全文获取类型
收费全文 | 7408篇 |
免费 | 1376篇 |
国内免费 | 1189篇 |
专业分类
化学 | 6057篇 |
晶体学 | 81篇 |
力学 | 391篇 |
综合类 | 83篇 |
数学 | 786篇 |
物理学 | 2575篇 |
出版年
2024年 | 30篇 |
2023年 | 149篇 |
2022年 | 324篇 |
2021年 | 311篇 |
2020年 | 359篇 |
2019年 | 411篇 |
2018年 | 306篇 |
2017年 | 286篇 |
2016年 | 403篇 |
2015年 | 416篇 |
2014年 | 459篇 |
2013年 | 586篇 |
2012年 | 709篇 |
2011年 | 665篇 |
2010年 | 414篇 |
2009年 | 425篇 |
2008年 | 458篇 |
2007年 | 368篇 |
2006年 | 358篇 |
2005年 | 321篇 |
2004年 | 277篇 |
2003年 | 242篇 |
2002年 | 325篇 |
2001年 | 267篇 |
2000年 | 167篇 |
1999年 | 150篇 |
1998年 | 128篇 |
1997年 | 74篇 |
1996年 | 83篇 |
1995年 | 63篇 |
1994年 | 64篇 |
1993年 | 51篇 |
1992年 | 77篇 |
1991年 | 49篇 |
1990年 | 50篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1936年 | 3篇 |
排序方式: 共有9973条查询结果,搜索用时 15 毫秒
991.
992.
Xue Liu Wenbi Guan Xianghong Hao Xiaoli Wu Yongqiang Ma Canping Pan 《Chromatographia》2014,77(1-2):31-37
Graphene is a novel class of carbon nanostructures with ultrahigh specific surface area. Graphene has already been used in many fields and has great promise for use in sorbent materials. In this study, we used graphene mixed with primary secondary amine (PSA) and graphitized carbon black (GCB) as dispersive solid-phase extraction materials for the cleanup of tea for the first time. Compared to the literature, the amount of PSA and GCB was greatly reduced. A multi-residue method combined with liquid chromatography–tandem mass spectrometry was validated for rapid determination of 25 pesticide residues in tea. Green tea, black tea, and white tea were selected as matrixes, representing the majority of tea types. Recoveries ranged from 71.1 to 108.3 % and consistent relative standard deviations <13.6 % for all 25 pesticides. Graphene has significant potential as a promising new adsorbent for pesticide residue analysis of teas. This method can be used to analyze tea samples with different degrees of fermentation. 相似文献
993.
994.
Huipeng ZhouPengchong Xue Yuan ZhangXin Zhao Junhui JiaXiaofei Zhang Xingliang LiuRan Lu 《Tetrahedron》2011,67(44):8477-8483
We have synthesized a series of new dipolar organic dyes Bn (n=0, 1, 2) employing triarylamine as the electron-donor, 2-cyanoacrylic acid as the electron-acceptor, and fluorenevinylene as the conjugated bridge, which were used as sensitizers in dye-sensitized solar cells. It is found that the solar-energy-to-electricity conversion efficiencies of the prepared DSSCs are in the range of 2.79-5.56%, which reach 35-70% of a standard device based on N719 fabricated and measured under the same conditions. The DSSC sensitized with B1 with balanced length of conjugated bridge shows the highest photo-to-electrical energy conversion efficiency and the open-circuit photovoltage (Voc) of 0.86 V. 相似文献
995.
996.
Non-aggregated spherical polystyrene (PS) particles were coated with GdPO4:Tb3+/Ce3+ phosphor layers by a conventional hydrothermal synthesis using poly(vinylpyrrolidone) (PVP) as an additive without further
annealing treatment. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy
(TEM), photoluminescence (PL), as well as luminescence decay experiments were used to characterise the resulting core-shell
structured PS@GdPO4:Tb3+/Ce3+ samples. The results of XRD indicated that the PS particles were successfully coated with the GdPO4:Tb3+/Ce3+ phosphor layers, which could be further verified by the images of FESEM. Under ultraviolet excitation, the PS@GdPO4:Tb3+/Ce3+ phosphors show Tb3+ characteristic emission, i.e. 5D4-7FJ (J = {6, 5, 4, 3}) emission lines with green emission 5D4-7F5 (543 nm) as the most prominent group. The core-shell phosphors so obtained have potential applications in field emission
display (FED) and plasma display panels (PDP). 相似文献
997.
