全文获取类型
收费全文 | 6702篇 |
免费 | 147篇 |
国内免费 | 35篇 |
专业分类
化学 | 4517篇 |
晶体学 | 93篇 |
力学 | 155篇 |
数学 | 1067篇 |
物理学 | 1052篇 |
出版年
2022年 | 38篇 |
2021年 | 49篇 |
2020年 | 57篇 |
2019年 | 76篇 |
2018年 | 62篇 |
2017年 | 52篇 |
2016年 | 130篇 |
2015年 | 128篇 |
2014年 | 127篇 |
2013年 | 345篇 |
2012年 | 300篇 |
2011年 | 356篇 |
2010年 | 170篇 |
2009年 | 166篇 |
2008年 | 318篇 |
2007年 | 344篇 |
2006年 | 298篇 |
2005年 | 321篇 |
2004年 | 282篇 |
2003年 | 314篇 |
2002年 | 260篇 |
2001年 | 131篇 |
2000年 | 108篇 |
1999年 | 100篇 |
1998年 | 79篇 |
1997年 | 90篇 |
1996年 | 122篇 |
1995年 | 105篇 |
1994年 | 96篇 |
1993年 | 82篇 |
1992年 | 74篇 |
1991年 | 85篇 |
1990年 | 64篇 |
1989年 | 73篇 |
1988年 | 83篇 |
1987年 | 66篇 |
1986年 | 65篇 |
1985年 | 92篇 |
1984年 | 103篇 |
1983年 | 70篇 |
1982年 | 95篇 |
1981年 | 102篇 |
1980年 | 96篇 |
1979年 | 81篇 |
1978年 | 90篇 |
1977年 | 81篇 |
1976年 | 72篇 |
1975年 | 69篇 |
1974年 | 61篇 |
1973年 | 47篇 |
排序方式: 共有6884条查询结果,搜索用时 0 毫秒
31.
32.
33.
We provide a proof of Connes’ formula for a representative of the Hochschild class of the Chern character for (p,∞)-summable spectral triples. Our proof is valid for all semifinite von Neumann algebras, and all integral p?1. We employ the minimum possible hypotheses on the spectral triples. 相似文献
34.
Let G be a d‐regular graph G on n vertices. Suppose that the adjacency matrix of G is such that the eigenvalue λ which is second largest in absolute value satisfies λ = o(d). Let Gp with p = α/d be obtained from G by including each edge of G independently with probability p. We show that if α < 1, then whp the maximum component size of Gp is O(log n) and if α > 1, then Gp contains a unique giant component of size Ω(n), with all other components of size O(log n). © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004 相似文献
35.
We prove lower bounds of the form exp(nε d), εd > 0, on the length of proofs of an explicit sequence of tautologies, based on the Pigeonhole Principle, in proof systems using formulas of depth d, for any constant d. This is the largest lower bound for the strongest proof system, for which any superpolynomial lower bounds are known. 相似文献
36.
37.
J. A. Ratto Paul T. Inglefield R. A. Rutowski K.-L. Li Alan Anthony Jones Ajoy K. Roy 《Journal of Polymer Science.Polymer Physics》1987,25(7):1419-1430
Carbon-13 and proton spin-lattice relaxation times were measured at two field strengths on solutions 10% by weight of two polycarbonates in C2D2Cl4 from ?20 to +120°C. The first polycarbonate is an asymmetrically substituted form with one chlorine on one of the two phenylene aromatic rings of the bisphenol unit, whereas the second polycarbonate is symmetrically substituted with two chlorines on each of the two rings. The nuclear spin relaxation data are interpreted in terms of several local motions likely in these polymers. Segmental motion was described by the Hall–Helfand correlation function. Segmental motion in the monosubstituted polycarbonate is somewhat slower than in unsubstituted polycarbonate, whereas segmental motion in the tetrasubstituted polycarbonate is considerably slower. Phenylene ring rotation is observed in unsubstituted polycarbonate and in the monosubstituted polycarbonate above 40°C. Below 40°C in the monosubstituted species, and at all temperatures in the tetrasubstituted species, ring rotation is replaced by ring libration as the predominant motion contributing to spin lattice relaxation. In addition, the rotational motion of the two types of rings in the asymmetric monosubstituted form are very similar although not identical. The substituted ring is slightly less mobile than the rings of unsubstituted polycarbonate. This indicates a strong coupling of ring motion, although the coupling leads to less than synchronous motion. Methyl group rotation is present in both polymers and is little affected by the various structural modifications. 相似文献
38.
39.
Abraham Mehrez Zilla Sinuany-Stern Alan Stulman 《The Journal of the Operational Research Society》1986,37(10):971-977
In this note, we examine the algorithm of Drezner and Wesolowsky for locating a facility with maximin rectilinear distance to a given set of demand points. The concept of the closest-point constraint is introduced as a technique for increasing the efficiency of the algorithm. This potential increase in efficiency is demonstrated by an example. 相似文献
40.