全文获取类型
收费全文 | 477篇 |
免费 | 20篇 |
国内免费 | 5篇 |
专业分类
化学 | 337篇 |
力学 | 30篇 |
数学 | 88篇 |
物理学 | 47篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 16篇 |
2020年 | 28篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 30篇 |
2016年 | 33篇 |
2015年 | 21篇 |
2014年 | 44篇 |
2013年 | 57篇 |
2012年 | 33篇 |
2011年 | 39篇 |
2010年 | 22篇 |
2009年 | 25篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 10篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有502条查询结果,搜索用时 15 毫秒
481.
Peiman Sahar Baharfar Robabeh Hosseinzadeh Rahman 《Research on Chemical Intermediates》2022,48(4):1365-1382
Research on Chemical Intermediates - Preparation of a nanocatalyst (Fe3O4@SiO2@DNHCS-Tr@CuI) containing PAMAM dendrimer and trypsin enzyme supported on magnetic nanosilica on which CuI NPs were... 相似文献
482.
Rahim Mohammad-Rezaei Javad Abbas-Zadeh Mahdi Golmohammadpour Elyas Hosseinzadeh 《Electroanalysis》2021,33(12):2428-2436
In this study, simultaneous deposition of copper oxide and electro-reduced graphene quantum dots (ErGQDs) on the surface of carbon ceramic electrode (CCE) was reported. The prepared ErGQDs-CuO/CCE was carefully characterized with Fourier transform infrared spectroscopy, X-ray diffraction, fluorescence spectroscopy, scanning electron microscopy and electrochemical techniques in details. According to scan rate studies in hexacyanoferrate, a remarkable increase in the surface coverage in the presence of ErGQDs was achieved. According to square wave voltammetry results, limit of detection, linear range and sensitivity of the developed biosensor for the simultaneous measurement of Adenine (A) and Guanine (G) were obtained to be 0.041 and 0.111 μM, 0.1–13 μM and 0.25–23 μM, and 4.261 and 1.311 μA μM cm−2 respectively. 相似文献
483.
Saeed Balalaie Morteza BararjanianSaeedeh Hosseinzadeh Frank RomingerHamid Reza Bijanzadeh Eckardt Wolf 《Tetrahedron》2011,67(38):7294-7300
An efficient strategy for the one-pot syntheses of indolo[1,2-a]quinoxalinones catalyzed by CuI have been developed. The procedures combine the Ugi four-component reaction of aldehydes, 2-iodoaniline, 2-indole carboxylic acid, and isocyanides followed by the copper-catalyzed intramolecular N-arylation of the Ugi product in one-pot procedure, which afford the desired products in good to very good yields. 相似文献
484.
A carbon‐paste electrode modified with 2,7‐bis(ferrocenyl ethyl)fluoren‐9‐one and carbon nanotubes was used for the sensitive voltammetric determination of levodopa (LD). The electrochemical response characteristics of the modified electrode toward LD, uric acid (UA) and folic acid (FA) were investigated. The results showed an efficient catalytic activity of the electrode for the electrooxidation of LD, which leads to lowering its overpotential by more than 320 mV. The modified electrode exhibits an efficient electron mediating behavior together with well‐separated oxidation peaks for LD, UA and FA. Also, the modified electrode was used for determination of LD in some real samples. 相似文献
485.
The initiation of atherosclerosis involves retention of colloidal atherogenic lipoproteins, primarily low density lipoprotein (LDL), in the arterial intima. This retention occurs when LDL binds to smooth muscle cell extracellular matrix (SMC ECM), and is enhanced by lipoprotein lipase (LpL) and sphingomyelinase (Smase). Here we use a fluorescence assay and dynamic light scattering to study the individual and combined effects of these two enzymes on LDL aggregation. Our results show: (1) LpL is self-sufficient to induce LDL aggregation with aggregate sizes up to ~400 nm; (2) Smase induces LDL aggregation due to generation of ceramide and subsequent hydrophobic interactions; (3) Smase hydrolysis of LpL-induced LDL aggregates does not cause further aggregation and results in a ~3-fold diminished production of ceramide, while LpL treatment of Smase-induced aggregates does enhance aggregation; (4) The simultaneous addition of LpL and Smase causes increased variability in aggregation with final sizes ranging from 50 to 110 nm. Our data suggest a new proatherogenic function for LpL, namely, bridging between LDL particles causing their aggregation and consequently enhanced retention by SMC ECM. The mechanism of LpL-and-Smase-mediated LDL aggregation and binding to SMC ECM provides specific points of intervention to design novel effective antiatherogenic therapeutics. 相似文献
486.
