全文获取类型
收费全文 | 568329篇 |
免费 | 5714篇 |
国内免费 | 2552篇 |
专业分类
化学 | 279990篇 |
晶体学 | 8310篇 |
力学 | 29120篇 |
综合类 | 68篇 |
数学 | 89792篇 |
物理学 | 169315篇 |
出版年
2021年 | 4185篇 |
2020年 | 4642篇 |
2019年 | 5101篇 |
2018年 | 16594篇 |
2017年 | 16592篇 |
2016年 | 15551篇 |
2015年 | 6765篇 |
2014年 | 9777篇 |
2013年 | 22849篇 |
2012年 | 21432篇 |
2011年 | 31224篇 |
2010年 | 21059篇 |
2009年 | 21236篇 |
2008年 | 25800篇 |
2007年 | 27768篇 |
2006年 | 18572篇 |
2005年 | 17475篇 |
2004年 | 16308篇 |
2003年 | 15014篇 |
2002年 | 14004篇 |
2001年 | 15299篇 |
2000年 | 11548篇 |
1999年 | 8798篇 |
1998年 | 7419篇 |
1997年 | 7182篇 |
1996年 | 6987篇 |
1995年 | 6014篇 |
1994年 | 6018篇 |
1993年 | 5799篇 |
1992年 | 6360篇 |
1991年 | 6557篇 |
1990年 | 6196篇 |
1989年 | 6072篇 |
1988年 | 5799篇 |
1987年 | 5840篇 |
1986年 | 5659篇 |
1985年 | 7251篇 |
1984年 | 7368篇 |
1983年 | 6133篇 |
1982年 | 6379篇 |
1981年 | 5954篇 |
1980年 | 5771篇 |
1979年 | 6160篇 |
1978年 | 6313篇 |
1977年 | 6316篇 |
1976年 | 6311篇 |
1975年 | 5898篇 |
1974年 | 5939篇 |
1973年 | 6058篇 |
1972年 | 4499篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Daniel L. Feldheim Del R. Lawson Charles R. Martin 《Journal of Polymer Science.Polymer Physics》1993,31(8):953-957
We report a strong dependence of the thermal stability of Nafion® perfluorosulfonate ionomer on the nature of the counterion associated with the fixed sulfonate site. These results were obtained using thermal gravimetric analysis on a series of alkali metal and alkyl ammonium cation-exchanged Nafion films. We have found that the temperature of decomposition of Nafion is inversely dependent on the size of the exchanged cation; i.e., Nafion films show improved thermal stability as the size of the counter cation decreases. We attribute this inverse relationship of thermal stability with counterion size to an initial decomposition reaction which is strongly influenced by the strength of the sulfonate-coun-terion interaction. © 1993 John Wiley & Sons, Inc. 相似文献
22.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
23.
24.
25.
26.
L. A. Khalfin 《Journal of Mathematical Sciences》1987,36(5):616-626
The article surveys the main results of the statistical approach to the solution of ill-posed problems of mathematical physics, in application to specific ill-posed inverse problems in geophysics.Invited paper presented at the International Seminar on Mathematical Foundations of the Interpretation of Geophysical Fields, Moscow, May–June 1972.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 79, pp. 67–81, 1978. 相似文献
27.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis 相似文献
28.
29.
Using the method of the tensor Green’s function of the wave equation, the differential and total cross sections for the scattering of surface optical electromagnetic waves (surface plasmon polaritons) by a spherical nanoparticle into surface plasmon polaritons and light have been obtained with the inclusion of the magnetic dipole contribution. Using the example of noble metal systems, it has been shown that the magnetic dipole contribution may significantly affect the angular dependence of the differential cross sections and increase their anisotropy as the plasmon wavelength increases. 相似文献
30.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献