全文获取类型
收费全文 | 363篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 223篇 |
晶体学 | 4篇 |
力学 | 10篇 |
数学 | 36篇 |
物理学 | 102篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 25篇 |
2021年 | 17篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 26篇 |
2017年 | 24篇 |
2016年 | 24篇 |
2015年 | 13篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 22篇 |
2010年 | 29篇 |
2009年 | 27篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有375条查询结果,搜索用时 0 毫秒
91.
92.
Nazar Ul Islam Kamran Jalil Muhammad Shahid Naveed Muhammad Abdur Rauf 《Arabian Journal of Chemistry》2019,12(8):2310-2319
This paper reports a rapid, facile and one-pot synthesis of environmentally safe gold nanoparticles capped and stabilized with galls extract of Pistacia integerrima. The aqueous gold ions when exposed to P. integerrima galls extract were rapidly reduced as evident from abrupt color change to ruby red, suggesting the biosynthesis of gold nanoparticles (Au-NPs) which were further characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Their stability was evaluated against varying pH and different volumes of sodium chloride (NaCl) as well as at a range of temperature (20–80 °C). Au-NPs were tested for enzyme inhibition, antibacterial, antifungal, antinociceptive, muscle relaxant and sedative activities. The UV–Vis spectra of the gold nanoparticles gave surface plasmon resonance at 540 nm while the SEM analysis revealed the particle size in the range of 20–200 nm. FTIR spectra confirmed the involvement of amines, amide groups and alcohols in capping and reduction of gold nanoparticles. Au-NPs showed remarkable stability in different NaCl and pH solutions as well as at elevated temperature. Au-NPs have good antifungal activity and possessed antinociceptive and muscle relaxant properties as observed from their zone of inhibition and significant attenuation of acetic acid induced writhing and reduction of time spent on the rota rod respectively. These results concluded that the gall extract of P. integerrima is a very good bioreductant for the synthesis of gold nanoparticles that have potential for various biomedical and pharmaceutical applications. 相似文献
93.
94.
This report presents the first example of nickel‐catalyzed mild decarboxylative cross‐coupling reaction for the regioselective formation of C–Si bond. An easily accessible and significantly stable Ni (dmg)2 owes the role of key promoter. This reaction is highly functional group tolerant and offers α,β‐unsaturated silanes in synthetically useful yields. The reaction gives access to the successful utilization of otherwise difficult trialkyl silanes as coupling partners and operates at a moderate temperature, which is beneficial to deal with highly volatile silanes. 相似文献
95.
Mir Azam Khan Zafar Iqbal Mohammad Rasul Jan Jasmin Shah Waqar Ahmad Zia Ul Haq Obaidullah 《Journal of Analytical Chemistry》2006,61(1):32-36
A simple spectrophotometric assay for the quantification of lactulose in pharmaceutical preparations was developed. The method
is based on hydrolysis of lactulose under acidic conditions. The hydrolyzed product reacts with resorcinol, giving absorption
peaks at 398 and 480 nm. Both absorption wavelengths can be used for the determination of lactulose. The limit of detection
of lactulose at 398 nm and 480 nm was 0.075 μg mL−1 and 0.65 μg mL−1, respectively. The calibration was linear in the range of 5–25 μg mL−1. Analytical conditions were optimized, and the method was validated for analysis of pharmaceutical preparations. The determined
amount of lactulose was found to be in good agreement with labeled claims in commercial products. The proposed method is economical,
convenient, and suitable for the quantification of lactulose in pharmaceutical preparations.
The text was submitted by the authors in English. 相似文献
96.
Zahoor Qadir Samra Sadaf Shabir Zainab Rehmat Mariam Zaman Aqsa Nazir Nadia Dar Muhammad Amin Athar 《Applied biochemistry and biotechnology》2010,162(3):671-686
Human serum paraoxonase 1 (PON1) is known as an antioxidant and is also involved in the detoxification of many compounds.
In this study, a novel purification strategy was employed to purify the PON1 by using cholesterol-conjugated magnetic nanoparticles.
