全文获取类型
收费全文 | 1177篇 |
免费 | 244篇 |
国内免费 | 71篇 |
专业分类
化学 | 471篇 |
晶体学 | 20篇 |
力学 | 13篇 |
数学 | 83篇 |
物理学 | 905篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 39篇 |
2020年 | 23篇 |
2019年 | 28篇 |
2018年 | 34篇 |
2017年 | 47篇 |
2016年 | 79篇 |
2015年 | 51篇 |
2014年 | 118篇 |
2013年 | 105篇 |
2012年 | 112篇 |
2011年 | 144篇 |
2010年 | 95篇 |
2009年 | 100篇 |
2008年 | 101篇 |
2007年 | 84篇 |
2006年 | 64篇 |
2005年 | 48篇 |
2004年 | 41篇 |
2003年 | 33篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1492条查询结果,搜索用时 421 毫秒
141.
Jonghee Lee Jeong‐Ik Lee Moo‐Jin Park Young Kwan Jung Nam Sung Cho Hoon Je Cho Do‐Hoon Hwang Sang‐Kyu Lee Jong‐Hwa Park Jiwon Hong Hye Yong Chu Hong‐Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1236-1246
A novel series of poly(10‐hexyl‐phenothiazine‐S,S‐dioxide‐3,7‐diyl) and poly(9,9′‐dioctyl‐fluorene‐2,7‐diyl‐alt‐10‐hexyl‐3,7‐phenothiazine‐S,S‐dioxide) (PFPTZ‐SS) compounds were synthesized through Ni(0)‐mediated Yamamoto polymerization and Pd(II)‐catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ‐SS compounds were highly fluorescent with bright blue emissions in the solid state. Light‐emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish‐blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine‐S,S‐dioxide property, triggered by the introduction of an electron‐deficient SO2 unit into the electron‐rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ‐SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236–1246, 2007 相似文献
142.
Valery A. Loiko Gennady I. Ruban Alexey D. Gruzdev Natalia V. Goncharova 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,102(1):73-84
The peripheral blood lymphocytes of normal individuals are investigated by methods of specialized light microscopy. Lymphocytes as a whole and T-cell subpopulation are considered. Lymphocyte structure is characterized with reference to polarizing scanning flow cytometry. The lymphocyte and lymphocyte nucleus shapes are analyzed. Linear correlation dependence between sizes of lymphocyte and its nucleus is indicated. A morphometric model of a lymphocyte is constructed using the obtained data. The findings can be used, for instance, as input parameters to solve the direct and inverse light-scattering problems of turbidimetry, nephelometry, and flow cytometry. 相似文献
143.
In this article, we develop a rigorous mathematical foundation of microscopic motors. The main characteristic is the combination of Brownian and Poisson noises. 相似文献
144.
极谱分析法连续测定痕量铅和镉 总被引:13,自引:0,他引:13
研究了 Pb2 + 和 Cd2 + 与 KCl-酒石酸钠 -三乙醇胺 -明胶体系的二次导数极谱波。在 p H=4 .5的 HAc-Na Ac介质中 ,Pb2 + 和 Cd2 + 分别于 - 0 .4 6 V和 - 0 .6 4V电位处产生一良好的极谱波。峰电流与 Pb2 + 和Cd2 + 的浓度分别在 1× 10 -5— 3× 10 -1g· L-1和 5× 10 -5— 6× 10 -3 g· L-1范围内呈线性关系。 Pb2 + 和Cd2 +的检出限分别为 1× 10 -7g·L-1和 5× 10 -7g·L-1。本法准确、简便、快速、选择性高。已直接用于饮料中铅和镉的连续测定 ,同时也对酒及面粉样品进行了测定 ,回收率分别为 99.9%— 10 0 .1%和 97.0 %—10 4 .8%。 相似文献
145.
146.
本文在文[1]的基础上进一步拓广了随机Solow经济增长模型.利用白噪声分析理论建立的广义随机Solow经济增长模型,将随机Solow模型推广到包含广义白噪声泛函及具有非可料扩散系数的情形,并且借助U—泛函方法表明了Picard迭代法在此仍十分有效. 相似文献
147.
