全文获取类型
收费全文 | 9304篇 |
免费 | 1535篇 |
国内免费 | 1254篇 |
专业分类
化学 | 6856篇 |
晶体学 | 146篇 |
力学 | 408篇 |
综合类 | 107篇 |
数学 | 1070篇 |
物理学 | 3506篇 |
出版年
2024年 | 37篇 |
2023年 | 153篇 |
2022年 | 323篇 |
2021年 | 333篇 |
2020年 | 356篇 |
2019年 | 428篇 |
2018年 | 305篇 |
2017年 | 302篇 |
2016年 | 421篇 |
2015年 | 494篇 |
2014年 | 594篇 |
2013年 | 717篇 |
2012年 | 881篇 |
2011年 | 860篇 |
2010年 | 672篇 |
2009年 | 664篇 |
2008年 | 718篇 |
2007年 | 633篇 |
2006年 | 549篇 |
2005年 | 422篇 |
2004年 | 374篇 |
2003年 | 274篇 |
2002年 | 252篇 |
2001年 | 200篇 |
2000年 | 141篇 |
1999年 | 147篇 |
1998年 | 109篇 |
1997年 | 91篇 |
1996年 | 107篇 |
1995年 | 97篇 |
1994年 | 76篇 |
1993年 | 68篇 |
1992年 | 59篇 |
1991年 | 44篇 |
1990年 | 39篇 |
1989年 | 25篇 |
1988年 | 32篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
71.
The polarization of a D-shaped fiber is modulated after immersing it in magnetic fluid(MF)and applying a magnetic field.Theoretical analysis predicts that magneto-optical dichroism of MF plays a key role in light polarization modulation.During light polarization modulation,the evanescent wave polarized parallel to the magnetic field has greater loss than its orthogonal component.Light polarization of a D-shaped fiber with a wide polished surface can be modulated easily.High concentration MF and a large magnetic field all have great ability to modulate light polarization. 相似文献
72.
Sha Xia Dan Wang Nian-Ke Chen Dong Han Xian-Bin Li Hong-Bo Sun 《Annalen der Physik》2020,532(3):1900318
Defects play a central role in controlling the electronic properties of two-dimensional (2D) materials and realizing the industrialization of 2D electronics. However, the evaluation of charged defects in 2D materials within first-principles calculation is very challenging and has triggered a recent development of the WLZ (Wang, Li, Zhang) extrapolation method. This method lays the foundation of the theoretical evaluation of energies of charged defects in 2D materials within the first-principles framework. Herein, the vital role of defects for advancing 2D electronics is discussed, followed by an introduction of the fundamentals of the WLZ extrapolation method. The ionization energies (IEs) obtained by this method for defects in various 2D semiconductors are then reviewed and summarized. Finally, the unique defect physics in 2D dimensions including the dielectric environment effects, defect ionization process, and carrier transport mechanism captured with the WLZ extrapolation method are presented. As an efficient and reasonable evaluation of charged defects in 2D materials for nanoelectronics and other emerging applications, this work can be of benefit to the community. 相似文献
73.
By using the generalized Boltzmann equation of transport and the first-order approximation of Chapman-Enskog expansion on the κ-distribution function, we study the thermal conductivity and Dufour effect in the weakly ionized and magnetized plasma. We show that the thermal conductivity and Dufour coefficient in the κ-distributed plasma are significantly different from those in the Maxwell-distributed plasma, and the transverse thermal conductivity and Dufour coefficient in the κ-distributed plasma are generally greater than those in the Maxwell-distributed plasma, and the Righi-Leduc coefficient and Hall Dufour coefficient in the κ-distributed plasma are also generally greater than those in the Maxwell-distributed plasma. 相似文献
75.
76.
Supposa that f(x) is a quasidifferentiable function, defined on S(?)R~n where S is an open set, with a -equivalent bounded quasidifferential subfam ily. Lenma I 相似文献
77.
78.
通过对草酸溶液中制备的多孔阳极氧化铝(PAA)的形貌、晶态结构和光致发光(PL)特性的表征和机理分析,研究了草酸电解液浓度、阳极氧化电压和退火等丁艺对PAA的形成及特性的影响.PAA的孔径在50~120 nm之间,且随着阳极氧化电压的升高而增大,而受电解液浓度的影响较小.X射线衍射结果表明:PAA为非晶态结构,退火之后结晶,并有多相共存.PL测试表明PAA在375~500 nm之间有一较宽的蓝色发光带,发光峰在425 nm左右,是由氧空位引起的,且其峰强可通过改变阳极氧化电压和草酸浓度等参数来调制. 相似文献
79.
经总酶活性测定和凝胶电泳图谱分析发现:剧烈运动后,小白鼠六种组织LDH总酶活性,骨骼肌有显著升高,(p<0.05),其余五种组织均变化不显著;心肌、骨骼肌、肾脏的M型LDH相对活性显著升高(P<0.05),而H型LDH相对活性显著下降(p<0.05);相应地,A亚基比例显著升高,B亚基比例显著下降,这种变化似能反应剧烈运动对小白鼠厌氧代谢的明显影响. 相似文献
80.
Semiconductor optical amplifier used as regenerator for degraded differential phase-shift keying signals 下载免费PDF全文
Phase and amplitude regeneration are necessary for degraded differential phase-shift keying communication systems.This paper proposes a regenerator based on semiconductor optical amplifier for differential phase-shift keying signals.The key regeneration mechanism is theoretically analysed.The effectiveness of semiconductor optical amplifier based regenerator is demonstrated by comparing the bit error rate and eye diagrams before and after regeneration for 40-Gbit/s differential phase-shift keying 1080-km transmission systems.The results show that regeneration effects are very well.Bit error rate is less than 10 12 with the regenerator. 相似文献