Magnetic nanoparticles were synthesized and conjugated with cholesterol through diazotized p-aminohippuric acid. In Fourier transform infrared spectrum of cholesterol-p-aminohippuric acid-Fe3O4 nanoparticles, the appearance of peaks at 3,358.3, 1,645 cm−1, and at 2,334.9 cm−1 confirmed the conjugation. The molecular weight of purified PON1 was nearly 45 kDa on sodium dodecyl sulfate (SDS)–polyacrylamide
gel electrophoresis (PAGE), and isoelectric point was 5.3. The specific activity was 438 U mg−1 protein, and the purification fold was 515 with 73% yield. The K
m values were 1.3 and 0.74 mM with paraoxon and phenyl acetate, respectively. Western blot of 2D-PAGE confirmed the homogeneity
and stability of the enzyme. Mg+2, Mn+2, glycerol, (NH4)2SO4, PEG 6000, Triton X-100, and phenylmethylsulfonyl fluoride did not show any effect on activity. Pb+2, Co+2, Zn2+, ethanol, β-mercaptoethanol, and acetone reduced the activity while Ni2+, Cd2+, Cu2+, iodoacetic acid, SDS, dimethylformamide, DMSO inhibited the activity. In vitro enzyme activity was slightly reduced by acetyl
salicylic and acetaminophen and reduced 50% with amino glycosides and ampicillin antibiotics at concentrations of 0.6 and
30 mg ml−1, respectively. This is the first report for the synthesis of cholesterol-conjugated magnetic nanoparticles for simple purification
of PON1 enzyme. 相似文献
97.
A. V. Pirogov E. B. Pashkova A. A. Bendryshev R. V. Ul’yanov O. A. Shpigun 《Moscow University Chemistry Bulletin》2012,67(5):236-240
A technique was developed for the quantitative determination of mitomycin C in urinary-bladder tissues. We used the method of gradient high-performance liquid chromatography with mass-spectrometry detection in the electrospray ionization mode. The range of linearity of the calibration plot was 20?C440 ??g/L. The detection limit was 15 ng/L. We proposed a sampling procedure that consisted of water extraction. Importantly, this procedure allows one to determine the quantity of mitomycin C in tissues. In our study, this method was utilized to estimate the quantity of mitomycin C in the urinary bladder. 相似文献
98.
99.
Lipids from seeds of three plants of the Asteraceae family, Cousinia franchetii, Arctium leiospermum, and Rhaponticum integrifolium, were studied. The principal constituents of lipids from the three plants were shown to be acylglycerides of ordinary fatty
acids and oxygenated fatty acids using chemical and chromatographic analyses. The composition of the ordinary unoxidized and
epoxy acids was determined by GC.
Presented at the 7th International Symposium on the Chemistry of Natural Compounds, October 16–18, 2007, Tashkent, Uzbekistan
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 115–117, March–April, 2008. 相似文献
100.
ZHOU Yun-shan HASSAN ul Sadaf LI Xian-qi ZHANG Li-juan AHMAD Waqar SHI Zong-hai 《高等学校化学研究》2013,29(4):621-626
Structural comparison of a new compound[(bpp)3H6]Fe2IIIFe2IIMo24V(H2PO4)8(HPO4)4(PO4)4O48(OH)12· (H2O)4·2H2O(1)[bpp=1,3-di(4-pyridyl)propane] with our previously reported two compounds[(bpy)3FeII]3· Fe2IIIFe2IIMo24V(H2PO4)8(HPO4)4(PO4)4O48(OH)12(H2O)4·12H2O(2) and[(bpy)3FeII]2FeIIFeIIIMo12V(H2PO4)2(H2-xPO4)·(H1+xPO4)(HPO4)2(PO4)2O24(OH)6(H2O)2·9H2O(x=0―1)(3)(bpy=2,2'-bipyridine), which all exhibit one-dimensional mixed-valence iron molybdophosphate anionic chains constructed by alternating connection of FeIII ions and magic[FeII(Mo6P4O31)2] units, reveals that the non-hydrogen atomic ratios of Mo:Fe:P:O within the polymeric anionic chains are the same for all the three compounds, while the polymeric anionic chains of the different compounds bear different numbers of negative charges. And therefore there exist different numbers of counter cations per {Fe2III[Fe2II(P16Mo24VO124)]} unit found in the titled compounds. It discloses that not only are the spatial assembling of counter cations and polymeric inorganic chains of three compounds quite different, but also the O―FeIII―O bond angles and FeIII―O bond lengths of the three different inorganic chains exhibit small differences. What is more important is that such small changes in bond length and bond angle in the assemblage of FeIII―O bonds lead to the considerable fluctuations of inorganic chains in their structural conformation within the three compounds, reflecting an interesting phenomenon of “flexibility" in the pure inorganic one dimensional mixed-valence iron molybdophosphate chains. 相似文献