全文获取类型
收费全文 | 219篇 |
免费 | 4篇 |
专业分类
化学 | 84篇 |
晶体学 | 4篇 |
力学 | 6篇 |
数学 | 19篇 |
物理学 | 110篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 6篇 |
2011年 | 12篇 |
2010年 | 14篇 |
2009年 | 4篇 |
2008年 | 17篇 |
2007年 | 7篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 1篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 10篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1932年 | 1篇 |
1900年 | 1篇 |
排序方式: 共有223条查询结果,搜索用时 15 毫秒
71.
J.A. Charlesworth R.L. Sekulin M.J. Emms J.B. Kinson L. Riddiford B.J. Stacey M.F. Votruba P.L. Woodworth I.G. Bell M. Dale J.V. Major 《Nuclear Physics B》1973,65(2):253-289
The production of ?0 and f0 mesons has been studied using a sample of 15485 fits to the reaction π+d → pspπ+π? at 4 GeV/c. Results are presented on the spin structure and production mechanisms of these resonances. An Estabrooks and Martin analysis has been carried out in the ?0 region, giving results similar to those obtained in their analysis of 17.2 GeV/c data. Natural parity exchange is less important at our momentum, however. In the case of f0 production, we find evidence for the presence of s-, p- and d-waves in the π π system. Averaging all events in the f0 peak, the s- and d-waves are found to be close in phase. The f0 production mechanism has been investigated using a positivity analysis of the complete J = 0, 1, 2 density matrix, and the same general features are observed as are seen in ?0 production. However, the unnatural parity exchange component is found to be even more dominant in f0 production than in ?0 production. Our results are compared with the predictions of various models. 相似文献
72.
73.
A partial wave analysis of the (3π)0 system from the charge exchange reaction π+n→π+π−πop AT 4 GeV/c
M.J. Emms G.T. Jones J.B. Kinson B.J. Stacey M.F. Votruba P.L. Woodworth I.G. Bell M. Dale J.V. Major J.A. Charlesworth D.J. Crennell R.L. Sekulin 《Physics letters. [Part B]》1975,60(1):109-112
From a partial wave analysis of the (3π)o state in the charge exchange reaction π+n→π+π?πop, we observe strong unnatural parity as well as natural parity production. The observed strong unnatural parity states are identified with well-established resonances. The unnatural parity production is consistent with Reggeized Deck model predictions, with the exception of the I = 1, JP = 1+ state. Here there is no evidence for A1 production at ~1.1 GeV, but the data could support resonance production at higher masses. 相似文献
74.
F. W. McLafferty J. Okamoto H. Tsuyama Y. Nakajima T. Noda H. W. Major 《Journal of mass spectrometry : JMS》1969,2(7):751-753
Measurement of metastable ion abundances over a dynamic range of 105 is possible with a specially designed mass spectrometer. 相似文献
75.
T. N. Mamedov D. G. Andrianov D. Herlach V. N. Gorelkin K. I. Gritsai O. Kormann J. Major A. V. Stoikov U. Zimmermann 《Journal of Experimental and Theoretical Physics》2001,92(6):1004-1009
A study is made into the temperature dependence of residual polarization of negative muons in crystalline silicon with the concentration of impurity of the n-and p-types ranging from 8.7×1013 to 4.1× 1018 cm?3. The measurements are performed in a magnetic field of 1000 G transverse to the muon spin, in the temperature range from 4.2 to 300 K. The form of the temperature dependence of the relaxation rate v of the magnetic moment of the μAl0 acceptor in silicon is determined. For a nondegenerate semiconductor, the relaxation rate depends on temperature as v ∝ T q (q ≈ 3). A variation in the behavior of the temperature dependence and a multiple increase in the relaxation rate are observed in the range of impurity concentration in excess of 1018 cm?3. The importance of phonon scattering and spin-exchange scattering of free charge carriers by an acceptor from the standpoint of relaxation of the acceptor magnetic moment is discussed. The constant of hyperfine interaction in an acceptor center formed by an atom of aluminum in silicon is estimated for the first time: |A hf (Al)/2π| ~ 2.5×106s?1. 相似文献
76.
