全文获取类型
收费全文 | 289篇 |
免费 | 7篇 |
国内免费 | 7篇 |
专业分类
化学 | 174篇 |
晶体学 | 1篇 |
力学 | 16篇 |
数学 | 59篇 |
物理学 | 53篇 |
出版年
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 21篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 36篇 |
2012年 | 17篇 |
2011年 | 30篇 |
2010年 | 19篇 |
2009年 | 19篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有303条查询结果,搜索用时 265 毫秒
31.
S. Shahidi A. Rashidi M. Ghoranneviss A. Anvari M. K. Rahimi M. Bameni Moghaddam J. Wiener 《Cellulose (London, England)》2010,17(3):627-634
In this work, the silver particle absorption and antibacterial activity of cotton fabric when modified by low temperature
plasma were investigated. The modification consisted of plasma pre-functionalization followed by one-step wet treatment with
silver nitrate solution. Oxygen and nitrogen were used as the working gases in the system, and the results were compared.
The results showed that nitrogen plasma-treated samples can absorb more silver particles than oxygen-treated samples, and
thus the antibacterial activity of the samples in this case, which was analyzed by the counting bacteria test, was increased
considerably. 相似文献
32.
H. Moosavi M. Mohammadi A. Farajpour S.H. Shahidi 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):135-140
In this article, we use shear deformable ring theory (SDRT) for the analysis of free in-plane vibration of nanorings based on nonlocal elasticity theory. The equations of motion of the nanoring are derived for the aforementioned problem by considering the small scale effect. Analytical solutions for the natural frequencies of the nanorings are presented. It is shown that the nonlocal effects play an important role in the vibration of nanorings and cannot be neglected. The effects of the small scale on the natural frequencies considering various parameters such as the radius of the nanoring, the thickness of the nanoring and mode numbers are investigated. 相似文献
33.
Amin Anjomshoa Ali Reza Shahidi Behrooz Hassani Emad Jomehzadeh 《Applied Mathematical Modelling》2014
Graphene-polymer nano-composites are one of the most applicable engineering nanostructures with superior mechanical properties. In the present study, a finite element (FE) approach based on the size dependent nonlocal elasticity theory is developed for buckling analysis of nano-scaled multi-layered graphene sheets (MLGSs) embedded in polymer matrix. The van der Waals (vdW) interactions between the graphene layers and graphene-polymer are simulated as a set of linear springs using the Lennard-Jones potential model. The governing stability equations for nonlocal classical orthotropic plates together with the weighted residual formulation are employed to explicitly obtain stiffness and buckling matrices for a multi-layered super element of MLGS. The accuracy of the current finite element analysis (FEA) is approved through a comparison with molecular dynamics (MD) and analytical solutions available in the literature. Effects of nonlocal parameter, dimensions, vdW interactions, elastic foundation, mode numbers and boundary conditions on critical in-plane loads are investigated for different types of MLGS. It is found that buckling loads of MLGS are generally of two types namely In-Phase (INPH) and Out-of-Phase (OPH) loads. The INPH loads are independent of interlayer vdW interactions while the OPH loads depend on vdW interactions. It is seen that the decreasing effect of nonlocal parameter on the OPH buckling loads dwindles as the interlayer vdW interactions become stronger. Also, it is found that the small scale and polymer substrate have noticeable effects on the buckling loads of embedded MLGS. 相似文献
34.
One‐Pot Synthesis of New 1,5‐Disubstituted Tetrazoles Bearing 2,2‐Bis(trimethylsilyl)ethenyl Groups via The Ugi Four‐Component Condensation Reaction Catalyzed by MgBr2·2Et2O
下载免费PDF全文
![点击此处可从《Journal of heterocyclic chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kazem D. Safa Tohid Shokri Hassan Abbasi Reza Teimuri‐Mofrad 《Journal of heterocyclic chemistry》2014,51(1):80-84
A simple one‐pot Ugi four‐component condensation reaction has been developed for the synthesis of tetrazoles bearing 2,2‐bis(trimethylsilyl)ethenyl groups from the synthesized 4‐[2,2‐bis(trimethylsilyl) ethenyl]benzaldehyde ( 1 ), various amines, isocyanides, and trimethylsilylazide at room temperature, without solvent, and in the presence of catalytic amounts of MgBr2·2Et2O as catalyst. 相似文献
35.
An efficient palladium catalytic system for microwave assisted cyanation of aryl halides 总被引:1,自引:0,他引:1
Abdol R. Hajipour Kazem Karami Azade Pirisedigh 《Journal of organometallic chemistry》2011,696(4):819-824
Application of a new catalytic system for cyanation reaction of various aryl halides using K4[Fe(CN)6] as cyanating source was examined. The reactions were performed under microwave irradiation and results showed that application of this catalytic system and DMF at 130 °C minimized the reaction times from hours to minutes in good to excellent yields. 相似文献
36.
Kazem D. Safa Farnaz Behmagham Khatereh Ghorbanpour 《Journal of organometallic chemistry》2011,696(9):1840-1844
The magnesium bromide-diethyl etherate-catalyzed ring-opening of (3-(naphthalen-2-yl)-2,2-bis(trimethylsilyl)oxiran 2 with thiophenols affords (1-trimethylsilylvinyl)sulfides 3 and the (1-bromovinyl)silane 4. Nucleophilic attack occurs regioselectively at the position α- to silicon. The compound 2 has been converted into the (1-trimethylsilylvinyl)amide 5 with an excess of acetonitrile and into the (1-trimethylsilylvinyl)acetate 6 with acetic acid/acetic anhydride. These reactions proceed with catalytic amounts of boron trifluoride-diethylether. Treatment of 2 with acetic acid alone gives naphthaldehyde. The epoxide 2 reacts also with MgBr2·OEt2, MeLi/CuI, HX (XBr or Cl) and LiAlH4 with nucleophilic attack at the bis(trimethylsilyl)-substituted carbon. 相似文献
37.
38.
In this paper a new element is developed that is based on Cosserat theory. In the finite element implementation of Cosserat theory shear locking can occur, especially for very thin shells. In the present investigation the director vector is constrained to remain perpendicular to the mid surface during deformation. It will be shown that this constraint yields accurate results in very large deformation of thin shells also the rate of convergency is very good. For plastic formulation, the model introduced by Simo is used and it has been reduced for constrained director vector and the consistent elasto-plastic tangent moduli is extracted for finite element solution. This model includes both kinematic and isotropic hardening. For numerical investigations an isoparametric nine node element is employed then by linearization of the principle of virtual work, material and geometric stiffness matrices are extracted. The validity and the accuracy of the proposed element is illustrated by the numerical examples and the results are compared with those available in the literature. 相似文献
39.
40.