全文获取类型
收费全文 | 1632篇 |
免费 | 60篇 |
国内免费 | 20篇 |
专业分类
化学 | 1088篇 |
晶体学 | 4篇 |
力学 | 64篇 |
数学 | 142篇 |
物理学 | 414篇 |
出版年
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 39篇 |
2020年 | 34篇 |
2019年 | 20篇 |
2018年 | 32篇 |
2017年 | 14篇 |
2016年 | 47篇 |
2015年 | 35篇 |
2014年 | 44篇 |
2013年 | 80篇 |
2012年 | 50篇 |
2011年 | 85篇 |
2010年 | 67篇 |
2009年 | 50篇 |
2008年 | 76篇 |
2007年 | 77篇 |
2006年 | 87篇 |
2005年 | 71篇 |
2004年 | 57篇 |
2003年 | 68篇 |
2002年 | 51篇 |
2001年 | 51篇 |
2000年 | 51篇 |
1999年 | 43篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 25篇 |
1995年 | 21篇 |
1994年 | 29篇 |
1993年 | 28篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 11篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1976年 | 15篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1973年 | 8篇 |
1972年 | 9篇 |
排序方式: 共有1712条查询结果,搜索用时 15 毫秒
101.
Giuseppina La Ganga Fausto Puntoriero Enza Fazio Mirco Natali Francesco Nastasi Antonio Santoro Maurilio Galletta Sebastiano Campagna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16904-16911
The luminophore Ru(bpy)2(dcbpy)2+ (bpy=2,2’-bipyridine; dcbpy=4,4’-dicarboxy-2,2’-bipyridine) is covalently linked to a chitosan polymer; crosslinking by tripolyphosphate produced Ru-decorated chitosan fibers (NS-RuCh), with a 20 : 1 ratio between chitosan repeating units and RuII chromophores. The properties of the RuII compound are unperturbed by the chitosan structure, with NS-RuCh exhibiting the typical metal-to-ligand charge-transfer (MLCT) absorption and emission bands of RuII complexes. When crosslinks are made in the presence of IrO2 nanoparticles, such species are encapsulated within the nanofibers, thus generating the IrO2⊂NS-RuCh system, in which both RuII photosensitizers and IrO2 water oxidation catalysts are within the nanofiber structures. NS-RuCh and IrO2⊂NS-RuCh have been characterized by dynamic light scattering, scanning electronic microscopy, and energy-dispersive X-ray analysis, which indicated a 2 : 1 ratio between RuII chromophores and IrO2 species. Photochemical water oxidation has been investigated by using IrO2⊂NS-RuCh as the chromophore/catalyst assembly and persulfate anions as the sacrificial species: photochemical water oxidation yields O2 with a quantum yield (Φ) of 0.21, definitely higher than the Φ obtained with a similar solution containing separated Ru(bpy)32+ and IrO2 nanoparticles (0.05) or with respect to that obtained when using NS-RuCh and “free” IrO2 nanoparticles (0.10). A fast hole-scavenging process (rate constant, 7×104 s−1) involving the oxidized photosensitizer and the IrO2 catalyst within the IrO2⊂NS-RuCh system is behind the improved photochemical quantum yield of IrO2⊂NS-RuCh. 相似文献
102.
Léna Sambe Victor R. de La Rosa Khaled Belal Dr. François Stoffelbach Dr. Joel Lyskawa Dr. François Delattre Marc Bria Prof. Graeme Cooke Prof. Richard Hoogenboom Prof. Patrice Woisel 《Angewandte Chemie (International ed. in English)》2014,53(20):5044-5048
A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host–guest interactions of poly(N‐isopropylacrylamide) (PNIPAM) with side‐chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat‐p‐phenylene) (CBPQT4+) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST=lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM–CBPQT4+ host–guest complex. When heated above the transition temperature, the polymer collapses, and the host–guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences. 相似文献
103.
Dr. Henry S. La Pierre Dr. Hajime Kameo MSc. Dominik P. Halter Dr. Frank W. Heinemann Prof. Dr. Karsten Meyer 《Angewandte Chemie (International ed. in English)》2014,53(28):7154-7157
Synthetic studies on the redox chemistry of trivalent uranium monoarene complexes were undertaken with a complex derived from the chelating tris(aryloxide)arene ligand (Ad,MeArO)3mes3?. Cyclic voltammetry of [{(Ad,MeArO)3mes}UIII] ( 1 ) revealed a nearly reversible and chemically accessible reduction at ?2.495 V vs. Fc/Fc+—the first electrochemical evidence for a formally divalent uranium complex. Chemical reduction of 1 indicates that reduction induces coordination and redox isomerization to form a uranium(IV) hydride, and addition of a crown ether results in hydride insertion into the coordinated arene to afford uranium(IV) complexes. This stoichiometric reaction sequence provides structural insight into the mechanism of arene functionalization at diuranium inverted sandwich complexes. 相似文献
104.
