全文获取类型
收费全文 | 4477篇 |
免费 | 821篇 |
国内免费 | 493篇 |
专业分类
化学 | 3352篇 |
晶体学 | 40篇 |
力学 | 219篇 |
综合类 | 44篇 |
数学 | 483篇 |
物理学 | 1653篇 |
出版年
2024年 | 13篇 |
2023年 | 75篇 |
2022年 | 160篇 |
2021年 | 130篇 |
2020年 | 178篇 |
2019年 | 196篇 |
2018年 | 155篇 |
2017年 | 132篇 |
2016年 | 247篇 |
2015年 | 208篇 |
2014年 | 271篇 |
2013年 | 305篇 |
2012年 | 374篇 |
2011年 | 366篇 |
2010年 | 271篇 |
2009年 | 291篇 |
2008年 | 307篇 |
2007年 | 268篇 |
2006年 | 254篇 |
2005年 | 223篇 |
2004年 | 163篇 |
2003年 | 143篇 |
2002年 | 181篇 |
2001年 | 152篇 |
2000年 | 92篇 |
1999年 | 103篇 |
1998年 | 64篇 |
1997年 | 60篇 |
1996年 | 70篇 |
1995年 | 43篇 |
1994年 | 56篇 |
1993年 | 32篇 |
1992年 | 20篇 |
1991年 | 42篇 |
1990年 | 37篇 |
1989年 | 29篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1959年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有5791条查询结果,搜索用时 15 毫秒
121.
The hexagram and arrayed β-FeOOH nanorods were first synthesized free of surfactants through the solvent-thermal method. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrum (EDAX) and thermal gravimetric analysis (TGA) were used to characterize the as-prepared products. The TEM and FESEM images showed that hexagram β-FeOOH and arrayed rod-like β-FeOOH with an average diameter of 10-15 nm and an average length of 100 nm (aspect ratio is about 10) were prepared. Electrochemical tests show that these nanorods deliver a large discharge capacity of 277 mA h g−1 versus Li metal at 0.1 mA cm−2 (voltage at 1.5-4.2 V). Treated the as-synthesized rod-like β-FeOOH by annealing, rhombus hematite was obtained. 相似文献
122.
Sh. Yu X. Li A. Ren D. Shao Ch. Chen X. Wang 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):387-392
Summary The
removal of heavy metal ion Co(II) from aqueous solution was studied usingg-Al2O3
by batch technique. The experiments were performed at T=20±2 °C, in 0.01M
NaNO3 solutions and under aerobic conditions. The effect of pH,
ionic strength, fulvic acid (FA) and alumina amount on the sorption of Co(II)
on alumina were also investigated. The pH affected the sorption of Co(II)
significantly as compared with the effect of FA and ionic strength. The results
indicated that strong chemical bonds are formed between Co(II) and functional
groups of the bare or FA coated alumina, and a precipitation of Co(II) takes
place on the alumina surface, induced by a transition from the adsorption to
surface. The addition sequences of Co/FA on Co(II) sorption were also studied:
the sorption of Co(II) in the ternary system was found independent of addition
sequences.</p>
</p> 相似文献
123.
利用自组装技术在金电极表面构造了具有不同前端健长度偶氮苯功能化的单分子膜体系:Au/S(CH2)nNHCO-N=N-OCH2CH3(n=2,3,4,6).研究结果表明,仍氮苯到金电极的表现电子转移速率随它们之间的距离长度的增加而呈指数性的下降趋势.基于Marcus电子隧穿理论,得到了此自组装膜体系的长程电子隧穿系数ρ=(1.35±0.2)/CH2在和可逆电活性分子自组装膜体系及理论计算相比较的基础上,从偶氮苯分子自组装膜结构与电子转移过程的关系角度对这一结果进行了分析和说明. 相似文献
124.
Kadish KM Phan TD Giribabu L Shao J Wang LL Thuriere A Van Caemelbecke E Bear JL 《Inorganic chemistry》2004,43(3):1012-1020
Eleven different Ru(2)(4+) and Ru(2)(3+) derivatives are characterized by thin-layer FTIR and UV-visible spectroelectrochemistry under a CO atmosphere. These compounds, which were in-situ electrogenerated from substituted anilinopyridine complexes with a Ru(2)(5+) core, are represented as Ru(2)(L)(4)Cl where L = 2-CH(3)ap, ap, 2-Fap, 2,3-F(2)ap, 2,4-F(2)ap, 2,5-F(2)ap, 3,4-F(2)ap, 3,5-F(2)ap, 2,4,6-F(3)ap, or F(5)ap. The Ru(2)(5+) complexes do not axially bind CO while mono- and bis-CO axial adducts are formed for the Ru(2)(4+) and Ru(2)(3+) derivatives, respectively. Six of the eleven investigated compounds exist in a (4,0) isomeric form while five adopt a (3,1) geometric conformation. These two series of compounds thus provide a large enough number of derivatives to examine trends and differences in the spectroscopic data of the two types of isomers in their lower Ru(2)(4+) and Ru(2)(3+) oxidation states. UV-visible spectra of the Ru(2)(4+) derivatives and IR spectra of the Ru(2)(3+) complexes under CO are both isomer dependent, thus suggesting that these data can be used to reliably predict the isomeric form, i.e., (3,1) or (4,0), of diruthenium complexes containing four unsymmetrical substituted anilinopyridinate bridging ligands; this was confirmed by X-ray crystallographic data for seven compounds whose structures were available. 相似文献
125.
Chen YW Liu YC Lu SX Xu CS Shao CL Wang C Zhang JY Lu YM Shen DZ Fan XW 《The Journal of chemical physics》2005,123(13):134701
Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394 nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In samples at 3.37 eV is observed in low-temperature PL spectra. The near-band-edge emission peak at room temperature was a mixture of excitons and impurity-related transitions for both of two samples. 相似文献
126.
127.
The invention of air conditioner (AC) has undoubtedly saved the world from the heat of summer. The development of AC is an important embodiment of continuous development and perfection of science and technology. This article explains the mechanism of freon pollution from the perspective of chemistry, and enumerates the important role of fluoride in daily life, to eliminates people's misunderstanding of fluorine element. The hardships of extracting fluorine reflect the chemists' research experience of collecting experience from failure and the scientific spirit of pursuing the truth. 相似文献
128.
129.
Bin XIN Dan PU Shao Xiang XIONG* Guang Hui WANG Beijing Mass Spectrometry Center Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2003,14(2)
Recently, capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI- MS) has been rapidly developed as a powerful analytical tool for charged species ranged from small molecules such as carboxylic acids1, phenolic compounds2, metal species3, tetramines4, herbicides5, drugs and drug metabolites6 to peptides and proteins7, 8. The ESI mode has proven to be sensitive, versatile and relatively easy to use in combination with CE. CE confers rapid analysis and efficient separ… 相似文献
130.