全文获取类型
收费全文 | 1071篇 |
免费 | 39篇 |
专业分类
化学 | 894篇 |
晶体学 | 1篇 |
力学 | 38篇 |
数学 | 96篇 |
物理学 | 81篇 |
出版年
2023年 | 6篇 |
2022年 | 23篇 |
2021年 | 45篇 |
2020年 | 27篇 |
2019年 | 22篇 |
2018年 | 22篇 |
2017年 | 14篇 |
2016年 | 50篇 |
2015年 | 33篇 |
2014年 | 32篇 |
2013年 | 91篇 |
2012年 | 90篇 |
2011年 | 71篇 |
2010年 | 42篇 |
2009年 | 44篇 |
2008年 | 59篇 |
2007年 | 53篇 |
2006年 | 60篇 |
2005年 | 42篇 |
2004年 | 46篇 |
2003年 | 47篇 |
2002年 | 40篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 13篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 21篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有1110条查询结果,搜索用时 31 毫秒
61.
Roberta Del Sole Anna Scardino Maria Rosaria Lazzoi Lucia Mergola Sonia Scorrano Giuseppe Vasapollo 《Mikrochimica acta》2013,180(15-16):1401-1409
A molecularly imprinted polymer (MIP) for the specific retention of neopterin has been developed. A set of 6 polymers was prepared by radical polymerization under different experimental condition using methacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinker, with the aim to understand their influence on the efficiency of the MIP. The performance of each MIP was tested in batch experiments via their binding capacity. The MIP prepared in the presence of nickel ions in dimethylsulfoxide-acetonitrile mixture (P4) exhibited the highest binding capacity for neopterin (260 μmol per gram of polymer). A selectivity study with two other pteridines demonstrated the polymer P4 also to possess the best selectivity. Figure
A molecularly imprinted polymer for the specific retention of neopterin was developed. A set of 6 polymers was prepared under different experimental condition. The performance of each MIP was tested through their binding capacity. The MIP P4 prepared in the presence of nickel ions exhibited the highest binding capacity 相似文献
62.
Ptaquiloside, a potent carcinogen present in bracken fern, a plant consumed by farm animals, may be detected in traces by converting it into the bromopterosine. A simple synthesis of bromopterosine d2, to be used as standard in GC/MS or LC/MS analyses, is described. 相似文献
63.
Condensation of 2-nitrothiophenol with ethyl propiolate afforded 3-(2-nitrophenylthio)propenoate. Oxidation of sulfur atom to sulfone group gave ethyl 3-(2-nitrophenylsulfonyl)propenoate, which underwent condensation with tosyl methylisocyanide (TosMIC) to yield ethyl 4-(2-nitrophenylsulfonyl)pyrrole-3-carboxylate. Reduction of nitro group afforded ethyl 4-(2-aminophenylsulfonyl)-1H-pyrrole-3-carboxylate, which was cyclized to 2H-pyrrolo[3,4-b][1,5] benzothiazepin-10(9H)-one 4,4-dioxide. Similar procedure was used for the synthesis of 9,10-dihydro-10-methyl-2H-pyrrolo[3,4-b][1,5]benzothiazepine 4,4-dioxide. 相似文献
64.
Lidia Alexandrova Michail Nedyalkov Dimo Platikanov Roberta Razzetti Federico Bianco 《Colloid and polymer science》2013,291(11):2725-2731
The wetting properties of pulmonary surfactant aqueous solutions with respect to solid surfaces with different degree of hydrophobicity have been studied. The contact angles θ of drops from a pulmonary surfactant solution onto SiO2-glass surfaces have been measured as a function of their degree of hydrophobicity θ w. The completely hydrophilic SiO2-glass surface is essentially hydrophobized by the animal-derived pulmonary surfactant Curosurf. The hydrophobization depends on the surfactant concentration—the contact angles increase with increasing the Curosurf concentration C s in the low concentration range, but they remain almost constant in a wide range of C s >90 μg/ml. Additions like NaCl and bovine serum albumin influence the θ-values. The contact angles θ naturally increase with increasing θ w but this dependence is not linear—the curve steepens at larger θ w values. The thickness h of the wetting thin liquid films from Curosurf aqueous solutions depends on the hydrophobicity θ w of the solid surface and the h(θ w) curves always pass a minimum. The h-values, as well as the h(θ w) curve, are mainly determined by the steric and hydrophobic disjoining pressures, which depend on the orientations and conformations of the molecules adsorbed on the solid surface from the very complicated multi-component aqueous solutions. 相似文献
65.
Motta Neves Roberta Ornaghi Heitor Luiz Duchemin Benoit Zattera Ademir Jos Campos Amico Sandro 《Cellulose (London, England)》2022,29(6):3209-3224
Cellulose - Microcrystalline cellulose (MCC) has unique properties and its use as reinforcement for polymer composites has been increasing. However, the intrinsic incompatibility with most polymers... 相似文献
66.
