全文获取类型
收费全文 | 869篇 |
免费 | 57篇 |
国内免费 | 131篇 |
学科分类
数理化 | 1057篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 25篇 |
2021年 | 41篇 |
2020年 | 39篇 |
2019年 | 37篇 |
2018年 | 23篇 |
2017年 | 33篇 |
2016年 | 31篇 |
2015年 | 49篇 |
2014年 | 67篇 |
2013年 | 65篇 |
2012年 | 82篇 |
2011年 | 92篇 |
2010年 | 57篇 |
2009年 | 58篇 |
2008年 | 51篇 |
2007年 | 41篇 |
2006年 | 55篇 |
2005年 | 38篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 20篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有1057条查询结果,搜索用时 0 毫秒
61.
62.
The crystal structure, electronic structure and hydrogen site occupancy of LaNi4.5Al0.5Hy intermediate phase (y=2.0, 3.0, 4.0) have been investigated using the full-potential linearized augmented plane wave (FLAPW) method. For the first time we analyzed the interstitial site occupation of hydrogen atoms. The H atoms were found to prefer the 6m, 3f and 12n sites, while no 4h sites were occupied. A narrowed Ni-d band is found due to the lattice expansion: the total DOS at EF increases with y, which indicates that the compounds become less stable. The interaction between Al and Ni, with H plays a dominant role in the stability of LaNi4.5Al0.5Hy intermediate phase. The smaller the shift of EF towards the higher energy region, the more stable the compounds will be. Our results are compared with experimental data and discussed in the light of previous works. 相似文献
63.
64.
Defeng Wu Yisheng Zhang Lijuan Yuan Ming Zhang Weidong Zhou 《Journal of Polymer Science.Polymer Physics》2010,48(7):756-765
Poly(ε‐caprolactone)/polylactide blend (PCL/PLA) is an interesting biomaterial because the two component polymers show good complementarity in their physical properties. However, PCL and PLA are incompatible thermodynamically and hence the interfacial properties act as the important roles controlling the final properties of their blends. Thus, in this work, the PCL/PLA blends were prepared by melt mixing using the block copolymers as compatibilizer for the studies of interfacial properties. Several rheological methods and viscoelastic models were used to establish the relations between improved phase morphologies and interfacial properties. The results show that the interfacial behaviors of the PCL/PLA blends highly depend on the interface‐located copolymers. The presence of copolymers reduces the interfacial tension and emulsified the phase interface, leading to stabilization of the interface and retarding both the shape relaxation and the elastic interface relaxation. As a result, besides the relaxation of matrices (τm) and the shape relaxation of the dispersed PLA phase (τF), a new relaxation behavior (τβ), which is attribute to the relaxation of Marangoni stresses tangential to the interface between dispersed PLA phase and matrix PCL, is observed on the compatibilized blends. In contrast to that of the diblock copolymers, the triblock copolymers show higher emulsifying level. However, both can improve the overall interfacial properties and enhance the mechanical strength of the PCL/PLA blends as a result. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 756–765, 2010 相似文献
65.
66.
67.
Chen Lijuan 《Annals of Differential Equations》2008,(4):379-386
In this paper, a set of sufficient conditions which ensure the permanence of a periodic predator-prey system with dispersal and general Holling type functional response are obtained. Our results generalize some known results. 相似文献
68.
Microchimica Acta - The authors describe an aptamer based fluorometric assay for the determination of ATP. It is based on deoxyribonuclease I-aided target recycling and signal amplification. The... 相似文献
69.
70.
A variety of single component rare earth aryloxides substituted by various alkyl groups [Ln(OAr)3] such as methyl, isopropyl, tert‐butyl have been surveyed in the ring‐opening copolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and ε‐caprolactone (ε‐CL). It was worthwhile to note that activity of the catalyst varied with both the ligands' structure and the number of alkyl groups on phenyl ring. The stronger ability of electron‐donation of alkyl groups on phenyl ring, and the more numbers of alkyl groups on phenyl ring, the higher catalytic activity. The experimental results show that lanthanum tris(2,4,6‐tri‐tert‐butylphenolate) [La(OTTBP)3] exhibits highest activity in all lanthanum aryloxides. 1H NMR spectral data of copolymer obtained showed that the polymerization mechanism is in agreement with the coordination insertion mechanism. 相似文献