全文获取类型
收费全文 | 223篇 |
免费 | 7篇 |
国内免费 | 4篇 |
专业分类
化学 | 167篇 |
力学 | 8篇 |
数学 | 28篇 |
物理学 | 31篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 21篇 |
2008年 | 18篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有234条查询结果,搜索用时 375 毫秒
51.
Masoud Salavati-Niasari Shirin Shafaie-Arani Mohammad Reza Ganjali Parviz Norouzi 《Transition Metal Chemistry》2006,31(7):964-969
12- and 13-Membered diaza dioxa Schiff-base nickel(II) complexes were successfully prepared in a nanoscale microreactor by
the template condensation of (1,8-diamino-3,6-dioxaoctane)nickel(II) complex with bifunctional diketones within the nanodimensional
pores of zeolite Y. The host–guest nanocatalyst (HGN); ([Ni((R2[12]1,3-dieneN2O2)]2+-NaY, [Ni(R2[13]1,4-dieneN2O2)]2+-NaY; R = H, Me and Ph) is catalytically very efficient as compared to other neat complexes for oxidation of cyclohexene with
molecular oxygen as oxidant in the absence of solvent at 70 °C, affording 2-cyclohexene-1-ol and 2-cyclohexene-1-one. 相似文献
52.
53.
54.
First principle calculations have been employed to investigate the effects of Y concentration, pressure and temperature on various properties of () alloys using density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) is used to perform the calculated results of this paper. Phase stability of alloys is studied using the total energy versus unit cell volume calculations. The equilibrium lattice parameters of these alloys are in good agreement with the available experimental results. The mechanical stability of alloys is proved using elastic constants calculations. Also, the influence of Y concentration on elastic properties of alloys such as Young's modulus, shear modulus, Poisson's ratio and anisotropy factor are investigated and analyzed. By considering both Pugh's ratio and Poisson's ratio, the ductility and brittleness of these alloys are studied. In addition, the total density of states and orbital's hybridizations of different atoms are investigated and discussed. Moreover, the effect of pressure and temperature on some important thermodynamic properties is investigated. 相似文献
55.
Mohammad S. Asgari Behnam Tahmasebi Somayeh Mojtabavi Mohammad A. Faramarzi Rahmatollah Rahimi Parviz R. Ranjbar Mahmood Biglar Bagher Larijani Hossein Rastegar Maryam Mohammadi-Khanaposhtani Mohammad Mahdavi 《Journal of heterocyclic chemistry》2020,57(12):4348-4357
A new series of acridine-9-carboxamide-1,2,3-triazole derivatives 7a-m were designed, synthesized, and evaluated as novel α-glucosidase inhibitors. Acridine-9-carboxamide-1,2,3-triazole scaffold has been designed by combination of effective moieties from potent α-glucosidase inhibitors. Most of the synthesized compounds were more potent than standard inhibitor acarbose. Among the title compounds, the most potent compounds were compounds 7j , 7k , and 7a with IC50 values of 120.2 ± 1.0, 151.1 ± 1.4, and 157.6 ± 1.6 μM, respectively (IC50 value of acarbose = 750.0 ± 10.0 μM). Docking study of the most potent compounds demonstrated that these compounds formed stable complexes with α-glucosidase active site. Anti-α-amylase assay of compounds 7j , 7k , and 7a was performed and no activity was observed. in vitro cytotoxicity assay of the latter compounds revealed that these compounds were not cytotoxic toward human normal (HDF) and cancer (MCF-7) cell lines. ADME and toxicity prediction of compounds 7j , 7k , and 7a were also performed. 相似文献
56.
Production, remanufacture and waste disposal models in the literature assume that produced and recovered (repaired or remanufactured) items are of the same quality. However, a recent study considered a more realistic situation where produced and remanufactured items are incompatible. That is, they are not perceived by customers to have the same quality characteristics. This results in a lost sales situation for produced (remanufactured) items when they are requested by customers during the remanufacturing (production) period. In today’s competitive market, where firms thrive to sustain or increase the market share for their products, a stock-out situation where demand is completely lost seems to go contrary to the objectives of these firms. In reality, a firm may choose to either backorder fully or partially their unsatisfied demand. This paper extends along this line of research by modelling these stock-out situations. Several stock-out cases are considered for which mathematical models are developed and numerical examples are provided with their results discussed. 相似文献
57.
