全文获取类型
收费全文 | 533篇 |
免费 | 31篇 |
专业分类
化学 | 459篇 |
力学 | 14篇 |
数学 | 51篇 |
物理学 | 40篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 24篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 18篇 |
2015年 | 25篇 |
2014年 | 29篇 |
2013年 | 45篇 |
2012年 | 32篇 |
2011年 | 45篇 |
2010年 | 21篇 |
2009年 | 30篇 |
2008年 | 28篇 |
2007年 | 26篇 |
2006年 | 34篇 |
2005年 | 25篇 |
2004年 | 35篇 |
2003年 | 11篇 |
2002年 | 19篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1947年 | 2篇 |
1943年 | 3篇 |
1937年 | 1篇 |
排序方式: 共有564条查询结果,搜索用时 15 毫秒
81.
Porphyrin–Schiff Base Conjugates Bearing Basic Amino Groups as Antimicrobial Phototherapeutic Agents
María E. Prez Javier E. Durantini Eugenia Reynoso María G. Alvarez María E. Milanesio Edgardo N. Durantini 《Molecules (Basel, Switzerland)》2021,26(19)
New porphyrin–Schiff base conjugates bearing one (6) and two (7) basic amino groups were synthesized by condensation between tetrapyrrolic macrocycle-containing amine functions and 4-(3-(N,N-dimethylamino)propoxy)benzaldehyde. This approach allowed us to easily obtain porphyrins substituted by positive charge precursor groups in aqueous media. These compounds showed the typical Soret and four Q absorption bands with red fluorescence emission (ΦF ~ 0.12) in N,N-dimethylformamide. Porphyrins 6 and 7 photosensitized the generation of O2(1Δg) (ΦΔ ~ 0.44) and the photo-oxidation of L-tryptophan. The decomposition of this amino acid was mainly mediated by a type II photoprocess. Moreover, the addition of KI strongly quenched the photodynamic action through a reaction with O2(1Δg) to produce iodine. The photodynamic inactivation capacity induced by porphyrins 6 and 7 was evaluated in Staphylococcus aureus, Escherichia coli, and Candida albicans. Furthermore, the photoinactivation of these microorganisms was improved using potentiation with iodide anions. These porphyrins containing basic aliphatic amino groups can be protonated in biological systems, which provides an amphiphilic character to the tetrapyrrolic macrocycle. This effect allows one to increase the interaction with the cell wall, thus improving photocytotoxic activity against microorganisms. 相似文献
82.
Elena Rojo Maria Eugenia Muoz Anton Santamaría Begoa Pea 《Macromolecular rapid communications》2004,25(14):1314-1318
Summary: New rheological results with molten polypropylenes of different degrees of syndiotacticity are presented. The temperature dependence of their dynamic viscoelastic functions is correlated with the characteristic ratio. Relaxation time and Newtonian viscosity values are plotted as a function of molecular weight. The very high values of both rheological parameters found for the most syndiotactic polypropylenes are explained considering the reptation model, which links conformational parameters with the viscoelastic response in the molten state.
83.
Nikolay L. Eremeev Alexandr V. Kukhtin Eugenia A. Belyaeva Novella F. Kazanskaya 《Applied biochemistry and biotechnology》1999,76(1):45-55
Temperature dependencies of kinetic and equilibrium parameters of urea hydrolysis catalyzed by native urease and the urease
immobilized in a thermosensitive poly-N-isopropylacrylamide gel have been studied. The swelling ratio of the collapsed urease-containing
gel is shown to increase in the presence of urea. Below a lower critical solution temperature (LCST) of the polymer, the immobilized
u reaseactually has thesame catalytic properties as the native enzyme. At temperatures above LCST, the observed catalytic
activity of the immobilized enzyme depends chiefly not only on the thermoreversible matrix state, but also on gel water content. 相似文献
84.
