全文获取类型
收费全文 | 596篇 |
免费 | 32篇 |
国内免费 | 5篇 |
专业分类
化学 | 273篇 |
晶体学 | 3篇 |
力学 | 70篇 |
数学 | 191篇 |
物理学 | 96篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 21篇 |
2021年 | 27篇 |
2020年 | 29篇 |
2019年 | 35篇 |
2018年 | 33篇 |
2017年 | 37篇 |
2016年 | 32篇 |
2015年 | 25篇 |
2014年 | 43篇 |
2013年 | 62篇 |
2012年 | 67篇 |
2011年 | 55篇 |
2010年 | 38篇 |
2009年 | 34篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1996年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有633条查询结果,搜索用时 281 毫秒
141.
Ehsan Karimi Meisam Habibi Mahdi Ebrahimi Ali Mehrafarin Farahnaz Khalighi-Sigaroodi 《Natural product research》2018,32(16):1991-1995
The antioxidant activities of crude extract fractions using Hexane, Chloroform, Ethyl Acetate, Butanol and Water of Clematis orientalis and Clematis ispahanica were investigated. 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay and the ferric reducing/antioxidant potential (FRAP) were used to evaluate the antioxidant capacity. The total phenolics were found to be 4.37–9.38 and 1.32–11.37 mg gallic acid equivalents (GAE)/g in different fractions for C. orientalis and C. ispahanica, respectively. The ethyl acetate fraction of C. orientalis and chloroform fraction of C. ispahanica showed the highest DPPH and FRAP activities at a concentration of 300 μg/mL. The predominant phenolic compounds identified by HPLC in C. orientalis were Resorcinol (603.5 μg/g DW) in chloroform fraction and Ellagic acid (811.7 μg/g DW) in chloroform fraction of C. ispahanica. 相似文献
142.
Ayoub Taavoni-Gilan Ehsan Taheri-Nassaj Mojtaba Shamsipur 《Journal of the Iranian Chemical Society》2018,15(12):2759-2769
Nanostructured TiO2/ZrO2 composite membranes with varying compositions were obtained by sol–gel technique. The influence of 0–30 mol% zirconia doping on microstructure, water permeability, photocatalytic and physical separation properties, removal of methyl violet of textile industries wastewater and thermal and mechanical stability of titania/zirconia composite membranes was described. Firstly, alumina supports were coated with TiO2 intermediate layers using the colloidal sol–gel route. The TiO2/ZrO2 composite sols were prepared via a polymeric sol–gel method and dip-coated on TiO2 intermediate layer. The samples were characterized by DLS, TG-DTA, XRD, FTIR, BET-BJH, UV–visible, SEM, TEM and AFM. It was shown that zirconia retards the phase transformation of anatase to rutile until at least 700 °C. The minimum pore size and maximum surface area obtained were 1.2 nm and 153 m2/g, respectively, attributed to the sample with 20 mol% zirconia. The mechanical strength of titania membranes was significantly improved by addition of zirconia. The most methyl violet removal efficiency obtained, with and without UV-irradiation, is 80.8 and 72.6%, respectively, attributed to the sample with 20 mol% zirconia. 相似文献
143.
The [3+3] cyclization of 1,3-bis-silyl enol ethers with 1,1-diacylcyclopentanes allows a convenient synthesis of spiro[5.4]decenones. Treatment of these compounds with trifluoroacetic acid (TFA) afforded a great variety of bicyclo[4.4.0]deca-1,4-dien-3-ones containing an angular alkyl group. This core structure occurs in a number of pharmacologically relevant natural products. 相似文献
144.
Ehsan Zahedi 《Comptes Rendus Chimie》2013,16(2):189-194
Adsorption of nitrogen dioxide on the exterior surface of C30B15N15 through B atom of adsorbent is studied using the DFT-B3LYP/6-31G* level. Independent to the orientation, the NO2 molecule presents strong chemisorption with large charge transfer from C30B15N15 to adsorbed gas. NBO (natural electron configuration of adsorbing B atom), AIM analysis and spin density distributions indicate that the chemisorption of NO2 on the C30B15N15 in all studied complexes are covalent in nature. 相似文献
145.
146.
Maithani Rajesh Kumar Anil Gholamali Zadeh Peyman Safaei Mohammad Reza Gholamalizadeh Ehsan 《Journal of Thermal Analysis and Calorimetry》2020,139(2):1195-1212
Journal of Thermal Analysis and Calorimetry - A study was conducted to enhance the thermo-hydraulic performance of a rectangular solar air passage with integrated spherical-shaped turbulence... 相似文献
147.
Pourhadi Ehsan Khrennikov Andrei Yu. Oleschko Klaudia de Jesús Correa Lopez María 《Journal of Fourier Analysis and Applications》2020,26(4):1-12
We consider the pointwise convergence problem for the solution of Schrödinger-type equations along directions determined by a given compact subset of the real line. This problem contains Carleson’s problem as the simplest case and was studied in general by Cho et al. We extend their result from the case of the classical Schrödinger equation to a class of equations which includes the fractional Schrödinger equations. To achieve this, we significantly simplify their proof by completely avoiding a time localization argument. 相似文献
148.
149.
150.
In this article, we introduce two new asynchronous multisplitting methods for solving the system of weakly nonlinear equations
Ax = G(x) in which A is an n × n real matrix and G(x) = (g
1(x), g
2(x), . . . , g
n
(x))
T
is a P-bounded mapping. First, by generalized accelerated overrelaxation (GAOR) technique, we introduce the asynchronous parallel
multisplitting GAOR method (including the synchronous parallel multisplitting AOR method as a special case) for solving the
system of weakly nonlinear equations. Second, asynchronous parallel multisplitting method based on symmetric successive overrelaxation
(SSOR) multisplitting is introduced, which is called asynchronous parallel multisplitting SSOR method. Then under suitable
conditions, we establish the convergence of the two introduced methods. The given results contain synchronous multisplitting
iterations as a special case. 相似文献