全文获取类型
收费全文 | 3537篇 |
免费 | 948篇 |
国内免费 | 1580篇 |
专业分类
化学 | 2882篇 |
晶体学 | 138篇 |
力学 | 279篇 |
综合类 | 197篇 |
数学 | 443篇 |
物理学 | 2126篇 |
出版年
2024年 | 10篇 |
2023年 | 38篇 |
2022年 | 107篇 |
2021年 | 116篇 |
2020年 | 121篇 |
2019年 | 127篇 |
2018年 | 131篇 |
2017年 | 168篇 |
2016年 | 133篇 |
2015年 | 214篇 |
2014年 | 234篇 |
2013年 | 337篇 |
2012年 | 290篇 |
2011年 | 330篇 |
2010年 | 328篇 |
2009年 | 336篇 |
2008年 | 384篇 |
2007年 | 324篇 |
2006年 | 345篇 |
2005年 | 268篇 |
2004年 | 254篇 |
2003年 | 145篇 |
2002年 | 162篇 |
2001年 | 184篇 |
2000年 | 205篇 |
1999年 | 137篇 |
1998年 | 66篇 |
1997年 | 54篇 |
1996年 | 55篇 |
1995年 | 45篇 |
1994年 | 58篇 |
1993年 | 46篇 |
1992年 | 38篇 |
1991年 | 30篇 |
1990年 | 33篇 |
1989年 | 38篇 |
1988年 | 39篇 |
1987年 | 30篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1965年 | 4篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有6065条查询结果,搜索用时 140 毫秒
221.
In Situ Observation of Skeletal Shape Transition during BaB2O4 Crystal Growth in High-Temperature Solution 下载免费PDF全文
The transition from a fiat solid-liquid interface to a skeletal shape during BaB2O4 (BBO) single crystal growth in Li2B4O7 flux is observed in real time by an optical high-temperature in-situ observation system. The movement of crystal step is also investigated. The observation results demonstrate that the steps propagate along and parallel to the fiat interface when the crystal size is small. Nevertheless, they will ‘bend' close to the face centre if the crystal size becomes greater. Atomic force microscopy reveals that more deposition places near the face centre give rise to the bending of advancing steps and thus the formation of a vicinal interface structure. Measurements of step velocity show that the velocity keeps nearly constant at different moments for one specific step, whereas the step on a newly formed layer advanced faster than that on a previously formed one when the crystal size is larger than 210μm or so. Thus interracial morphological instability occurs and a skeletal interface is obtained. 相似文献
222.
The solid-liquid interface motion of NaBi(WO4)2 (NBWO) melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are visualized. The spacing of the dendrite under smaller temperature gradient turns out to be larger than that under larger temperature gradient, which is found to be sensitive to the temperature distribution. The mechanism of dendrite growth of NBWO is studied based on the model of the growth units of anion coordination polyhedra. The { 001} face has two apex links, so it shows higher stability and has high growth rate and forms the arm of dendrite, whereas the {010} face has only one apex link, and thus shows relative slower growth rate and firstly forms the branches. 相似文献
223.
Simulation of Patterns and Qualitative Analysis of Pattern Rotation in an End-Pumped Nd:YVO4 Laser 下载免费PDF全文
We simulate some laser output patterns observed in our previous experiment employing superposition of Laguerre- Gaussian modes. The rotating pattern is qualitatively analysed from the point of contemporary spatial burning hole effect of the lasing crystal. 相似文献
224.
Crystal-Orientation Dependent Evolution of Edge Dislocations from a Void in Single Crystal Cu 下载免费PDF全文
The micro-void growth by dislocation emission under tensile loading is explored with focus on the influence of crystal orientations. Based on the elastic theory, a dislocation emission criterion is formulated. It is predicted that the preferential location of dislocation nucleation and its threshold stress are dependent on the crystal orientation. Large-scale molecular dynamics (MD) simulations are also performed for single crystal copper to illustrate the dislocation evolution pattern associated with a nano-void growth. The results are in line with those given by the theoretical prediction. As revealed by MD simulations, the characteristics of void growth at micro-scale depend greatly on the crystal-orientation. 相似文献
225.
226.
227.
HUANG Xiao-Xuan PAN Zheng-Quan XU Zhao-Xin DAI Jian-Hui YING He-Ping 《理论物理通讯》2006,46(5):923-928
In this paper, by using the level spectroscopy method and bosonization theory, we discuss the evolution of the bond-order-wave (BOW) phase in a one-dimensional half-filled extended Hubbard model wlth the on-site Coulomb repulsion U as well as the inter-site Coulomb repulsion V and antiferromagnetic exchange J. After clarifying the generic phase diagrams in three limiting cases with one of the parameters being fixed at zero individually, we find that the BOW phase in the U-V phase diagram is initially enlarged as J increases from zero but is eventually suppressed as J increases further in the strong-coupling regime. A three-dimensional phase diagram is suggested where the BOW phase exists in an extended region separated from the spin-density-wave and charge-density-wave phases. 相似文献
228.
以高纯ZnS粉末为基质,采用高温转相、扩散,以及表面涂敷工艺,制得了147Pm激发的ZnS∶Cu,Cl发光粉。分析了ZnS∶Cu,Cl的晶体结构,测量了ZnS∶Cu,Cl的激发光谱、发射光谱、发光亮度。其晶体结构主要是六方纤锌矿型结构,激发光谱峰值波长为341nm,发射光谱峰值波长为513nm,初始发光亮度达到312mcd/m2。由激发光谱的峰值波长341nm推算得到六方ZnS晶体的禁带宽度为3.64eV。分析了147Pm激发的ZnS∶Cu,Cl发光粉的发光寿命,其发光寿命达到5年以上。还探讨了该放射性发光粉的发光机理。147Pm激发的ZnS∶Cu,Cl的稳定发光,实际上是激发过程与复合过程的准平衡。ZnS∶Cu,Cl的绿色发光来源于深施主-深受主对的复合发射。实验结果的分析表明,ZnS∶Cu,Cl中深施主-深受主之间的能级间隔约为2.42eV。 相似文献
229.
利用无穷维李代数方法得到了相互作用sl玻色子体系在U( 2l+ 1 ) O( 2l+ 2 )过渡区的能谱和波函数的严格解 .给出了该系统Bethe假定方程的数值解法 . 相似文献
230.
Dependence of bimodal size distribution on temperature and optical properties of InAs quantum dots grown on vicinal GaAs (100) substrates by using MOCVD 下载免费PDF全文
Self-assembled InAs quantum dots (QDs) are grown on vicinal GaAs (100)
substrates by using metal-organic chemical vapour deposition (MOCVD). An
abnormal temperature dependence of bimodal size distribution of InAs quantum
dots is found. As the temperature increases, the density of the small dots
grows larger while the density of the large dots turns smaller, which is
contrary to the evolution of QDs on exact GaAs (100) substrates. This trend
is explained by taking into account the presence of multiatomic steps on the
substrates. The optical properties of InAs QDs on vicinal GaAs(100)
substrates are also studied by photoluminescence (PL) . It is found that
dots on a vicinal substrate have a longer emission wavelength, a narrower PL
line width and a much larger PL intensity. 相似文献