全文获取类型
收费全文 | 376篇 |
免费 | 9篇 |
国内免费 | 8篇 |
专业分类
化学 | 230篇 |
晶体学 | 2篇 |
力学 | 22篇 |
数学 | 41篇 |
物理学 | 98篇 |
出版年
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 11篇 |
2014年 | 24篇 |
2013年 | 78篇 |
2012年 | 23篇 |
2011年 | 23篇 |
2010年 | 17篇 |
2009年 | 12篇 |
2008年 | 22篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有393条查询结果,搜索用时 171 毫秒
61.
Joshaghani M Gholivand MB Ahmadi F 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1073-1078
The complexation reaction between Cu(2+), Co(2+) and Ni(2+) metal cations with N,N'-bis(salicylidene)-1,2-phenylenediamine (salophen), in three nonaqueous polar solvents such as: acetonitrile (AN), dimethyl sulfoxide (DMSO), methanol (MeOH) and two binary mixtures of AN:DMSO and AN:MeOH at 25 degrees C were studied by spectrophotometric and conductometric methods. All investigated metal ions form 1:1 ML complex which their stability constants were determined and increase as Irving-Williams stability order of Co(2+)相似文献
62.
Alpha-PW(12)O(40)(3-) (PW(12)) supported on the surface of silica gel derivatized by 3-aminopropyl(triethoxy)silane (devoted briefly as SiNH(3)PW(12)) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry. There is an ionic bonding character between PW(12) and the surface amino groups of modified silica, which greatly improves the stability of SiNH(3)PW(12)-modified carbon paste electrode due to insolubility of silica gel in water. The SiNH(3)PW(12) bulk-modified carbon paste electrode not only maintains the electrochemical activity of PW(12), but also exhibits remarkable advantages of renewability, as well as simple preparation and inexpensive material. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of IO(3)(-) and hydrogen peroxide. The SiNH(3)PW(12)-CPE is successfully applied as an electrochemical detector to monitor IO(3)(-) in flow injection analysis (FIA). The catalytic peak current was found to be linear with the IO(3)(-) concentration in the range 5x10(-6) to 1x10(-3)molL(-1). The detection limit of the proposed method was found to be 3.1x10(-6)molL(-1) for IO(3)(-) determination. 相似文献
63.
Malek Taher Maghsoodlou Sayyed Mostafa Habibi Khorassani Lotfali Saghatforoush Farhad Maghfuri Ghasem Marandi Roya Kabiri 《Journal of heterocyclic chemistry》2008,45(1):289-293
64.
Abedini Masoumeh Shirini Farhad Mohammad-Alinejad Omran Javad Seddighi Mohadeseh Goli-Jolodar Omid 《Research on Chemical Intermediates》2016,42(5):4443-4458
Research on Chemical Intermediates - Succinimidinium N-sulfonic acid hydrogen sulfate ([SuSA-H]HSO4) as a new ionic liquid is prepared and characterized using a variety of techniques, including... 相似文献
65.
The second moment numerical method (SMM) of Egan and Mahoney [Numerical modeling of advection and diffusion of urban area source pollutant. Journal of Applied Meteorology 1972; 11 : 312–322] is adapted to solve for the pure advection transport equation in a variety of flow fields. SMM eliminates numerical diffusion by employing a procedure that takes into account the first and second moments of mass distribution in each grid element. For pure translational flow fields, the method is conservative, positive definite and shape‐preserving. In rotational and/or shear flows, the accuracy of SMM is significantly reduced. Two improvements are presented to make the SMM applicable to a wider range of flow problems. It is shown that the improved SMM (ISMM) is less diffusive and more shape‐preserving than the SMM in rotational and/or deformational flows. The ISMM can also be used to solve for a color function in compressible flow fields. The computational efficiency of this method is compared with that of other methods and, for a given accuracy, it is shown that ISMM is a cost‐effective, non‐diffusive and shape‐preserving method. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
66.
Robert D. Lotz Brian E. Thompson Christopher A. Konings Farhad Davoudzadeh 《国际流体数值方法杂志》1997,24(4):355-373
Numerical uncertainties are quantified for calculations of transonic flow around a divergent trailing edge (DTE) supercritical aerofoil. The Reynolds-averaged Navier–Stokes equations are solved using a linearized block implicit solution procedure and mixing-length turbulence model. This procedure has reproduced measurements around supercritical aerofoils with blunt trailing edges that have shock, boundary layer and separated regions. The present effort quantifies numerical uncertainty in these calculations using grid convergence indices which are calculated from aerodynamic coefficients, shock location, dimensions of the recirculating region in the wake of the blunt trailing edge and distributions of surface pressure coefficients. The grid convergence index is almost uniform around the aerofoil, except in the shock region and at the point where turbulence transition was fixed. The grid convergence index indicates good convergence for lift but only fair convergence for moment and drag and also confirms that drag calculations are more sensitive to numerical error. © 1997 by John Wiley and Sons, Ltd. 相似文献
67.
68.
V. V. Samedov 《Physics of Atomic Nuclei》2017,80(9):1489-1494
All processes occurring in semiconductor detectors during detection of primary monoenergetic particles lead to broadening of spectral lines. In this work, a general expression for the energy resolution of semiconductor detectors is obtained using the theory of branching cascade processes. It is shown that the general formula involves all contributions to the spectral line broadening described in the literature and additional contributions associated with fluctuations of electron and hole lifetimes caused by inhomogeneity of traps in the semiconductor material and fluctuations of the electronic channel gain. 相似文献
69.
A variety of alcohols and phenols are efficiently acetylated with acetic anhydride in the presence of a catalytic amount of V(HSO4)3 in solution and under solvent free conditions.Mild reaction conditions,high yields of the products,easy procedure and selective acetylation of alcohols and phenols in the presence of amines and thiols are the main advantages of this procedure. 相似文献
70.
Farhad Shirini Mohammad Ali Zolfigol Masoumeh Abedini 《Monatshefte für Chemie / Chemical Monthly》2009,141(10):61-64