全文获取类型
收费全文 | 144篇 |
免费 | 4篇 |
专业分类
化学 | 94篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 22篇 |
物理学 | 27篇 |
出版年
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 21篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 203 毫秒
131.
Oussama Kamal Tarik Eljaddi El Houssine EL Atmani Imane Touarssi Laurent Lebrun Miloudi Hlaïbi 《先进技术聚合物》2017,28(4):541-548
To conduct experiments related to the facilitated extraction phenomenon and recovery of vanadium ions VO2+, two grafted polymer membranes were prepared; containing respectively cholic acid and azithromycin as extractive agents and the obtained membranes were characterized. All experiments for the facilitated extraction phenomenon of these ions were carried out. Kinetic and thermodynamic models, based on the interaction of the substrate S (VO2+) with the extractive agent T, and the diffusion of the formed entity (TS) through the membrane were developed, to determine the macroscopic parameters, permeability P and initial fluxes J0, and the microscopic parameters, association constants Kass and apparent diffusion coefficients D*, related to the formation of entities TS and their diffusion. A clear evolution of these parameters, depending on various factors (substrate concentration C0, extractive agent concentration and feed and receiving phases temperature), and high permeabilities for this extraction phenomenon of VO2+ ions were observed for this membrane type. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
132.
Philippe Michel Tarik Mohamed Touaoula 《Mathematical Methods in the Applied Sciences》2013,36(3):323-335
In this paper, we consider nonlinear age‐structured equation with diffusion under nonlocal boundary condition and non‐negative initial data. More precisely, we prove that under some assumptions on the nonlinear term in a model of McKendrick–Von Foerster with diffusion in age, solutions exist and converge (long‐time convergence) towards a stationary solution. In the first part, we use classical analysis tools to prove the existence, uniqueness, and the positivity of the solution. In the second part, using comparison principle, we prove the convergence of this solution towards the stationary solution. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
133.
Zuhair M. Kassir Ala-Din M. Al-Muaibed Ali H.A. Kareem Tarik A.K. Nasser 《Analytica chimica acta》1984
The candoluminescence of terbium and indium was studied in various matrices coated on CaO/CaSO4 rods. Terbium was studied in Y2O3, Gd2O3, ThO2 and La2O3. Calibration graphs were linear over different ranges, up to 90 ng in some cases, with 0.2–0.3 ng μl?1 detection limits and 2.8–3.2% relative standard deviations (c.s.d.). The candoluminescence of indium in Y2O3, Gd2O3 and Al2O3 was also examined. Calibration graphs were linear over different ranges, up to 20 ng in some cases, with detection limits of 0.08 ng μl?1 for Y2O3 and Al2O3 and 0.2 ng μl?1 for Gd2O3 with r.s.d. of 2.5–2.9%. There are many interferences. 相似文献
134.
Mehmet Karakaplan Yı
ılmaz Turgut Tarik Aral Halil Hoşgören 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):315-319
Chiral mono aza-18-crown-6 derivatives have been prepared in optically active form and high yield from amino alcohols via a cyclization reaction with tetraethylene glycol ditosylate.The enantiomeric recognition by these chiral aza-crown ethers between chiral primary ammonium perchlorate salts has been characterized by UV–Vis at 25 °C in chloroform. 相似文献
135.
Shihab A. Kadum Nabeel A. Baker Tarik E. Al-Edanee 《Monatshefte für Chemie / Chemical Monthly》1991,122(5):349-358
Summary The virtual charge model (Tapia model) in conjunction with the CNDO/S-CI approximation in the frame of SCF-MO theory was employed to study the effects of solvent on the electronic structures and spectra of benzaldehyde and acetophenone molecules. The CNDO/S calculations in presence of solvation indicate a satisfactory interpretation of the medium effects on the electronic structures and spectra of the molecules investigated. The prediction of our MO calculations by means of the Tapia model concerning the solvochromic shifts of n * and * transitions are in accord with the observed trends which indicate a blue shift for the n * band and a red shift for the * band upon a change of solvent from non-polar to polar solvents.
