全文获取类型
收费全文 | 482573篇 |
免费 | 9969篇 |
国内免费 | 4275篇 |
专业分类
化学 | 270859篇 |
晶体学 | 7065篇 |
力学 | 20734篇 |
综合类 | 284篇 |
数学 | 54684篇 |
物理学 | 143191篇 |
出版年
2020年 | 3887篇 |
2019年 | 3883篇 |
2018年 | 3827篇 |
2017年 | 3582篇 |
2016年 | 6859篇 |
2015年 | 5652篇 |
2014年 | 7656篇 |
2013年 | 21805篇 |
2012年 | 16767篇 |
2011年 | 20451篇 |
2010年 | 12976篇 |
2009年 | 12829篇 |
2008年 | 18114篇 |
2007年 | 18377篇 |
2006年 | 17539篇 |
2005年 | 15917篇 |
2004年 | 14222篇 |
2003年 | 12569篇 |
2002年 | 12352篇 |
2001年 | 14267篇 |
2000年 | 11081篇 |
1999年 | 9090篇 |
1998年 | 7313篇 |
1997年 | 7187篇 |
1996年 | 7304篇 |
1995年 | 6585篇 |
1994年 | 6300篇 |
1993年 | 5924篇 |
1992年 | 6761篇 |
1991年 | 6461篇 |
1990年 | 6080篇 |
1989年 | 5927篇 |
1988年 | 6083篇 |
1987年 | 5818篇 |
1986年 | 5553篇 |
1985年 | 7773篇 |
1984年 | 7853篇 |
1983年 | 6435篇 |
1982年 | 6853篇 |
1981年 | 6856篇 |
1980年 | 6497篇 |
1979年 | 6762篇 |
1978年 | 6942篇 |
1977年 | 6829篇 |
1976年 | 6725篇 |
1975年 | 6506篇 |
1974年 | 6303篇 |
1973年 | 6477篇 |
1972年 | 3927篇 |
1968年 | 3379篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
981.
H. G. Georgiadis 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1992,43(4):742-755
A wave-heat correspondence principle is established by utilizing previous operational relations of van der Pol and Bremmer. By the suggested procedure, heat conduction problems can be solved by using an auxiliary wave-propagation problem in conjunction with the correspondence principle. A check on this procedure was provided by solving a mixed BVP of transient heat flow. The present correspondence principle is particularly useful in dealing with IBVPs involving wedge-shaped domains, and characteristic lengths. 相似文献
982.
983.
Flux jumps have been observed in a large (138 mg) single crystal of La1.86Sr0.14CuO4. Both complete and incomplete flux jumps are observed with the energy dissipated by complete flux jumps consistent with temperature rises to nearly Tc. The systematics of these flux jumps with respect to field history, temperature and the time duration of the hysteresis measurements are reported. The field at which flux jumps first occur and their subsequent spacing are not consistent with a simple adiabatic theory of flux jumps for our experimental conditions. Instead, the crystal is observed to be stabilized against flux jumps by flux creep which occurs during the time interval over which field steps are accomplished as well as during imposed time intervals between field steps. 相似文献
984.
R. H. Enns D. E. Edmundson S. S. Rangnekar A. E. Kaplan 《Optical and Quantum Electronics》1992,24(11):S1295-S1314
In this paper we summarize what is currently known about optical switching between bright bistable soliton states in one and higher dimensions. A guideline to selecting media with appropriate intensity-dependent refractive indices to support bistable solitary waves is presented. The stability criterion for robustness of the solitary waves is discussed. Finally, some methods and numerical examples of optical switching are presented. 相似文献
985.
986.
987.
In this paper we construct a primitive, non-symmetric 3-class association scheme with parameters v = 36, v1 = 7, p111 = 0 and p211 = 4 and show that such a scheme is determined by its parameters. 相似文献
988.
Baumgarten N. Jung H. Mehlhorn K. 《Journal of Algorithms in Cognition, Informatics and Logic》1994,17(3)
The dynamic planar point location problem is the task of maintaining a dynamic set S of n nonintersecting (except possibly at endpoints) line segments in the plane under the following operations:
- • Locate (: point): Report the segment immediately above , i.e., the first segment intersected by an upward vertical ray starting at ;
- • Insert (: segment): Add segment to the collection of segments;
- • Delete (: segment): Remove segment from the collection of segments.
989.
Ho K. I. J. Leung J. Y. T. Wei W. D. 《Journal of Algorithms in Cognition, Informatics and Logic》1994,16(3)
We consider the problem of preemptively scheduling a set of imprecise computation tasks on m ≥ 1 identical processors, with each task Ti having two weights, wi and w′i. Two performance metrics are considered: (1) the maximum w′-weighted error; (2) the total w-weighted error subject to the constraint that the maximum w′-weighted error is minimized. For the problem of minimizing the maximum w′-weighted error, we give an algorithm which runs in O(n3 log2n) time for multiprocessors and O(n2) time for a single processor. For the problem of minimizing the total w-weighted error subject to the constraint that the maximum w′-weighted error is minimized, we give an algorithm which also has the same time complexity. 相似文献
990.
The authors study a one-dimensional model for optical tunnellingwith a refractive index in the shape of a square well. The relevanceof the model and its limiting cases are discussed. The mainresult is the leading behaviour of the exponentially small imaginarypart of the eigenvalue which determines the radiation loss.The leading behaviour of the imaginary part is calculated usingBerry's formula which controls the asymptotic expansion of theAiry function Bi(z) to better-than-exponential accuracy. 相似文献