全文获取类型
收费全文 | 27341篇 |
免费 | 6486篇 |
国内免费 | 4873篇 |
专业分类
化学 | 6018篇 |
晶体学 | 325篇 |
力学 | 5182篇 |
综合类 | 929篇 |
数学 | 9971篇 |
物理学 | 16275篇 |
出版年
2024年 | 186篇 |
2023年 | 820篇 |
2022年 | 807篇 |
2021年 | 863篇 |
2020年 | 643篇 |
2019年 | 872篇 |
2018年 | 537篇 |
2017年 | 804篇 |
2016年 | 911篇 |
2015年 | 1047篇 |
2014年 | 2127篇 |
2013年 | 1480篇 |
2012年 | 1713篇 |
2011年 | 2055篇 |
2010年 | 1878篇 |
2009年 | 2013篇 |
2008年 | 2473篇 |
2007年 | 1722篇 |
2006年 | 1647篇 |
2005年 | 1518篇 |
2004年 | 1571篇 |
2003年 | 1462篇 |
2002年 | 1243篇 |
2001年 | 1122篇 |
2000年 | 949篇 |
1999年 | 811篇 |
1998年 | 725篇 |
1997年 | 671篇 |
1996年 | 623篇 |
1995年 | 614篇 |
1994年 | 526篇 |
1993年 | 392篇 |
1992年 | 458篇 |
1991年 | 379篇 |
1990年 | 366篇 |
1989年 | 325篇 |
1988年 | 82篇 |
1987年 | 82篇 |
1986年 | 50篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 30篇 |
1982年 | 25篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Nonpolar a-plane light-emitting diode with an in-situ SiNx interlayer on r-plane sapphire grown by metal-organic chemical vapour deposition 下载免费PDF全文
We report on the growth and fabrication of nonpolar a-plane light emitting diodes with an in-situ SiNx interlayer grown between the undoped a-plane GaN buffer and Si-doped GaN layer. X-ray diffraction shows that the crystalline quality of the GaN buffer layer is greatly improved with the introduction of the SiNx interlayer. The electrical properties are also improved. For example, electron mobility and sheet resistance are reduced from high resistance to 31.6 cm2/(V·s) and 460 Ω/口 respectively. Owing to the significant effect of the SiNx interlayer, a-plane LEDs are realized. Electroluminescence of a nonpolar a-plane light-emitting diode with a wavelength of 488nm is demonstrated. The emission peak remains constant when the injection current increases to over 20 mA. 相似文献
992.
We give an analytic quantitative relation between Hardy's non-locality and Bell operator. We find that Hardy's non-locality is a sufficient condition for the violation of Bell inequality, the upper bound of Hardy's non-locality allowed by information causality just corresponds to Tsirelson bound of Bell inequality and the upper bound of Hardy's non- locality allowed by the principle of no-signaling just corresponds to the algebraic maximum of Bell operator. Then we study the CabeUo's argument of Hardy's non-locality (a generalization of Hardy's argument) and find a similar relation between it and violation of Bell inequality. Finally, we give a simple derivation of the bound of Hardy's non-locality under the constraint of information causality with the aid of the above derived relation between Hardy's non-locality and Bell operator. 相似文献
993.
In this paper, we investigate an Al2O3/HfSiO stack as the blocking layer of a metal-oxide-nitride-oxide-silicon-type (MONOS) memory capacitor. Compared with a memory capacitor with a single HfSiO layer as the blocking layer or an Al2O3/HfO2 stack as the blocking layer, the sample with the Al2O3/HfSiO stack as the blocking layer shows high program/erase (P/E) speed and good data retention characteristics. These improved performances can be explained by energy band engineering. The experimental results demonstrate that the memory device with an Al2O3/HfSiO stack as the blocking layer has great potential for further high-performance nonvolatile memory applications. 相似文献
994.
This paper investigates the current-voltage (I-V) characteristics of Al/Ti/4H-SiC Schottky barrier diodes (SBDs) in the temperature range of 77 K-500 K, which shows that Al/Ti/4H SiC SBDs have good rectifying behaviour. An abnormal behaviour, in which the zero bias barrier height decreases while the ideality factor increases with decreasing temperature (T), has been successfully interpreted by using thermionic emission theory with Gaussian distribution of the barrier heights due to the inhomogeneous barrier height at the A1/Ti/4H-SiC interface. The effective Richardson constant A* = 154 A/cm2 . K2 is determined by means of a modified Richardson plot In(I0/T2) - (qσ)2/2(κT)2 versus q/kT, which is very close to the theoretical value 146 A/cm2 · K2. 相似文献
995.
Computations have been widely used to explore new Li ion battery materials because of its remarkable advantages. In this review, we summarize the recent progress on computational investigation on anode materials in Li ion batteries. By introducing the computational studies on Li storage capability in carbon nanotubes, graphene, alloys and oxides, we reveal that computations have successfully addressed many fundamental problems and are powerful tools to understand and design new anode materials for Li ion batteries. 相似文献
996.
997.
报道了放电引发的非链式HF(DF)激光器中的激活介质由电子碰撞负离子分离引起的电离非稳定性。这种非稳性出现在电极空间分离、脉冲CO2激光加热的基于sF6的混合气体的大体积放电中。实验研究了自引发体放电过程中由激光加热引起的放电等离子体的自组织现象以及由此在放电间隙的大部分区域形成的准周期等离子体结构。重点分析了等离子体结构随气体温度和注入能量的变化,讨论了等离子体自组织对电子碰撞分离不稳定性所产生的影响,解释了混合气体中由于电子碰撞使负离子消失导致的单等离子体通道移动的产生机理。 相似文献
998.
The third-order ghost imaging with the second-order intensity correlation is theoretically and experimentally demonstrated.The resolution and visibility of the reconstructed image are discussed,and the relationship between resolution and visibility is analyzed.The theoretical results show that a tradeoff exists between the visibility and resolution of the reconstructed image;the better the image resolution,the worse the image visibility.Numerical simulations are carried out to verify this theory,and a ghost... 相似文献
999.
1000.