Luminescent quantum dots (QDs) are colloidal semiconductor nanocrystals consisting of an inorganic core covered by a molecular layer of organic surfactants. Although QDs have been known for more than thirty years, they are still attracting the interest of researchers because of their unique size-tunable optical and electrical properties arising from quantum confinement. Moreover, the controlled decoration of the QD surface with suitable molecular species enables the rational design of inorganic-organic multicomponent architectures that can show a vast array of functionalities. This minireview highlights the recent progress in the use of surface-modified QDs – in particular, those based on cadmium chalcogenides – as supramolecular platforms for light-related applications such as optical sensing, triplet photosensitization, photocatalysis and phototherapy. 相似文献
105.
Microbial biosynthesis of hydrocarbon from CO2 reduction driven by electron uptake process from the cathodic electrode has gained intensive attention in terms of potential industrial application. However, a lack of a model system for detailed studies on the mechanism of the CO2 reduction hinders the improvement in efficiency for microbial electrosynthesis. Here, we examined the mechanism of microbial CO2 reduction at the cathode by a well‐described microbe for extracellular electron uptake, Shewanella oneidensis MR‐1, capable of reducing gaseous CO2 to produce formic acid. Using whole‐cell electrochemical assay, we observed stable cathodic current production at ?0.65 V vs Ag/AgCl KCl sat. associated with the introduction of CO2. The observed cathodic current was enhanced by the addition of 4 μM riboflavin, which specifically accelerates the electron uptake process of MR‐1 by the interaction to its outer‐membrane c‐type cytochromes. The significant impact of an uncoupler agent and a mutant strain of MR‐1 lacking sole F‐type ATPase suggested the importance of proton import to the cytoplasm for the cathodic CO2 reduction. The present data suggest that MR‐1 potentially serves as a model system for microbial electrosynthesis from CO2. 相似文献
106.
Dr. Santosh K. Singh Jesse La Jeunesse Vasant Vuppuluri Prof. Steven F. Son Dr. Bing-Jian Sun Mr. Yue-Lin Chen Prof. Agnes H. H. Chang Prof. Alexander M. Mebel Prof. Dr. Ralf I. Kaiser 《Chemphyschem》2020,21(9):837-842
Understanding of the fundamental mechanisms involved in the decomposition of 1,3,5-trinitro-1,3,5-triazinane (RDX) still represents a major challenge for the energetic materials and physical (organic) chemistry communities mainly because multiple competing dissociation channels are likely involved and previous detection methods of the products are not isomer selective. In this study we exploited a microsecond pulsed infrared laser to decompose thin RDX films at 5 K under mild conditions to limit the fragmentation channels. The subliming decomposition products during the temperature programed desorption phase are detected using isomer selective single photoionization time-of-flight mass spectrometry (PI-ReTOF-MS). This technique enables us to assign a product signal at m/z=42 to ketene (H2CCO), but not to diazomethane (H2CNN; 42 amu) as speculated previously. Electronic structure calculations support our experimental observations and unravel the decomposition mechanisms of RDX leading eventually to the elusive ketene (H2CCO) via an exotic, four-membered ring intermediate. This study highlights the necessity to exploit isomer-selective detection schemes to probe the true decomposition products of nitramine-based energetic materials. 相似文献
107.
Deemed as poorly represented in nature, aurones have been often overlooked by researchers compared to other members of the flavonoid superfamily. However, over the past two decades, they have been reassessed by the scientific community, who are increasingly appreciating their ability to modulate several biological pathways. This review summarizes the recent literature on this class of compounds, which has been analyzed from both a chemical and a functional point of view. Original articles, reviews and editorials featured in Pubmed and Scifinder over the last twenty years have been taken into account to provide the readers with a view of the chemical strategies to obtain them, their functional properties, and their potential of technological use. The resulting comprehensive picture aims at raising the awareness of these natural derivatives as effective drug candidates, fostering the development of novel synthetic analogues. 相似文献
108.
The European Physical Journal H - The widespread positivist approach of physics research in Italy at the turn of the XIX and XX centuries did not provide a fertile ground for the scientific debate... 相似文献
109.
Ratios for target Ar K-shell ionization associated with single and double electron capture, as well as the ratios corresponding to total capture and the projectile K x rays, were determined for 1.8- to 2.2-MeV/u F7 + ,8 + ,9+ projectiles. This work was performed at Western Michigan University with the tandem Van de Graaff accelerator. Coincidences between emitted K-shell X-rays (both target and projectile) and the corresponding charge-changed particles were observed. The F9+ Ar K X-ray coincidence ratios for double to single capture are found to well exceed unity over the limited energy range of the measurements. Possible explanations for this anomalous behavior are discussed. 相似文献
110.
DFT calculations have been carried out to describe the pathway of a sodium ion along the stacking direction of a tubular structure set up by five cyclopeptidic units, which can be considered a suitable model of a hollow tubular structure of indefinite length. A lattice of points inside the tubular structure is defined and the DFT interaction energy values with a sodium ion are obtained. The data allow predicting a zigzag path of the ion inside the hosting structure. 相似文献