全文获取类型
收费全文 | 162篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 90篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 60篇 |
出版年
2019年 | 3篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 13篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 6篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 9篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有164条查询结果,搜索用时 185 毫秒
41.
D. Lambrecht T. Blaich T. W. Elze H. Emling H. Freiesleben K. Grimm W. Henning R. Holzmann J. G. Keller H. Klingler J. V. Kratz R. Kulessa S. Lange Y. Leifels E. Lubkiewicz E. F. Moore W. Prokopowicz R. Schmidt C. Schütter H. Spies K. Stelzer J. Stroth E. Wajda W. Waluś M. Zinser E. Zude 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):115-120
We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of197Au+197Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile.
The members of the FOPI-collaboration: J.P. Alard, Z. Basrak, N. Bastid, I.M. Belayev, M. Bini, R. Bock, A. Buta, R. aplar, C. Cerruti, N. Cindro, J.P. Coffin, M. Crouau, P. Dupieux, J. Erö, Z.G. Fan, P. Fintz, Z. Fodor, R. Freifelder, L. Fraysse, S. Frolov, A. Gobbi, Y. Grigorian, G. Guillaume, N. Herrmann, K.D. Hildenbrand, S. Hölbling, O. Houari, S.C. Jeong, M. Jorio, F. Jundt, J. Kecskemeti, P. Koncz, Y. Korchagin, R. Kotte, M. Krämer, C. Kuhn, I. Legrand, A. Lebedev, C. Maguire, V. Manko, T. Matulewicz, G. Mgebrishvili, J. Mösner, D. Moisa, G. Montarou, P. Morel, W. Neubert, A. Olmi, G. Pasquali, D. Pelte, M. Petrovici, G. Poggi, F. Rami, W. Reisdorf, A. Sadchikov, D. Schüll, Z. Seres, B. Sikora, V. Simion, S. Smolyankin, U. Sodan, N. Taccetti, K. Teh, R. Tezkratt, M. Trzaska, M.A. Vasiliev, P. Wagner, J.P. Wessels, T. Wienold, Z. Wilhelmi, D. Wohlfarth, A.V. Zhilin. 相似文献
42.
Bitterer F Herd O Hessler A Kühnel M Rettig K Stelzer O Sheldrick WS Nagel S Rösch N 《Inorganic chemistry》1996,35(14):4103-4113
Chiral water-soluble secondary phosphines (2-6) were obtained by nucleophilic phosphination of FC(6)H(4)-4-SO(3)K (1a), FC(6)H(3)-2,4-(SO(3)K)(2) (1b), and FC(6)H(4)-2-SO(3)K (1c) with RPH(2) (R = Ph, 2,4,6-Me(3)C(6)H(2), 2,4,6-iPr(3)C(6)H(2)) in the superbasic medium DMSO/KOH by employing steric control of substitution at phosphorus by bulky substituents R and sulfonic groups in the ortho position of the aromatic ring systems in 1b or 1c. The secondary phosphines may be deprotonated in DMSO/KOH to give phosphido anions which on reaction with alkyl halides (PhCH(2)Cl, Br(CH(2))(3)Br, and C(12)H(25)Br) yield mono- or bidentate tertiary phosphines (7-10). Ligands of this type are alternatively accessible by nucleophilic arylation of secondary phosphines, e.g. Ph(Me)PH or Ph(H)P(CH(2))(3)P(H)Ph with 1a or 1b, respectively. The crystal structure of the starting material 1b.H(2)O (space group P2(1)/m) has been determined. In the solid state of 1b.H(2)O the individual molecules are interconnected by ionic interactions between the potassium cations and the SO(3)(-) anions. The C-F bond (C(1)-F 1.347(4) ?) is shorter than that in C(6)H(5)F (1.356(4) ?). The unit cell of 7a.0.5H(2)O (space group P&onemacr;), the first structurally characterized chiral phosphine with a sulfonated phenyl substituent, contains the two enantiomers. Due to the asymmetrical substitution at phosphorus the PC(3) skeletons are significantly distorted (P(1)-C(1,11,31) 1.864(10), 1.825(8), 1.841(7) ?). The electronic structure of sulfonated fluorobenzenes FC(6)H(5)(-)(n)()(SO(3)M)(n)() (M = K, NH(4), n = 1-3) is discussed on the basis of quantum chemical calculations. In particular, the reactivity difference toward nucleophilic phosphination within the series is rationalized in terms of steric factors and of the -I effect of the sulfonic groups. 相似文献
43.
Zusammenfassung Die Metathese-Reaktion von 1,4-Polybutadien mit 4-Octen wurde unter Anwendung eines WCl6/C2H5AlCl2
2-Katalysators kinetisch untersucht. Das Gemisch niedermolekularer Produkte wurde gaschromatographisch analysiert. Die Ergebnisse
wurden mit einer vonW. Kuhn angegebenen Gleichung berechnet. Hieraus und nach der Methode der „Gleichwertszeit” wurde die experimentelle Aktivierungsenergie
bestimmt. Der Abbau ist eine statistische Spaltung.