Sun Z Jin L Shi W Wei M Evans DG Duan X 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):7113-7120
This article reports a novel method to tune the photoluminance properties of ammonium 1-anilinonaphthalene-8-sulfonate (ANS) in a 2D matrix of layered double hydroxide (LDH) by changing the interlayer microenvironment. ANS and a series of surfactants with different alkyl chain lengths (pentanesulphonate (PES), hexanesulphonate (HES), heptanesulphonate (HPS), decanesulphonate (DES), and dodecylsulphonate (DDS)) were respectively cointercalated into the galleries of ZnAl-LDH by the anion exchange method. Thin films of ANS/surfactant-LDHs obtained by the solvent evaporation method possess good c orientation as revealed by XRD and SEM. It was found that the ANS/HPS-LDH film showed the maximum fluorescence efficiency and the longest intensity-average lifetime among these ANS/surfactant-LDH composites owing to the "size-matching" rule between the organic dye and surfactant. Moreover, the fluorescence properties can be tuned by changing the relative molar ratio of ANS/HPS, and the film containing 20% ANS (molar percentage, expressed as ANS(20%)/HPS-LDH) exhibits the maximum fluorescence efficiency, the longest average lifetime, and significantly enhanced photo and thermal stability. In addition, the composite films show fluorescence anisotropy, attributed to the preferential orientation of ANS in the LDH gallery. Therefore, this work demonstrates a feasible approach to tuning the photoluminescence properties of a dye confined in an inorganic 2D matrix via changing the interlayer microenvironment, which may be considered to be a good candidate for solid photoluminescence materials, nonlinear optics, and polarized luminescence materials. 相似文献
998.
Hua Liu Xuan Wu Ying Huang Jing He Sai-Feng Xue Zhu Tao Qian-Jiang Zhu Gang Wei 《Journal of inclusion phenomena and macrocyclic chemistry》2011,71(3-4):583-587
Interaction between cucurbit[8]uril (Q[8]) with a fungicide, carboxin in aqueous solution, was investigated by 1H-NMR, electronic absorption spectroscopy, and fluorescence spectroscopy. Spectroscopy analysis established a basic interaction model which formed an inclusion complex with a host:guest ratio of 1:1. 1H-NMR showed that Q[8] encapsulated the phenyl ring into its cavity and the rest of the guest molecule stayed outside the host. Comparative in vitro evaluations of the growth inhibitory effects of the inclusion complex solution toward Rhizoctonia solani demonstrated appreciable improvements in the antifungal activity of carboxin through the addition of Q[8]. In comparison with the positive control, improvement was evaluated in terms of area covered by the mycelia of R. solani and their growth inhibition rate. Inclusion complexation of carboxin with Q[8] suggests a potential means for production of an environmentally friendly carboxin-based fungicide to counteract R. solani. 相似文献
999.
The hydroxide of meso-tetraphenylporphyrin derivatives functionalized carbon nanotubes (CNTs) was fabricated in our research to explore the interaction between porphyrin and explosive. It was turned out that in the formation of grid porphyrin film, carbon nanotubes as a cruciul base materials promoted the electron transfer rate. Most of important, the results also showed that the electrochemical response was enhanced through increasing the number of -OH substitution in porphyrin. Such information provides the platform for a practical strategy for rational design of the sensor of explosives. 相似文献
1000.
Deming Huang Shanhong Wan Liping Wang Qunji Xue 《Surface and interface analysis : SIA》2011,43(7):1064-1068
Tungsten trioxide‐incorporated hydrogenated amorphous carbon (WO3/a‐C:H) films have been fabricated on a single‐crystal silicon wafer by liquid phase electrodeposition using methanol as carbon source and tungsten carbonyl as incorporated reagent. The morphology, composition and structure of the films have been investigated by SEM, XPS, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscope (TEM), respectively. The effects of WO3 incorporation on the electrical and wetting properties were studied in detail. The characterization results showed that tungsten trioxide nanocrystalline particles with diameters in the range of 10–20 nm were homogenously embedded in the amorphous carbon films. Also, the electrical conductivity and wetting ability of the films were strongly improved due to the contribution of the tungsten trioxide. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献