全文获取类型
收费全文 | 2462篇 |
免费 | 367篇 |
国内免费 | 363篇 |
专业分类
化学 | 345篇 |
晶体学 | 12篇 |
力学 | 96篇 |
综合类 | 24篇 |
数学 | 245篇 |
物理学 | 675篇 |
综合类 | 1795篇 |
出版年
2024年 | 10篇 |
2023年 | 56篇 |
2022年 | 80篇 |
2021年 | 60篇 |
2020年 | 44篇 |
2019年 | 64篇 |
2018年 | 68篇 |
2017年 | 51篇 |
2016年 | 49篇 |
2015年 | 64篇 |
2014年 | 122篇 |
2013年 | 81篇 |
2012年 | 98篇 |
2011年 | 100篇 |
2010年 | 132篇 |
2009年 | 111篇 |
2008年 | 141篇 |
2007年 | 126篇 |
2006年 | 125篇 |
2005年 | 113篇 |
2004年 | 99篇 |
2003年 | 113篇 |
2002年 | 95篇 |
2001年 | 90篇 |
2000年 | 125篇 |
1999年 | 79篇 |
1998年 | 64篇 |
1997年 | 60篇 |
1996年 | 62篇 |
1995年 | 77篇 |
1994年 | 76篇 |
1993年 | 67篇 |
1992年 | 52篇 |
1991年 | 52篇 |
1990年 | 36篇 |
1989年 | 51篇 |
1988年 | 29篇 |
1987年 | 37篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 29篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1963年 | 6篇 |
1960年 | 7篇 |
1957年 | 5篇 |
排序方式: 共有3192条查询结果,搜索用时 8 毫秒
121.
HL-2A装置激光吹气系统采用了全新自动控制的设计方法,实现了杂质注入量、靶片位移以及激光器被触发的时刻的精确自动控制.运行结果表明,该系统能把杂质的注入量控制在适当的水平,既不对等离子体约束产生影响,又便于光谱测量和杂质粒子输运研究.给出了激光吹气系统的设计,以及初步的实验结果. 相似文献
122.
Research on evolutionary games in a noisy environment is still a non-solved problem. By using Markov process, we build a dynamic model for two-player and two-strategy symmetric game in noisy environment. Some illustrative examples are presented and the results are determined by simulation experiments. 相似文献
123.
124.
Strong white light emission is observed from femtosecond laser propagation in air. The divergence angle of the white light emission is measured to be about 5mrad. Young's double-slits and a Michelson interferometer are used to investigate the coherence. The wavelength components of the white light emission are identified to have a good spatial coherence and a coherence time of about 0.5ps. 相似文献
125.
电子回旋共振加热(ECRH)是托卡马克等离子体一种最常用的辅助加热手段,也是进行等离子体电子热输运和约束性能研究的一种有效手段。本文介绍了HL-2A装置上ECRH实验的初步结果,分析了在ECRH实验期间的电子热输运特征和约束情况。 相似文献
126.
127.
Realization of Ultraviolet Electroluminescence from ZnO Homojunction Fabricated on Silicon Substrate with p-Type ZnO:N Layer Formed by Radical N2O Doping 下载免费PDF全文
ZnO homojunction light-emitting diodes are fabricated on Si(100) substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3 V and a reverse breakdown voltage higher than 6 V. Distinct electrolumineseence emissions centred at 395nm and 490nm are detected from this device at forward current higher than 20mA at room temperature. 相似文献
128.
Non-recycling impurities are injected into ohmic HL-2A plasma for the first time. The impurities of titanium and aluminium are injected in the discharges with varying plasma density and current. The convection and diffusion process of the injected impurity ions during the inward phase are qualitatively investigated. The results show that the transport of impurities is much slower in the central region of the plasma than outside of it and that it is greatly enhanced during sawtooth crashes. 相似文献
129.
We report the effects of post-thermal treatment on the quality of 2-inch 6H-SiC wafer cut from a crystal boule grown by physical vapour transportation method. The full widths at half maximum of x-ray diffraction rocking curves measured on sites across the 2-inch wafer become narrower, indicating the quality improvement after a three-step post-thermal treatment. It is found that the most common defects such as micropipes and inclusions can be significantly reduced after the treatment. Our results show that the post-thermal treatment is an effective route to improve the quality of SiC single crystals. 相似文献
130.
Establishment of Configuration with Optimized Current Profile in Pellet Fuelled Discharge on HL-2A 下载免费PDF全文
A sawtooth-free period is produced following the pellet injection in the pellet fuelled discharge of qa = 3.4 (where qa is the safety factor at the plasma boundary) in the HL-2A tokamak. Establishment of the current profile such as in the hybrid scenario is studied under the condition of pellet injection in HL-2A. It is shown that a q-profile of weak negative shear is produced immediately after the pellet injection, and it then evolves to a broad flat profile with q0 〉 1 (where qo is the safety factor at the centre). The measured MHD mode structures evidence consistencies of the evaluated q-profile with locations of the q = 1 surface in the sawtoothing period and of the q = 2 surface in the sawtooth-free period. TRANSP analysis indicates that the energy confinement is enhanced substantially during and after pellet injection, which is resulted from the q-profile optimization and the plasma density peaking. 相似文献