Rempel AA Sprengel W Blaurock K Reichle KJ Major J Schaefer HE 《Physical review letters》2002,89(18):185501
The identification of atomic defects in solids is of pivotal interest for understanding atomistic processes and solid state properties. Here we report on the exemplary identification of vacancies on each of the two sublattices of SiC by making use of (i) electron irradiation, (ii) measurements of the positron lifetimes, (iii) coincident Doppler broadening studies of the positron-electron annihilation radiation, and (iv) a comparison of the experimental data with theoretical studies. After 0.3 MeV electron irradiation, carbon vacancies V(C) are identified, where, after 0.5 MeV electron irradiation, predomi-nantly silicon vacancies V(Si) are observed. After 2.5 MeV irradiation, divacancies V(Si)-V(Si) are detected. The present results are expected to be of general importance for reliable identification of defects and atomic processes in complex solids. 相似文献
77.
Continuous-wave passive mode locking of a diode-pumped Nd:KGd(WO(4))(2) laser is demonstrated. The use of a saturable Bragg reflector as the mode-locking element permits the generation of 6.3-ps pulses, assuming a sech(2) pulse shape. An output power of 1 W was obtained, which corresponds to a slope efficiency of 34.5%. 相似文献
78.
Milan Králik Zuzana Vallušová Peter Major Adriana Takáčová Milan Hronec Dana Gašparovičová 《Chemical Papers》2014,68(12):1690-1700
Liquid phase hydrogenation of chloronitrobenzene isomers (x-CNB x = 2, 3, 4) to the corresponding chloroanilines (x-CAN) at mild reaction conditions (0.6 MPa, 25°C, diethyl ether-methanol as solvents) over palladium and platinum catalysts containing 1 mass % of metal on trimethylammonium functionalized poly{styrene-co-divinylbenzene} (Dowex-D) was studied. The average selectivities to x-CAN over Pd/D-Cl and Pd/D-OH catalysts were 72 % and 42 %, respectively, at the x-CNB conversion of about 80 %. The average selectivities of 81 % and 84 % were achieved using Pt/D-Cl and Pt/D-OH, respectively, at the x-CNB conversion of approximately 90 %, whereas the average starting reaction rates were 1.2 × 10?3 mol g?1 s?1 and 2.6 × 10?3 mol g?1 s?1 (hydrogen consumption rate per mass of platinum), respectively. Under similar reaction conditions, using palladium catalysts supported on a resin with anionic groups anchored to polymeric chains at the average reaction rate equal to 3.8 × 10?3 mol g?1 s?1 (hydrogen consumption rate per mass of palladium), the selectivities from 85 % (2-CAN and 3-CAN) to 95 % (4-CAN) were achieved (Kratky et al., 2002). 相似文献
79.
We present a rigorous analysis of unique, wide electrochemical window solutions for rechargeable magnesium batteries, based on aromatic ligands containing organometallic complexes. These solutions are comprised of the transmetalation reaction products of Ph(x)MgCl(2-x) and Ph(y)AlCl(3-y) in different proportions, in THF. In principle, these reactions involve the exchange of ligands between the magnesium and the aluminum based compounds, forming ionic species and neutral molecules, such as Mg(2)Cl(3)(+)·6THF, MgCl(2)·4THF, and Ph(y)AlCl(4-y)(-) (y = 0-4). The identification of the equilibrium species in the solutions is carried out by a combination of Raman spectroscopy, multinuclear NMR, and single-crystal XRD analyses. The association of the spectroscopic results with explicit identifiable species is supported by spectral analyses of specially synthesized reference compounds and DFT quantum-mechanical calculations. The correlation between the identified solution equilibrium species and the electrochemical anodic stability window is investigated. This study advances both development of new nonaqueous solution chemistry and possible development of high-energy density rechargeable Mg batteries. 相似文献
80.
M. Koch K. Maier J. Major A. Seeger W. Sigle W. Staiger W. Templ E. Widmann R. Abela V. Claus M. Hampele D. Herlach 《Hyperfine Interactions》1991,65(1-4):1039-1045
μ− SR experiments have been performed on Si between room temperature and 6 K. The amplitude of the muon spin precession signal
in an applied magnetic field of 0.04 T decreased below 30 K. A zero-field measurement at 6 K revealed a μ− spin precession frequency of 650 MHz. The muonic atom represents an aluminium acceptor in the silicon matrix, its electronic
state is responsible for the μSR signal. A possible influence of the γ recoil produced by the X-ray cascade is discussed. 相似文献