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271.
Adeel?AfzalEmail author Humaira?M.?Siddiqi Adnan?Mujahid Shaukat?Saeed 《Journal of Sol-Gel Science and Technology》2012,61(1):44-48
Silica packed epoxy networks are prepared in two steps via in situ, solvent free sol–gel processing of tetraethoxysilane in
liquid epoxy monomer and curing the mixture with a flexible diamine afterwards. The influence of filler content and processing
conditions on the mechanical properties and the fracture behavior is studied by means of the static mechanical analysis and
AFM characterization of the pristine and the fractured polymer surfaces, and a mechanism to enhance polymer strength and toughness
is proposed. The in–situ evolution and packing of silica nanostructures into epoxy networks influences the overall morphology
and performance of polymers under high stress. It is found that smaller silica domains distributed at the molecular level
cause efficient crack distribution by absorbing energy and thus improve the strength and toughness of silica packed epoxy
polymers. 相似文献
272.
Ashish Pandey Anoop Kelkar R. K. Singhal Chetan Baghra Amrit Prakash Mohd. Afzal J. P. Panakkal 《Journal of Radioanalytical and Nuclear Chemistry》2012,293(3):743-749
Pyrohydrolysis is a fast, reliable and convenient method for the decomposition of solid refractory samples. Thoria based mixed oxide nuclear fuels requires more than 1,200?°C reaction temperature to lose its structural integrity so as to release the halides. In the present paper, we report WO3 accelerated pyrohydrolytic extraction technique for the separation of F? and Cl? from thoria based fuels along with the feasibility of using MoO3 and V2O5. The mechanism of extraction has been investigated in detail using X-ray diffraction and recovery studies. ThO2 along with its halides undergo high temperature solid state reaction with WO3 forming Th(WO4)2 and releasing the halides for their subsequent hydrolysis. The quantification was carried out by ion chromatography with suppressed ion conductivity detection. The average recoveries of the spiked samples for F? and Cl? were 93?C99%. The method was successfully applied for simultaneous determination of F? and Cl? in thorium based nuclear fuel samples at 950?°C. 相似文献
273.
Zhang D Gao R Afzal S Vargas M Sharma S McCurdy A Yousufuddin M Stewart T Bau R Selke M 《Organic letters》2006,8(22):5125-5128
Singlet oxygen reacts with binaphthyl phosphine derivatives such as 1,1'-binaphthyl di-tert-butyl phosphine to form the corresponding binaphthyl-2-oxide phosphine oxides. This new intramolecular arene epoxidation reaction proceeds with complete retention of stereochemistry. The binaphthyl-2-oxide di-tert-butyl phosphine oxide undergoes a slow "NIH-rearrangement" to form the corresponding hydroxylated product. A transient phosphadioxirane intermediate has been directly observed by low-temperature NMR. Kinetic analyses show that all of the phosphadioxirane intermediate is converted to product. [reaction: see text] 相似文献
274.
Anoop Kelkar Amrit Prakash Mohd. Afzal J. P. Panakkal H. S. Kamath 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(2):443-449
An ion chromatographic method has been developed for the determination of traces of Li+, Na+, K+, Ca2+, Mg2+, Sr2+, Fe3+, Cu2+, Ni2+, Co2+, Zn2+, Cd2+, Mn2+ in UO2, ThO2 powders and sintered (Th,U)O2 pellets. This new method utilizes poly-(butadiene-maleic acid) (PBDMA) coated silica cation exchange column and mixed functionality
column of anion and cation exchange to achieve the separation of alkali, alkaline earths and transition metal ions, respectively.
It involves matrix separation after sample dissolution by solvent extraction with TBP (tri butyl phosphate)-TOPO (tri octyl
phosphine oxide)/CCl4. Interference of transition metal ions in the determination of alkali, alkaline earth metal ions are removed by using pyridine
2,6-dicarboxylic acid (PDCA) in the tartaric acid mobile phase. Mobile phase composition is optimized for the base line separation
of alkali, alkaline earth and transition metal ions. Linear calibration graphs in the range 0.01–20 μg mL−1 were obtained with regression coefficients better than 0.999. The respective relative standard deviations were also determined.
Recoveries of the spiked samples are within ±10% of the expected value. The developed method is authenticated by comparison
with certified standards of UO2 and ThO2 powders. 相似文献
275.
