全文获取类型
收费全文 | 147篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
化学 | 98篇 |
力学 | 17篇 |
数学 | 19篇 |
物理学 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 15篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有158条查询结果,搜索用时 31 毫秒
151.
Composite structures are often used in the aerospace industry due to the advantages offered by a high strength to weight ratio. Sound transmission through an infinite laminated composite cylindrical shell is studied in the context of the transmission of airborne sound into the aircraft interior. The shell is immersed in an external fluid medium and contains internal fluid. Airflow in the external fluid medium moves with a constant velocity. An exact solution is obtained by simultaneously solving the first-order shear deformation theory (FSDT) of a laminated composite shell and the acoustic wave equations. Transmission losses (TL) obtained from numerical solutions are compared with those of other authors. The effects of structural properties and flight conditions on TL are studied for a range of values, especially, the Mach number, stack sequences, and the angle of warp. Additionally, comparisons of the transmission losses are made between the classical thin shell theory (CST) and FSDT for laminated composite and isotropic cylindrical shells. 相似文献
152.
Self-broadening coefficients of NH3 in the ν2 and ν4 bands and absolute line intensities in the ν2 band have been measured at room temperature for some selected lines in the P- and R-branches. Using a Fourier transform spectrometer, line intensities and collisional widths were obtained by fitting Voigt profiles to the measured shapes of the lines. The results of self-broadening coefficients are in reasonable agreement with calculated linewidths using a semiclassical model which reproduce rather well the systematic experimental J and K quantum numbers dependencies. Satisfactory agreement was also obtained for line intensities with previous measurements in the ν2 band. From the intensity measurements, we have determined effective transition dipole moments as well as Herman–Wallis parameters for the ν2 band. 相似文献
153.
A. Sztraka H. -P. Haug und A. Nouri 《Fresenius' Journal of Analytical Chemistry》1984,317(3-4):373-374
Zusammenfassung Die Hemmung der Atmungsaktivität von Belebtschlamm wird mit Hilfe biochemischer Verfahren ermittelt. Hierfür sind verschiedene respirometrische Verfahren bekannt. Alle diese Verfahren beruhen auf der Messung des Sauerstoffverbrauchs während der Meßzeit. Die ermittelte Zeit ist ein Maß für die Atmungsaktivität der Mikroorganismen im untersuchten Medium. Man kann die Atmungsaktivität jedoch auch durch die Messung der Zunahme des Endprodukts der Stoffwechselprozesse erfassen, d. h. durch die Messung der Kohlenstoffdioxidkonzentration im untersuchten Medium. Es wird ein Verfahren vorgestellt, das durch Anwendung gassensitiver Elektroden ermöglicht, die Kohlenstoffdioxidkonzentration zu messen und so die Atmungsaktivität zu ermitteln.
Prof. Dr. W. Fresenius zum 70. Geburtstag gewidmet 相似文献
Cadmium and lead in the biological sewage treatment — Respiration measurements with gas-sensitive electrodes
Summary The inhibition of the respiratory activity is determined by means of biochemical procedures. Various respiration measurement procedures are known for this purpose. All of these procedures are based on the measurement of the oxygen consumption during the measurement period. The determined time is an index for the respiratory activity of the micro-organisms in the examined medium. One can, however, also determine the respiratory activity by measuring the increase of the end product of the metabolism processes, i.e., by measuring the concentration of carbon dioxide in the examined medium. A procedure is proposed, which, by the utilization of gas-sensitive electrodes, enables the measurement of the carbon dioxide concentration and thereby the determination of the respiratory activity.
Prof. Dr. W. Fresenius zum 70. Geburtstag gewidmet 相似文献
154.
A. Nouri 《Journal of statistical physics》2002,106(3-4):589-622
An existence theorem is derived for a system of kinetic equations describing the evolution of a gas in a radiation field from a kinetic point of view. The geometrical setting is the slab and given indata. The photons ingoing distribution functions are Dirac measures. 相似文献
155.
Four new ligands, (4-methyl-phenyl)-pyridin-2-ylmethylene-amine (A), (2,3-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (B), (2,4-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (C) and (2,5-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (D), and their corresponding copper(I) complexes, [Cu(A)2]ClO4 (1a), [Cu(B)2]ClO4 (1b), [Cu(C)2]ClO4 (1c), [Cu(D)2]ClO4 (1d), [Cu(A)(PPh3)2]ClO4 (2a), [Cu(B)(PPh3)2]ClO4 (2b), [Cu(C)(PPh3)2]ClO4 (2c) and [Cu(D)(PPh3)2]ClO4 (2d), have been synthesized and characterized by CHN analyses, 1H and 13C NMR, IR and UV–Vis spectroscopy. The crystal structures of [Cu(B)2]ClO4 (1b), [Cu(C)2]ClO4 (1c) and [Cu(A)(PPh3)2]ClO4 · 1/2CH3CN (2a) were determined from single crystal X-ray diffraction. The coordination polyhedron about the copper(I) center in the three complexes is best described as a distorted tetrahedron. A quasireversible redox behavior is observed for the complexes. 相似文献
156.
Mechanical alloying/milling technique is characterized by the repeated welding and fracturing of powder particles in a high-energy ball mill, which often results in excessive cold welding and agglomeration of ductile particles. To achieve the critical balance between cold welding and fracturing, the surface of the deforming particles is modified by introducing a suitable organic material, called surfactant or process control agent (PCA). However, the use of surfactants is self-contradictory by nature and requires further consideration of the milling variables and type/amount of surfactant. The current article provides a practical approach to the promises and challenges associated with surfactants in mechanical alloying/milling. An attempt has been made to address the most crucial aspects correlated with surfactants, including contamination, the morphology and size of powder particles, formation of alloy and microstructural evolution, and powder yield, as well as the physico-mechanical properties, such as magnetism, density, hardness, and compressive strength. An overview is also given on the adsorption mechanism of surfactants onto the surface of powder particles, with a special emphasis on type, amount, and the addition time of surfactants in the mechanical alloying process. 相似文献
157.
We study a finite Larmor radius model used to describe the ions distribution function in the core of a tokamak plasma, that consists in a gyro-kinetic transport equation coupled with an electro-neutrality equation. Since the last equation does not provide enough regularity on the electric potential, we introduce a simple linear collision operator adapted to the finite Larmor radius approximation. We next study the two-dimensional dynamics in the direction perpendicular to the magnetic field. Thanks to the smoothing effects of the collision and the gyro-average operators, we prove the global existence of solutions, as well as short time uniqueness and stability. 相似文献
158.
A. Nouri 《Mathematical Methods in the Applied Sciences》2000,23(6):561-574
The distance to a set of Maxwellians is determined for a family of functions with bounded mass, energy and a small entropy production term. Functions with small masses are close to the null Maxwellian. Functions with masses bounded from below by a constant are approached by functions proportional to the gain term of the Boltzmann operator, taking advantage of its regularity. For these regularizations, the integrands of the entropy production term are small everywhere. Hence classical arguments can be used to obtain the closedness to the set of Maxwellians. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献