全文获取类型
收费全文 | 242篇 |
免费 | 2篇 |
专业分类
化学 | 92篇 |
晶体学 | 9篇 |
力学 | 11篇 |
数学 | 54篇 |
物理学 | 78篇 |
出版年
2019年 | 2篇 |
2014年 | 2篇 |
2013年 | 14篇 |
2012年 | 8篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 15篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1907年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有244条查询结果,搜索用时 15 毫秒
51.
Jane O'Leary John D. Wallis Michael L. Wood 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(7):851-853
The title compounds, 2‐(dimethylamino)biphenyl‐2′‐carboxaldehyde, C15H15NO, and 2‐(dimethylamino)biphenyl‐2′,6′‐dicarboxaldehyde, C16H15NO2, show similar 1,6‐interactions [N?C=O 2.929 (3) to 3.029 (3) Å] between the dimethylamino and aldehyde groups located in the ortho positions of the two rings, which lie at 58.1 (1)–62.4 (1)° to each other. 相似文献
52.
M. J. Uren D. Lee B. T. Hughes P. J. M. Parmiter J. C. Birbeck R. Balmer T. Martin R. H. Wallis S. K. Jones 《Journal of Crystal Growth》2001,230(3-4):579-583
Undoped 28 nm AlGaN on 1 μm GaN was grown by MOVPE for high power microwave HFETs. Non-destructive methods for rapid characterisation of the layers are described. Double contact mercury probe capacitance voltage measurements gave valuable information on AlGaN layer leakage, thickness and quality, but only gave an estimate of the carrier concentration and pinch-off voltage due to the absence of an ohmic contact to the 2DEG layer. A non-contact resistivity mapping system gave accurate average sheet resistance, but underestimated the cross-wafer variation. 相似文献
53.
The idea of an arc in a finite plane or block design, and in particular of a maximal arc, is extended to nets. This concept is explored, and in particular 3-arcs in cubic nets are characterized. 相似文献
54.
John?P.?McsorleyEmail author N.?C.?K.?Phillips W.?D.?Wallis J.?L.?Yucas 《Designs, Codes and Cryptography》2005,35(1):21-45
Triple arrays are a class of designs introduced by Agrawal in 1966 for two-way elimination of heterogeneity in experiments. In this paper we investigate their existence and their connection to other classes of designs, including balanced incomplete block designs and balanced grids.AMS Classification:05B05, 05B30 相似文献
55.
W.D Wallis 《Journal of Combinatorial Theory, Series A》1974,17(3):379-383
We prove that if there is a Room square of side r with a subsquare of side s, then there is a Room square of side 5(r ? s) + s. This enables us to construct a Room square of side 257, thus proving that Room squares exist for all odd positive integer sides except 3 and 5. 相似文献
56.
We have studied the dynamics of atom motion at face centered metal (111) surfaces. The interactions between atoms are modelled with central forces and angle bending forces. Results for frequencies and polarizations of surface modes are presented for the following metals: Ag, Al, Au, Cu, Ni, Pd and Pt. In addition, the results obtained for phonon spectral densities are presented for nickel. 相似文献
57.
58.
A theoretical investigation has been carried out on the effect of a drift current on surface polaritons in n-type silicon. The current direction is taken to be parallel to the direction of propagation of the surface polaritons. From the dispersion curves, there is evidence that an interaction takes place between the current and the polaritons which gives rise to polariton instability or amplification for certain frequency ranges. These instabilities are believed to be due to the presence of the surface. 相似文献
59.
60.
Jennifer Seberry Wallis 《Journal of Combinatorial Theory, Series A》1976,21(2):188-195
Given any natural number q > 3 we show there exists an integer t ? [2log2(q ? 3)] such that an Hadamard matrix exists for every order 2sq where s > t. The Hadamard conjecture is that s = 2.This means that for each q there is a finite number of orders 2υq for which an Hadamard matrix is not known. This is the first time such a statement could be made for arbitrary q.In particular it is already known that an Hadamard matrix exists for each 2sq where if q = 2m ? 1 then s ? m, if q = 2m + 3 (a prime power) then s ? m, if q = 2m + 1 (a prime power) then s ? m + 1.It is also shown that all orthogonal designs of types (a, b, m ? a ? b) and (a, b), 0 ? a + b ? m, exist in orders m = 2t and 2t+2 · 3, t ? 1 a positive integer. 相似文献