全文获取类型
收费全文 | 246篇 |
免费 | 13篇 |
专业分类
化学 | 216篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 29篇 |
物理学 | 12篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 21篇 |
2012年 | 11篇 |
2011年 | 16篇 |
2010年 | 13篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有259条查询结果,搜索用时 312 毫秒
61.
Summary: The solubilization and encapsulation of the weakly soluble protein hemoglobin was investigated at the nanoscale using self-assembly with the branched polymer polyethyleneimine (PEI), the lipid glycerol monooleate (GMO), and two amphiphilic poly(ethylenglycol) monooleate derivatives with molecular weights 2100 g/mol (MO-PEG1) and 860 g/mol (MO-PEG2). The created self-assembly nanovehicles were analyzed by quasi-elastic light scattering (QELS) in order to determine their sizes as well as by circular dichroism in order to characterize the protein presence in the nanoobjects. The cationic polymer PEI formed mixed nano-objects with the protein hemoglobin. The polymer conformation in the nanovehicle was established to be sensitive to dilution, a property that can be essential for the protein release upon administration. The amphiphile MO-PEG1 was a co-surfactant in the dispersion of monoglyceride lipid nanoobjects needed for the hemoglobin encapsulation. The amphiphile MO-PEG2 formed small micelles in the absence of a lipid. The nanoobjects dispersions were studied for their stability on storage and reproducibility. 相似文献
62.
Fiorentino A D'Abrosca B Pacifico S Izzo A D'Angelo G Monaco P 《Natural product communications》2010,5(10):1539-1542
Two new clerodane diterpenes were isolated from roots of Carex distachya Desf., a perennial plant widely distributed in the coastal area of the Mediterranean basin. Chemical characterization of the metabolites was carried out mainly by 1D and 2D NMR spectroscopy. The isolated compounds influenced either positively or negatively the plant growth (root and shoot elongation) of three coexisting herbaceous species. 相似文献
63.
64.
A simple, one step conversion of aldol adducts 1 derived from cyclic 1,2,3-tricarbonyl compound with 1,3-cycloalkanediones into title compounds 2 is described. 相似文献
65.
Silvia Kneubühler Bernard Testa Vincenzo Carta Cosimo Altomare Angelo Carotti 《Helvetica chimica acta》1993,76(5):1956-1963
The one-pot synthesis of nine 5H-indeno[1,2-c]pyridazines is described. These compounds are shown to be potent, reversible inhibitors of monoamine oxidase B (MAO-B) with little or no effect on monoamine oxidase A (MAO-A). Qualitative structure-activity relations indicate that the MAO-B inhibitory activity is strongly influenced by electronic and bulk properties of substitutents. 相似文献
66.
Eduardo Dfaz Hector Barrios Jose Luis Nava Raul G. Enriquez Angel Guzmn Len G. Leticia Jose Fernando Fuentes Fuentes B. Aidee Angelina Quintero Jose Dolores Solano 《Journal of heterocyclic chemistry》1997,34(3):1037-1041
The Stereoselective addition of the pyrimidine derivative 1 to the exocyclic methylene of the α,β unsaturated dehydrocostus lactone 2, Ivalin acetate 3 and Zaluzanin A diacetate 4, was achieved resulting in a new C-C bond formation. In the cases of compounds 3 and 4, after the addition, the lactone was cleaved followed by reclosure into a lactam ring system. 相似文献
67.
Jellen EE Chappell AM Ryzhov V 《Rapid communications in mass spectrometry : RCM》2002,16(19):1799-1804
The size-dependent stability of noncovalent complexes under collision-induced dissociation (CID) conditions was studied on a quadrupole ion trap mass spectrometer. Complexes of heme, tetraphenylporphyrin iron(III) (TPP-Fe), and tetraphenylporphyrin manganese(III) (TPP-Mn) with several histidine-containing peptides and model compounds were formed by electrospray ionization (ESI) and their stability was probed by variable-energy CID. It was found that the stability of complexes with the same (or nearly the same) binding energy has a linear dependence on the complex size (or total number of degrees of freedom). This approach will allow comparisons of variable-energy CID data for noncovalent complexes with different binding energies and could be used to help in structural elucidation of some complexes formed by multidentate ligands. The linearity of size effects on the stability of the complexes was also tested in three crown ether/protonated primary amine systems. 相似文献
68.
Angelina Pena Sofia Duarte Andr M. P. T. Pereira Liliana J. G. Silva Clia S. M. Laranjeiro Marta Oliveira Celeste Lino Simone Morais 《Molecules (Basel, Switzerland)》2022,27(1)
Human biomonitoring (HBM) data provide information on total exposure regardless of the route and sources of exposure. HBM studies have been applied to quantify human exposure to contaminants and environmental/occupational pollutants by determining the parent compounds, their metabolites or even their reaction products in biological matrices. HBM studies performed among the Portuguese population are disperse and limited. To overcome this knowledge gap, this review gathers, for the first time, the published Portuguese HBM information concerning polycyclic aromatic hydrocarbons (PAHs), metals, metalloids, and pesticides concentrations detected in the urine, serum, milk, hair, and nails of different groups of the Portuguese population. This integrative insight of available HBM data allows the analysis of the main determinants and patterns of exposure of the Portuguese population to these selected hazardous compounds, as well as assessment of the potential health risks. Identification of the main difficulties and challenges of HBM through analysis of the enrolled studies was also an aim. Ultimately, this study aimed to support national and European policies promoting human health and summarizes the most important outcomes and lessons learned through the HBM studies carried out in Portugal. 相似文献
69.
Angelina Pena Sofia Duarte Andr M. P. T. Pereira Liliana J. G. Silva Clia S. M. Laranjeiro Marta Oliveira Celeste Lino Simone Morais 《Molecules (Basel, Switzerland)》2022,27(1)
Human biomonitoring (HBM) data provide information on total exposure regardless of the route and sources of exposure. HBM studies have been applied to quantify human exposure to contaminants and environmental/occupational pollutants by means of determining the parent compounds, their metabolites, or even their reaction products in biological matrices. HBM studies performed among the Portuguese population are dispersed and limited. Thus, to overcome this knowledge gap, this work reviews the published Portuguese HBM information concerning mycotoxins detected in the urine, serum, milk, hair, and nails of different groups of the Portuguese population. This integrative approach to the available HBM data allows us to analyze the main determinants and patterns of exposure of the Portuguese population to the selected hazardous compounds, as well as to assess the potential health risks. We also aimed to identify the main difficulties and challenges of HBM through the analysis of the enrolled studies. Ultimately, this study aims to support national and European policies in promoting human health by summarizing the most important outcomes and lessons learned through the HBM studies carried out in Portugal. 相似文献
70.
Commercial and synthetic azobenzene derivatives were used for the synthesis of hydrophilic polymeric dyes. Two strategies based respectively on the polymerization of dye methacrylic derivatives with different monomers and on the functionalization of reactive polymers were investigated. Polymers containing rather small amounts of the selected dyes were generally obtained, very likely because of the electron withdrawing effect of azo chromophores. Almost quantitative conversions were recorded in the reaction of commercial dyes with maleic anhydride/methyl vinyl ether alternating copolymers. Some of the prepared polymeric dyes were preliminarily tested as textile finishing agents. 相似文献