全文获取类型
收费全文 | 2408篇 |
免费 | 96篇 |
国内免费 | 9篇 |
专业分类
化学 | 1531篇 |
晶体学 | 21篇 |
力学 | 43篇 |
数学 | 607篇 |
物理学 | 311篇 |
出版年
2023年 | 25篇 |
2022年 | 26篇 |
2021年 | 55篇 |
2020年 | 64篇 |
2019年 | 67篇 |
2018年 | 58篇 |
2017年 | 66篇 |
2016年 | 111篇 |
2015年 | 87篇 |
2014年 | 108篇 |
2013年 | 186篇 |
2012年 | 176篇 |
2011年 | 214篇 |
2010年 | 116篇 |
2009年 | 94篇 |
2008年 | 157篇 |
2007年 | 125篇 |
2006年 | 134篇 |
2005年 | 107篇 |
2004年 | 76篇 |
2003年 | 70篇 |
2002年 | 61篇 |
2001年 | 24篇 |
2000年 | 23篇 |
1999年 | 29篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 11篇 |
1973年 | 7篇 |
1969年 | 6篇 |
1939年 | 3篇 |
排序方式: 共有2513条查询结果,搜索用时 15 毫秒
1.
2.
In this research article, we describe the synthesis and characterization of mononuclear and dinuclear Cu complexes bound by a family of tridentate redox-active ligands with tunable H-bonding donors. The mononuclear Cu-anion complexes were oxidized to the corresponding “high-valent” intermediates by oxidation of the redox-active ligand. These species were capable of oxidizing phenols with weak O−H bonds via H-atom abstraction. Thermodynamic analysis of the H-atom abstractions, which included reduction potential measurements, pKa determination and kinetic studies, revealed that modification of the anion coordinated to the Cu and changes in the H-bonding donor did not lead to major differences in the reactivity of the “high-valent” CuY complexes (Y: hydroxide, phenolate and acetate), which indicated that the tridentate ligand scaffold acts as the H+ and e− acceptor. 相似文献
3.
Lagrangian and Eulerian modelling approaches are compared for simulating turbulent dispersion and coalescence of droplets within a spray. Both models predict similar droplet dispersion rates and shifts in droplet size distribution due to coalescence within the spray, over a wide range of droplet and gas flows, and for sprays with different droplet-size distributions at the nozzle exit. The computer time required for simulating coalescence within a steady axisymmetric spray is of a similar order of magnitude regardless of which formulation, Eulerian or Lagrangian, is adopted. However, the Lagrangian formulation is more practical in terms of the range of applicability and ease of implementation. 相似文献
4.
5.
A new parallel storm surge model, the Parallel Environmental Model (PEM), is developed and tested by comparisons with analytic solutions. The PEM is a 2‐D vertically averaged, wetting and drying numerical model and can be operated in explicit, semi‐implicit and fully implicit modes. In the implicit mode, the propagation, Coriolis and bottom friction terms can all be treated implicitly. The advection and diffusion terms are solved with a parallel Eulerian–Lagrangian scheme developed for this study. The model is developed specifically for use on parallel computer systems and will function accordingly in either explicit of implicit modes. Storm boundary conditions are based on a simple exponential decay of pressure from the centre of a storm. The simulated flooding caused by a major Category 5 hurricane making landfall in the Indian River Lagoon, Florida is then presented as an example application of the PEM. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
In this paper we consider operators of the form H=λ(-i∇), with λ analytic in a strip and with some specific growth conditions at infinity, and prove Hardy type estimates in L
2(ℝ
n
) with exponential weights. In fact we extend our previous results [19] from bounded analytic functions on a strip to analytic
functions with polynomial growth in that strip. 相似文献
7.
C. Zălinescu 《Mathematical Methods of Operations Research》1991,35(4):291-298
In this paper there is stated a result on sets in ordered linear spaces which can be used to show that some properties of the sets are inherited by their convex hulls under suitable conditions. As applications one gives a characterization of weakly efficient points and a duality result for nonconvex vector optimization problems. 相似文献
8.
9.
10.
Symmetric Hilbert spaces such as the bosonic and the fermionic Fock spaces over some lsquo;one particle space’ are formed by certain symmetrization procedures performed on the full Fock space. We investigate alternative ways of symmetrization
by building on Joyal's notion of a combinatorial species. Any such species F gives rise to an endofunctor of the category of Hilbert spaces with contractions mapping a Hilbert space to a symmetric Hilbert space with the same symmetry as the species F. A general framework for annihilation and creation operators on these spaces is developed, and compared to the generalised
Brownian motions of R. Speicher and M. Bożejko. As a corollary we find that the commutation relation with admits a realization on a symmetric Hilbert space whenever f has a power series with infinite radius of convergence and positive coefficients.
Received: 7 April 2000; in final form: 28 November 2000 / Published online: 19 October 2001 相似文献