全文获取类型
收费全文 | 167篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 126篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 28篇 |
物理学 | 16篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 11篇 |
2008年 | 3篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 3篇 |
排序方式: 共有182条查询结果,搜索用时 31 毫秒
11.
Mohammad Nikpassand Manouchehr Mamaghani Mohammad Ali Zanjanchi Nosrat Olah Mahmoodi Massomeh Mirzaeinejad 《中国化学快报》2010,21(1):5-8
<正>A facile and convenient protocol was developed for the synthesis of 1,5-diarylpyrazoles using Baylis-Hillman adducts in the presence of HY-zeolite as an efficient recyclable heterogeneous catalyst in reasonable reaction times(1.5-2.5 h) and high yields (78-90%). 相似文献
12.
13.
Application of Monte Carlo simulation method to polymerization kinetics over Ziegler–Natta catalysts
In the current work, the Monte Carlo simulation method was applied to ethylene polymerization over Ziegler–Natta catalysts. As expected, polymerization over each center of a Ziegler–Natta catalyst leads to a polymer having a Schultz–Flory molecular weight distribution. Notwithstanding, the total molecular weight distribution obtained by all catalyst centers together is at least twice as broad as that of each center. As another interesting finding, the introduction of hydrogen to the reaction deactivates the catalyst active centers and thereby reduces the catalyst activity. Nevertheless, it does not mainly affect the polymerization kinetics. In addition, the polymer molecular weight falls as hydrogen is added to the reaction since it acts as a strong transfer agent. The same effect is seen when cocatalyst concentration increases. Hydrogen also widens the polymer molecular weight distribution. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 45–56, 2009 相似文献
14.
Yousef Abdossalami Asl Yadollah Yamini Shahram Seidi Behnam Ebrahimpour 《Analytica chimica acta》2015
In the present research, an effective on chip electromembrane extraction (CEME) coupled with high performance liquid chromatography was presented for analysis of nortriptyline (NOR) and amitriptyline (AMI) as basic model analytes from urine samples. The chip consists of two polymethyl methacrylate (PMMA) parts with two craved microfluidic channels in each part. These channels were used as flow path for the sample solution and a thin compartment for the acceptor phase. A porous polypropylene sheet membrane impregnated with an organic solvent was placed between two parts of chip device to separate the channels. Two platinum electrodes were mounted at the bottom of these channels that were connected to a power supply providing the electrical driving force for migration of ionized analytes from sample solution through the porous sheet membrane into the acceptor phase. This new setup provides effective and reproducible extractions with low volume of sample solution. Efficient parameters on CEME of the model analytes were optimized using one variable at a time method. Under the optimized conditions, the calibration curve was linear in the range of 10.0–500 μg L−1 with coefficient of determination (r2) more than 0.9902. The relative standard deviations (RSDs %) for extraction and determination of the analytes were less than 6.8% based on six replicate measurements. LODs less than 4.0 μg L−1 were obtained for both of the model analytes. The preconcentration factors higher than 17.0-fold were obtained. The results demonstrated that CEME would be used efficiently for extraction and determination of AMI and NOR from urine samples. 相似文献
15.
Poly(dodecylmethacrylate-co-methyleugenol) P(DDMA-co-Meu) and poly(dodecylmethacrylate-co-methylchavicol) P(DDMA-co-Mch) gels were synthesized in ethanol using free radical cross-linking polymerization method at 60 °C for 24 h in the presence of azobisisobutyronitrile (AIBN) and triethylene glycol dimethacrylate (TEGDMA) as initiator and cross-linker, respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the gels. These gels were used to investigate swelling behaviors in linalool and methyl eugenol, in essential oil mixture of phenyl propanoid and terpenoid, and also in various solvents. While the equilibrium swelling values (ESV) of both gels were higher in linalool than in methyl eugenol, the result was vice versa in the case of essential oil mixture. ESVs of both gels were also obtained in various solvents with different functional groups and the highest ESV of both gels were obtained in toluene, and the lowest ESV of P(DDMA-co-Meu) and P(DDMA-co-Mch) was in methanol and in ethylene glycol, respectively. While P(DDMA-co-Meu) is sensitive to carbon number change in alcohol, P(DDMA-co-Mch) is less sensitive. In the case of esters, increase of carbon number in functional group causes a more significant change in ESV than an increase of carbon number in aliphatic chain. Experimental results were correlated by the first-order and second-order models. The second-order model was more suitable than the other. While P(DDMA-co-Meu) gel swelled in linalool exhibits a Fickian diffusion character, the diffusion mechanism of the gel in methyl eugenol is a non-Fickian one. In the case of P(DDMA-co-Mch), the result is vice versa. 相似文献
16.
Realization of a Framework for Simulation-Based Large-Scale Shape Optimization Using Vertex Morphing
Ghantasala Aditya Najian Asl Reza Geiser Armin Brodie Andrew Papoutsis Efthymios Bletzinger Kai-Uwe 《Journal of Optimization Theory and Applications》2021,189(1):164-189
Journal of Optimization Theory and Applications - There is a significant tendency in the industry for automation of the engineering design process. This requires the capability of analyzing an... 相似文献
17.
Manouchehr Saljoughian 《Monatshefte für Chemie / Chemical Monthly》1983,114(4):509-511
Oxidation of alcoholsR-CHD-OH by CrO3/pyridine gave the aldehydesR-CDO with a relatively small loss of D thus indicating a pronounced isotope effect. 相似文献
18.
We analyze the problem of pricing and hedging contingent claims in the multi-period, discrete time, discrete state case using the concept of a “λ gain–loss ratio opportunity”. Pricing results somewhat different from, but reminiscent of, the arbitrage pricing theorems of mathematical finance are obtained. Our analysis provides tighter price bounds on the contingent claim in an incomplete market, which may converge to a unique price for a specific value of a gain–loss preference parameter imposed by the market while the hedging policies may be different for different sides of the same trade. The results are obtained in the simpler framework of stochastic linear programming in a multi-period setting, and have the appealing feature of being very simple to derive and to articulate even for the non-specialist. They also extend to markets with transaction costs. 相似文献
19.
Aslı Deniz 《Journal of Difference Equations and Applications》2013,19(12):1627-1640
In this article, we present a landing theorem for periodic dynamic rays for transcendental entire maps which have bounded post-singular sets, by using standard hyperbolic geometry results. 相似文献
20.
Kayvan Habibi Manouchehr Mamaghani Mohammad Nikpassand 《Journal of inclusion phenomena and macrocyclic chemistry》2018,92(3-4):411-417
Intelligent drug delivery systems are growing and changing too fast, these systems usually show a proper response at the proper time to one or several environmental factors. In the current research a biodegradable drug delivery system (pectin-g-PMA-co-PAAm) was designed and synthesized to release 5 aminosalicylic acid (5-ASA). The synthesized hydrogel is based on natural pectin and is in the form of simultaneous graft copolymerization of synthesized acryl-acid and acryl-amid. Using vinylized bovine serum albumin (VBSA) as cross linker agent is amongst important characteristics of this hydrogel. VBSA was synthesized through BSA modification with methylene-bis-acrylamide (MBA). In addition to having high water absorption, this hydrogel is pH-sensitive. In vitro tests under acid and base conditions of stomach show that this hydrogel is an appropriate option to release drugs through mouth. SEM analysis images show that synthesized hydrogel has a porous surface composed of nano and micro cavities. 相似文献