全文获取类型
收费全文 | 420329篇 |
免费 | 4192篇 |
国内免费 | 1437篇 |
专业分类
化学 | 227807篇 |
晶体学 | 6406篇 |
力学 | 17224篇 |
综合类 | 8篇 |
数学 | 48346篇 |
物理学 | 126167篇 |
出版年
2020年 | 3449篇 |
2019年 | 3976篇 |
2018年 | 5236篇 |
2017年 | 5101篇 |
2016年 | 7499篇 |
2015年 | 4593篇 |
2014年 | 7165篇 |
2013年 | 18945篇 |
2012年 | 13839篇 |
2011年 | 16944篇 |
2010年 | 11710篇 |
2009年 | 11462篇 |
2008年 | 15649篇 |
2007年 | 15880篇 |
2006年 | 14650篇 |
2005年 | 13422篇 |
2004年 | 12039篇 |
2003年 | 10824篇 |
2002年 | 10670篇 |
2001年 | 11784篇 |
2000年 | 9112篇 |
1999年 | 6966篇 |
1998年 | 5973篇 |
1997年 | 6004篇 |
1996年 | 5614篇 |
1995年 | 5010篇 |
1994年 | 4925篇 |
1993年 | 5007篇 |
1992年 | 5401篇 |
1991年 | 5495篇 |
1990年 | 5224篇 |
1989年 | 5182篇 |
1988年 | 5173篇 |
1987年 | 4997篇 |
1986年 | 4802篇 |
1985年 | 6439篇 |
1984年 | 6737篇 |
1983年 | 5510篇 |
1982年 | 6030篇 |
1981年 | 5835篇 |
1980年 | 5539篇 |
1979年 | 5781篇 |
1978年 | 6083篇 |
1977年 | 5953篇 |
1976年 | 6142篇 |
1975年 | 5613篇 |
1974年 | 5670篇 |
1973年 | 6131篇 |
1972年 | 3952篇 |
1971年 | 3222篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Ablation of an optically homogeneous absorbing medium by scattered pulsed laser radiation 总被引:1,自引:0,他引:1
V. V. Golovlyov R. O. Esenaliev V. S. Letokhov 《Applied physics. B, Lasers and optics》1993,57(6):451-457
We have studied the ablation of an aqueous CuCl2 solution in a pulsed Nd:YAG laser field featuring a speckle-patterned structure characterized by spatial radiation energy fluence fluctuations. This leads to a nonuniform distribution of the energy absorbed in the bulk of the sample being irradiated and causes local overheating centers to form, wherein ablation is observed to take place at laser energy fluences below the threshold value found in experiments with a homogeneous laser beam. This effect should be manifest in the laser irradiation of biotissues which, as a rule, scatter light strongly. 相似文献
994.
A technique is proposed for improving the accuracy of the heat of fusion of semicrystalline polymers by DSC. The results of three commercially available instruments are compared. 相似文献
995.
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
996.
997.
Summary X-ray reflectivity may be used to determine the internal structure of thin polymer films. An electron density difference of 10% for polystyrene and polyisoprene is sufficient to distinguish between a random distribution of lamellae, complete orientation parallel to the substrate surface and a surface induced formation of lamellae. The disappearance of the lamellar Bragg-peaks, with heating of the film, shows the transition into the disordered state. 相似文献
998.
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
999.
Graham R. Knox Peter L. Pauson Debra Willison 《Journal of organometallic chemistry》1993,450(1-2):177-184
Phenylazoferrocene undergoes nickelation and palladation exclusively on the phenyl group. Lithium phenylazocyclopentadienide has been converted into derivatives of Mo, Mn, Fe, Ru and Rh. 相似文献
1000.
The alkaloid compositions of young shoots and leaves ofBerberis nummularia Bge. have been studied. The new alkaloids bernumidine (II) and bernumicine (III) have been isolated from the leaves, and their structures have been established. 相似文献