全文获取类型
收费全文 | 810篇 |
免费 | 15篇 |
专业分类
化学 | 690篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 36篇 |
物理学 | 91篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 24篇 |
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 36篇 |
2017年 | 28篇 |
2016年 | 19篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 62篇 |
2012年 | 25篇 |
2011年 | 48篇 |
2010年 | 43篇 |
2009年 | 38篇 |
2008年 | 43篇 |
2007年 | 59篇 |
2006年 | 45篇 |
2005年 | 43篇 |
2004年 | 34篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 18篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有825条查询结果,搜索用时 0 毫秒
751.
Differential UV spectroscopy was used to study the temperature dependence of the conformational equilibrium in aqueous poly I . poly A . poly I (A2I) solutions containing Na+ (0.1-2 M) and Mg2+ (10(-5)-0.005 M) ions. Over the whole range of the studied Na+ and Mg2+ concentrations, the heating-induced destruction of the triple A2I helix is actually the A2I --> A + I + I (3 --> 1) transition. The rise of the transition temperature with increasing Na+ and Mg2+ contents is well described by Manning's and the "ligand" theories, which makes it possible to estimate the linear charge density on the single-stranded poly I (xi = 1.9 +/- 0.1) and the Mg2+-A2I binding constant (K = 1,250 M(-1) for the zero degree of binding). An analytical expression has been obtained, which correlates the constants of Mg2+ binding to three- and single-stranded polynucleotides (K3 and K1, respectively) and the linear charge density on them. There are only minor distinctions between the K3 values for A2U and A2I because these polynucleotides have similar structures. The difference in the K1 values is also slight as single-stranded poly U, poly I, and poly A have similar conformations. Dependence of the conformational transition temperatures of two triple helices with changing Mg2+ concentration. 相似文献
752.
Rusanova MY Tsirlina GA Nazmutdinov RR Fawcett WR 《The journal of physical chemistry. A》2005,109(7):1348-1356
The effect of charge distribution within Cr(III) and Eu(III) aquacomplexes on the kinetics of simple electron-transfer reactions at electrodes is considered. The construction of corrected Tafel plots using noninteger effective charges for the reactant and product estimated on the basis of quantum-chemical data was shown to be more reasonable than the traditional approach in which integer charges are assumed. The potential distribution near the electrode has been estimated both by the Gouy-Chapman model and from Monte Carlo simulations for 1-1 supporting electrolytes. Kinetic parameters obtained using the two approaches are compared. 相似文献
753.
Andrei V. Churakov Sergey S. Karlov Elmira Kh. Lermontova Galina S. Zaitseva Judith A. K. Howard 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):o761-o762
The title compound, C24H17F10N3O2, exhibits intramolecular N—H...O hydrogen bonding, as well as intramolecular Ar...ArF face‐to‐face interactions. The molecules are linked together by N—H...F—C hydrogen bonds, forming chains parallel to the a axis. Adjacent symmetry‐related chains are combined in double zipper‐like ribbons by parallel ArF...ArF offset π‐stacking interactions. 相似文献
754.
755.
The paper presents the first empirical investigation of the relationship between present value of net revenue from a revolving credit account and times to default and to second purchase. The analysis is based on the data for a store card which is used to buy ‘white’ durable goods in Germany. It is demonstrated that there exists a relationship between the above given measures. It appears that there is a scope for improving profit if an application for a store card is assessed by using a model which estimates the revenue and includes the survival probability of default and the survival probability of second purchase (a survival combination model) rather than merely a static probability of default predicted by a logistic regression. 相似文献
756.
