全文获取类型
收费全文 | 22415篇 |
免费 | 223篇 |
国内免费 | 91篇 |
专业分类
化学 | 11490篇 |
晶体学 | 462篇 |
力学 | 667篇 |
综合类 | 7篇 |
数学 | 2118篇 |
物理学 | 7985篇 |
出版年
2019年 | 192篇 |
2018年 | 236篇 |
2017年 | 232篇 |
2016年 | 354篇 |
2015年 | 239篇 |
2014年 | 368篇 |
2013年 | 1101篇 |
2012年 | 688篇 |
2011年 | 759篇 |
2010年 | 573篇 |
2009年 | 548篇 |
2008年 | 758篇 |
2007年 | 779篇 |
2006年 | 697篇 |
2005年 | 622篇 |
2004年 | 539篇 |
2003年 | 513篇 |
2002年 | 498篇 |
2001年 | 716篇 |
2000年 | 534篇 |
1999年 | 440篇 |
1998年 | 363篇 |
1997年 | 342篇 |
1996年 | 313篇 |
1995年 | 383篇 |
1994年 | 356篇 |
1993年 | 323篇 |
1992年 | 349篇 |
1991年 | 394篇 |
1990年 | 368篇 |
1989年 | 372篇 |
1988年 | 336篇 |
1987年 | 335篇 |
1986年 | 331篇 |
1985年 | 408篇 |
1984年 | 433篇 |
1983年 | 318篇 |
1982年 | 327篇 |
1981年 | 352篇 |
1980年 | 328篇 |
1979年 | 338篇 |
1978年 | 338篇 |
1977年 | 316篇 |
1976年 | 334篇 |
1975年 | 291篇 |
1974年 | 286篇 |
1973年 | 299篇 |
1968年 | 189篇 |
1967年 | 335篇 |
1966年 | 284篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
S. A. J. Wiegers B. Tieke U. Zeitler R. Fletcher A. K. Geim J. C. Maan M. Henini 《Czechoslovak Journal of Physics》1996,46(5):2461-2462
We have investigated the interaction of phonons with a 2DEG in the FQH regime with phonon drag thermoelectric power (TEP). We find that the TEP at filling factors with the same even denominator is identical and at other even denominator filling factors they differ only by a constant. Assuming these states to be Composite Fermions (CF), we can explain our observations by extending a zero magnetic field theory for phonon drag to the CF-phonon interaction. This analysis is further corroborated by the observed T4 dependence of the CF TEP. 相似文献
82.
G. Baldsiefen H. Hübel W. Korten U. J. van Severen J. A. Cizewski N. H. Medina D. R. Napoli C. Rossi Alvarez G. Lo Bianco S. Signorelli 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):337-338
High-spin states in196Pb have been populated using the reaction170Er(30Si,4n). The previously observed shears bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. 相似文献
83.
84.
The1H and13C chemical shifts of 11 sparteine derivatives are reported. Substituent and group effects are interpreted in terms of structural properties. The conformational equilibrium of aphyllin is determined.Ruhr-Universität Bochum, Fakultät für Chemie, Bochum, Germany. Universität Hannover, Institut für Organische Chemie, Hannover, Germany (present address). Department of Organic Chemistry, Poznan Academy of Economics, Poznan, Poland. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1026–1033, August, 1995. Original article submitted May 10, 1995.Dedicated to Prof. N. S. Zefirov on the occasion of his 60th birthday. 相似文献
85.
New Spiro Compounds from Cyclophosphazenes and Cyclodi[phosphadiazanes] Chlorocyclophosphazenes (Cl2P = N)3 and (Cl2p = N)4 react with dihydrazidophosphoric acid derivatives in THF in the presence of triethylamine to give the spirocyclic compounds Cl4N3P3(NHN(CH3))2P(S)OC6H5, Cl6N4P4(NHNH)2P(S)OC6H5. Constitutions have been confirmed by MS, NMR, IR and elemental analysis. 相似文献
86.
W. Hoheisel U. Schulte M. Vollmer F. Träger 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):381-383
This paper reports new results on the optical spectra of Na particles and on laser-induced photodissociation of Na atoms from the surface of these particles. In continuation of our earlier studies we have performed experiments to elucidate the mechanism of thenonthermal dissociation process. Furthermore, theoretical calculations have been carried out with the goal to correlate the wavelength dependence of the photodissociation yield with the optical absorption spectra of the metal particles. In addition, manipulation of the size distribution of metal particles on supports is outlined as an application of the effect. This allows for the preparation of very special surfaces with novel physical and chemical properties. 相似文献
87.
88.
Summary Dielectric measurements on Na2B4O7(99.5%)−V2O5(0.5%) glass system, in the frequency range 10−3 to 104 Hz and temperature range 300 to 500 K, have been carried out. The normalized plots of complex capacitance have shown a single
mechanism responsible for conduction for both volume and surface measurements with their close values of activation energies
(0.67±0.03) eV and (0.64±0.03) eV, respectively. The low-frequency dispersion (LFD) behaviour has been observed to be perturbed
by the presence of more than one competing process. The impedance plots have shown a parallel combination of a capacitor (C) and a resistor (R), with some contribution of a dispersive element due to charge accumulation in the vicinity of the electrodes. The values
ofR andC were found to be of the same order of magnitude, for both surface and volume measurements. The observedR has shown a decrease with an increase in temperature due to an increase in mobility of Na+ ions, whereasC remains practicaly constant. The complex capacitance surface behaviour is dominated by volume, due to hygroscopy of this
glass system. 相似文献
89.
The root heartwood of Dalbergia odorifera T. Chen (Leguminosae) is a Chinese medicinal drug (Japanese name koshinko) used for a stagnant blood syndrome (stagnation of disordered blood; Japanese, oketsu). In addition to 10 known compounds, five new phenolic compounds, isomucronustyrene and hydroxyobtustyrene (cinnamylphenols), (+)-isoduartin (isoflavan), odoriflavene (isoflav-3-ene) and (-)-odoricarpan (pterocarpan) were isolated and their structures were elucidated on the basis of chemical and spectroscopic methods. Of the fifteen compounds isolated, cinnamylphenols, isoflavans, isoflavene and benzoic acid derivative significantly inhibited prostaglandin biosynthesis as well as platelet aggregation induced by arachidonic acid. 相似文献
90.
Örn Helgason Haraldur P. Gunnlaugsson Siguröur Steinthorsson Steen Mørup 《Hyperfine Interactions》1992,70(1-4):981-984
Mössbauer spectroscopy of basalt lava samples, exhibiting reversible thermal magnetization (JS-T) curves with Curie temperatures of about 580°C, has revealed considerable amounts of maghemite (γ-Fe2O3) in many samples. In view of the expected instability, of maghemite at temperatures above 350°C, this reversibility is rather surprising. Here we report Mössbauer studies on heated lava samples, showing high content of maghemite. The samples were kept at 600°C in oxidizing, reducing, and inactive atmospheres, respectively, for different lengths of time, and then analyzed with Mössbauer spectroscopy at room temperature. The Mössbauer spectra showed that maghemite is stable in the oxidizing atmosphere for at least several hours. In the inactive atmosphere a considerable amount of maghemite still exists after two hours heating. In the reducing atmosphere maghemite had transformed to magnetite after only 30 minutes. 相似文献