Fushun Liang Takashi Kurata Hiroyuki Nishide Junji Kido 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5765-5773
An N‐phenylcarbazole‐containing poly(p‐phenylenevinylene) (PPV), poly[(2‐(4′‐carbazol‐9‐yl‐phenyl)‐5‐octyloxy‐1,4‐phenylenevinylene)‐alt‐(2‐(2′‐ethylhexyloxy)‐5‐methoxy‐1,4‐phenylenevinylene)] (Cz‐PPV), was synthesized, and its optical, electrochemical, and electroluminescent properties were studied. The molecular structures of the key intermediates, the carbazole‐containing boronic ester and the dialdehyde monomer, were crystallographically characterized. The polymer was soluble in common organic solvents and exhibited good thermal stability with a 5% weight loss at temperatures above 420 °C in nitrogen. A cyclic voltammogram showed the oxidation peak potentials of both the pendant carbazole group and the PPV main chain, indicating that the hole‐injection ability of the polymer would be improved by the introduction of the carbazole‐functional group. A single‐layer light‐emitting diode (LED) with a simple configuration of indium tin oxide (ITO)/Cz‐PPV (80 nm)/Ca/Al exhibited a bright yellow emission with a brightness of 1560 cd/m2 at a bias of 11 V and a current density of 565 mA/cm2. A double‐layer LED device with the configuration of ITO/poly(3,4‐ethylenedioxy‐2,5‐thiophene):poly (styrenesulfonic acid) (60 nm)/Cz‐PPV (80 nm)/Ca/Al gave a low turn‐on voltage at 3 V and a maximum brightness of 6600 cd/m2 at a bias of 8 V. The maximum electroluminescent efficiency corresponding to the double‐layer device was 1.15 cd/A, 0.42 lm/W, and 0.5%. The desired electroluminescence results demonstrated that the incorporation of hole‐transporting functional groups into the PPVs was effective for enhancing the electroluminescent performance. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5765–5773, 2005 相似文献
148.
149.
Poly(p‐phenylenevinylene) presenting pendent pentaphenylene dendron groups for light‐emitting diodes
Ya‐Hsien Tseng Fang‐Iy Wu Ping‐I Shih Ching‐Fong Shu 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5147-5155
We have synthesized, using the Gilch method, a novel poly(p‐phenylenevinylene) derivative (PPV‐PP) containing two pendent pentaphenylene dendritic wedges, and have characterized its structure and properties. The incorporated side chain pentaphenylene dendrons serve as solubilizing groups, prevent π‐stacking interactions from occurring between the polymer main chains, and suppress the formation of excimers in the solid state. Photoluminescence studies indicate that efficient intramolecular energy transfer occurred from the photoexcited pentaphenylene groups to the poly(p‐phenylenevinylene) backbone. The polymer film exhibits a maximum emission at 510 nm and had a photoluminescence efficiency of 46%, which is similar to that measured in dilute solution. The photoluminescence spectra remained almost unchanged after thermal annealing at 150 °C for 20 h, and displayed inhibited excimer formation. Polymer light‐emitting diodes that we fabricated in the configuration ITO/PEDOT/PPV‐PP/Mg:Ag/Ag exhibited a maximum emission peak at 513 nm, corresponding to the green region [x = 0.30 and y = 0.62 in the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates]. The maximum brightness and maximum luminance efficiency were 1562 cd/m2 and 1.93 cd/A, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5147–5155, 2005 相似文献
150.
Yoon Soo Han Sang Dae Kim Lee Soon Park Dong Uk Kim Younghwan Kwon 《Journal of polymer science. Part A, Polymer chemistry》2003,41(16):2502-2511
Four different types of conjugated copolymers, consisting of alternating structures of phenothiazinylene vinylene and phenylene vinylene derivatives such as phenylene vinylene, 1,1′‐biphenyl‐4,4′‐ylene vinylene, 2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene, and 9,10‐anthrylene vinylene, were prepared by Horner–Emmons condensation between appropriate diphosphonates and dialdehydes. Single‐layer and double‐layer light‐emitting diodes were fabricated with the synthesized conjugated polymers, and their electroluminescent properties were investigated. Poly(N‐2‐ethylhexyl‐3,6‐phenothiazinylene vinylene‐alt‐9,10‐anthrylene vinylene), containing phenothiazinylene vinylene and anthrylene vinylene as repeat units, emitted a reddish‐orange color with Commission Internationale de l'Eclairage coordinates of x = 0.6173 and y = 0.3814 that was very similar to the National Television System Committee standard red, and it showed a bipolar carrier‐injection/transporting capability caused by electron‐withdrawing anthracene and electron‐donating amino groups. Poly[N‐2‐ethylhexyl‐3,6‐phenothiazinylene vinylene‐alt‐2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene], containing phenothiazinylene vinylene and dialkoxy phenylene vinylene moieties, showed excellent hole‐injection/transporting capability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2502–2511, 2003 相似文献