全文获取类型
收费全文 | 2107篇 |
免费 | 419篇 |
国内免费 | 193篇 |
专业分类
化学 | 1377篇 |
晶体学 | 26篇 |
力学 | 110篇 |
综合类 | 11篇 |
数学 | 287篇 |
物理学 | 908篇 |
出版年
2024年 | 4篇 |
2023年 | 51篇 |
2022年 | 77篇 |
2021年 | 104篇 |
2020年 | 99篇 |
2019年 | 86篇 |
2018年 | 77篇 |
2017年 | 84篇 |
2016年 | 125篇 |
2015年 | 114篇 |
2014年 | 135篇 |
2013年 | 165篇 |
2012年 | 204篇 |
2011年 | 209篇 |
2010年 | 141篇 |
2009年 | 147篇 |
2008年 | 123篇 |
2007年 | 106篇 |
2006年 | 97篇 |
2005年 | 88篇 |
2004年 | 68篇 |
2003年 | 55篇 |
2002年 | 49篇 |
2001年 | 48篇 |
2000年 | 32篇 |
1999年 | 26篇 |
1998年 | 21篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2719条查询结果,搜索用时 15 毫秒
41.
42.
Chao-Qiang Geng Da Huang Lu-Hsing Tsai 《The European Physical Journal C - Particles and Fields》2015,75(11):557
We study the CP-violation effects from two types of neutrino mass matrices with (i) \((M_\nu )_{ee}=0\), and (ii) \((M_\nu )_{ee}=(M_\nu )_{e\mu }=0\), which can be realized by the high-dimensional lepton number violating operators \(\bar{\ell }_R^c\gamma ^\mu L_L (D_\mu \Phi )\Phi ^2\) and \(\bar{\ell }_R^c l_R (D_\mu {\Phi })^2\Phi ^2\), respectively. In (i), the neutrino mass spectrum is in the normal ordering with the lightest neutrino mass within the range \(0.002\,\mathrm{eV}\lesssim m_0\lesssim 0.007\,\mathrm{eV}\). Furthermore, for a given value of \(m_0\), there are two solutions for the two Majorana phases \(\alpha _{21}\) and \(\alpha _{31}\), whereas the Dirac phase \(\delta \) is arbitrary. For (ii), the parameters of \(m_0\), \(\delta \), \(\alpha _{21}\), and \(\alpha _{31}\) can be completely determined. We calculate the CP-violating asymmetries in neutrino–antineutrino oscillations for both mass textures of (i) and (ii), which are closely related to the CP-violating Majorana phases. 相似文献
43.
Jia-Jia Geng Rui-Yun Guo Dong-Ze He Jing-Fei Zhang Xin Zhang 《Frontiers of Physics》2015,10(5):109501
We explore the impact of the Sandage−Loeb (SL) test on the precision of cosmological constraints for f(T) gravity theories. The SL test is an important supplement to current cosmological observations because it measures the redshift drift in the Lyman-α forest in the spectra of distant quasars, covering the “redshift desert” of 2 ≲ z ≲ 5 . To avoid data inconsistency, we use the best-fit models based on current combined observational data as fiducial models to simulate 30 mock SL test data. We quantify the impact of these SL test data on parameter estimation for f(T) gravity theories. Two typical f(T) models are considered, the power-law model f(T)PL and the exponential-form model f(T)EXP. The results show that the SL test can effectively break the existing strong degeneracy between the present-day matter density Ωm and the Hubble constant H0 in other cosmological observations. For the considered f(T) models, a 30-year observation of the SL test can improve the constraint precision of Ωm and H0 enormously but cannot effectively improve the constraint precision of the model parameters. 相似文献
44.
Xiaojun He Jiangwei Lei Yejing Geng Xiaoyong Zhang Mingbo Wu Mingdong Zheng 《Journal of Physics and Chemistry of Solids》2009,70(3-4):738-744
Microporous activated carbons were prepared by microwave heating petroleum coke with potassium hydroxide as activation agent. Microporous activated carbons were characterized by infrared spectroscopy, X-ray diffraction and nitrogen adsorption/desorption isotherms. Electrochemical properties of an electric double layer capacitor using microporous activated carbon as electrode materials were investigated by constant current charge-discharge and electrochemical impedance spectroscopic techniques. The results show that the specific surface area and the pore volume of microporous activated carbon increase with increasing activation time before the activation time reaches 37 min. The microporous volume totals 94.0% in the microporous activated carbons and the average pore diameter of microporous activated carbon is 2.00 nm. Microporous activated carbons prepared in the activation time of 31, 35 and 37 min are named as AC-31, AC-35 and AC-37, respectively. Compared with AC-27 electrode, the internal resistance for ions transferring in AC-31, AC-35 or AC-37 electrode is relatively small. The specific capacitance of AC-31 is the biggest among the microporous activated carbons, and it retains 279.6 F g?1 maintaining 93.5% capacity after 200 recycling number. 相似文献
45.
Ronald C. Scherer Fariborz Alipour Eileen Finnegan Chwen Geng Guo 《Journal of voice》1997,11(3):277-284
The membranous contact quotient (MCQ) is introduced as a measure of dynamic glottal competence. It is defined as the ratio of the membranous contact glottis (the anterior-posterior length of contact between the two membranous vocal folds) and the membranous vocal fold length. An elliptical approximation to the vocal fold contour during phonation was used to predict MCQ values as a function of vocal process gap (adduction), maximum glottal width, and membranous glottal length. MCQ is highly dependent on the vocal process gap and the maximum glottal width, but not on vocal fold length. Five excised larynges were used to obtain MCQ data for a wide range of vocal process gaps and maximum glottal widths. Predicted and measured MCQ values had a correlation of 0.93, with an average absolute difference of 9.6% (SD = 10.5%). The model is better at higher values of MCQ. The theory for MCQ is also expressed as a function of vocal process gap and subglottal pressure to suggest production control potential. The MCQ measure is obtainable with the use of stroboscopy and appears to be a potentially useful clinical measure. 相似文献
46.
47.
48.
原子光谱线增宽的原因 总被引:3,自引:0,他引:3
本文从理论上给出了原子光谱线增宽的几种原因 ,即 :①自然线宽 ,它是原子的内禀特性 (即在跃迁中所涉及到的能级的特性 ) ;②多普勒增宽 ,它是原子无规则热运动的结果 ;③碰撞增宽 ,它是原子间相互作用的结果。并对这几种原因分别给出了数量级上的估算。对原子光谱的测定具有参考意义。 相似文献
49.
50.
采用密度泛函理论的B3LYP方法和二次组态相互作用(QCISD(T))方法优化计算了OH分子基态(X2Π)的平衡结构、振动频率和离解能.根据原子分子反应静力学原理,导出了OH分子基态(X2Π)的合理离解极限,采用最小二乘法拟合Murrell-Sorbie函数得到了相应的势能函数和与该基态相对应的光谱常数(Be,αe,ωe和ωeχe),计算结果与实验数据符合得相当好.
关键词:
OH分子
2Π)')" href="#">基态(X2Π)
势能函数 相似文献