全文获取类型
收费全文 | 449篇 |
免费 | 17篇 |
国内免费 | 9篇 |
专业分类
化学 | 326篇 |
晶体学 | 1篇 |
力学 | 18篇 |
数学 | 49篇 |
物理学 | 81篇 |
出版年
2023年 | 8篇 |
2022年 | 17篇 |
2021年 | 17篇 |
2020年 | 36篇 |
2019年 | 23篇 |
2018年 | 29篇 |
2017年 | 27篇 |
2016年 | 28篇 |
2015年 | 23篇 |
2014年 | 28篇 |
2013年 | 37篇 |
2012年 | 23篇 |
2011年 | 30篇 |
2010年 | 35篇 |
2009年 | 20篇 |
2008年 | 18篇 |
2007年 | 21篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1991年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 2篇 |
排序方式: 共有475条查询结果,搜索用时 15 毫秒
1.
A 2D HgII coordination polymer containing ligands 1,2,4‐triazole (Htrz) and thiocyanate, [Hg(μ3‐trz)(SCN)]n ( 1 ) has been synthesized and characterized by elemental analysis and IR spectroscopy. The single‐crystal X‐ray data show the coordination number of Hg atoms is four and the ligand trz? acts as a three‐fold donor. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses. The composition and formation of the complex in methanol solution were found to be in support of its solid state structure. 相似文献
2.
3.
JPC – Journal of Planar Chromatography – Modern TLC - A new stability-indicating HPTLC assay has been established for leuprolide acetate. Silica gel 60F254 was used as stationary phase.... 相似文献
4.
Czechoslovak Mathematical Journal - We investigate signed graphs with just 2 or 3 distinct eigenvalues, mostly in the context of vertex-deleted subgraphs, the join of two signed graphs or... 相似文献
5.
AbstractBacterial cellulose (BC) is an extracellular natural polymer produced by many microorganisms and its properties could be tailored via specific fabrication methods and culture conditions. There is a growing interest in BC derived materials due to the main features of BC such as porous fibrous structure, high crystallinity, impressive physico-mechanical properties, and high water content. However, pristine BC lacks some features, limiting its practical use in varied applications. Thus, fabrication of BC composites has been attempted to overcome these constraints. This review article overviews most recent advance in the development of BC composites and their potential in biomedicine including wound dressing, tissue engineering scaffolds, and drug delivery. Special emphasis is placed on the fabrication and applications of BC-containing nanofibrous composites for biomedical usage. It summarizes electrospinning of BC-based nanofibers and their surface modification with an outline on challenges and future perspective. 相似文献
6.
K. Nazari A. Mahmoudi R. Khodafarin A. A. Moosavi-Movahedi A. Mohebi 《Journal of the Iranian Chemical Society》2005,2(3):232-237
The present research discusses the structure stabilizing and protecting effects of Ni2+ against suicide-peroxide inactivation of horseradish peroxidase (HRP). Suicide inactivation of HRP by hydrogen peroxide (3 mM) was monitored by measuring change in the absorbance of the colored product (tetraguaiacol) of the catalytic reaction cycle at 470 nm. Progress curves of the catalytic reaction cycle were obtained at 27 °C, phosphate buffer (5 mM), pH 7.0. The corresponding kinetic parameters (e.g., initial enzyme activity (αo) and the apparent rate constant (ki) of suicide inactivation of HRP by peroxide) were evaluated using a kinetic equation derived in this study. Comparative activatory and inhibitory effects of Ni2+ on the kinetics of suicide-peroxide inactivation of HRP are discussed. 相似文献
7.
Raissi H Nowroozi A Farzad F Bojd MS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):343-352
Fourier transform infrared and Fourier transform Raman spectra of Cu(II) bis-acetylacetone have been obtained. The geometry, frequency and intensity of the vibrational bands of this compound and its 1,5-(13)C(2), 3-(13)C, 1,3,5-(13)C(3), 2,4-(13)C(2), (18)O(2) and 2,4-(13)C(2)-(18)O(2) derivatives were obtained by the density functional theory (DFT) with the B3LYP functional and using the 6-31G(*) and 3-21G(*) basis sets. The calculated frequencies are compared with the solid infrared and Raman spectra. All the measured infrared and Raman bands were interpreted in terms of the calculated vibrational modes. The percentage of deviation of the bond lengths and bond angles gives a good picture of the normal modes, and serves as a basis for the assignment of the wavenumbers. Most computed bands are predicted to be at higher wavenumbers than the experimental bands. The calculated geometrical parameters show slight differences compared with the experimental results. These differences can be explained by the different physical state of Cu(II) bis-acetylacetone. The DFT-B3LYP calculations assumed a free molecule in the gas phase. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. 相似文献
8.
When exposed to a corona discharge, a dielectric droplet spreads over a grounded substrate. In the present work, the spreading of dielectric liquids subjected to a short-term exposure is investigated. A simple theoretical model was developed to find the spreading law at the very beginning of exposure. The asymptotic approximation for the surface charge density and the interfacial pressure showed that the droplet spreading immediately after the exposure obeys t1/2 law. The high speed imaging of the spreading revealed the same trend as predicted by the theoretical model. 相似文献
9.
10.
A novel heterogeneous nanocatalyst: 2‐Methoxy‐1‐phenylethanone functionalized MCM‐41 supported Cu(II) complex for C‐S coupling of aryl halides with thiourea 下载免费PDF全文
An environmentally friendly copper‐based catalyst supported on 2‐Methoxy‐1‐phenylethanone functionalized MCM‐41 was prepared and characterized by FT‐IR, FE‐SEM, TEM, XRD, EDX, BET and ICP techniques. The catalyst was applied for the C?S cross‐coupling reaction of aryl halides with thiourea. Corresponding products were produced in good yields in aerobic conditions. The catalyst could be recovered and recycled for several times. 相似文献