全文获取类型
收费全文 | 682篇 |
免费 | 39篇 |
国内免费 | 1篇 |
专业分类
化学 | 530篇 |
晶体学 | 8篇 |
力学 | 19篇 |
数学 | 27篇 |
物理学 | 138篇 |
出版年
2024年 | 4篇 |
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 21篇 |
2020年 | 20篇 |
2019年 | 24篇 |
2018年 | 18篇 |
2017年 | 24篇 |
2016年 | 33篇 |
2015年 | 24篇 |
2014年 | 46篇 |
2013年 | 64篇 |
2012年 | 35篇 |
2011年 | 45篇 |
2010年 | 24篇 |
2009年 | 26篇 |
2008年 | 32篇 |
2007年 | 40篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 21篇 |
2003年 | 19篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 6篇 |
1971年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有722条查询结果,搜索用时 49 毫秒
51.
Resource optimization is a very important issue related with restoration in optical networks. In the proactive restoration, backup lightpaths are established along with the primary light paths. In this paper, we have proposed a strategy for resource optimization, which works with proactive restoration. The performance of the proposed strategy is evaluated by applying on the sample network. 相似文献
52.
53.
Novel camphor sulfonamide based organocatalysts were evaluated for their catalytic activity in the Michael reaction of ketones with nitroolefins. Reaction of ketones with β-nitrostyrenes in the presence of 20 mol % organocatalyst 1a and benzoic acid under solvent-free conditions at 0 °C provided the desired Michael adducts with high chemical yields (up to 97%) and excellent stereoselectivities (>99:1). 相似文献
54.
55.
M. Aulice Scibioh P. V. Ragini S. Rani V. R. Vijayaraghavan B. Viswanathan 《Journal of Chemical Sciences》2001,113(4):343-350
With the aim of finding a suitable electrocatalyst for the efficient reduction of carbon dioxide, the electrochemistry of
nickel (II) complex of 1,3,6,9,11,14-hexaazatricyclo [12·2·1·1] octadecane was studied using cyclic voltammetry (CV) and controlled-potential
electrolysis (CPE) techniques in the presence and absence of CO2 in 100% H2O, CH3CN-H2O mixtures (20–100%) and DMF-H2O (70–100%) mixtures. The efficiency of this process is determined using the coulometry technique. CO is the major product
in the gaseous phase and HCOOH the sole product formed in the solution phase. 相似文献
56.
57.
The transmitted photon spectra of133Ba,22Na,137Cs,54Mn and60Co point sources are measured through different thicknesses of water, concrete and sand. The multiple-scatter peaks observed
in these materials at 60, 90 and 100 keV energies respectively are found to be independent of incident photon energy and thickness
of the medium. 相似文献
58.
A numerical solution for the transient natural convection flow over a vertical cylinder under the combined buoyancy effect
of heat and mass transfer is presented. The velocity, temperature and concentration profiles, local and average skin-friction,
Nusselt number and Sherwood number are shown graphically. It is observed that time taken to reach steady state increases with
Schmidt number and decreases as combined buoyancy ratio parameter N increases. Stability and convergence of the finite difference scheme are established.
Received on 8 July 1997 相似文献
59.
A rare asymmetric end-on double azido-bridged copper(II) complex has been synthesized and characterized structurally and magnetically. The Cu-N(azide)-Cu angle in this complex is calculated to be 89.1 degrees. This is unusually low in comparison to the same angle in other end-on azido-bridged binuclear complexes reported so far. Though a strong ferromagnetic interaction between the metal centers is expected in the complex, the coupling has actually been found to be antiferromagnetic, instead. 相似文献
60.