Mit 3 Abbildungen und 1 Tabelle 相似文献
Summary The metathesis reaction of 1,4-polybutadiene with 4-octene was investigated kinetically, using a WCl6/C2H5AlCl2 catalyst. The mixture of low molecular products was analysed by gas chromatography. Results were calculated with an equation developed byW. Kuhn. From this and with the method of “equivalent time” the experimental activation energy was calculated. The degradation is a random scission.
Mit 3 Abbildungen und 1 Tabelle 相似文献
44.
Reinhard Schmutzler Othmar Stelzer Joel F. Liebman 《Journal of fluorine chemistry》1984,25(3):289-299
In this paper we discuss the mechanism of the related disproportionation reactions 2 RPF2 → (RP)n + RPF4 3 R2PF → R2P?PR2 + R2PF3 We consider displacement reactions on both fluorine and phosphorus, catalysis and autocatalysis by hydrogen fluoride and the product fluorophosphorane, the effect of substituents on the rate, and iso- electronic analogies involving both other group V atoms and halogens. We also consider related disproportionation reactions of lower valence fluorides of other nonmetals such as S, Cl and Xe. From these comparisons, we deduce the following mechanism (Z = R,F) 相似文献
45.
H. Stark J. Stelzer R. Bernhard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):515-523
Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a
point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes
a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For
such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental
observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets,
but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order
phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two
boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a
defect between them.
Received 11 December 1998 相似文献
46.
47.
Martina Sandholzer Sabine Bichler Franz Stelzer Christian Slugovc 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2402-2413
Statistical and amphiphilic block copolymers bearing cinnamoyl groups were prepared by ring opening metathesis polymerization (ROMP). The UV‐induced [2 + 2] cycloaddition reaction of polymer bound cinnamic acid groups was studied in polymer thin films as well as in block copolymer micelles. In both cases, exposure to UV‐light for 10 min led to a crosslinking conversion of about 60%, as determined by FT‐IR spectroscopy and UV–vis absorption measurements. Time based IR‐spectroscopy revealed a maximum conversion of 78% reached after an irradiation time of about 16 min. For micelles obtained from polymers bearing 5 mol % or more cinnamoyl groups, the crosslinking reaction proceeded smoothly, yielding in crosslinked particles which were stable in a non‐selective solvent (CHCl3). Diameters determined by dynamic light scattering in the selective solvent (MeOH) were similar for both, non‐crosslinked and crosslinked micelles, whereas diameters of crosslinked micelles in the non‐selective solvent (CHCl3) were significantly larger compared to MeOH samples. This strategy of direct self assembly of block‐copolymers in a selective solvent followed by “clean” crosslinking, without the need for additional crosslinking reagents or crosslinking initiators, provides a straight forward approach toward ROMP‐based polymeric nano‐particles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2402–2413, 2008 相似文献
48.
G. Rudolf A. Gobbi H. Stelzer U. Lynen A. Olmi H. Sann R.G. Stokstad D. Pelte 《Nuclear Physics A》1979,330(1):243-252
Projectile-like products from the reaction 86Kr on 166Er at 8.18 MeV/amu have been measured using a large-area position-sensitive ionization chamber. The observed element distributions for a given energy loss are found to be asymmetric. An analysis of the data in terms of the residual kinetic energy above the Coulomb barrier, however, yields symmetric and Gaussian-shaped element distributions. At large energy losses, the centroids of these Gaussian distributions exhibit a drift towards symmetric mass splits. The correlation between the variance of the element distribution σz2 and the number of exchanged nucleons Nex is discussed. The exchange mechanism, as described by a simple one-body dissipation model, can account for a large portion of the measured energy loss. 相似文献
49.
K.H. Althoff R.M. Brown D. Freytag K.S. Heard J. Heintze R. Mundhenke H. Rieseberg V. Soergel H. Stelzer A. Wagner 《Physics letters. [Part B]》1973,43(3):237-239
From the analysis of 817 kinematically resonstructed beta decay events of polarized Λ hyperons for the coefficient αν of the neutrino correlation with respect to the Λ spin, αν = 0.89 ± 0.08, for the coefficient αT of the T-odd correlation σΛ(pe × pν), αT = ?0.14 ± 0.13. The proton recoil spectrum yields …g1/f1… = 0.64 ± 0.06. 相似文献
50.
H. Ower Th.W. Elze J. Idzko K. Stelzer E. Grosse H. Emling P. Fuchs D. Schwalm H.J. Wollersheim N. Kaffrell N. Trautmann 《Nuclear Physics A》1982,388(2):421-444
Multiple Coulomb excitation of 232Th, 234U and 236U by 5.3 208Pb ions has been studied using γ-ray spectroscopy. Excitation of ground-band levels is observed up to spin Iπ = 26+ (tentatively 28 +) in 232Th and 234U and Iπ = 28+ (tentatively 30+)in 236U. High-spin levels of the Kπ = 0? octupole-vibrational bands are also observed in these nuclei. The measured transition energies between ground-band levels suggest that at several units of angular momentum are carried by single particles aligned with the rotation axis.This result can be understood in terms of a super band built on aligned two-quasiparticle configurations which crosses the ground-state rotational band at a rotational frequency of . The E2 transition-matrix elements deduced from the experimental γ-yields agree within their errors with the rigid-rotor predictions up to the highest spins observed.The experimental results are discussed using the concept of rotation alignment and are compared with predictions of the rotation-vibration model and the interacting-boson model. 相似文献