全文获取类型
收费全文 | 15268篇 |
免费 | 1694篇 |
国内免费 | 1478篇 |
专业分类
化学 | 7553篇 |
晶体学 | 118篇 |
力学 | 681篇 |
综合类 | 67篇 |
数学 | 1282篇 |
物理学 | 3743篇 |
综合类 | 4996篇 |
出版年
2024年 | 89篇 |
2023年 | 324篇 |
2022年 | 494篇 |
2021年 | 513篇 |
2020年 | 513篇 |
2019年 | 485篇 |
2018年 | 446篇 |
2017年 | 447篇 |
2016年 | 589篇 |
2015年 | 643篇 |
2014年 | 785篇 |
2013年 | 992篇 |
2012年 | 1101篇 |
2011年 | 1117篇 |
2010年 | 849篇 |
2009年 | 788篇 |
2008年 | 962篇 |
2007年 | 810篇 |
2006年 | 718篇 |
2005年 | 561篇 |
2004年 | 494篇 |
2003年 | 416篇 |
2002年 | 481篇 |
2001年 | 383篇 |
2000年 | 330篇 |
1999年 | 461篇 |
1998年 | 349篇 |
1997年 | 304篇 |
1996年 | 307篇 |
1995年 | 294篇 |
1994年 | 225篇 |
1993年 | 211篇 |
1992年 | 168篇 |
1991年 | 165篇 |
1990年 | 149篇 |
1989年 | 132篇 |
1988年 | 112篇 |
1987年 | 70篇 |
1986年 | 39篇 |
1985年 | 39篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In this paper, a new type of resonant Brewster filters (RBF) with surface relief structure for the multiple channels is first presented by using the rigorous coupled-wave analysis and the S-matrix method. By tuning the depth of homogeneous layer which is under the surface relief structure, the multiple channels phenomenon is obtained. Long range, extremely low sidebands and multiple channels are found when the RBF with surface relief structure is illuminated with Transverse Magnetic incident polarization light near the Brewster angle calculated with the effective media theory of sub wavelength grating. Moreover, the wavelengths of RBF with surface relief structure can be easily shifted by changing the depth of homogeneous layer while its optical properties such as low sideband reflection and narrow band are not spoiled when the depth is changed. Furthermore, the variation of the grating thickness does not effectively change the resonant wavelength of RBF, but have a remarkable effect on its line width, which is very useful for designing such filters with different line widths at desired wavelength. 相似文献
992.
Performance of gain-switched all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have made a gain-switched all-solid-state quasi-continuous-wave (QCW) tunable Ti:sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd:YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti:sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti:sapphire laser from 700 to 950nm can be achieved. It has a maximum average output power of 5.6W at 800nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 mn pump laser to the Ti:sapphire laser. 相似文献
993.
从LD端面抽运固体激光器的激光阈值公式出发,建立了双波长激光同时振荡的阈值条件,理论计算了腔镜对于两个波长的透过率关系,实现了LD端面抽运Nd:YAG 1319nm/1338nm双波长激光连续和准连续输出.双波长激光连续输出功率可达6W,斜效率为30%;准连续输出功率在重复频率50kHz时可达4.75W,斜效率为24.73%,脉冲宽度为55.05ns;腔内插入布儒斯特片,在重复频率为50kHz时,双波长激光准连续线偏振输出功率可达2.22W,不稳定性小于0.52%,M2 相似文献
994.
995.
Chunling Liu Yanping Yao Chunwu Wang Xin Gao Zhongliang Qiao Mei Li Yuxia Wang Baoxue Bo 《中国光学快报(英文版)》2008,6(3)
In order to improve the optical properties of the Ⅲ-Ⅴ laser diodes(LDs) by means of H2S plasma passivation technology,H2S plasma passivation treatment is performed on the GaAs(110) surface.The optimum passivation conditions obtained are 60-W radio frequency(RF)power and 20-min duration.So the laser cavity surfaces axe treated under the optimum passivation conditions.Consequently,compared with unpassivated lasers with only AR/HR-coatings,the catastrophic optical damage (COD) threshold value of the passivated lasers by H2S plasma treatment is increased by 33%,which is almost the same as that of (NH4)2Sx treatment.And the life-test experiment has demonstrated that this passivation method is more stable than(NH4)2Sx solution wet-passivated treatment. 相似文献
996.
A periodically poled lithium niobate (PPLN) optical parametric generator (OPG) pumped by a laser diode (LD)-pumped Q-switched Tm,Ho:GdVO4 laser operated at 2.048 μm with pump pulse of 25 ns and repetition rate of 10 kHz is reported. 相似文献
997.
In a capillary discharge experiment for the neon-like argon lasing, we have proposed an experimental scheme to verify that the multi-spike of X-ray diode (XRD) signal is a multi-pulse laser or is a reflection of the laser pulse in the XRD.The ceramic capillary has an inner diameter of 3mm and a length of 200mm.At the gas pressure of 28Pa and discharge current of 27kA, stable lasing has been realized.The experimental results prove that the multi-spike of XRD signal is a reflection of the electromagnetic signal produced by the laser pulse in the XRD.The improved electrocircuit scheme of the XRD to minimize the reflection phenomena is also found. 相似文献
998.
本文利用一个能产生稳定的离子浓度的独立的离子源,在被研究的间隙中形成一定的离子背景,用升降法观测了正、负背景离子对棒-板间隙百分之五十击穿电压的影响;测量了正、负背景离子对正棒-板间隙伏秒特性的影响;用截波静止摄影法观测了正、负离子背景对放电通道的形态及先导发展速度的影响。文中对这些观测结果的物理机理给予了解释。 相似文献
999.
1000.
本文将Pade′逼近方法应用于定积分的数值计算。讨论了收敛性,给出了若干近似计算公式。当应用这些公式计算某些定积分时,得到了较为精确的结果。 相似文献