Mohammad Reza Ganjali Hamid Khoshsafar Farnoush Faridbod Ali Shirzadmehr Mehran Javanbakht Parviz Norouzi 《Electroanalysis》2009,21(19):2175-2178
Room temperature ionic liquids (RTILs), 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate, [bmim]BF4, and multiwalled carbon nanotubes (MWCNTs) were used for improvement of a praseodymium carbon paste ion selective sensor response. [bmim]BF4 can be a better binder than mineral oils. MWCNTs have a good conductivity which helps the transduction of the signal in carbon paste electrode. The characteristics of these electrodes as potentiometric sensors were evaluated and compared with PVC membrane sensor. The results indicate that potentiometric sensor constructed with ionic liquid shows an increase in performance in terms of Nernstian slope, selectivity, response time, and response stability compared to Pr(III) PVC membrane sensor. 相似文献
58.
Hadi Farahani Parviz Norouzi Rassoul Dinarvand Mohammad Reza Ganjali 《Journal of separation science》2009,32(2):314-320
A simple and sensitive methodology based on liquid‐phase microextraction (LPME) followed by GC‐MS, was developed for the determination of trihalomethanes (THMs) in drinking water. A microdrop of organic solvent was floated on the surface of the aqueous sample and it was agitated for a desired time. Then, the sample vial was cooled by inserting it into an ice bath for 4 min. The solidified solvent was transferred into a suitable vial and immediately melted. The extract was directly injected into the GC. Microextraction efficiency factors were investigated and optimized: 7 μL 1‐undecanol microdrop exposed for 15 min floated on the surface of a 10.0 mL aqueous sample with the temperature of 60°C containing 3 M of NaCl and stirred at 750 rpm. Under the selected conditions, enrichment factors (EFs) up to 482‐fold, LOD of 0.03–0.08 μg/L (S/N = 3) and dynamic linear ranges of 0.10–100 μg/L were obtained. A reasonable repeatability (RSD < 8.6%, n = 8) with satisfactory linearity (r2 ? 0.9947) of results illustrated a good performance of the present method. The protocol proved to be rapid, cost‐effective, and is a green procedure for the screening purposes. 相似文献
59.
Peter Baláž Parviz Pourghahramani Erika Dutková Martin Fabián Jaroslav Kováč Alexander Šatka 《Central European Journal of Chemistry》2009,7(2):215-221
PbS nanocrystals using surfactant assisted mechanochemical route has been successfully prepared. The methods of XRD, SEM,
surface area and particle size measurements were used for nanocrystals characterization. The XRD patterns confirmed the presence
of galena PbS (JCPDS 5–592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline
nature in formation of PbS nanostructures where preferential crystal growth in the (200) direction after chelating agent (EDTANa2•2H2O) addition has been observed. The mean volume weighted crystallite size 4.9 nm and 35 nm has been calculated from XRD data
using Williamson-Hall method for PbS synthesized without and/or with chelating agent, respectively corresponding with surface
weighted crystallites sizes of 2.9 and 18.8 nm. The sample prepared without surfactant yields the smaller crystallites and
the higher microstrain compared with surfactant assisted synthesis. The obtained results illustrate a possibility to manipulate
crystal morphology by combining effect of milling and surfactant application.
相似文献
60.
In this paper, flexible job shop scheduling problem with a new approach, overlapping in operations, is discussed. In many flexible job shops, a customer demand can be released more than one for each job, where demand determines the quantity of each finished job ordered by a customer. In these models each job has a demand more than one. This assumption is an important and practical issue for many flexible job shops such as petrochemical industries. To consider this assumption, we use a new approach, named overlapping in operations. In this approach, embedded operations of each job can be performed due to overlap considerations in which each operation may be overlapped with the others because of its nature. The overlapping is limited by structural constraints, such as the dimensions of the box to be packed or the capacity of the container used to move the pieces from one machine to the next. Since this problem is well known as NP-Hard class, a hierarchical approach used simulated annealing algorithm is developed to solve large problem instances. Moreover, a mixed integer linear programming (MILP) method is presented. To evaluate the validity of the proposed SA algorithm, the results are compared with the optimal solution obtained with the traditional optimization technique (The Branch and Bound method). The computational results validate the efficiency and effectiveness of the proposed algorithm. Also the computational results show that the overlapping considering can improve the makespan and machines utilization measures. So the proposed algorithm can be applied easily in real factory conditions and for the large size problems and it should thus be useful to both practitioners and researchers. 相似文献