全文获取类型
收费全文 | 601篇 |
免费 | 27篇 |
国内免费 | 10篇 |
专业分类
化学 | 494篇 |
力学 | 23篇 |
数学 | 37篇 |
物理学 | 84篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 20篇 |
2019年 | 27篇 |
2018年 | 39篇 |
2017年 | 23篇 |
2016年 | 50篇 |
2015年 | 25篇 |
2014年 | 55篇 |
2013年 | 65篇 |
2012年 | 58篇 |
2011年 | 43篇 |
2010年 | 34篇 |
2009年 | 29篇 |
2008年 | 17篇 |
2007年 | 22篇 |
2006年 | 11篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有638条查询结果,搜索用时 15 毫秒
1.
Mojtaba Shamsipur Mohammad Bagher Gholivand Mohammad Shamizadeh Payman Hashemi 《Chromatographia》2015,78(11-12):795-803
2.
Mahsa Kiani Mojtaba Bagherzadeh Soraia Meghdadi Farzaneh Fadaei-Tirani Maryam Babaie Kurt Schenk-Joß 《应用有机金属化学》2020,34(11):e5911
The new Co(II) - carboxamide complex ( 1 ) and Co3O4 nanoparticles ( 2 ), by way of thermal decomposition of ( 1 ) have been efficiently synthesised in the environment-friendly. X-ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in ( 1 ) and regular octahedral or tetrahedral ones (oxygens only) in ( 2 ). The investigation of ( 1 ) and ( 2 ) in the Mizoroki-Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts. 相似文献
3.
Ali Pourjavadi Maryam Tavakolizadeh Seyed Hassan Hosseini Navid Rabiee Mojtaba Bagherzadeh 《Journal of polymer science. Part A, Polymer chemistry》2020,58(15):2062-2073
A number of synthetic hydrogels suffer from low mechanical strength. Despite of the recent advances in the fabrication of tough hydrogels, it is still a great challenge to simultaneously construct high stretchability, and self-adhesive and self-healing capability in a hydrogel. Herein, a new type of double network hydrogel was prepared based on irreversible cross-linking of polyacrylamide chains and Schiff-base reversible cross-linking between glycidyl methacrylate-grafted ethylenediamine and oxidized sodium alginate (OSA). The combination of both cross-linkings and their synergistic effect provided a novel hydrogel with high strength, stretchable, rapid self-healing, and self-adhesiveness to different material. Besides, the hydrogels with diverse OSA content could maintain their original shapes after loading–unloading tensile test. The resulting hydrogel has a great potential in various fields for supporting and load-bearing substance. 相似文献
4.
In this study, a new polymeric functionalized magnetic nanocatalyst containing a molybdenum Schiff base complex was prepared using a few consecutive steps. Poly (methylacrylate)-coated magnetic nanoparticles were synthesized via radical polymerization of methyl acrylate onto modified magnetic nanoparticles followed by the amidation of the methyl ester groups with hydrazine. Polymeric functionalization efficiently provides the advantage that more catalytic units can be grafted on the surface of magnetic nanoparticles. The functionalization process was continued with salicylaldehyde which introduced Schiff base groups on to the surface of the polymeric support. In the final step, the desired catalytic system was prepared via complexation of the Schiff base groups with MoO2(acac)2. The resulting nanoparticles were characterized by infrared spectroscopy, powder X-ray diffraction, scanning and transmission electron microscopy, elemental analysis, inductively coupled plasma optical emission spectrometry, vibrating sample magnetometry and thermogravimetric analysis. This heterogenized catalytic system was also found to be highly active, sustainable and recyclable nanocatalyst in alkene epoxidation. Eventually, the attractive features of the synthesized catalyst such as simple work-up, good stability, magnetic separation, high TOF and high surface area; make it appropriate for oxidation reactions. 相似文献
5.