Aline Salvi Corinne Brühlmann Eugenia Migliavacca Pierre‐Alain Carrupt Kurt Hostettmann Bernard Testa 《Helvetica chimica acta》2002,85(3):867-881
In this work, a convenient test of antioxidant activity was developed, with BChE‐contaminated HSA as the target of AAPH‐induced oxidation and its esterase activity as the marker of protein integrity or degradation. The method is relatively simple, of low cost, and convenient to use. Its application to natural polyphenols showed that quercetin ( 1 ), verbascoside ( 2 ), chlorogenic acid ( 3 ), caffeic acid ( 4 ), 1,3,6,7‐tetrahydroxyxanthone ( 5 ), and mangiferin ( 6 ), are good antioxidants (IC50<9 μM ). 1,5‐Dihydroxy‐3‐methoxyxanthone ( 7 ), flemichin D ( 8 ), and cordigone ( 9 ) showed modest activities (ca. 50 μM <IC50<350 μM ), whereas danthrone ( 10 ) was inactive. Complementary experiments with two of the more active antioxidants, namely quercetin ( 1 ) and chlorogenic acid ( 3 ) showed that both antioxidants were better radical scavengers than chain‐breaking antioxidants. The relative adiabatic oxidation potential (ΔHox), the relative H‐bond dissociation energy (ΔHabs), and the first oxidation potential measured by cyclic voltammetry were found to be related to the radical‐scavenging activity of these antioxidants. 相似文献
85.
86.
87.
88.
Juan‐José Cid Dr. Miguel García‐Iglesias Jun‐Ho Yum Dr. Amparo Forneli Josep Albero Eugenia Martínez‐Ferrero Dr. Purificación Vázquez Prof. Michael Grätzel Prof. Mohammad K. Nazeeruddin Prof. Emilio Palomares Prof. Tomás Torres Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5130-5137
Let it shine! The impact of the anchoring group on photovoltaic performance by a series of phthalocyanine sensitisers (see figure) has been demonstrated.
89.
Daniela Chirio Marina Gallarate Michele Trotta Maria Eugenia Carlotti Emanuela Calcio Gaudino Giancarlo Cravotto 《Journal of inclusion phenomena and macrocyclic chemistry》2009,65(3-4):391-402
Solid lipid nanoparticles (SLN) made of different triglycerides (TG) in the presence and in the absence of various modified α- and γ-cyclodextrins (CD) were prepared by the solvent injection technique. A new synthesis of lipophilic derivatives of γ- CD was developed in this work. Curcumin (CU), a natural polyphenol with antitumor, antioxidant and anti-inflammatory properties, was used as model drug. SLNs mean sizes were in the 250–800 nm range and afforded CU entrapment efficiency in the 12–85% range. The presence of CD derivatives with almost the same chain length of TG induced an improvement of nanoparticle characteristics decreasing mean size values and increasing CU entrapment efficiency. A significant reduction in CU photodegradation was noted only when the drug was vehicled in tristearin-SLN, which became less pronounced in the presence of CD-derivatives, determining a loss in photoprotection. The hydrolytic stability of curcumin was highly improved by drug loading in tristearin-SLN, and only slightly by loading it in tricaprin-SLN, and this seemed not to be influenced by the presence of CD derivatives. Skin uptake studies revealed an increase in CU skin accumulation when CU was loaded in SLN obtained with all CD derivatives, particularly with most lipophilic one. 相似文献
90.
Manfred Scheer Prof. Dr. Andrea Schindler Dipl.‐Chem. Christian Gröger Dr. Alexander V. Virovets Dr. Eugenia V. Peresypkina Dr. 《Angewandte Chemie (International ed. in English)》2009,48(27):4870-4870
Template‐controlled self‐assembly of discrete molecular pentaphosphaferrocene and CuCl units was used to form the first entirely carbon‐free molecule that has C80 topology and encapsulates a carborane unit. In their Communication on page 5046 ff. , M. Scheer and co‐workers report the synthesis and characterization of this impressive supramolecular compound, which displays an electronic interaction between the carborane and the spherical host molecule. C blue, Fe olive, P pink, Cl green, C gray, B/C orange, H white.