Sergey O. Bachurin Galina F. Makhaeva Elena F. Shevtsova Alexey Yu. Aksinenko Vladimir V. Grigoriev Pavel N. Shevtsov Tatiana V. Goreva Tatiana A. Epishina Nadezhda V. Kovaleva Elena A. Pushkareva Natalia P. Boltneva Sofya V. Lushchekina Alexey V. Gabrelyan Vladimir L. Zamoyski Lyudmila G. Dubova Elena V. Rudakova Vladimir P. Fisenko Elena V. Bovina Rudy J. Richardson 《Molecules (Basel, Switzerland)》2021,26(18)
A new series of conjugates of aminoadamantane and γ-carboline, which are basic scaffolds of the known neuroactive agents, memantine and dimebon (Latrepirdine) was synthesized and characterized. Conjugates act simultaneously on several biological structures and processes involved in the pathogenesis of Alzheimer’s disease and some other neurodegenerative disorders. In particular, these compounds inhibit enzymes of the cholinesterase family, exhibiting higher inhibitory activity against butyrylcholinesterase (BChE), but having almost no effect on the activity of carboxylesterase (anti-target). The compounds serve as NMDA-subtype glutamate receptor ligands, show mitoprotective properties by preventing opening of the mitochondrial permeability transition (MPT) pore, and act as microtubule stabilizers, stimulating the polymerization of tubulin and microtubule-associated proteins. Structure–activity relationships were studied, with particular attention to the effect of the spacer on biological activity. The synthesized conjugates showed new properties compared to their prototypes (memantine and dimebon), including the ability to bind to the ifenprodil-binding site of the NMDA receptor and to occupy the peripheral anionic site of acetylcholinesterase (AChE), which indicates that these compounds can act as blockers of AChE-induced β-amyloid aggregation. These new attributes of the conjugates represent improvements to the pharmacological profiles of the separate components by conferring the potential to act as neuroprotectants and cognition enhancers with a multifunctional mode of action. 相似文献
757.
Mark E. Perel''man Galina M. Rubinstein Vitali A. Tatartchenko 《Physics letters. A》2008,372(22):4100-4103
Dendrites formation in the course of crystallization presents very general phenomenon, which is analyzed in details via the example of ice crystals growth in deionized water. Neutral molecules of water on the surface are combined into the double electric layer (DEL) of oriented dipoles; its field reorients approaching dipoles with observable radio-emission in the range of 150 kHz. The predominant attraction of oriented dipoles to points of gradients of this field induces dendrites growth from them, e.g., formation of characteristic form of snowflakes at free movement of clusters through saturated vapor in atmosphere. The constant electric field strengthens DELs' field and the growth of dendrites. Described phenomena should appear at crystallization of various substances with dipole molecules, features of radio-emission can allow the monitoring of certain processes in atmosphere and in technological processes. Crystallization of particles without constant moments can be stimulated by DELs of another nature with attraction of virtual moments of particles to gradients of fields and corresponding dendrites formation. 相似文献
758.
Jorge Royes Oana Ilioaia Quentin Lubart Federica Angius Galina V. Dubacheva Marta Bally Bruno Miroux Christophe Tribet 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7473-7477
Despite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high‐yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria‐based proteoliposomes are an attractive eco‐friendly alternative that can outperform currently used liposomes. 相似文献
759.
Jorge Royes Oana Ilioaia Quentin Lubart Federica Angius Galina V. Dubacheva Marta Bally Bruno Miroux Christophe Tribet 《Angewandte Chemie (International ed. in English)》2019,58(22):7395-7399
Despite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high‐yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria‐based proteoliposomes are an attractive eco‐friendly alternative that can outperform currently used liposomes. 相似文献
760.
Borchert H Borchert Y Kaichev VV Prosvirin IP Alikina GM Lukashevich AI Zaikovskii VI Moroz EM Paukshtis EA Bukhtiyarov VI Sadykov VA 《The journal of physical chemistry. B》2005,109(43):20077-20086
Nanostructured ceria doped with other rare earth elements is a good oxygen ion conductor, which gives rise to various catalytic applications such as the construction of membranes for syngas production by partial oxidation of methane. This article focuses on the Gd-doped cerium dioxides, which can be modified with Pt or Pd to enhance the reactivity of the lattice oxygen in interaction with methane. The aim of the work is the elucidation of correlations between the structural, electronic, and chemical properties of these nanomaterials. Detailed studies were performed for a series of samples with and without surface modification by noble metals using a complex combination of physicochemical methods: XRD, TEM, CH(4) TPR, XPS, SIMS, and FTIR spectroscopy of adsorbed CO. XPS and TPR data revealed that surface modification with noble metals enhances the reducibility of the doped ceria support, where the effect is more pronounced for Pd than for Pt. The formation of highly cationic Pd species due to strong metal support interactions provides a possible explanation for this behavior. Furthermore, the results obtained in the present work for the Gd-doped ceria system are compared to those obtained previously for the Pr-doped ceria system. 相似文献