Somayeh Rahaiee Mojtaba Ranjbar Hossein Azizi Mostafa Govahi Mahboobeh Zare 《应用有机金属化学》2020,34(8):e5705
To increase the profitability and sustainability of agricultural waste, a facile green approach was established to synthesize zinc oxide nanoparticles (ZnO NPs) using saffron leaf extract as a reducing and stabilizing agent. Structural characteristics of NPs were investigated by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), field emission scanning electron microscopy (FESEM), and UV–Visible (UV–Vis) spectroscopy. Characterization results revealed that ZnO NPs is highly crystalline with a hexagonal wurtzite structure and spherical particles with diameter less than 50 nm, as confirmed by XRD and FESEM techniques. UV–Vis absorption spectra depicted an absorption peak at 370 nm, which confirms the formation of ZnO NPs. FTIR spectral analysis confirmed the presence of functional groups and metal oxygen groups. The biological activities of ZnO NPs were also investigated. The antibacterial effect of ZnO NPs was investigated against selected food pathogens (Salmonella Typhimurium, Listeria monocytogenes, and Enterococcus faecalis). The study results prove that the green synthesized ZnO NPs show enhanced antibacterial activity against S. Typhimurium when compared with other strains. A dose-dependent free radical scavenging activity was observed for ZnO NPs in both 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and fluorescence recovery after photobleaching (FRAP) assays. The ZnO NPs were evaluated for their photocatalytic activity during the degradation of methylene blue (MB) dye in aqueous solutions. The maximum removal of MB achieved was 64% with an initial ZnO NP concentration of 12 mg/mL under UV light. The present study revealed that the agricultural waste (saffron leaf) provides a simple and eco-friendly option to sustainably synthesize ZnO NPs for use as a photocatalyst. In addition, this is the first report on saffron leaf-mediated synthesis of ZnO NPs. 相似文献
6.
We theoretically investigate optomechanical force sensing via precooling and quantum noise cancellation in two coupled cavity optomechanical systems.We show that force sensing based on the reduction of noise can be used to dramatically enhance the force sensing and that the precooling process can eifectively improve the quantum noise cancellation.Specifically,we examine the effect of optomechanical cooling and noise reduction on the spectral density of the noise of the force measurement;these processes can significantly enhance the performance of optomechanical force sensing,and setting up the system in the resolved sideband regime can lead to an optimization of the cooling processes in a hybrid system.Such a scheme serves as a promising platform for quantum back-action-evading measurements of the motion and a framework for an optomechanical force sensor. 相似文献
7.
Meccanica - Simple formulas for calculating equivalent von Mises stress and von Mises effective plastic strain in an elastic–plastic ordinary peridynamic analysis are proposed. The equivalent... 相似文献
8.
Hosseini Seyed Ghorban Gholami Setareh Mahyari Mojtaba 《Research on Chemical Intermediates》2019,45(3):1527-1543
Research on Chemical Intermediates - Nickel cobalt bimetallic nanoparticles (NiCo NPs) with different molar ratios were stabilized over three-dimensional nitrogen-doped graphene [3D-(N)G] by a... 相似文献
9.
Dr. Mojtaba Alidoost Anna Mangini Dr. Fabrizio Caldera Dr. Anastasia Anceschi Dr. Julia Amici Dr. Daniele Versaci Dr. Lucia Fagiolari Prof. Francesco Trotta Prof. Carlotta Francia Prof. Federico Bella Prof. Silvia Bodoardo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(6):e202104201
Manufactured globally on industrial scale, cyclodextrins (CD) are cyclic oligosaccharides produced by enzymatic conversion of starch. Their typical structure of truncated cone can host a wide variety of guest molecules to create inclusion complexes; indeed, we daily use CD as unseen components of food, cosmetics, textiles and pharmaceutical excipients. The synthesis of active material composites from CD resources can enable or enlarge the effective utilization of these products in the battery industry with some economical as well as environmental benefits. New and simple strategies are here presented for the synthesis of nanostructured silicon and sulfur composite materials with carbonized hyper cross-linked CD (nanosponges) that show satisfactory performance as high-capacity electrodes. For the sulfur cathode, the mesoporous carbon host limits polysulfide dissolution and shuttle effects and guarantees stable cycling performance. The embedding of silicon nanoparticles into the carbonized nanosponge allows to achieve high capacity and excellent cycling performance. Moreover, due to the high surface area of the silicon composite, the characteristics at the electrode/electrolyte interface dominate the overall electrochemical reversibility, opening a detailed analysis on the behavior of the material in different electrolytes. We show that the use of commercial LP30 electrolyte causes a larger capacity fade, and this is associated with different solid electrolyte interface layer formation and it is also demonstrated that fluoroethylene carbonate addition can significantly increase the capacity retention and the overall performance of our nanostructured Si/C composite in both ether-based and LP30 electrolytes. As a result, an integration of the Si/C and S/C composites is proposed to achieve a complete lithiated Si−S cell. 相似文献
10.
Periodica Mathematica Hungarica - In this paper, first we study surjective isometries (not necessarily linear) between completely regular subspaces A and B of $$C_0(X,E)$$ and $$C_0(Y,F)$$ where X... 相似文献