Anwendung des Virtual Charge-Modells auf die Elektronenstrukturen und Spektren von Benzaldehyd und Acetophenon
Zusammenfassung Das Virtual-Charge-Modell (Tapia-Modell) im Zusammenhang mit der CNDO/S-CI-Näherung im Rahmen der SCF-MO-Theorie wurde zum Studium der Lösungsmitteleffekte auf die Elektronenstrukturen und Spektren von Benzaldehyd und Acetophenon herangezogen. Die CNDO/S-Rechnungen bei Anwesenheit von Solvens erlauben eine befriedigende Interpretation der Mediumeffekte auf Elektronenstrukturen und Spektren der untersuchten Verbindungen. Die aus MO-Rechnungen folgenden Voraussagen ergeben auf Basis des Tapia-Modells solvatochrome Verschiebungen für die n *- und *-Übergänge. Die vorausgesagten Effekte stehen im Einklang mit den experimentell beobachteten Trends: Blauverschiebung für die n *-Bande und Rotverschiebung für die *-Bande beim Wechsel von nichtpolarem zu polarem Lösungsmittel.相似文献
136.
Matrab T Chehimi MM Perruchot C Adenier A Guillez A Save M Charleux B Cabet-Deliry E Pinson J 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4686-4694
This paper reports on the preparation of poly(methyl methacrylate) (PMMA), poly(n-butyl acrylate) (PBA), and polystyrene (PS) brushes at the surface of conducting materials that were modified by the electrochemical reduction of a brominated aryl diazonium salt BF4-, +N2-C6H4-CH(CH3)-Br (D1). The grafted organic species -C6H4-CH(CH3)-Br was found to be very effective in initiating atom transfer radical polymerization (ATRP) of vinyl monomers. This novel approach combining diazonium salts and ATRP allowed PMMA, PBA, and PS brushes to be grown from the surface of iron electrodes. The polymer films were characterized in terms of their chemical structure by infrared reflection absorption spectroscopy and X-ray photoelectron spectroscopy. Atomic force microscopy studies indicated that the polymer brushes are densely packed. Contact angle measurements of water drops on PS and PMMA brushes were 88.1 +/- 2.0 and 70.3 +/- 2.1 degrees, respectively, which is consistent with the published wettability data for the corresponding polymer sheets. 相似文献
137.
138.
Yardibi T Li J Stoica P Cattafesta LN 《The Journal of the Acoustical Society of America》2008,123(5):2631-2642
Using microphone arrays for estimating source locations and strengths has become common practice in aeroacoustic applications. The classical delay-and-sum approach suffers from low resolution and high sidelobes and the resulting beamforming maps are difficult to interpret. The deconvolution approach for the mapping of acoustic sources (DAMAS) deconvolution algorithm recovers the actual source levels from the contaminated delay-and-sum results by defining an inverse problem that can be represented as a linear system of equations. In this paper, the deconvolution problem is carried onto the sparse signal representation area and a sparsity constrained deconvolution approach (SC-DAMAS) is presented for solving the DAMAS inverse problem. A sparsity preserving covariance matrix fitting approach (CMF) is also presented to overcome the drawbacks of the DAMAS inverse problem. The proposed algorithms are convex optimization problems. Our simulations show that CMF and SC-DAMAS outperform DAMAS and as the noise in the measurements increases, CMF works better than both DAMAS and SC-DAMAS. It is observed that the proposed algorithms converge faster than DAMAS. A modification to SC-DAMAS is also provided which makes it significantly faster than DAMAS and CMF. For the correlated source case, the CMF-C algorithm is proposed and compared with DAMAS-C. Improvements in performance are obtained similar to the uncorrelated case. 相似文献
139.
140.
Yaşar F Arkin H Celik T Berg BA Meirovitch H 《Journal of computational chemistry》2002,23(12):1127-1134
The advantage of the multicanonical (MUCA) simulation method of Berg and coworkers over the conventional Metropolis method is in its ability to move a system effectively across energy barriers thereby providing results for a wide range of temperatures. However, a MUCA simulation is based on weights (related to the density of states) that should be determined prior to a production run and their calculation is not straightforward. To overcome this difficulty a procedure has been developed by Berg that calculates the MUCA weights automatically. In a previous article (Ya?ar et al. J Comput Chem 2000, 14, 1251-1261) we extended this procedure to continuous systems and applied it successfully to the small pentapeptide Leu-enkephalin. To investigate the performance of the automated MUCA procedure for larger peptides, we apply it here to deltorphin, a linear heptapeptide with bulky side chains (H-Tyr(1)-D-Met(2)-Phe(3)-His(4)-Leu(5)-Met(6)-Asp(7)-NH(2)). As for Leu-enkephalin, deltorphin is modeled in vacuum by the potential energy function ECEPP. MUCA is found to perform well. A weak second peak is seen for the specific heat, which is given a special attention. By minimizing the energy of structures along the trajectory it is found that MUCA provides a good conformational coverage of the low energy region of the molecule. These latter results are compared with conformational coverage obtained by the Monte Carlo minimization method of Li and Scheraga. 相似文献