全文获取类型
收费全文 | 424篇 |
免费 | 30篇 |
国内免费 | 145篇 |
专业分类
化学 | 461篇 |
晶体学 | 27篇 |
力学 | 7篇 |
综合类 | 8篇 |
数学 | 2篇 |
物理学 | 94篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 20篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 50篇 |
2012年 | 19篇 |
2011年 | 22篇 |
2010年 | 15篇 |
2009年 | 26篇 |
2008年 | 16篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 36篇 |
2002年 | 42篇 |
2001年 | 38篇 |
2000年 | 36篇 |
1999年 | 20篇 |
1998年 | 21篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
排序方式: 共有599条查询结果,搜索用时 31 毫秒
591.
Sihui Zhan Cairong Gong Xiuling Jiao 《Journal of Dispersion Science and Technology》2013,34(7):931-933
Zinc ferrite gel fibers were prepared from the sol precursor by the electrospinning method, and the ZnFe2O4 polycrystalline nanofibers were obtained upon calcination of the gel fibers. The obtained ZnFe2O4 nanofibers composed of 20–30 nm nanocrystals were about one hundred to several hundred nanometers in diameter. The materials have been characterized by means of SEM, TEM, XRD, TGA, and IR techniques. 相似文献
592.
Martin A. Niedermeier Monika Rawolle Dr. Philipp Lellig Dr. Volker Körstgens Dr. Eva M. Herzig Dr. Adeline Buffet Dr. Stephan V. Roth Prof. Jochen S. Gutmann Thomas Fröschl Prof. Nicola Hüsing Prof. Peter Müller‐Buschbaum 《Chemphyschem》2013,14(3):597-602
A low‐temperature route to directly obtain polymer/titania hybrid films is presented. For this, a custom‐made poly(3‐alkoxy thiophene) was synthesized and used in a sol‐gel process together with an ethylene‐glycol‐modified titanate (EGMT) as a suitable titania precursor. The poly(3‐alkoxy thiophene) was designed to act as the structure‐directing agent for titanium dioxide through selective incorporation of the titania precursor. The nanostructured titania network, embedded in the polymer matrix, is examined with atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. By means of the scattering technique grazing incidence wide‐angle X‐ray scattering (GIWAXS), a high degree of crystallinity of the polymer as well as successful transformation of the precursor into the rutile phase of titania is verified. UV/Vis measurements reveal an absorption behavior around 500 nm which is similar to poly(3‐hexyl thiophene), a commonly used polymer for photoelectronic applications, and in addition, the typical UV absorption behavior of rutile titania is observed. 相似文献
593.
In this study, high performance shape memory polyurethane (SMPU)/silica nanocomposites with different silica weight fraction including SMPU bulk, 3%, 4.5%, 6%, 7.5%, 10%, were prepared by sol‐gel process initiated by the solid acid catalyst of p‐toluenesulfonic acid (PTSA). Field emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) observation show that the silica nanoparticles are dispersed evenly in SMPU/silica nanocomposites. Tensile test and dynamic mechanical analysis (DMA) suggest that the mechanical properties and the glass transition temperature (Tg) of the nanocomposites were significantly influenced by silica weight fraction. Thermogravimetric analysis (TGA) was utilized to evaluate the thermal stability and determine the actual silica weight fraction. The TGA results indicate that the thermal stability can be enhanced with the hybridization of silica nanoparticles. Differential scanning calorimetry (DSC) was conducted to test the melting enthalpy (ΔH) and the results suggest that the ΔH was markedly improved for the SMPU/silica nanocomposites. Thermomechanical test was conducted to investigate the shape memory behavior and the results show that the shape fixity is improved by hybridization of silica and good shape recovery can be obtained with the increasing of cycle number for all the samples. 相似文献
594.
Zhen Xu Huanyu Zhao Zhuojun Yan Sibing Wang Yuanli Chen Baozong Li Yi Li Yonggang Yang 《中国化学》2011,29(8):1595-1600
Silica nanococoons with coiled or concentric circular pore channels in the walls attracted much attention, recently. However, the formation of them is not well illustrated. Herein, hollow silica shells with organized pore channels parallel to the shell surface were prepared through a single‐templating method using the self‐assemblies of a chiral low‐molecular‐weight amphiphile,L‐18Phe6PyBr, as templates under a dilute concentration. These nanococoons were characterized using X‐ray diffractometer and N2 sorption. The formation of them was clearly shown in the field‐emission electron microscopy images which were taken at a low voltage. Moreover, transmission electron microscopy images taken after different reaction times indicated a cooperative self‐assemble mechanism. It was also found that the nanocoons were formed from coiled nanoribbons. 相似文献
595.
O. S. Bezkrovnyi N. V. Babayevskaya P. V. Mateychenko O. M. Vovk A. G. Doroshenko D. S. Sofronov 《Crystal Research and Technology》2014,49(2-3):85-91
(Lu1–xEux)2O3 smooth, crack‐free, transparent films were prepared by the Pechini sol–gel method and a spin‐coating technique. Thermogravimetric analysis, differential thermal analysis and FITR spectroscopy were used to study the chemical processes during annealing of the films. Film structure, morphology and optical properties were investigated. X‐ray diffraction (XRD) analysis reveals the cubic phase of (Lu1–xEux)2O3 films annealed in the 600–1000 °C temperature range. Smooth and crack‐free films with thicknesses of 250–1000 nm were obtained in the 600–800 °C temperature range. The thickness upper limit (1000 nm) of morphological stability of films (Lu1–xEux)2O3 on sapphire substrates has been studied. 相似文献
596.
