全文获取类型
收费全文 | 297篇 |
免费 | 3篇 |
专业分类
化学 | 160篇 |
晶体学 | 1篇 |
力学 | 17篇 |
数学 | 48篇 |
物理学 | 74篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 13篇 |
2012年 | 12篇 |
2011年 | 18篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 17篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1942年 | 2篇 |
1941年 | 1篇 |
1939年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有300条查询结果,搜索用时 0 毫秒
21.
R. Ficarra M. L. Calabrò S. Tommasini D. Costantino M. Carulli S. Melardi M. R. Di Bella F. Casuscelli R. Romeo P. Ficarra 《Chromatographia》1996,43(7-8):365-368
Summary A high-performance liquid chromatographic method is reported for the resolution of the enantiomers of a series of fused -lactams (2,7-diaza-3-oxo[3.3.0]octan-6-ones) with probable anti-HIV and anticancer activity. Resolution was achieved on a Chiralcel® OD column, cellulose tris-(3,5-dimethylphenyl carbamate) adsorbed on macroporous silica gel; mixtures ofn-hexane and isopropyl alcohol in different proportions were used as the mobile phase. The analysis was studied at different temperatures. 相似文献
22.
The thermal decomposition of some mixed uranyl complexes with Schiff bases and DMSO, EtOH or (Ph)3PO as neutral ligand, were investigated and the corresponding activation energy, E*a, and enthalpy of dissociation, ΔHd, values were calculated.
The results obtained indicate that for the same neutral ligand, the thermal stability of the uranyl complexes is influenced by the Schiff base used; for the same Schiff base, the presence of (Ph)3PO results in a greater thermal stability of the mixed complexes than when the other two neutral ligands are present. 相似文献
23.
24.
In this paper, the magnetorheological (MR) and magnetoviscous properties of ferrofluid-based iron particle suspensions were investigated. The 2.1-µm mean size Fe particles were dispersed in high-concentration transformer oil-based ferrofluid, the iron particle volume fraction in the resulting nano-micro composite magnetorheological fluid samples varying from Φ Fe = 5 to 40 %. The ferrofluid carrier has φ p = 23 % solid volume fraction of magnetic nanoparticles stabilized with chemisorbed oleic acid monolayer and without any excess surfactant. In the absence of the field, the ferrofluid has a quasi-Newtonian behavior with a weak shear thinning tendency. The static yield stress shows an increase of about 3 orders of magnitude for an iron particle content of approx. Φ Fe = 25 % (Φ tot = 42.25 %), while above this value, a saturation tendency is observed. The dynamic yield stress (Bingham model) also increases with the magnetic induction and the particle volume fraction; however, the saturation of the MR effect is less pronounced. The relative viscosity change has a maximum at Φ Fe = (10–15) % due to the accelerated increase of the effective viscosity of the composite for higher Fe content. Addition of micrometer-sized iron particles to a concentrated ferrofluid without any supplementary stabilizing agent proved to be a direct and simple way to control the magnetorheological and magnetoviscous behavior, as well as the saturation magnetization of the resulting nano-micro composite fluid to fulfill the requirements of their use in various MR control and rotating seal devices. 相似文献
25.
The main topic consists of enhancing the geometrical and positioning accuracy of the machine tools with numerical control.
Currently, in order to minimize the errors met during the vertical motions of the moving elements in the structure of a machine
tool, various systems are used that are relatively complex and whose adjustments are difficult to do. This work is presenting
a balancing–compensation system of the elements moving vertically that includes three invention patents; it has a simple structure
that is easily adaptable to various types of machine tools. The newness element of the balancing-compensation system is represented
by the pressure regulator being used, whose operation principle and design is described into detail. The related results have
been reified in increasing by approximately 10 times the geometrical accuracy and, by default, the positioning accuracy of
the element moving in a vertical plane. 相似文献
26.
F. Romeo 《Journal of sound and vibration》2003,268(3):601-615
The problem of minimizing transmitted vibrations through finitely long periodic structures is addressed. Bi-coupled periodic element properties and arrangement are tailored to localize the response around the excitation source within any assigned frequency range. Bi-dimensional analytical maps of the single unit free-wave propagation domains (stop, pass and complex domains) provide the optimal choice of the cell properties and ordering. Moreover, the amount of vibration suppression along the periodic structure is also controlled as it can be described through iso-attenuation curves representing the contour plot of the real part of the propagation constants. Applications to both undamped and damped beams resting on elastic supports are illustrated. The response of the periodic structures to harmonic excitations is expressed through the wave vector method taking into account the effects of wave reflection due to changes in the cell properties along the structure and boundary conditions. Such computational schemes enables one to overcome numerical difficulties arising in the transfer matrix formulation for structures with a large number of periodic units. 相似文献
27.
28.
29.
H. Schmalfuß H. Werner G. Curli T. P. Hilditch H. E. Longenecker Fr. Kiermeier Fr. X. Maier C. I. Kruisheer P. C. den Herder G. Roeder B. Segal A. Romeo V. Crupi G. Dorta G. Lunde H. Kringstad E. Mathiesen A. Olsen F. N. Woodward S. R. Hoover S. Schmidt-Nielsen und J. Stone 《Fresenius' Journal of Analytical Chemistry》1941,121(1-2):55-59
Ohne Zusammenfassung 相似文献