全文获取类型
收费全文 | 2891篇 |
免费 | 49篇 |
国内免费 | 11篇 |
专业分类
化学 | 1857篇 |
晶体学 | 25篇 |
力学 | 59篇 |
数学 | 262篇 |
物理学 | 748篇 |
出版年
2019年 | 20篇 |
2016年 | 39篇 |
2015年 | 39篇 |
2014年 | 39篇 |
2013年 | 93篇 |
2012年 | 133篇 |
2011年 | 121篇 |
2010年 | 72篇 |
2009年 | 70篇 |
2008年 | 109篇 |
2007年 | 79篇 |
2006年 | 114篇 |
2005年 | 91篇 |
2004年 | 83篇 |
2003年 | 76篇 |
2002年 | 67篇 |
2001年 | 64篇 |
2000年 | 58篇 |
1999年 | 44篇 |
1998年 | 47篇 |
1997年 | 52篇 |
1996年 | 56篇 |
1995年 | 58篇 |
1994年 | 59篇 |
1993年 | 47篇 |
1992年 | 53篇 |
1991年 | 49篇 |
1990年 | 40篇 |
1989年 | 30篇 |
1988年 | 46篇 |
1987年 | 31篇 |
1986年 | 34篇 |
1985年 | 47篇 |
1984年 | 45篇 |
1983年 | 24篇 |
1982年 | 37篇 |
1981年 | 63篇 |
1980年 | 37篇 |
1979年 | 35篇 |
1978年 | 58篇 |
1977年 | 46篇 |
1976年 | 44篇 |
1975年 | 44篇 |
1974年 | 37篇 |
1973年 | 33篇 |
1972年 | 18篇 |
1970年 | 33篇 |
1967年 | 20篇 |
1966年 | 17篇 |
1965年 | 18篇 |
排序方式: 共有2951条查询结果,搜索用时 0 毫秒
121.
The preparation of nano-sized BaCeO3 powder using starch as a polymerization agent is described herein. Phase evolution during the decomposition process of a (BaCe)-gel was monitored by XRD. A phase-pure nano-sized BaCeO3 powder was obtained after calcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4 m2/g. TEM investigations reveal particles mainly in the size range of 30 to 65 nm. The shrinkage and sintering behavior of resulting powder compacts were studied in comparison to a coarse-grained mixed-oxide BaCeO3 powder (SBET = 2.1 m2/g). Dilatometric measurements show that the beginning of shrinkage of compacts from the nano-sized powder is downshifted by 300 °C compared to mixed-oxide powder. Compacts from the nano-sized powder reach a relative density of 91% after sintering at 1450 °C for 10 h. 相似文献
122.
D. Wayne Cooke Melvin Leon Michael A. Paciotti Peter F. Meier Stephen F. J. Cox Edward A. Davis Thomas L. Estle Bassam Hitti Roger L. Lichti Carolus Boekema John Lam Anny Morrobel-Sosa Jean Oostens 《Hyperfine Interactions》1994,86(1):699-704
A distinctive longitudinal magnetic field dependence of the muon polarization for anomalous muonium in polycrystalline semiconductor targets has been predicted. The polarization exhibits a cusp,i.e., a discontinuous jump in the slope from negative to positive. Measurements of the longitudinal polarization for polycrystalline silicon in fields up to 0.5 T, and temperatures 53 and 200 K have been made at LAMPF. A cusp in the field dependence indeed occurs at 0.345 T, in excellent agreement with the prediction. No cusp is observed at 200 K because Mu* has been thermally ionized. 相似文献
123.
H. H. Deubler K. Lekkas P. Sperr K. Dietrich 《Zeitschrift für Physik A Hadrons and Nuclei》1978,284(2):237-244
The process of instantaneous fission in deep inelastic collisions is investigated in a classical model. Kinetic energies and angular distributions of the fragments are calculated for the proposed reaction Pb+U atE cm inc =750 MeV; an experimental setup for the separation of the fragments originating from instantaneous fission from the fragments of thermal fission is explained. We also discuss fusion following instantaneous fission as a mechanism for the production of superheavy elements and arrive at rather promising estimates. 相似文献
124.
