全文获取类型
收费全文 | 297178篇 |
免费 | 3114篇 |
国内免费 | 1080篇 |
专业分类
化学 | 162524篇 |
晶体学 | 4485篇 |
力学 | 12855篇 |
综合类 | 10篇 |
数学 | 30210篇 |
物理学 | 91288篇 |
出版年
2021年 | 1897篇 |
2020年 | 2171篇 |
2019年 | 2253篇 |
2018年 | 2669篇 |
2017年 | 2736篇 |
2016年 | 4613篇 |
2015年 | 3278篇 |
2014年 | 4535篇 |
2013年 | 13007篇 |
2012年 | 10314篇 |
2011年 | 12792篇 |
2010年 | 8427篇 |
2009年 | 8611篇 |
2008年 | 12029篇 |
2007年 | 11810篇 |
2006年 | 11451篇 |
2005年 | 10563篇 |
2004年 | 9484篇 |
2003年 | 8467篇 |
2002年 | 8301篇 |
2001年 | 10502篇 |
2000年 | 7833篇 |
1999年 | 6017篇 |
1998年 | 4395篇 |
1997年 | 4500篇 |
1996年 | 4344篇 |
1995年 | 3930篇 |
1994年 | 3810篇 |
1993年 | 3526篇 |
1992年 | 4251篇 |
1991年 | 4308篇 |
1990年 | 3935篇 |
1989年 | 3866篇 |
1988年 | 3867篇 |
1987年 | 3795篇 |
1986年 | 3548篇 |
1985年 | 4844篇 |
1984年 | 4841篇 |
1983年 | 3915篇 |
1982年 | 4081篇 |
1981年 | 3834篇 |
1980年 | 3754篇 |
1979年 | 3971篇 |
1978年 | 4126篇 |
1977年 | 4059篇 |
1976年 | 3904篇 |
1975年 | 3774篇 |
1974年 | 3673篇 |
1973年 | 3789篇 |
1972年 | 2342篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A. Paesano Jr. S. C. Zanatta S. N. De Medeiros L. F. CÓtica J. B. M. Da Cunha 《Hyperfine Interactions》2005,161(1-4):211-220
We have investigated the mechanosynthesis of gadolinium and yttrium iron garnets by high-energy ball-milling of α-Fe2O3 and Gd2O3 or α-Fe2O3 and Y2O3, respectively, followed by short thermal annealings conducted at moderate temperatures. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy, in order to determine the influence of the milling time and annealing conditions on the final products. For as-milled samples of each rare-earth system, the results revealed the formation of perovskite phases, in relative amounts that depend on the milling time. The formation of garnet phases was observed in as-annealed samples treated at 1000°C for 2 h or 1100°C for 3 h, i.e., at very modest annealing requirements when compared with ordinary solid-state-reaction processes performed without previous high-energy milling. Also, the occurrence was verified of a milling time for which the relative amount of garnet phases formed by annealing was maximized. This time depends on the rare-earth composing the garnet phase and on the annealing temperature. 相似文献
992.
D. L. Myalochkin T. A. Kochina D. V. Vrazhnova V. V. Avrorin E. N. Sinotova 《Russian Journal of General Chemistry》2007,77(7):1187-1189
A microsynthetic procedure for preparing tritium-labeled alkyl-substituted germanes is developed. The resulting dimethylditritiogermane can be used as a source of dimethylgermylium ions. The synthesis was performed by the reduction of dibromodimethylgermane with lithium tritide in presence of AlBr3. 相似文献
993.
Summary We have recently reported on a new scaling theory of the rupture of colloid aggregates. The scaling theory is compared with
a simulation study of the transient response of sheared 2d aggregates. In this paper we discuss the origins of deviations from the predicted scaling behaviour. We also report some
of the steady-state configurations formed post rupture.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
994.
995.
996.
V. T. Filippov 《Siberian Mathematical Journal》1991,32(6):1038-1044
997.
R. Murugesan P. Sami T. Jeyabalan A. Shunmugasundaram 《Journal of Chemical Sciences》1995,107(1):1-10
Bonding and redox properties of mono- and dititanium substituted 12-heteropolytungsto-phosphates and their complexes with
bivalent Mn, Co, Ni and Cu are studied by UV-Vis, ESR and cyclicvoltammetric techniques. The heteropoly blue analogue [TiIIITiIVW10PO40]8− is unstable and its presence in solution is proved by optical and ESR spectroscopy. ESR results reveal that the odd electron
is trapped on the titanium atom at 77 K. The optical electronegativity of Ti(III) in this heteropoly blue is estimated to
be 2.4 from the intervalence charge transfer (IVCT) bands. X-ray powder diffraction results show that the complexes K5MII[Ti2W10PO40].xH2O(MII = Cu or Mn) are isomorphous with K7[Ti2W10PO40].6H2O. Electronic spectroscopy indicates very high symmetry around the bivalent metal ion M in the K5MII[Ti2W10PO40].xH2O complexes. This high symmetry is confirmed in K5Cu[Ti2W10PO40] by the observation of dynamic Jahn-Teller (JT) distortion at 300 K and static JT distortion at 77 K. 相似文献
998.
In [1, 2] we established and dicussed the algebra of observables for 2+1 gravity at both the classical and quantum level. Here our treatment broadens and extends previous results to any genusg with a systematic discussion of the centre of the algebra. The reduction of the number of independent observables to 6g-6(g>1) is treated in detail with a precise classification forg=1 andg=2. 相似文献
999.
N. M. Agababyan M. R. Atayan M. Charlet J. Czyżewski E. A. De Wolf K. Dziunikowska A. M. F. Endler Z. Sh. Garutchava H. R. Gulkanyan R. Sh. Hakobyan J. K. Karamyan D. Kisielewska W. Kittel S. S. Mehrabyan Z. V. Metreveli E. C. Oliveira K. Olkiewicz F. K. Rizatdinova E. K. Shabalina L. N. Smirnova M. D. Tabidze L. A. Tikhonova A. V. Tkabladze A. G. Tomaradze F. Verbeure S. A. Zotkin 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):405-414
The NA22 data onπ ? π ? correlations are analyzed in terms of a number of two- and three-dimensional parametrizations (Gaussian space-time, Goldhaber, Bowler string-like, Bertsch hydrodynamical, Kopylov-Podgoretskii, etc.). Contrary to the results obtained for e+e? andµp collisions, the Goldhaber parametrization, as well as string-like models, fail in describing the hadron-hadron data. Better fits are obtained in the framework of surface-emitting fireball-like models, both when including and excluding hydrodynamical expansion of nuclear matter. Our results indicate that pion radiation occurs at earlier stages of matter evolution than in nuclear collisions. 相似文献
1000.
R. Buccellato M. M. Michaelis C. A. Dempers A. Prause P. F. Cunningham 《Optics & Laser Technology》1993,25(4)
The concept of a pulsed gas lens is proposed. Potential applications are envisaged and preliminary experiments with pulsed ray refraction are reported. 相似文献