全文获取类型
收费全文 | 1755篇 |
免费 | 153篇 |
国内免费 | 175篇 |
专业分类
化学 | 1036篇 |
晶体学 | 20篇 |
力学 | 54篇 |
综合类 | 36篇 |
数学 | 301篇 |
物理学 | 636篇 |
出版年
2022年 | 26篇 |
2021年 | 29篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 32篇 |
2016年 | 30篇 |
2015年 | 34篇 |
2014年 | 34篇 |
2013年 | 96篇 |
2012年 | 74篇 |
2011年 | 95篇 |
2010年 | 55篇 |
2009年 | 78篇 |
2008年 | 81篇 |
2007年 | 99篇 |
2006年 | 104篇 |
2005年 | 98篇 |
2004年 | 78篇 |
2003年 | 97篇 |
2002年 | 53篇 |
2001年 | 59篇 |
2000年 | 31篇 |
1999年 | 26篇 |
1998年 | 21篇 |
1997年 | 21篇 |
1996年 | 35篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 31篇 |
1992年 | 30篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 25篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 20篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 27篇 |
1975年 | 26篇 |
1974年 | 21篇 |
1973年 | 17篇 |
排序方式: 共有2083条查询结果,搜索用时 15 毫秒
1.
Francis K. Bell 《Journal of Graph Theory》2003,43(2):137-149
It is shown that, if t is an integer ≥3 and not equal to 7 or 8, then there is a unique maximal graph having the path Pt as a star complement for the eigenvalue ?2. The maximal graph is the line graph of Km,m if t = 2m?1, and of Km,m+1 if t = 2m. This result yields a characterization of L(G ) when G is a (t + 1)‐vertex bipartite graph with a Hamiltonian path. The graphs with star complement Pr ∪ Ps or Pr ∪ Cs for ?2 are also determined. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 137–149, 2003 相似文献
2.
3.
Daria E. Lonsdale Geoffrey Johnston‐Hall Amanda Fawcett Craig A. Bell Carl N. Urbani Michael R. Whittaker Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3620-3625
In this work, we propose that retardation in vinyl acetate polymerization rate in the presence of toluene is due to degradative chain transfer. The transfer constant to toluene (Ctrs) determined using the Mayo method is equal to 3.8 × 10?3, which is remarkably similar to the value calculated from the rate data, assuming degradative chain transfer (2.7 × 10?3). Simulations, including chain‐length‐dependent termination, were carried out to compare our degradative chain transfer model with experimental results. The conversion–time profiles showed excellent agreement between experiment and simulation. Good agreement was found for the Mn data as a function of conversion. The experimental and simulation data strongly support the postulate that degradative chain transfer is the dominant kinetic mechanism. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3620–3625, 2007 相似文献
4.
We complete our previous(1, 2) demonstration that there is a family of new solutions to the photon and Dirac equations using spatial and temporal circles and four-vector behaviour of the Dirac bispinor. We analyse one solution for a bound state, which is equivalent to the attractive two-body interaction between a charged point particle and a second, which remains at rest. We show this yields energy and angular momentum eigenvalues that are identical to those found by the usual method of solving of the Dirac equation,(4) including fine structure. We complete our previous derivation(2) of QED from a set of rules for the two-body interaction and generalise these. We show that QED may be decomposed into a two-body interaction at every point in spacetime. 相似文献
5.
Capacity Constrained Transit Assignment with Common Lines 总被引:1,自引:0,他引:1
Fumitaka Kurauchi Michael G. H. Bell Jan-Dirk Schmöcker 《Journal of Mathematical Modelling and Algorithms》2003,2(4):309-327
This paper proposes the use of absorbing Markov chains to solve the capacity constrained transit network loading problem taking
common lines into account. The approach handles congested transit networks, where some passengers will not be able to board
because of the absence of sufficient space. The model also handles the common lines problem, where choice of route depends
on frequency of arrivals. The mathematical formulation of the problem is presented together with a numerical example.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
聚醚醚酮链结构与反应的模型化合物的量子化学研究 总被引:1,自引:1,他引:0
利用AM1方法对聚醚醚酮模型化合物全优化,结果为:芳环平均相互扭转角为33.0度,桥键角117.0-118.0度,其分子结构拓扑图形表明:所有苯环(核)为平面构型,但其内角扭曲;其氢原子对苯环构型无实质性贡献,在更长链的计算中,冻结苯核与氢原子也得出满意结果,根据Mulliken键序与电荷讨论了醚交换与磺化反应。 相似文献
7.
8.
Surface reconstructions of InGaAs alloys 总被引:1,自引:0,他引:1
The surface reconstructions of InxGa1−xAs alloys grown by molecular beam epitaxy on the (0 0 1) surfaces of GaAs and InAs have been studied by reflection high-energy electron diffraction and scanning tunnelling microscopy. A surface phase diagram is presented for the nominally strain-free alloy as a function of substrate temperature and alloy composition, and structural models for the commonly observed 3× reconstructions are discussed. Two new, electronically stable structural models are described that account for the transition of the InxGa1−xAs surface alloy from a c(4 × 4) to an asymmetric 3× reconstruction and that are fully consistent with all current experimental evidence. 相似文献
9.
10.