Xenon ions in the metastable state 5d 4D are excited by means of a tunable dye laser at 6051 Å. The excitation is monitored by non-resonant fluorescence at 5292 Å. 相似文献
125.
We study theoretically the spin dynamics of antiferromagnetic molecular rings, such as the ferric wheel Fe10. For a single nuclear or impurity spin coupled to one of the electron spins of the ring, we calculate nuclear and electronic spin correlation functions and show that nuclear magnetic resonance (NMR) and electron spin resonance (ESR) techniques can be used to detect coherent tunneling of the Néel vector in these rings. The location of the NMR/ESR resonances gives the tunnel splitting and its linewidth an upper bound on the decoherence rate of the electron spin dynamics. We illustrate the experimental feasibility of our proposal with estimates for Fe10 molecules. 相似文献
126.
Dietrich Braess 《Numerische Mathematik》1981,37(3):387-404
Summary The treatment of a multigrid method in the framework of numerical analysis elucidates that regularity of the solution is not necessary for the convergence of the multigrid algorithm but only for fast convergence. For the linear equations which arise from the discretization of the Poisson equation, a convergence factor 0,5 is established independent of the shape of the domain and of the regularity of the solution.Dedicated to Professor Dr.Dr.h.c. Lothar Collatz on the occasion of his 70 th birthday 相似文献
127.
128.
Abe K Akagi T Anthony PL Antonov R Arnold RG Averett T Band HR Bauer JM Borel H Bosted PE Breton V Button-Shafer J Chen JP Chupp TE Clendenin J Comptour C Coulter KP Court G Crabb D Daoudi M Day D Dietrich FS Dunne J Dutz H Erbacher R Fellbaum J Feltham A Fonvieille H Frlez E Garvey D Gearhart R Gomez J Grenier P Griffioen KA Hoibraten S Hughes EW Hyde-Wright C Johnson JR Kawall D Klein A Kuhn SE Kuriki M Lindgren R Liu TJ Lombard-Nelsen RM Marroncle J Maruyama T Maruyama XK McCarthy J Meyer W 《Physical review letters》1995,74(3):346-350
129.
van den Brand JF Ent R Anthony PL Arnold RG Arrington J Beise EJ Belz JE Bosted PE Bulten H Chapman MS Coulter KP Dietrich FS Epstein M Filippone BW Gao H Gearhart RA Geesaman DF Hansen J Holt RJ Jackson HE Jones CE Keppel CE Kinney ER Kuhn S Lee K Lorenzon W Lung A Makins NC Margaziotis DJ McKeown RD Milner RG Mueller B Napolitano J Nelson J O'Neill TG Papavassiliou V Petratos GG Potterveld DH Rock SE Spengos M Szalata ZM Tao LH van Bibber K Wasson DA White JL Zeidman B 《Physical review D: Particles and fields》1995,52(9):4868-4871
130.
A. O. Vyrodov J. Heinze M. Dillmann U. E. Meier W. Stricker 《Applied physics. B, Lasers and optics》1995,61(5):409-414
Laser-Induced Fluorescence (LIF) excitation spectra in the NOA–X (0-0) band were used for temperature measurements in the postflame region of high-pressure CH4/air flames. To improve the quality of the measured spectra and to perform reliable line-shape measurements, the initial mixture was doped with approximately 400 ppm NO. At pressures up to 18 bar, excellent agreement was obtained between NO LIF temperatures and NARS/rotational Raman temperatures. Effective broadening coefficients were also determined in these flames. Problems with quantitative concentration measurements of NO and single-pulse temperature measurements at high pressures are discussed. 相似文献