全文获取类型
收费全文 | 276篇 |
免费 | 8篇 |
专业分类
化学 | 209篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 16篇 |
物理学 | 55篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 19篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 14篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有284条查询结果,搜索用时 46 毫秒
181.
Antonio Evidente Mónica Fernández-Aparicio Diego Rubiales Andrea Motta 《Tetrahedron letters》2009,50(50):6955-9724
Two new strigolactone-like metabolites, named peagol and peagoldione, with germinative activity for root parasitic plants, were isolated from pea root exudates and were characterized by spectroscopic methods. Peagol was more active on Orobanche foetida and Phelipanche aegyptiaca seeds, while peagoldione was active on P. aegyptiaca only. Low activity was found on Orobanche crenata and Orobanche minor. Stimulatory activity of peagol on O. foetida seeds is most relevant as this species does not respond to the synthetic strigolactone analogue GR24, usually used as Orobanche germination standard. 相似文献
182.
183.
Tomofumi Santa 《Biomedical chromatography : BMC》2010,24(9):915-918
The applicability of 3‐pyridyl isothiocyanate, p‐(dimethylamino)phenyl isothiocyanate and m‐nitrophenyl isothiocyanate as the derivatization reagents for amines in high‐performance liquid chromatography/electrospray ionization–tandem mass spectrometry (LC/ESI‐MS/MS) was examined. The generated derivatives of amines with these reagents were favorably separated on the reversed‐phase column and detected by ESI‐MS/MS. The C–N bond of the generated thiourea structure was efficiently cleaved by collision‐induced dissociation and gave the single and intense product ion. Among the three reagents, 3‐pyridyl isothiocyanate was the most suitable as the derivatization reagent with regard to the reactivity to amines and the detection sensitivity. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
184.
Laura Starvaggi Cucuzza Massimiliano Motta Silvia Miretti Paolo Accornero Mario Baratta 《Experimental & molecular medicine》2008,40(6):647-657
Curcumin (from the rhizome of Curcuma longa) is well documented for its medicinal properties in Indian and Chinese systems of medicine where it is widely used for the treatment of several diseases. Epidemiological observations are suggestive that curcumin consumption may reduce the risk of some form of cancers and provide other protective biological effects in humans. These biological properties have been attributed to curcuminoids that have been widely studied for their anti-inflammatory, anti-angiogenic, antioxidant, wound healing and anti-cancer effects. In this study we have investigated on the effect of a curcumin phospholipid complex on mammary epithelial cell viability. HC11 and BME-UV cell lines, validated models to study biology of normal, not tumoral, mammary epithelial cells, were used to analyse these effects. We report that curcumin acts on STAT-3 signal pathway to reduce cell viability and increase apoptosis evaluated by the the amount of activated caspase 3. Further it reduces MAPK and AKT activations. JSI-124, a STAT-3 inhibitor (100 nM) was able to block the negative effect of curcumin on cell viability and caspase 3 activation. Finally the negative effect of cucumin on cell viability has been impaired in STAT-3i HC11, where STAT-3 protein was greatly reduced by shRNA-interference. These results indicate that curcumin presents a potential adverse effect to normal mammary epithelial cells and that it has a specific effect on signal trasduction in mammary epithelium. 相似文献
185.
Condorelli GG Motta A Favazza M Fragalà IL Busi M Menozzi E Dalcanale E Cristofolini L 《Langmuir : the ACS journal of surfaces and colloids》2006,22(26):11126-11133
Cavitand molecules having double bond terminated alkyl chains and different bridging groups at the upper rim have been grafted on H-terminated Si(100) surface via photochemical hydrosilylation of the double bonds. Pure and mixed monolayers have been obtained from mesitylene solutions of either pure cavitand or cavitand/1-octene mixtures. Angle resolved high-resolution X-ray photoelectron spectroscopy has been used as the main tool for the monolayer characterization. The cavitand decorated surface consists of Si-C bonded layers with the upper rim at the top of the layer. Grafting of pure cavitands leads to not-well-packed layers, which are not able to efficiently passivate the Si(100) surface. By contrast, monolayers obtained from cavitand/1-octene mixtures consist of well-packed layers since they prevent silicon oxidation after aging. AFM measurements showed that these monolayers have a structured topography, with objects protruding from the Si(100) surface with average heights compatible with the expected ones for cavitand molecules. 相似文献
186.
