全文获取类型
收费全文 | 254篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
化学 | 182篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 24篇 |
物理学 | 55篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 18篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 14篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有272条查询结果,搜索用时 453 毫秒
101.
This article discusses the role of nanoscale calcium carbonate (nCC) surface treatment in affecting the mechanical, rheological, and thermal properties of linear low-density polyethylene (LLDPE). The mechanical tests indicated that nCC could simultaneously reinforce and toughen LLDPE. In addition, the composite sample with methacrylic acid (MA)-treated nanoparticles shows further increased mechanical properties as compared to unmodified nanoparticles. In the presence of dicumyl peroxide (DCP), a small amount of MA could increase markedly the mechanical properties of LLDPE/nCC composites. The results of rheological property analysis indicated that the viscosity increased with increasing amount of the filler, especially at low shear rates, but showed a substantial reduction with increasing concentration of the reactive monomer. The thermal behavior of these materials is evaluated by differential scanning calorimetry and thermogravimetric analysis. The addition of a small amount of MA and DCP enhances the stabilization of the blends. 相似文献
102.
The paper presents a new giving up smoking model for which interaction term is square root of potential and occasional smokers of model presented in Zaman (2011) [15]. First, we will show formulation of the model. Then we will discuss local and global stability of the model and its general solutions. The non-standard finite difference method (NSFD) is used to solve the new giving up smoking model. Both non-negativity and conservative law for differential equations system are discussed. Numerical results are presented graphically and compared well with those obtained by Runge–Kutta fourth-order method (RK4) and ODE45. 相似文献
103.
S Jan A Wajid Khan S Parveen RA Khan A Saeed AJ Tanveer A Ali Shad 《Chemistry Central journal》2012,6(1):76
ABSTRACT: BACKGROUND: Aerva javanica (Burm. f.) Juss. ex Schult. (Amaranthacea) is traditionally used for the treatment of wound healings, cough, diarrhoea, ulcer and hyperglycaemia. The current study was aimed to fractionate and isolate bioactive compounds and ultimately to evaluate their anti-ulcereogenic potential. RESULTS: In order to achieve these aims, the fractionation, purifications and then biological potential determination of the isolated compounds was carried out. For purification purpose, initially extraction of the plant material was done with aqueous MeOH in the order of increasing polarity by using solvent-solvent extraction method. Phytochemical analysis revealed the presence of three compounds, 3-hydroxy-4 methoxybenzaldehyde (1), ursolic acid (2) and (E)-N-(4-hydroxy-3-methoxyphenethyl)-3-(4-hydroxy-3-ethoxyphenyl) acryl amide (3). Inhibition of urease activity of various fractions revealed that ethyl acetate fraction showed significant activity (P <0.05) as compared to other fractions. (E)-N-(4-hydroxy-3- methoxyphenethyl)-3-(4-hydroxy-3-ethoxyphenyl) acryl amide (3) showed marked anti ulcer activity (P <0.05). CONCLUSION: These results suggested the mild potential of A. javanica against ulcer. 相似文献
104.
Some biologically important tin(IV) complexes derived from 5,5-diethyl sodium barbital have been synthesized and characterized through various analytical and spectroscopic techniques such as IR, 1H-, 13C-NMR and 119mSn mssbauer. On the basis of these spectroscopic techniques, octahedral geometry has been assigned to all the novel compounds. These complexes, soluble in DMSO and DMF, were screened against a wide range of microorganisms. The results proved that the diphenyltin(IV) and dibutyltin(IV) complexes exhibit excellent activity against all types of microorganisms, while the rest of the compounds show significant activity that can be used during the biological study. 相似文献
105.
Mohammad Zaman Kassaee Farnaz Alipour Shakib Mohammad Reza Momeni Mehdi Ghambarian Seyed Majid Musavi 《Monatshefte für Chemie / Chemical Monthly》2009,140(1):33-38
Abstract Based on geometries and relative energies, three different mechanisms are proposed for the rearrangements of five isomers
of silacyclohexadienylidenes to silabenzene at B3LYP and MP2 levels: (1) [1,2]-hydrogen migration through a planar transition
state, (2) [1,4]-hydrogen migration through a boat transition state, and (3) zip-zap mechanism, comprised of three successive
[1,2]-hydrogen migrations. The above results are compared and contrasted to rearrangements of the corresponding cyclohexadienylidenes
to benzene.
Graphical abstract
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
106.
M. Hussain M. Zaman M. Hanif M. Altaf S. Ali H. Stoeckli-Evans 《Journal of the Iranian Chemical Society》2009,6(4):769-775
Triphenyltin(IV) [2-(2,3-dimethylanilino)nicotinate] was prepared by the interaction of triphenyltin(IV) hydroxide and 2-(2,3-dimethylanilino)nicotinic acid in 1:1 ratio. This compound was characterized by elemental analyses, IR, multinuclear NMR spectroscopy (1H and 13C) and mass spectrometry. The structure of title compound was confirmed by single crystal X-ray crystallography. The coordination around the tin atom was studied both in solution and solid state. The geometry around tin is trigonal bipyramidal in solid state while it is tetrahedral in solution. The compound belongs to Monoclinic system, having space group P 21/c with unit cell dimensions a = 17.002(8) Å, b = 9.0793(3) Å, c = 18.2616(9) Å, α = 90 (°) β = 107.381(4) (°), γ = 90 (°). 相似文献
107.
Atteeque Ahmed Aamer Saeed Omar M. Ali Zeinhom M. El-Bahy Pervaiz Ali Channar Asma Khurshid Arfa Tehzeeb Zaman Ashraf Hussain Raza Anwar Ul-Hamid Mubashir Hassan 《Molecules (Basel, Switzerland)》2021,26(23)
This article describes the design and synthesis of a series of novel amantadine-thiourea conjugates (3a–j) as Jack bean urease inhibitors. The synthesized hybrids were assayed for their in vitro urease inhibition. Accordingly, N-(adamantan-1-ylcarbamothioyl)octanamide (3j) possessing a 7-carbon alkyl chain showed excellent activity with IC50 value 0.0085 ± 0.0011 µM indicating that the long alkyl chain plays a vital role in enzyme inhibition. Whilst N-(adamantan-1-ylcarbamothioyl)-2-chlorobenzamide (3g) possessing a 2-chlorophenyl substitution was the next most efficient compound belonging to the aryl series with IC50 value of 0.0087 ± 0.001 µM. The kinetic mechanism analyzed by Lineweaver–Burk plots revealed the non-competitive mode of inhibition for compound 3j. Moreover, in silico molecular docking against target protein (PDBID 4H9M) indicated that most of the synthesized compounds exhibit good binding affinity with protein. The compound 3j forms two hydrogen bonds with amino acid residue VAL391 having a binding distance of 1.858 Å and 2.240 Å. The interaction of 3j with amino acid residue located outside the catalytic site showed its non-competitive mode of inhibition. Based upon these results, it is anticipated that compound 3j may serve as a lead structure for the design of more potent urease inhibitors. 相似文献
108.
Mst. Sharmin Sultana Shimu Shafi Mahmud Trina Ekwati Tallei Saad Ahmed Sami Ahmad Akroman Adam Uzzal Kumar Acharjee Gobindo Kumar Paul Talha Bin Emran Shahriar Zaman Md. Salah Uddin Md. Abu Saleh Sultan Alshehri Mohammed M Ghoneim Maha Alruwali Ahmad J. Obaidullah Nabilah Rahman Jui Junghwan Kim Bonglee Kim 《Molecules (Basel, Switzerland)》2022,27(3)
109.
110.