疲劳磨损为主时,摩擦振动信号频谱的固有频率更加明显,边频显著减弱,平均幅值最大.因此,谐波小波包变换可实现微弱摩擦振动信号的特征提取. 相似文献