全文获取类型
收费全文 | 4228篇 |
免费 | 315篇 |
国内免费 | 410篇 |
专业分类
化学 | 3431篇 |
晶体学 | 4篇 |
力学 | 65篇 |
综合类 | 91篇 |
数学 | 119篇 |
物理学 | 560篇 |
无线电 | 683篇 |
出版年
2024年 | 10篇 |
2023年 | 67篇 |
2022年 | 225篇 |
2021年 | 187篇 |
2020年 | 133篇 |
2019年 | 121篇 |
2018年 | 113篇 |
2017年 | 175篇 |
2016年 | 171篇 |
2015年 | 161篇 |
2014年 | 190篇 |
2013年 | 251篇 |
2012年 | 368篇 |
2011年 | 281篇 |
2010年 | 228篇 |
2009年 | 269篇 |
2008年 | 287篇 |
2007年 | 303篇 |
2006年 | 213篇 |
2005年 | 189篇 |
2004年 | 158篇 |
2003年 | 105篇 |
2002年 | 118篇 |
2001年 | 73篇 |
2000年 | 88篇 |
1999年 | 75篇 |
1998年 | 53篇 |
1997年 | 52篇 |
1996年 | 46篇 |
1995年 | 36篇 |
1994年 | 36篇 |
1993年 | 27篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 15篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 1篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有4953条查询结果,搜索用时 0 毫秒
111.
The interactions between bovine serum albumin (BSA) and polymer (poly (METAC-co-NIPAm-co-Eu(AA)3Phen), PMNEu) containing rare earth element (Europium) were detailedly investigated by both of experimental techniques, such as fluorescence spectroscopic analysis, zeta-potential characterization, hydrodynamic size measurements and transmission electron microscopy (TEM) observation, and theoretical calculations. As a result, we concluded that PMNEu could interact with BSA through electrostatic force and quench the fluorescence of BSA, which was regarded as the static quenching mechanism. In addition, the binding constant and binding sites number of BSA with PMNEu were calculated, and the distance between PMNEu and BSA was also estimated to be 1.9?nm based on Föster’s theory. Furthermore, the two fluorescence peaks of PMNEu at 594?nm and 618?nm were detected, and the density of them increased with the more BSA being added to couple with PMNEu. Additionally, The zeta-potential results confirmed the electrostatic interaction mode between BSA and PMNEu, which was concluded with the previous thermodynamic analysis. At last, the results from the hydrodynamic size measurement had a good agreement with those from the TEM observation about the structure and size variation during the complexation of PMNEu with different concentrations of BSA. 相似文献
112.
Monica Averna Alessandro A. Casazza Antonino Martines Marco Pedrazzi Alice Franchi Roberta De Tullio 《Natural product research》2019,33(10):1449-1455
We are reporting in the present study that molecules extracted from olive pomace prevent cell death induced by Ca2+-overloading in different cell types. Exposure of cells to these molecules counteracts the Ca2+-induced cell damages by reducing the activation of the Ca2+-dependent protease calpain, acting possibly through the modification of the permeability to Ca2+ of the plasma membrane. The purification step by RP-HPLC suggests that effective compound(s), differing from the main biophenols known to be present in the olive pomace extract, could be responsible for this effect. Our observations suggest that bioactive molecules present in the olive pomace could be potential candidates for therapeutic applications in pathologies characterised by alterations of intracellular Ca2+ homeostasis. 相似文献
113.
Patricia C DamianiMariano D Borraccetti Alejandro C Olivieri 《Analytica chimica acta》2002,471(1):87-96
A direct method for the simultaneous determination of naproxen and salicylate in human serum is reported, based on a combination of spectrofluorometric measurements with two multivariate calibration techniques: partial least-squares (PLS-1) and the novel net analyte preprocessing (NAP). The method is rapid, selective and sensitive, and is based on the measurement of the fluorescence spectra of NH3 alkalinized whole human sera at the excitation wavelength of 315 nm. It can be applied within the ranges of concentrations 50-200 ng ml−1 for naproxen and 100-300 ng ml−1 for salicylate. The employed chemometric techniques have been compared on the basis of the statistical indicators for calibration and validation. Reproducibility and interference studies in abnormal sera have also been carried out. 相似文献
114.
血清微量元素与儿童少年身高生长的相关研究 总被引:1,自引:0,他引:1
报道了6-18岁在校学生身高生长突增的情况以及身高突增期前后血清中Ca、Mg、Zn、Fe、Cu、Mn、Se、Pb8种元素含量的变化。结果表明,女生身高生长突增开始、达到高峰及突增结束年龄均早于男生约2年。在身高生长的三个阶段,血清Ga、Mn、Cu、Se、Pb含量都有显著或极显著差异。血清Ca在身高突增期以后水平较低,血清Mn在身高突增期以前水平较低,血清Cu在身高突增期以前水平较高,血清Se、Pb则呈渐减趋势。而两性间除血清Cu女生高于男生外,其它各元素均无显著性羌异。 相似文献
115.
116.
117.
118.
盐酸丙咪嗪-人血清白蛋白结合作用的毛细管区带电泳测定法 总被引:3,自引:0,他引:3
采用毛细管区带电泳(CZE)技术,研究了抗抑郁三环类碱性药物盐酸丙咪嗪与人血清白蛋白(HSA)的结合作用。通过经典方法(超滤法)对该方法进行了方法学确证。该法适宜于水溶性良好的碱性药物(迁移时间足够短,且与蛋白质形成的复合物较稳定)-蛋白系统中分子间相互作用的定量考察。应用SAS 统计软件中非线性回归分析平台自编程序,求得了丙咪嗪与HSA的结合常数和结合位点数:K=0.18 L/μmol;n=2.2。 实验证明:该法可靠、简单、高效、低耗。 相似文献
119.
The effect of surfactants on surface instabilities of thin liquid film flow on a rotating disk was studied at different flow rates Q (0.5相似文献
120.
Gotti R Bertucci C Andrisano V Pomponio R Cavrini V 《Analytical and bioanalytical chemistry》2003,377(5):875-879
The interaction between human serum albumin (HSA) and the acetylcholinesterase inhibitor donepezil, has been studied by means of capillary electrophoresis frontal analysis (CE/FA) and circular dichroism. CE/FA enabled rapid and direct estimation of the quantity of free donepezil present at equilibrium with a physiological level of serum albumin (600 mol L–1). Application of Scatchard analysis enabled estimation of the binding parameters of HSA towards donepezil, such as association constant and number of binding sites on one protein molecule. Furthermore, due to enantioseparation ability shown by HSA on donepezil in CE mode, displacement experiments were carried out using ketoprofen and warfarin as coadditives to the HSA based running buffer. The addition of these compounds reduced the enantioresolution of donepezil by HSA only when used at high concentration. These data were confirmed and corroborated by circular dichroism (CD) experiments. Using CD, bilirubin was also applied as a ligand specific to site III of HSA. The observed behaviour suggested that donepezil could be considered a ligand with independent binding to sites I and II; although site III is not the highest affinity site, indirect interaction (i.e. cooperative binding) can be assumed. 相似文献