Condorelli GG Motta A Favazza M Nativo P Fragalà IL Gatteschi D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(13):3558-3566
A synthetic strategy to control the density of Mn12 clusters anchored on silicon(100) was investigated. Diluted monolayers suitable for Mn12 anchoring were prepared by Si-grafting mixtures of the methyl 10-undecylenoate precursor ligand with 1-decene spectator spacers. Different ratios of these mixtures were tested. The grafted surfaces were hydrolyzed to reveal the carboxylic groups available for the subsequent exchange with the [Mn12O12(OAc)16(H2O)4]4 H2O2 AcOH cluster. Modified surfaces were analyzed by attenuated total reflection (ATR)-FTIR spectroscopy, X-ray photoemission spectroscopy (XPS), and AFM imaging. Results of XPS and ATR-FTIR spectroscopy show that the surface mole ratio between grafted ester and decene is higher than in the source solution. The surface density of the Mn12 cluster is, in turn, strictly proportional to the ester mole fraction. Well-resolved and isolated clusters were observed by AFM, using a diluted ester/decene 1:1 solution. 相似文献
187.
E.A. Prigo H. Takiishi C.C. Motta R.N. Faria N.B. Lima 《Journal of magnetism and magnetic materials》2008,320(14):e40-e42
An alternative method for determining the degree of crystallographic alignment (cos Θ) of the magnetic Pr2Fe14B phase (Φ) is proposed. The method is based on the relative X-ray diffracted intensities of the Φ planes of sintered magnets with and without texture. The degree of crystallographic alignment is also determined by X-ray pole figures using the (0 0 4) reflection and considered as a standard reference for comparison. The method is applied to Pr16Fe76B8 magnets with 0.51cos Θ0.97. The difference between the crystallographic alignments determined by these two methods is 3% within the experimental error. The advantages and limitations of using X-ray diffraction patterns to quantitatively evaluate the texture of sintered magnets are also discussed. 相似文献
188.
Brocca P Cantù L Corti M Del Favero E Motta S 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2141-2148
In the present paper, we apply the dynamic laser light scattering technique to investigate the dependence of the characteristic times of thermally induced shape fluctuation of large unilamellar vesicles (LUVs) on bilayer composition. After addressing single-component LUVs made of two common phospholipids, dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC), we investigate the changes in vesicle shape fluctuation times due to the presence of cholesterol and gangliosides (GM1), added in small amounts. The experimental results show that the addition of a second component, even in small amount, to DMPC vesicles induces a change in membrane fluctuation times. Moreover, in the case of ganglioside addition, also the disposition of GM1 within the bilayer is of importance. Quite unexpectedly, the symmetric or asymmetric disposition of GM1 has opposite effects on bilayer dynamics, the first resulting in a "hardening" and the second in a "softening" of the membrane. Those results support that the small-scale structure of the bilayer is important in determining the overall dynamics of the vesicle. They also suggest that the physiological disposition of GM1 in the outer leaflet of real cells has a significative result in mechanical terms, positively affecting the dynamics of the membrane. 相似文献
189.
The Si-C bond of N,N-dimethylcarbamoylsilanes added regiospecifically to the C=C bond of electrophilically functionalized alkenes to afford beta-silyl-beta-functionalized amides. Carbonyl addition products were formed when hindered alkenic esters were used. [reaction: see text] 相似文献
190.
N. Motta A. Balzarotti P. Letardi A. Kisiel M.T. Czyzyk M. Zimnal-Starnawska M. Podgorny 《Solid State Communications》1985,53(6):509-512
We report EXAFS measurements above the LIII edge of Te in Cd1?x ZnxTe for five compositions x. We find that the distribution of near-neighbours is bimodal, as in other II–VI zincblende ternary alloys. This behaviour is predicted by a model based on a random distribution of cations on a fcc sublattice and a highly distorted fcc sublattice for anions. The distribution of second neighbours is apparently bimodal, but a closer analysis reveals that this distribution is actually multimodal. 相似文献