Plastic has made our lives comfortable as a result of its widespread use in today’s world due to its low cost, longevity, adaptability, light weight and hardness; however, at the same time, it has made our lives miserable due to its non-biodegradable nature, which has resulted in environmental pollution. Therefore, the focus of this research work was on an environmentally friendly process. This research work investigated the decomposition of polypropylene waste using florisil as the catalyst in a salt bath over a temperature range of 350–430 °C. A maximum oil yield of 57.41% was recovered at 410 °C and a 40 min reaction time. The oil collected from the decomposition of polypropylene waste was examined using gas chromatography-mass spectrometry (GC-MS). The kinetic parameters of the reaction process were calculated from thermogravimetric data at temperature program rates of 3, 12, 20 and 30 °C·min−1 using the Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunnose (KAS) equations. The activation energy (Ea) and pre-exponential factor (A) for the thermo-catalytic degradation of polypropylene waste were observed in the range of 102.74–173.08 kJ·mol−1 and 7.1 × 108–9.3 × 1011 min−1 for the OFW method and 99.77–166.28 kJ·mol−1 and 1.1 × 108–5.3 × 1011 min−1 for the KAS method at a percent conversion (α) of 0.1 to 0.9, respectively. Moreover, the fuel properties of the oil were assessed and matched with the ASTM values of diesel, gasoline and kerosene oil. The oil was found to have a close resemblance to the commercial fuel. Therefore, it was concluded that utilizing florisil as the catalyst for the decomposition of waste polypropylene not only lowered the activation energy of the pyrolysis reaction but also upgraded the quantity and quality of the oil. 相似文献
276.
Xian Zhou Sualiha Afzal Hans Wohlmuth Gerald Münch David Leach Mitchell Low Chun Guang Li 《Molecules (Basel, Switzerland)》2022,27(12)
This study aims to investigate the combined anti-inflammatory activity of ginger and turmeric extracts. By comparing the activities of individual and combined extracts in lipopolysaccharide and interferon-γ-induced murine RAW 264.7 cells, we demonstrated that ginger-turmeric combination was optimal at a specific ratio (5:2, w/w) in inhibiting nitric oxide, tumour necrosis factor and interleukin 6 with synergistic interaction (combination index < 1). The synergistic inhibitory effect on TNF was confirmed in human monocyte THP-1 cells. Ginger-turmeric combination (5:2, w/w) also upregulated nuclear factor erythroid 2–related factor 2 activity and heme oxygenase-1 protein expression. Additionally, 6-shogaol, 8-shogaol, 10-shogaol and curcumin were the leading compounds in reducing major proinflammatory mediators and cytokines, and a simplified compound combination of 6-s, 10-s and curcumin showed the greatest potency in reducing LPS-induced NO production. Our study provides scientific evidence in support of the combined use of ginger and turmeric to alleviate inflammatory processes. 相似文献
277.
David M. Haddleton Alex M. Heming Adam P. Jarvis Afzal Khan Andrew Marsh Sebastien Perrier Stefan A.F. Bon Stuart G. Jackson Ryan Edmonds Elizabeth Kelly Dax Kukulj Carl Waterson 《Macromolecular Symposia》2000,157(1):201-208
The use of copper(I) Schiff base complex catalysed atom transfer polymerisation of methacrylates is described. The use of a range of functional and multi‐functional initiators enables the synthesis of a range of functional and star polymers to be prepared under undemanding synthetic conditions. End capping with silyl enol ethers allows for ω‐functional polymers. The combination of novel initiators, functional monomers and end capping allows an unprecedented array of macromolecular structures to be produced with limited need for protecting group chemistry. 相似文献
278.
Hassan Haseebul Iqbal Muhammad Waqas Afzal Amir Muhammad Asghar Mazia Aftab Sikandar 《Journal of Solid State Electrochemistry》2023,27(1):125-137
Journal of Solid State Electrochemistry - A hybrid supercapacitor, also known as a supercapattery, combines the high power density of supercapacitors with the high energy density of batteries. In... 相似文献
279.
Yaowen Liu Martin C. Dietl Robin Heckershoff Chunyu Han Hongwei Shi Dr. Matthias Rudolph Dr. Frank Rominger Dr. Isabella Caligiuri Kanwal Asif Muhammad Adeel Dr. Thomas Scattolin Prof. Dr. A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2023,62(34):e202304672
Due to its excellent bioactivity profile, which is increasingly utilized in pharmaceutical and synthetic chemistry, spirooxindole is an important core scaffold. We herein describe an efficient method for the construction of highly functionalized new spirooxindolocarbamates via a gold-catalyzed cycloaddition reaction of terminal alkynes or ynamides with isatin-derived ketimines. This protocol has a good functional group compatibility, uses readily available starting materials, mild reaction conditions, low catalyst loadings and no additives. It enables the transformation of various functionalized alkyne groups into cyclic carbamates. Gram-scale synthesis was achieved and DFT calculations verify the feasibility of the mechanistic proposal. Some of the target products exhibit good to excellent antiproliferative activity on human tumor cell lines. In addition, one of the most active compounds displayed a remarkable selectivity towards tumor cells over normal ones. 相似文献