全文获取类型
收费全文 | 95篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 38篇 |
力学 | 4篇 |
数学 | 34篇 |
物理学 | 22篇 |
出版年
2018年 | 2篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2013年 | 5篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 2篇 |
1999年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有98条查询结果,搜索用时 15 毫秒
21.
22.
Abstract— The diaphototropic responses of the solar-tracking leaves of Lavatera cretica were studied under constant levels of vectorial photo-excitation (negligible variations in angle of incidence and fluence rates). The results showed the following:
(a) The photoreceptors, that are associated with the (major) veins, can equally perceive vectorial excitation (by an oblique light-beam in the plane of symmetry of the vein), directed either towards its tip (tip-oriented: TO), or towards its base (base-oriented: BO).
(b) The mechanism of photo-perception is apparently qualitatively the same for TO and BO excitation.
(c) The response to TO and BO vectorial excitation, which takes place in a circular sheath of motor-cell tissue in the pulvinus (a2–3 mm long segment at the top of the petiole), is also highly directional and results in bending in the vertical plane of the oblique beam. Each sector of the motor tissue can expand longitudinally in response to TO excitation, presumably by influx of solutes, and contract longitudinally in response to BO excitation of the same vein, presumably by efflux of solutes.
(d) The angular velocity of the vectorial response to a constant level of vectorial excitation remains constant over large angular displacements and long periods, and was similar for TO and BO over a wide range of fluence rates (30-400 μmol m−2 s−1 ) of white light (400-700 nm).
(e) Reversal of the direction of vectorial excitation (TO to BO, and vice versa) results in reversal of the direction of the vectorial response (laminar reorientation). The change in the direction of laminar reorientation involved a larger overshoot in the original direction when the change was from BO to TO, than in the reverse case. 相似文献
(a) The photoreceptors, that are associated with the (major) veins, can equally perceive vectorial excitation (by an oblique light-beam in the plane of symmetry of the vein), directed either towards its tip (tip-oriented: TO), or towards its base (base-oriented: BO).
(b) The mechanism of photo-perception is apparently qualitatively the same for TO and BO excitation.
(c) The response to TO and BO vectorial excitation, which takes place in a circular sheath of motor-cell tissue in the pulvinus (a2–3 mm long segment at the top of the petiole), is also highly directional and results in bending in the vertical plane of the oblique beam. Each sector of the motor tissue can expand longitudinally in response to TO excitation, presumably by influx of solutes, and contract longitudinally in response to BO excitation of the same vein, presumably by efflux of solutes.
(d) The angular velocity of the vectorial response to a constant level of vectorial excitation remains constant over large angular displacements and long periods, and was similar for TO and BO over a wide range of fluence rates (30-400 μmol m
(e) Reversal of the direction of vectorial excitation (TO to BO, and vice versa) results in reversal of the direction of the vectorial response (laminar reorientation). The change in the direction of laminar reorientation involved a larger overshoot in the original direction when the change was from BO to TO, than in the reverse case. 相似文献
23.
Agakichiev G Baur R Breskin A Chechik R Drees A Jacob C Faschingbauer U Fischer P Fraenkel Z Fuchs C Gatti E Glässel P Günzel T de los Heros CP Hess F Irmscher D Lenkeit B Olsen LH Panebrattsev Y Pfeiffer A Ravinovich I Rehak P Schön A Schukraft J Sampietro M Shimansky S Shor A Specht HJ Steiner V Tapprogge S Tel-Zur G Tserruya I Ullrich T Wurm JP Yurevich V 《Physical review letters》1995,75(7):1272-1275
24.
Dov Talmor Joshua Hermolin Emilia Kirowa-Eisner 《Journal of Electroanalytical Chemistry》1982,139(1):81-95
The applications of the reverse pulse method are extended in order to distinguish between different paths of electrodimerization. The method for determination of rate constants of the chemical reaction coupled with charge transfer (ec2) is further developed. Measurements of K′d vs. tp provide valuable information for the determination of rate constants.The reverse pulse method is applied in the study of the electrodimerization of 1-alkyl-4-t-butylpyridinium ions (1-alkyl=?CH3; ?CH2CH3; ?CH(CH 3)2) in acetonitrile. It is found that the electrodimerization mechanism is consistent with the sequence: Py+ + e = Py ? Py2. The formal potential Eo′ is measured directly for 1-CH(CH3)2, and indirectly for the other pyridium ions. All values are identical within experimental error (Eo′ = ?1.835 V vs. Ag/Ag+).The values of kd and km are measured. With an increase in the size of the l-alkyl group, kd decreases and km increases. This is consistent with the expected “stabilization” of the radicals due to the increase of the l-alkyl group size which hinders the dimerization site (2- and 6-positions). 相似文献
25.
26.
Daniel Lehmann Kurt Engesser Dov M. Gabbay 《International Journal of Theoretical Physics》2006,45(4):698-723
In quantum physics, a measurement is represented by a projection on some closed subspace of a Hilbert space. We study algebras of operators that abstract from the algebra of projections on closed subspaces of a Hilbert space. The properties of such operators are justified on epistemological grounds. Commutation of measurements is a central topic of interest. Classical logical systems may be viewed as measurement algebras in which all measurements commute.
PACS: 02.10.-V. 相似文献
27.
28.
Dov Sherman 《Journal of the mechanics and physics of solids》2005,53(12):2742-2757
The speed of Rayleigh surface waves, denoted CR, is the accepted upper limit for Mode I crack velocity in monolithic solids. In the current contribution, we discuss several critical issues associated with the velocity of Rayleigh surface waves and crack velocity in single crystal (SC) brittle solids, and the global and local influence of CR on crack path selection in particular.Recent cleavage experiments in SC silicon showed that crack velocity at certain cleavage planes and crystallographic orientations cannot exceed a small fraction of CR, and thereafter the crack deflects to other cleavage planes. Indeed, CR defined by the continuum mechanics ignores atomistic phenomena occurring during rapid crack propagation, and therefore is limited in predicting the crack velocity. Examination of these anomalies shows that this limitation lies in microstructural lattice arrangement and in anisotropic phonon radiation during rapid crack propagation. Globally, CR has no influence on the crack deflection phenomenon. However, the misfit in CR between the original plane of propagation and the deflected plane generates local instabilities along the deflection zone. 相似文献
29.
30.
On decidable,finitely axiomatizable,modal and tense logics without the finite model property Part II
Dov M. Gabbay 《Israel Journal of Mathematics》1971,10(4):496-503
This paper is a continuation of Part I. A decidable extension of model K4 that lacks the finite model property is described.
It is not known whether there are extensions of B that are decidable and lack the finite model property. 相似文献