全文获取类型
收费全文 | 672299篇 |
免费 | 5655篇 |
国内免费 | 1965篇 |
专业分类
化学 | 340815篇 |
晶体学 | 10035篇 |
力学 | 33431篇 |
综合类 | 18篇 |
数学 | 87824篇 |
物理学 | 207796篇 |
出版年
2021年 | 5849篇 |
2020年 | 6410篇 |
2019年 | 7290篇 |
2018年 | 9712篇 |
2017年 | 9751篇 |
2016年 | 13623篇 |
2015年 | 7642篇 |
2014年 | 12709篇 |
2013年 | 30038篇 |
2012年 | 22936篇 |
2011年 | 27535篇 |
2010年 | 20261篇 |
2009年 | 20209篇 |
2008年 | 25726篇 |
2007年 | 25668篇 |
2006年 | 23556篇 |
2005年 | 21143篇 |
2004年 | 19607篇 |
2003年 | 17574篇 |
2002年 | 17493篇 |
2001年 | 18863篇 |
2000年 | 14589篇 |
1999年 | 11430篇 |
1998年 | 9806篇 |
1997年 | 9592篇 |
1996年 | 9058篇 |
1995年 | 8211篇 |
1994年 | 8179篇 |
1993年 | 7992篇 |
1992年 | 8468篇 |
1991年 | 8934篇 |
1990年 | 8520篇 |
1989年 | 8386篇 |
1988年 | 8263篇 |
1987年 | 8027篇 |
1986年 | 7615篇 |
1985年 | 9948篇 |
1984年 | 10408篇 |
1983年 | 8619篇 |
1982年 | 9018篇 |
1981年 | 8611篇 |
1980年 | 8211篇 |
1979年 | 8732篇 |
1978年 | 8994篇 |
1977年 | 8871篇 |
1976年 | 8853篇 |
1975年 | 8369篇 |
1974年 | 8260篇 |
1973年 | 8561篇 |
1972年 | 6205篇 |
排序方式: 共有10000条查询结果,搜索用时 1 毫秒
151.
A fast-frequency modulated (FM) diode laser has been optically narrowed using the technique of resonant optical feedback, to provide linewidths in each FM mode of ≈ 200 kHz peak-to-peak. With a drive frequency of 50 MHz and modulation index of 0.2, the FM laser has been used for the first time to obtain Doppler-free FM spectra of the Rb D1 line at 795 nm. The potential use of this system for laser frequency stabilisation is discussed. 相似文献
152.
A. P. Prudnikov Yu. A. Brychkov O. I. Marichev 《Journal of Mathematical Sciences》1991,54(6):1239-1341
Translated from Itogi Nauki i Tekhniki, Seriya Matematicheskii Analiz, Vol. 27, pp. 3–146, 1989. 相似文献
153.
V. K. Malyutenko A. I. Liptuga V. A. Botte V. I. Chernyakhovskii 《Journal of Applied Spectroscopy》1991,55(4):1024-1028
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 624–629, October, 1991. 相似文献
154.
Summary Considered here are model equations for weakly nonlinear and dispersive long waves, which feature general forms of dispersion and pure power nonlinearity. Two variants of such equations are introduced, one of Korteweg-de Vries type and one of regularized long-wave type. It is proven that solutions of the pure initial-value problem for these two types of model equations are the same, to within the order of accuracy attributable to either, on the long time scale during which nonlinear and dispersive effects may accumulate to make an order-one relative difference to the wave profiles.This research was supported in part by the National Science Foundation. A considerable portion of the project was completed while the first author was resident at the Institute for Mathematics and Its Applications, University of Minnesota. 相似文献
155.
The stressed state of a thick three-layer plate with two circular holes is studied. Resolving functions are expressed in terms of Kolosov-Muskhelishvili integral potentials and modified Bessel functions. The problem is reduced to solving an infinite set of linear algebraic equations.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 25–28, 1987. 相似文献
156.
A. Hertz 《Graphs and Combinatorics》1989,5(1):149-157
We consider the graphs that can be obtained by deleting in a Meyniel graphG all the edges induced by an arbitrary set of nodes. These graphs will be called Slim and we prove that they are perfect. We study relations between Slim graphs and other well known classes of perfect graphs; particularly we show that the perfection of Slim graphs gives a proof to the conjecture of M. Preissmann that Meyniel graphs are locally perfect. 相似文献
157.
158.
159.
160.
P. M. Gandini A. Zucco 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》1989,59(1):15-21
Some well-known theorems on typical properties of real-valued continuous functions defined on [0, 1] are improved using the
notion of porosity. 相似文献