Dr. Maria Petrosino Dr. Francesco Stellato Prof. Roberta Chiaraluce Prof. Valerio Consalvi Dr. Giovanni La Penna Dr. Alessandra Pasquo Dr. Olivier Proux Prof. Giancarlo Rossi Prof. Silvia Morante 《ChemistryOpen》2021,10(11):1133-1141
We present in this work a first X-ray Absorption Spectroscopy study of the interactions of Zn with human BST2/tetherin and SARS-CoV-2 orf7a proteins as well as with some of their complexes. The analysis of the XANES region of the measured spectra shows that Zn binds to BST2, as well as to orf7a, thus resulting in the formation of BST2-orf7a complexes. This structural information confirms the the conjecture, recently put forward by some of the present Authors, according to which the accessory orf7a (and possibly also orf8) viral protein are capable of interfering with the BST2 antiviral activity. Our explanation for this behavior is that, when BST2 gets in contact with Zn bound to the orf7a Cys15 ligand, it has the ability of displacing the metal owing to the creation of a new disulfide bridge across the two proteins. The formation of this BST2-orf7a complex destabilizes BST2 dimerization, thus impairing the antiviral activity of the latter. 相似文献
67.
As part of our continuing interest in the chemistry of cationic antimony Lewis acids as ligands for late transition metals, we have now investigated the synthesis of platinum complexes featuring a triarylstibine ligand substituted by an o-[(dimethylamino)methyl]phenyl group referred to as ArN. More specifically, we describe the synthesis of the amino stibine ligand Ph2SbArN (L) and its platinum dichloride complex [LPtCl]Cl which exists as a chloride salt and which shows weak coordination of the amino group to the antimony center. We also report the conversion of [LPtCl]Cl into a tricationic complex [LHPt(SMe2)]3+ which has been isolated as a tris-triflate salt after reaction of [LPtCl]Cl with SMe2, HOTf and AgOTf. Finally, we show that [LHPt(SMe2)][OTf]3 acts as a catalyst for the cyclization of 2-allyl-2-(2-propynyl)malonate. 相似文献
68.
Francesca Cal Chiara Roberta Girelli Federica Angil Laura Del Coco Lucia Mazzi Daniele Barbini Francesco Paolo Fanizzi 《Molecules (Basel, Switzerland)》2021,26(8)
Considering the growing number of extra virgin olive oil (EVOO) producers in the world, knowing the influence of olive oils with different geographical origins on the characteristics of the final blend becomes an interesting goal. The present work is focused on commercial organic EVOO blends obtained by mixing multiple oils from different geographical origins. These blends have been studied by 1H-NMR spectroscopy supported by multivariate statistical analysis. Specific characteristics of commercial organic EVOO blends originated by mixing oils from Italy, Tunisia, Portugal, Spain, and Greece were found to be associated with the increasing content of the Italian component. A linear progression of the metabolic profile defined characteristics for the analysed samples—up to a plateau level—was found in relation to the content of the main constituent of the Italian oil, the monocultivar Coratina. The Italian constituent percentage appears to be correlated with the fatty acids (oleic) and the polyphenols (tyrosol, hydroxytyrosol, and derivatives) content as major and minor components respectively. These results, which highlight important economic aspects, also show the utility of 1H-NMR associated with chemometric analysis as a powerful tool in this field. Mixing oils of different national origins, to obtain blends with specific characteristics, could be profitably controlled by this methodology. 相似文献
69.
Bermel W Bertini I Felli IC Matzapetakis M Pierattelli R Theil EC Turano P 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,188(2):301-310
Attempts are made to efficiently decouple (13)C nuclei without significant loss of coherence during the application of the decoupling package. Such attempts are based on the S(3)E spin-state selection method. A newly developed double S(3)E (DS(3)E) is particularly efficient for C(alpha) detection for proteins as large as 480 kDa. 相似文献
70.
Roberta Sulcis Francesco Vizza Werner Oberhauser Francesco Ciardelli Roberto Spiniello Nadka Tz. Dintcheva Elisa Passaglia 《先进技术聚合物》2014,25(9):1060-1068
A sustainable procedure for recycling powdered rubber coming from scrap tires (ground tire rubber [GTR]) is proposed as based on the dispersion in polyketone (PK) matrix, obtained in situ by CO/ethylene copolymerization. Three types of catalysts are used operative in solvents of different polarities. The catalyst productivity and the hybrids morphology are evaluated and optimized to final composites features. The obtained products are characterized by scanning electron microscopy, atomic force microscopy, and solvent extractions in order to investigate the occurrence and the extent of interactions between PK macromolecular chains and the GTR components; and their effects on the final properties were tested by differential scanning calorimetry, thermogravimetric analysis, and rheological measurements. For comparison purpose, a composite with GTR included into the matrix through blending is prepared. The results evidenced the key role exerted by the catalyst that, when operative in apolar solvent (able to swell the rubber phase), provides composites with good interfacial adhesion and breaking up of the particles with beneficial effects on final properties particularly thermal features and processability. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献