全文获取类型
收费全文 | 1076篇 |
免费 | 82篇 |
国内免费 | 267篇 |
专业分类
化学 | 981篇 |
晶体学 | 23篇 |
力学 | 48篇 |
综合类 | 12篇 |
数学 | 138篇 |
物理学 | 223篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 35篇 |
2021年 | 51篇 |
2020年 | 46篇 |
2019年 | 43篇 |
2018年 | 29篇 |
2017年 | 50篇 |
2016年 | 36篇 |
2015年 | 70篇 |
2014年 | 77篇 |
2013年 | 88篇 |
2012年 | 99篇 |
2011年 | 111篇 |
2010年 | 77篇 |
2009年 | 72篇 |
2008年 | 67篇 |
2007年 | 57篇 |
2006年 | 78篇 |
2005年 | 62篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 19篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 33篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有1425条查询结果,搜索用时 15 毫秒
121.
In this paper, photovoltaic characteristics of ITO/PEDOT:PSS/SubPc:Rubrene (mixed ratio R by weight)/C60/Bphen/Ag organic solar cells (OSCs) are analyzed in detail. The intrinsic properties of a SubPc:rubrene doped layer on device performance were discussed based on theoretical analysis of the experimental OSCs. The ratio R was 0, 0.25, 0.5, and 0.75,1, respectively. The results showed that when R was 0.75 performing the best, which owned the highest short circuit current (J sc ) 6.61 mA/cm2 and highest power conversion efficiency (PCE) 2.44%, the FF was 41% and the open circuit current (V oc ) was 0.905 V. The suitable HOMO level, absorption capacity, carrier transport ability and exciton diffusion length (L D ) of organic material are very important for the performance of the device. 相似文献
122.
123.
124.
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
125.
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
126.
127.
128.
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
129.
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
130.
采用内部萃取电喷雾电离质谱(iEESI-MS)技术,以甲醇作为萃取溶剂,无需样品预处理,在优化条件下分别对牛油果果肉和果皮中化学成分进行快速直接鉴定,并考察了不同成熟度牛油果果肉中化学成分的差异.实验结果表明,在负离子检测模式下,从果肉中鉴定出棕榈酸、硬脂酸、棕榈油酸、油酸和亚麻酸等12种有效营养成分,从果皮中鉴定出儿茶素、绿原酸等11种营养成分.利用正交偏最小二乘判别分析法(OPLS-DA)对不同成熟度的牛油果果肉的iEESI-MS指纹谱图数据进行分析发现,此方法能够有效判别不同成熟程度的牛油果且5种化学成分差异显著.本方法无需样品预处理、样品耗量少、分析速度快(单个样品检测时间小于1 min)且操作简便,为植物有效营养成分和医用价值的开发提供了一种快速质谱分析新方法. 相似文献