全文获取类型
收费全文 | 4039篇 |
免费 | 86篇 |
国内免费 | 398篇 |
专业分类
化学 | 3112篇 |
晶体学 | 56篇 |
力学 | 26篇 |
综合类 | 1篇 |
数学 | 21篇 |
物理学 | 1307篇 |
出版年
2024年 | 36篇 |
2023年 | 422篇 |
2022年 | 88篇 |
2021年 | 111篇 |
2020年 | 133篇 |
2019年 | 124篇 |
2018年 | 92篇 |
2017年 | 97篇 |
2016年 | 164篇 |
2015年 | 140篇 |
2014年 | 222篇 |
2013年 | 205篇 |
2012年 | 203篇 |
2011年 | 284篇 |
2010年 | 214篇 |
2009年 | 260篇 |
2008年 | 197篇 |
2007年 | 237篇 |
2006年 | 186篇 |
2005年 | 189篇 |
2004年 | 145篇 |
2003年 | 84篇 |
2002年 | 87篇 |
2001年 | 80篇 |
2000年 | 56篇 |
1999年 | 59篇 |
1998年 | 53篇 |
1997年 | 49篇 |
1996年 | 38篇 |
1995年 | 31篇 |
1994年 | 26篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 22篇 |
1990年 | 22篇 |
1989年 | 14篇 |
1988年 | 31篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有4523条查询结果,搜索用时 0 毫秒
111.
《Current Applied Physics》2015,15(7):829-832
Inverted organic solar cells (OSCs) based on poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) bulk heterojunctions (BHJ) were fabricated with optimized ZnO/Ag/ZnO multilayer and conventional indium–tin oxide (ITO) cathode electrodes and their performance was compared. The ZnO/Ag/ZnO multilayer films showed sheet resistances in the range 3.6–3.9 Ω/sq, while ITO exhibited 14.2 Ω/sq. On the one hand, the carrier concentration gradually decreased from 1.74 × 1022 to 4.33 × 1021 cm−3 as the ZnO thickness increased from 8 to 80 nm, respectively. The transmittance of the ZnO(40 nm)/Ag(19 nm)/ZnO(40 nm) films was ∼95% at 550 nm, which is comparable to that of ITO (∼96%). The multilayer films were smooth with a root mean square (RMS) roughness of 0.81 nm. OSCs fabricated with the ZnO(40 nm)/Ag(19 nm)/ZnO(40 nm) film showed a power conversion efficiency (2.63%) comparable to that of OSCs with a conventional ITO cathode (2.71%). 相似文献
112.
André L. Santos Regina M. Takeuchi Rodrigo A. A. Muñoz Lúcio Angnes Nelson R. Stradiotto 《Electroanalysis》2014,26(2):233-242
This article critically reviews the electroanalytical methods devoted for the determination of organic compounds in automotive fuels that can range from contaminants to additives typically introduced into liquid biofuels and liquid fossil fuels. Contaminants such as aldehydes and ketones in bioethanol, free fatty acids and glycerol in biodiesel, and sulfur and nitrogen organic compounds in gasoline and diesel fuel, and additives such as colour markers and antioxidants added to fuels were determined by electroanalytical methods. Special focus is given to electrodes, electrochemical techniques, and sample preparation strategies. Future directions of research on electroanalysis of liquid fuels are presented. 相似文献
113.
Determination of Bismuth by Adsorptive Stripping Voltammetry Using Aluminum Oxide for Elimination of Environmental Sample Matrix Interferences 下载免费PDF全文
The aim of this work was to find a fast new and simple method for efficient elimination of negative influence of humic substances and synthetic surfactants in the voltammetric determination of bismuth. The negative influence of the organic matrix present in environmental water samples due to their adsorption on aluminum oxide was successfully evaluated. The organic compounds such as humic substances and surface active compounds were removed by adsorption on the surface of aluminum oxide from the water samples. The application of this method was the recovery of Bi(III) from spiked water samples. 相似文献
114.
Facile Preparation of α‐Zirconium Phosphate/Polyaniline Hybrid Film for Detecting Potassium Ion in a Wide Linear Range 下载免费PDF全文
Yanhong Wang Chunfeng Xue Xiumin Li Xiao Du Zhongde Wang Guozhang Ma Xiaogang Hao 《Electroanalysis》2014,26(2):416-423
A novel α‐zirconium phosphate/polyaniline (α‐ZrP/PANI) hybrid film used as K+ ion sensor was fabricated on carbon paper by electrochemical method. Mechanisms of film formation and detection of K+ ions were also proposed. The exfoliated α‐ZrP was mixed with PANI and deposited on carbon paper. The resultant α‐ZrP/PANI film exhibited a good current response to K+ ion with different concentrations. It also showed a wide logarithmic linear response in detecting K+ ions in the ranges of 10?8–10?4 M and 10?4–10?2 M, respectively. The results can be attributed to the synergetic effect of α‐ZrP and PANI. 相似文献
115.
116.
117.
118.
本文介绍了3,3’-(苯亚甲基)双吲哚的制备和柱层析分离实验的原理和操作步骤。该实验具有以下特点:(1)反应时间短,30min左右便可完成;(2)产物为粉红色,在进行硅胶板层析和层析柱时比较直观,适合于学生的实验教学;(3)反应物、催化剂和产物的极性相差很大,容易进行柱层析分离产物。该实验特别适合于综合性大学和地方高等师范院校化学和相关本科专业的"有机化学实验"或"综合化学实验"进行开设。 相似文献
119.
In this paper, we present recent results of our attempts to produce nanoporous zirconia, as well as our investigations of a hybrid material consisting of nanoporous zirconia loaded with Ag-nanoparticles, Ag-n/ZrO2-NT/Zr, which could be used as an active SERS substrate. The Zr-based hybrid material, as our investigations have shown, is an active and stable substrate in SERS investigations aimed at detecting various organic molecules: mercaptobenzoic acid, pyridine and two different dyes – rodhanine derivatives. The SERS spectra for the probe molecules adsorbed on silver nanoparticles on a ZrO2-NT/Zr platform display characteristic intensity ratios different from those measured on previously studied nanoporous substrates based on Ti and Al, which ensure a different (alternative) interaction between the investigated adsorbate and adsorbent. In order to characterize our new substrate we used high-resolution SEM and surface analytical techniques: XPS (X-ray photoelectron spectroscopy) and SERS (surface enhanced Raman spectroscopy). 相似文献
120.
The characterization of novel metal reinforced electro-dialysis ion exchange membranes, for water desalination, by attenuated total reflectance Fourier transform infrared spectroscopy mapping is presented in this paper. The surface of the porous stainless steel fibre meshes was treated in order to enhance the amount of surface oxide groups and increase the material hydrophilicity. Then, the metal membranes were functionalized through a sol–gel reaction with silane coupling agents to enhance the affinity with the ion exchange resins and avoid premature metal oxidation due to redox reactions at the metal–polymer interface. Polished cross sections of the composite membranes embedded into an epoxy resin revealed interfaces between metallic frameworks and the silane layer at the interface with the ion exchange material. The morphology of the metal–polymer interface was investigated with scanning electron microscopy and Fourier transform infrared micro-spectroscopy. Fourier transform infrared mapping of the interfaces was performed using the attenuated total reflectance mode on the polished cross-sections at the Australian Synchrotron. The nature of the interface between the metal framework and the ion exchange resin was shown to be homogeneous and the coating thickness was found to be around 1 μm determined by Fourier transform infrared micro-spectroscopy mapping. The impact of the coating on the properties of the membranes and their potential for water desalination by electro-dialysis are also discussed. 相似文献