全文获取类型
收费全文 | 21046篇 |
免费 | 3414篇 |
国内免费 | 2403篇 |
专业分类
化学 | 14554篇 |
晶体学 | 209篇 |
力学 | 1534篇 |
综合类 | 197篇 |
数学 | 2335篇 |
物理学 | 8034篇 |
出版年
2024年 | 70篇 |
2023年 | 407篇 |
2022年 | 715篇 |
2021年 | 810篇 |
2020年 | 839篇 |
2019年 | 806篇 |
2018年 | 686篇 |
2017年 | 589篇 |
2016年 | 976篇 |
2015年 | 1019篇 |
2014年 | 1161篇 |
2013年 | 1530篇 |
2012年 | 1792篇 |
2011年 | 1966篇 |
2010年 | 1250篇 |
2009年 | 1195篇 |
2008年 | 1222篇 |
2007年 | 1130篇 |
2006年 | 1120篇 |
2005年 | 931篇 |
2004年 | 832篇 |
2003年 | 614篇 |
2002年 | 571篇 |
2001年 | 510篇 |
2000年 | 461篇 |
1999年 | 434篇 |
1998年 | 380篇 |
1997年 | 325篇 |
1996年 | 335篇 |
1995年 | 320篇 |
1994年 | 300篇 |
1993年 | 234篇 |
1992年 | 247篇 |
1991年 | 206篇 |
1990年 | 182篇 |
1989年 | 152篇 |
1988年 | 91篇 |
1987年 | 89篇 |
1986年 | 75篇 |
1985年 | 76篇 |
1984年 | 42篇 |
1983年 | 44篇 |
1982年 | 37篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1969年 | 4篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
紧凑型PFN-Marx脉冲发生器中,级与级之间存在着较大的寄生电容,该电容和PFN节电感构成了寄生传输线。对两种排布方式下的寄生传输线的放电过程进行了简单分析,重点开展了双列排布方式下全电路仿真模拟,对负载类型、寄生电容、负载电感等参数对输出波形的影响进行了计算,得到了二极管负载会在波形前沿上造成下降、寄生电容大小决定振荡频率、负载电感放大振荡幅值等结论。开展的PFN-Marx实验研究也进一步验证了上述分析结果。根据分析,提出了一种有效抑制输出波形振荡的方法,从电路上进行了仿真验证,进一步实验证实了该方法的有效性。 相似文献
932.
Respiratory noise is a confounding factor in functional magnetic resonance imaging (MRI) data analysis. A novel method called Respiratory noise Correction using Phase information is proposed to retrospectively correct for the respiratory noise in functional MRI (fMRI) time series. It is demonstrated that the respiratory movement and the phase of functional MRI images are highly correlated in time. The signal fluctuation due to respiratory movements can be effectively estimated from the phase variation and removed from the functional MRI time series using a Wiener filtering technique. In our experiments, this new method is compared with RETROICOR, which requires recording respiration signal simultaneously in an fMRI experiment. The two techniques show comparable performance with respect to the respiratory noise correction for fMRI time series. However, this technique is more advantageous because there is no need for monitoring the subjects’ respiration or changing functional MRI protocols. This technique is also potentially useful for correcting respiratory noise from abnormal breathing or when the respiration is not periodic. 相似文献
933.
An experimental study of runaway electrons in the EAST tokamak has been performed by a recently developed multi‐channel hard x‐ray diagnostics based on NaI(TL) scintillator detectors. It is found that in the current quench phase, the inductive loop voltage plays an important role in the generation of runaway electrons. And the avalanche mechanism was the main mechanism for runaway electrons after the disruptions. The distribution and transportation of runaway electrons were also investigated by multi‐channel hard x‐ray diagnostics. It is also found that the intensity of runaway electrons emission in the core plasma was much higher than those in the downside of the cross‐section, while the emission intensity of runaway electrons in the core plasma was almost the same. Calculated shrinking coefficient of runaway electrons emission after the plasma disruption was about 26 m/s according to the experimental data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
934.
基于马丁-侯方程,提出二氧化碳亚临界压力区具有统一形式的热力性质和传输特性的显式计算模型。显式形式保证了热物理性质计算的高速性和稳定性;同时所有热物性的计算模型形式统一,便于系统仿真的调用。以REFPROP7的计算结果作为数据源,对环保制冷剂中重要的工质二氧化碳的热物性在压力为三相点压力至临界压力,过热度0—200K,过冷度0—100K的数据范围内进行拟合,并将该计算模型与REFPROP7相应公式的计算结果和计算速度进行对比。对比结果表明,所有快速计算模型的总平均偏差小于0.7%,最大偏差小于12.928%;计算速度较REFPROP7提高了2个数量级。。 相似文献
935.
This paper studies the two-vibron bound states in the β- Fermi Pasta-Ulam model by means of the number conserving approximation combined with the number state method. The results indicate that on-site, adjacent-site and mixed two-vibron bound states may exist in the model. Specially, wave number has a significant effect on such bound states, which may be considered as the quantum effects of the localized states in quantum systems. 相似文献
936.
937.
Using the daily precipitation data of 740 stations in China from 1960 to 2000, the analysis on the variations and distributions of the frequency and the percentage of extreme precipitation to the annual rainfall have been performed in this paper. Results indicate that the percentage of heavy rains (above 25mm/day) in the annual rainfall has increased, while on average the day number of heavy rains has slightly reduced during the past 40 years. In the end of 1970s and the beginning of 1980s, both the number of days with extreme precipitation and the percentage of extreme precipitation abruptly changed over China, especially in the northern China. By moving t test, the abrupt change year of extreme precipitation for each station and its spatial distribution over the whole country are also obtained. The abrupt change years concentrated in 1978-1982 for most regions of northern China while occurred at various stations in southern China in greatly different/diverse years. Besides the abrupt change years of extreme precipitation at part stations of Northwest China happened about 5 years later in comparison with that of the country's average. 相似文献
938.
从电磁统一到电弱统一 总被引:1,自引:0,他引:1
概括介绍从“电磁统一”到“电弱统一”的研究历程,并指出这一研究的科学意义以及可能给予后继研究者在科研方法上的启示. 相似文献
939.
940.
Eapen J Williams WC Buongiorno J Hu LW Yip S Rusconi R Piazza R 《Physical review letters》2007,99(9):095901
Transient hot-wire data on thermal conductivity of suspensions of silica and perfluorinated particles show agreement with the mean-field theory of Maxwell but not with the recently postulated microconvection mechanism. The influence of interfacial thermal resistance, convective effects at microscales, and the possibility of thermal conductivity enhancements beyond the Maxwell limit are discussed. 相似文献