J. H. Yang L. Y. Zhao Y. J. Zhang Y. X. Wang H. L. Liu 《Crystal Research and Technology》2008,43(9):999-1003
Mn‐doped ZnO were synthesized by solid state reaction and sol‐gel method respectively. It was found that samples synthesized by solid state reaction containing Mn2O3 and MnO2 are a mixture of ferromagnetic and paramagnetic phases. Contrary, samples without second phases were found to be paramagnetic at room temperature. According to previous report, interface effects between Zn‐rich Mn2O3 and MnO2 interfaces may be the origin of the ferromagnetic behavior observed in our samples prepared by solid reaction, so the alloy of Zn1−xMnxO may be paramagnetic at room temperature. Prepared by sol‐gel technique, the samples without second phases in the XRD patterns are also room‐temperature paramagnetic. Therefore we believe that the magnetism of Zn1−xMnxO is paramagnetic at room temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
597.
《Arabian Journal of Chemistry》2023,16(4):104575
Due to the fact that researchers and scientists have been interested in environmentally friendly synthesis using plant extracts because of the wide distribution of plants, their ease of availability, and their safety in use, in the current work, ErFeO3/Fe3O4/rGO nanocomposite was produced using a green chemistry method via sucrose indicating the importance of both an active capping and reducing agent for the synthesis of nanocomposite materials with well-organized biological properties. Number of methods, including TEM, SEM, XRD, BET-BJH, VSM, and HRTEM, were used to characterize the produced nanocomposite. The XRD data showed that the produced nanocomposite had pure particles with a range of 37 ± 2 nm in size, which was validated by TEM examination. Additionally, the nanocomposite's cytotoxicity was examined to test its anti-proliferative effect against the T98, and SH-SY5Y cancer cell lines. It was also discussed how to effectively induce cancer cell death in vitro when manufactured nanocomposite was present. The results showed that the percentage of cells that survived was drastically decreased by the synthesized nanocomposite. However, further research must be done to identify the precise linked mechanisms. 相似文献
598.
《Journal of Saudi Chemical Society》2023,27(3):101642
Based on a few noteworthy features, cerium oxide nanoparticles have gained significance in nanotechnology. The effective microwave combustion method (MCM) and the conventional sol–gel (CRSGM) technologies are used in this study to successfully generate the crystalline CeO2 nanoparticles (NPs). Additionally, using a variety of spectroscopic and analytical methods, the synthesized CeO2 NPs are examined to assess to understand their structure and morphology. The XRD patterns of CeO2 NPs show that the structure exhibits a face-centered cubic lattice. Then, with demonstrated good conversion and selectivity, the impact of the epoxidation reaction of cyclohexene was examined. Finally, it can be said that using CeO2 nanoparticles is an efficient strategy to increase the catalytic activity toward the epoxidation reaction of cyclohexene. In the presence of acetonitrile as a solvent and H2O2 as an oxidant, the catalyst samples utilized in the cyclohexene epoxidation reaction were examined. In this study, the CeO2 catalyst outperformed all other catalysts in terms of cyclohexene maximal conversion and selectivity. After six prolonged cycles, the conversion of cyclohexene oxidation using CeO2 NPs shows reasonable recyclability and conversion efficiency, making it the best catalyst for an industrial production application.Additionally, the upgraded CeO2 nanoparticle electrode for nitrite detection has a linear concentration range (0.02–1200 M), a low detection limit (0.22 M), and a higher sensitivity (1.735 A M−1 cm−2). CeO2 NPs, on the other hand, have a quick response time, excellent sensitivity, and high selectivity. Additionally, the manufactured electrode is used to find nitrite in various water samples. Finally, it can be said that using CeO2 NPs is an efficient strategy to increase the catalytic activity toward cyclohexene oxidation and nitrite. 相似文献
599.
Adib Bin Rashid Shariful Islam Shishir Md. Azim Mahfuz Md. Tanvir Hossain Md Enamul Hoque 《Particle & Particle Systems Characterization》2023,40(6):2200186
Silica aerogels have drawn considerable attention due to their low density (almost 95% of the total volume is composed of air), hydrophobicity, optical transparency, low conductivity of heat, and large surface to volume ratio. Sol–gel processing is used to prepare aerogels from molecular precursors. To replace the pore fluid with air while retaining the solid network, a supercritical drying process (the most frequent approach) is used. However, recent technologies use atmospheric pressure to allow for liquid removal followed by chemical alteration of the gel's internal layer, which leaves only a silica network with a porous structure filled with air. This study discusses the sol–gel method for preparing silica aerogels and their various drying processes. Furthermore, various areas of applications of silica aerogels, including electronics, construction, aerospace, purification of water and air, sensing, catalyst, biomedical, absorbent, food packing, textile, etc., are also discussed. Lastly, this review provides a perception of the recent scientific progress along with the futuristic development of silica aerogel. 相似文献