F. Hosseinzadeh LotfiG.R. Jahanshahloo M.R. Mozaffari J. Gerami 《Journal of Computational and Applied Mathematics》2011,235(5):1227-1231
This paper suggests a method for finding efficient hyperplanes with variable returns to scale the technology in data envelopment analysis (DEA) by using the multiple objective linear programming (MOLP) structure. By presenting an MOLP problem for finding the gradient of efficient hyperplanes, We characterize the efficient faces. Thus, without finding the extreme efficient points of the MOLP problem and only by identifying the efficient faces of the MOLP problem, we characterize the efficient hyperplanes which make up the DEA efficient frontier. Finally, we provide an algorithm for finding the efficient supporting hyperplanes and efficient defining hyperplanes, which uses only one linear programming problem. 相似文献
487.
G.R. Jahanshahloo M. Khodabakhshi F. Hosseinzadeh Lotfi M.R. Moazami Goudarzi 《Mathematical and Computer Modelling》2011,53(9-10):1946-1955
One of the most important approaches for ranking decision-making units in data envelopment analysis is the cross-efficiency method. The main idea of cross-efficiency is to use data envelopment analysis in peer evaluation, instead of only a self evaluation. However, in the cross-efficiency method, optimal weights corresponding to evaluation of decision-making units may not be unique. In this research with modifying the cross-efficiency method we are going to overcome this problem. Then with regard to the changes and using the TOPSIS method we present a new super-efficient method to rank all decision-making units. Furthermore, we extend the proposed method to the case that data are intervals. 相似文献
488.
M. Salehi M. Kubicki G. Dutkiewicz A. Rezaei M. Behzad S. Etminani 《Russian Journal of Coordination Chemistry》2013,39(10):716-722
The synthesis, characterization, spectroscopic and electrochemical properties of trans-[CoIII(L1)(Py)2]ClO4 (I) and trans-[CoIII(L2)(Py)2]ClO4 (II) complexes, where H2L1 = N,N′-bis(5-chloro-2-hydroxybenzylidene)-1,3-propylenediamine and H2L2 = N,N′-bis(5-bromo-2-hydroxybenzylidene)-1,3-propylenediamine, have been investigated. Both complexes have been characterized by elemental analysis, FT-IR, UV-Vis, and 1H NMR spectroscopy. The crystal structure of I has been determined by X-ray diffraction. The coordination geometry around cobalt(III) ion is best described as a distorted octahedron. The electrochemical studies of these complexes revealed that the first reduction process corresponding to Co(III/II) is electrochemically irreversible accompanied by dissociation of the axial Co-N(Py) bonds. The in vitro antimicrobial activity of the Schiff bse ligands and their corrsponding complexes have been tested against human pathogenic bacterias such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli. The cobalt(III) complexes showed lower antimicrobial activity than the free Schiff base ligands. 相似文献
489.
Karim Akbari Dilmaghani Behzad Zeynizadeh Maryam Amirpoor 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):1634-1642
Abstract A fast and efficient Biginelli synthesis of 3,4-dihydropyrimidin-2-(1H)-ones (or thiones) by the reaction of aromatic aldehydes, β-dicarbonyls, and urea/thiourea using NaHSO4·H2O/ultrasound system is presented. The reactions were carried out in refluxing n-hexane/CH3CN (2.5:0.5 mL) to afford the products in excellent yields. 相似文献
490.
The emphasis of this paper is on investigation of the TM/TE depolarization along a magnetized surface. In this regard, initially, the wave equation with appropriate boundary conditions is solved for the propagation constant of the wave along the interface. Next, in order to investigate the electromagnetic field TM/TE depolarization along a linear magnetoplasmon–dielectric interface, coupled partial differential equations are derived for the amplitudes of the TE and TM polarized fields along the surface. These equations are then solved using the Fourier transform and 4th order Runge–Kutta methods and the envelopes of the electric field are obtained. The dependency of the propagation constants of the slow and fast modes on the frequency and magnitude of DC magnetic bias field is investigated. A discussion of TE mode deflection is also provided. 相似文献