全文获取类型
收费全文 | 3646篇 |
免费 | 1776篇 |
国内免费 | 194篇 |
专业分类
化学 | 89篇 |
晶体学 | 54篇 |
力学 | 35篇 |
综合类 | 16篇 |
数学 | 7篇 |
物理学 | 5415篇 |
出版年
2024年 | 20篇 |
2023年 | 97篇 |
2022年 | 127篇 |
2021年 | 97篇 |
2020年 | 92篇 |
2019年 | 91篇 |
2018年 | 67篇 |
2017年 | 84篇 |
2016年 | 107篇 |
2015年 | 133篇 |
2014年 | 325篇 |
2013年 | 207篇 |
2012年 | 243篇 |
2011年 | 312篇 |
2010年 | 200篇 |
2009年 | 262篇 |
2008年 | 313篇 |
2007年 | 258篇 |
2006年 | 284篇 |
2005年 | 239篇 |
2004年 | 258篇 |
2003年 | 216篇 |
2002年 | 177篇 |
2001年 | 160篇 |
2000年 | 143篇 |
1999年 | 135篇 |
1998年 | 101篇 |
1997年 | 117篇 |
1996年 | 139篇 |
1995年 | 132篇 |
1994年 | 91篇 |
1993年 | 104篇 |
1992年 | 75篇 |
1991年 | 54篇 |
1990年 | 63篇 |
1989年 | 48篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
排序方式: 共有5616条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
《化学物理学报(中文版)》2013,(6):I0002-I0002
Chemical kinetics and reaction dynamics, as a crucial branch of physical chemistry, mostly concerns with the "how, why and when" of chemical reactions, which is not only an exciting intellectual frontier but also addresses grand societal needs. These two aspects promote rapidly developing a series of experimental techniques, including ultrafast lasers, high resolution mass spectrometry and optical spectroscopy, and crossed molecular beam etc. Thanks to the rapid development of computer sci- ence, nowadays it is possible to calculate the reaction rates of complex reaction systems by advanced statistical kinetic theories based on accurate potential energy surfaces, 相似文献
95.
Jiancong Du Suhui Deng Shangguo Hou Lingling Qiao Jianfang Chen Qing Huang Chunhai Fan Ya Cheng Yun Zhao 《中国光学快报(英文版)》2014,12(4):41101-38
DNA tetrahedral nanostructures are considered to be uew nanocarriers because they can be precisely controlled and hold excellent penetration ability to the cellular membrane. Although the DNA tetrahedral nanostructure is extensively studied in biology and medicine, its behavior in the cells with nanoscale resolution is not understood clearly. In this letter, we demonstrate superrcsolution fluorescence imaging of the distribution of DNA tetrahedral nanostructures in the cell with a simulated emission depletion (STED) microscope, which is built based on a conventional eonfocal microscope and can t)rovide a resolution of 70 nm. 相似文献
96.
We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser (EDFL) operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ. 相似文献
97.
98.
Material growth and device fabrication of terahertz quantum-cascade laser based on bound-to-continuum structure 下载免费PDF全文
The terahertz quantum-cascade laser (THz QCL) based on bound-to-continuum structure is demonstrated. The X-ray diffraction measurement of the material shows a high crystalline quality of the active region. A THz QCL device was fabricated with semi-insulating surface-plasmon waveguide. The test device is lasing at about 3 THz and operating up to 60 K. It shows a single frequency property under different drive currents and temperatures. At 9 K, the maximum output power is greater than 2 mW with a threshold current density of 159 A/cm2. 相似文献
99.
In this letter, numerical simulation and experimental study of a radial-slab solid-state laser are presented. The laser includes four crossing-slabs pumped by four Xe flashlamps. The numerical simulation of coherent intensity in the near field and the far field indicates that the laser with the structure can improve the quality of output beam compared with incoherent beam combination. The radial-slab solid-state laser is fabricated, and initial experiments are carried out at a pulse repetition of 1 Hz. Nine beams in the near field and one combined beam in the far field are obtained in our initial experiment. The experimental results are consistent with the numerical analysis in the coherent condition. The results show that coherent beam combination is obtained by this laser. 相似文献
100.
报道了自主研制的面向Li原子D1线频率测量应用的掺铒飞秒光纤光学频率梳,包括飞秒激光源,频率探测及控制单元,光谱展宽及拍频单元.光纤光梳系统中飞秒激光光源是一套基于非线性偏振旋转锁模机制的掺铒飞秒光纤激光器,重复频率为196.5MHz,中心波长为1 572nm.利用f-2f法探测载波包络相移频率,获得信噪比约为40dB的信号(分辨率带宽300kHz).改变飞秒激光光源泵浦控制载波包络相移频率、频率稳定度是3.74×10-18/τ1/2;通过电光晶体和压电陶瓷改变飞秒激光光源腔长来控制重复频率frep、频率稳定度是1.75×10-13/τ1/2.利用高非线性光纤和倍频晶体将光纤光梳直接输出光谱由1 520~1 607nm扩展到671nm,获得了单模功率为208nW的光信号.与671nm单频激光拍频产生约为60dB(分辨率带宽1Hz)信号,满足Li原子D1线频率测量实验的需求. 相似文献