全文获取类型
收费全文 | 1849篇 |
免费 | 333篇 |
国内免费 | 309篇 |
专业分类
化学 | 1545篇 |
晶体学 | 36篇 |
力学 | 100篇 |
综合类 | 23篇 |
数学 | 113篇 |
物理学 | 674篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 71篇 |
2021年 | 75篇 |
2020年 | 79篇 |
2019年 | 91篇 |
2018年 | 65篇 |
2017年 | 64篇 |
2016年 | 94篇 |
2015年 | 98篇 |
2014年 | 129篇 |
2013年 | 118篇 |
2012年 | 177篇 |
2011年 | 196篇 |
2010年 | 135篇 |
2009年 | 150篇 |
2008年 | 131篇 |
2007年 | 90篇 |
2006年 | 97篇 |
2005年 | 78篇 |
2004年 | 61篇 |
2003年 | 56篇 |
2002年 | 59篇 |
2001年 | 33篇 |
2000年 | 27篇 |
1999年 | 47篇 |
1998年 | 38篇 |
1997年 | 29篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有2491条查询结果,搜索用时 15 毫秒
21.
Ultracold two-component fermionic gases with a magnetic field gradient near a feshbach resonance 总被引:1,自引:0,他引:1
We study theoretically the ultracold two-component fermionic gases when a gradient magnetic field is used to tune the scattering length between atoms. For 6Li at the narrow resonance B0=543.25 G, it is shown that the gases would be in a coexistence of the regimes of BCS, Bose-Einstein condensation (BEC), and unitarity limit with the present experimental technique. In the case of thermal and chemical equilibrium, we investigate the density distribution of the gases and show that a double peak of the density distribution can give us a clear evidence for the coexistence of BCS, BEC, and unitarity limit. 相似文献
22.
23.
24.
采用光纤技术实现拉曼光谱和扫描隧道显微镜实时联用测试 总被引:1,自引:0,他引:1
设计并制作了与扫描隧道显微镜(STM)探头和拉曼光谱仪相适配的光纤探测装置,该装置采用配有不很短焦距的自聚焦透镜以获得较大的相对孔径,并使用多束光纤以充分利用扫描隧道显微镜探针周围有限空间,提高了拉曼散射光的收集效率,获得具有较高信噪比的拉曼谱图,在该装置的基础上进一步建立拉曼-扫描隧道显微镜联用系统,初步实验表明该联用系统用于实时研究固/气和固/液界面体系是可行的,即利用扫描隧道显微镜可获得固体 相似文献
25.
26.
Transparent phosphate glass ceramics co-doped with Er3+ and Yb3+ in the system P2O5Li2OCaF2TiO2 were successfully synthesized by melt-quenching and subsequent heating. Formation of the nanocrystals was confirmed by X-ray powder diffraction. Judd–Ofelt analyses of Er3+ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω2,4,6. Under 975 nm excitation, intense upconversion (UC) and infrared emission (1545 nm) were observed in the glass ceramics by efficient energy transfer from Yb3+ to Er3+. The luminescence processes were explained and the emission cross section was calculated by Fuchtbauer–Ladenburg (F–L) formula. The results confirm the potential applications of Er3+/Yb3+ co-doped glass ceramics as laser and fiber amplifier media. 相似文献
27.
Yin‐Feng Wang Qing Wang Zhuo Li Zhi‐Ru Li Jiangen Huang Jiuhui Liu Guangpei Zhou 《Journal of Physical Organic Chemistry》2012,25(8):674-679
How does the endo C–F bond influence the excess electron binding motif? For lithium‐doped endohedral perfluorofullerenes with endo C–F bonds, under both internal‐push (from exo C–F bonds) and external‐push (from endo C–F bonds) electron effects, the singly occupied molecular orbital electron cloud of the sphere‐like Li···F8@C60F52 (D2) is partially dispersed within the σp–s antibonding orbital of endo C–F bonds and the space between Cδ+–Fendoδ– double electric layers, which makes Li···F8@C60F52 have partial excess electron (electride characteristics) and partial lithium salt characteristics, while in the tube‐like Li···F2@C60F58 (Cs), as the Li is changing from approaching F to keeping away from F and to approaching another one, the singly occupied molecular orbital electron cloud is mainly dispersed from within the p orbital of the short endo C–F bond to within the middle of the two F atoms and again to within the p orbital of the short endo C–F bond, which indicates an evolution from lithium salt characteristic to excess electron characteristic, and again to lithium salt characteristic. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
28.
29.
为了解决蒙特卡罗模拟S(, )模型只能求解特定温度条件下中子输运问题的局限性,建立了中子在不同温度液态水中输运的等效质量热运动模型。在分析自由气体热运动模型的基础上,采用不同的等效质量对中子与水中氢原子的弹性散射模拟过程进行改进,对中子穿过水层后的流量进行模拟计算,通过与S(, )模型的计算结果的比较,得到了5个不同的温度点水中氢原子的最佳等效质量。根据5个不同温度点的数据拟合给出了最佳等效质量和温度的函数关系。采用该模型计算得到的中子在不同温度条件下水中输运参数与S(, )模型相符。等效质量热运动模型突破了S(, )模型只能计算有限温度点的局限性,能有效处理300~800 K任意温度水中的中子输运问题。 相似文献
30.
Influence of different oxidants on band alignment of HfO2 films deposited by atomic layer deposition 下载免费PDF全文
Based on X-ray photoelectron spectroscopy (XPS), influences of different oxidants on band alignment of HfO2 films deposited by atomic layer deposition (ALD) are investigated in this paper. The measured valence band offset (VBO) value for H2O-based HfO2 increases from 3.17 eV to 3.32 eV after annealing, whereas the VBO value for O3-based HfO2 decreases from 3.57 eV to 3.46 eV. The research results indicate that the silicate layer changes in different ways for H2O-based and O3-based HfO2 films after annealing process, which plays a key role in generating the internal electric field formed by the dipoles. The variations of the dipoles at the interface between the HfO2 and SiO2 after annealing may lead the VBO values of H2O-based and O3-based HfO2 to vary in different ways, which is in agreement with the varition of flat band (VFB) voltage. 相似文献