全文获取类型
收费全文 | 226篇 |
免费 | 5篇 |
专业分类
化学 | 92篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 12篇 |
物理学 | 121篇 |
出版年
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 13篇 |
2011年 | 10篇 |
2010年 | 2篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 3篇 |
2005年 | 11篇 |
2004年 | 2篇 |
2003年 | 13篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1988年 | 7篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1938年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1919年 | 1篇 |
1916年 | 2篇 |
1914年 | 1篇 |
1912年 | 2篇 |
1907年 | 1篇 |
排序方式: 共有231条查询结果,搜索用时 31 毫秒
51.
We extend a recent three-loop calculation of nuclear matter by including the effects from two-pion exchange with single and double virtual Δ(1232)-isobar excitation. Regularization dependent short-range contributions from pion-loops are encoded in a few NN-contact coupling constants. The empirical saturation point of isospin-symmetric nuclear matter, , ρ0=0.16 fm−3, can be well reproduced by adjusting the strength of a two-body term linear in density (and tuning an emerging three-body term quadratic in density). The nuclear matter compressibility comes out as K=304 MeV. The real single-particle potential U(p,kf0) is substantially improved by the inclusion of the chiral πNΔ-dynamics: it grows now monotonically with the nucleon momentum p. The effective nucleon mass at the Fermi surface takes on a realistic value of M*(kf0)=0.88M. As a consequence of these features, the critical temperature of the liquid-gas phase transition gets lowered to the value Tc15 MeV. In this work we continue the complex-valued single-particle potential U(p,kf)+iW(p,kf) into the region above the Fermi surface p>kf. The effects of 2π-exchange with virtual Δ-excitation on the nuclear energy density functional are also investigated. The effective nucleon mass associated with the kinetic energy density is . Furthermore, we find that the isospin properties of nuclear matter get significantly improved by including the chiral πNΔ-dynamics. Instead of bending downward above ρ0 as in previous calculations, the energy per particle of pure neutron matter and the asymmetry energy A(kf) now grow monotonically with density. In the density regime ρ=2ρn<0.2 fm−3 relevant for conventional nuclear physics our results agree well with sophisticated many-body calculations and (semi)-empirical values. 相似文献
52.
F. Hinterberger F. Bauer J. Bisplinghoff K. Büer M. Busch T. Colberg L. Demirrs C. Dahl P. D. Eversheim O. Eyser O. Felden R. Gebel J. Greiff E. Jonas H. Krause C. Lehmann J. Lindlein R. Maier A. Meinerzhagen C. Pauli D. Prasuhn H. Rohdje D. Rosendaal P. Von Rossen N. Schirm W. Scobel K. Ulbrich E. Weise T. Wolf R. Ziegler 《Progress in Particle and Nuclear Physics》2003,50(2):537-546
Excitation functions of the differential cross sections dσ/dgw, analyzing powers AN and spin correlation parameters ANN, ASS and ASL have been measured with internal targets at the Cooler Synchrotron COSY. Data were taken continously during the acceleration and deceleration of the internal beam for kinetic energies between 450 and 2500 MeV and scattering angles 30° σcm 90°. Details of the experimental method are presented. The results provide excitation functions and angular distributions of high precision and internal consistency. No evidence for narrow structures are found. Upper limits on the coupling of narrow resonances to elastic scattering in the mass range √s = 2.2…2.8 GeV are deduced. The data have significant impact on phase shift solutions. 相似文献
53.
54.
S. Mundigl M. Vicente Vacas W. Weise 《Zeitschrift für Physik A Hadrons and Nuclei》1991,338(1):103-110
The available branching ratios for protonium annihilation into two mesons are analyzed in terms of a hadronic picture. We start from protonium wave functions calculated using a realistic OBE potential, a phenomenological part to account for the annihilation, and a particularly simple transition operatorV(N¯N meson
a
+ meson
b
). Flavour effects, sensitivity to tensor mixing and to isospin mixing are investigated.Work supported in part by German BMFT grant 06 OR 762, and by European Community project SC1-0233-C 相似文献
55.
56.
Systematic nuclear effects discovered in the production ofJ/ψ particles in high-energy proton-nucleus collisions cannot be explained within the conventional picture in which a heavy color singlet $Q\bar Q$ pair, after its production, experiences multiple scattering from nucleons of the residual nucleus. We propose to take into account color octet intermediate states formed in the primary production of the heavy-quark pairs. Using a perturbative QCD analysis we study the microscopic production mechanism for $Q\bar Q$ pairs through gluon-gluon fusion with subsequent color neutralization in a strongly interacting medium. The influence of the surrounding matter on this process is investigated. 相似文献
57.
58.
59.
S.?St?ckelEmail author K.?Weise T.?Thamm K.-U.?K?rner D.?Dietrich G.?Marx 《Analytical and bioanalytical chemistry》2003,375(7):884-890
Hard BCN films were deposited by chemical vapour deposition (CVD) on Si(100) substrates. TCVD (thermal activated) and PECVD (GD or RF microwave plasma-activated, respectively) were used. The films were analysed with respect to chemical state, composition, morphology and microstructure, oxidation behaviour and hardness. Wavelength dispersive X-ray spectroscopy (EPMA), infrared spectroscopy (IR), transmission electron microscopy (TEM), differential thermal analysis (DTA) and hardness evaluation were employed for film characterization. A correlation between deposition parameters and film composition, structure and hardness could be proved in every CVD process. Parallels between TCVD and PECVD films emerged in the case of chemical composition and the correlation between carbon content and hardness values. Considerable differences exist with regard to the microstructure, especially the texture of the films. Moreover in TCVD films the carbon is preferentially incorporated between the BN basal planes, whereas in PECVD films it is incorporated preferentially in as well as between the BN basal planes. 相似文献
60.
Sensitivity data for low energy photon spectroscopy used in photon activation analysis are compiled and compared with those
for classical gamma-spectroscopy. All elements of the periodic table with a few exceptions were irradiated with 30 MeV-bremsstrahlung
of a linear electron accelerator. Low energy photon spectra were taken with a LEP-detector as well as with a coaxial Ge(Li)-detector.
Resulting data were processed by computer. The results show that in some cases low energy photon spectroscopy used in photon
activation analysis provides higher sensitivity than can be achieved by classical gamma-spectroscopy. 相似文献