全文获取类型
收费全文 | 239篇 |
免费 | 60篇 |
国内免费 | 91篇 |
专业分类
化学 | 248篇 |
晶体学 | 6篇 |
力学 | 13篇 |
综合类 | 2篇 |
数学 | 18篇 |
物理学 | 103篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 20篇 |
2016年 | 18篇 |
2015年 | 18篇 |
2014年 | 26篇 |
2013年 | 23篇 |
2012年 | 22篇 |
2011年 | 15篇 |
2010年 | 19篇 |
2009年 | 26篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 16篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有390条查询结果,搜索用时 31 毫秒
1.
2.
Qingbiao Yang Zhenyu Li Youliang Hong Yiyang Zhao Shilun Qiu Ce Wang Yen Wei 《Journal of Polymer Science.Polymer Physics》2004,42(20):3721-3726
Although there have been many reports on the preparation and applications of various polymer nanofibers with the electrospinning technique, the understanding of synthetic parameters in electrospinning remains limited. In this article, we investigate experimentally the influence of solvents on the morphology of the poly(vinyl pyrrolidone) (PVP) micro/nanofibers prepared by electrospinning PVP solution in different solvents, including ethanol, dichloromethane (MC) and N,N‐dimethylformamide (DMF). Using 4 wt % PVP solutions, the PVP fibers prepared from MC and DMF solvents had a shape like a bead‐on‐a‐string. In contrast, smooth PVP nanofibers were obtained with ethanol as a solvent although the size distribution of the fibers was somewhat broadened. In an effort to prepare PVP nanofibers with small diameters and narrow size distributions, we developed a strategy of using mixed solvents. The experimental results showed that when the ratio of DMF to ethanol was 50:50 (w/w), regular cylindrical PVP nanofibers with a diameter of 20 nm were successfully prepared. The formation of these thinnest nanofibers could be attributed to the combined effects of ethanol and DMF solvents that optimize the solution viscosity and charge density of the polymer jet. In addition, an interesting helical‐shaped fiber was obtained from 20 wt % PVP solution in a 50:50 (w/w) mixed ethanol/DMF solvent. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3721–3726, 2004 相似文献
3.
报道了Pr(0.5):ZBLAN玻璃在双频双光束光源激发下的激发态上转换现象.发现上转换发射谱的荧光与常规荧光发射谱的荧光一致,还发现双频激发下的上转换激发谱有3个明显的谱峰,它们依此对应于788.5nm 1G4→3P2,850.5nm 1G4→1I6和805.0nm 3H6→1D2的激发态吸收跃迁,而大的850.5nm上转换激发谱峰是由大的1G4(Pr3+ )→1I6(Pr3+)跃迁的振子强度f=23.04×10-6所致.这说明起源于1G4能级的激发态吸收上转换尤其1G4(Pr3+)→1I6(Pr3+) 相似文献
4.
5.
6.
利用静电纺丝法与气固反应相结合, 成功地制备了硫化锌掺锰/聚乙烯醇复合纳米纤维, 并对所制备的复合物进行了表征, 探讨了复合物的结构及其性能. 相似文献
7.
8.
Summary The reaction of warm alcoholic solutions of acetates of CoII, MnII, ZnII and NiII with 2, 6-diacetylpyridine andS-methylisothiosemicarbazide hydrogen iodide yielded the complexes: [Co(H2L)I2]·H2O, [Mn(H2L)(MeOH)2]I2, [Zn(H2L)(MeOH)I]I and [Ni(HL)]I, (H2L=the pentadentate pentaaza-ligand 2, 6-diacetylpyridine bis(S-methylisothiosemicarbazone)). The reaction of methanolic solutions of [Ni(HL)]I and NH4NCS or LiOAc.2H2O, give [Ni(HL)]NCS and NiL, respectively. For the complexes of CoII, MnII and ZnII, a pentagonal bipyramidal configuration is proposed, with H2L in the equatorial plane and two unidentate ligands (I and/or MeOH) in the axial positions. The complexes [Ni(HL)]X (X=I or NCS) and NiL probably have monomeric five- and dimeric six-coordinate structures, respectively, in which only the chelate ligand is involved in coordination. 相似文献
9.
INDO方法研究了C70R2(R=OH,CH3)4种异构体的结构和稳定性,表明1,9-C70(OH)2比7,8-C70(OH)2稳定,两者能量差为38.5kJ/mol,而7,8-C70(CH3)2比1,9-C70(CH3)2能量低23.0kJ/mol.以优化构型为基础,对C70R2(R=OH,CH3)的电子光谱进行了理论预测. 相似文献
10.
Poly(aryl ether ketone) composite membrane as a high‐performance lithium‐ion batteries separator
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Min Xie Mingying Yin Guangdi Nie Jun Wang Ce Wang Danming Chao Xincai Liu 《Journal of polymer science. Part A, Polymer chemistry》2016,54(17):2714-2721
We described the design and synthesis of a modified poly(aryl ether ketone) bearing phenolphthalein and allyl groups (P‐PAEK) via nucleophilic polycondensation. A new kind of composite separator, crosslinked P‐PAEK/polyvinylidene fluoride (c‐P‐PAEK/PVDF) membrane was successfully prepared using phase separation, phase inversion method, and UV crosslinking technique. As a separator of lithium‐ion battery, c‐P‐PAEK/PVDF membrane demonstrates high porosity and uniform distribution of pores with interconnected pathways. Low thermal shrinkage, distinct shut‐down effect, high liquid electrolyte uptake capacity, and exciting liquid electrolyte wettability of the prepared c‐P‐PAEK/PVDF membrane have been revealed through comprehensive study. Moreover, the c‐P‐PAEK/PVDF membrane was applied to assemble a conventional Li/LiFePO4 coin cell, which exhibited hopeful cell performance. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2714–2721 相似文献