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121.
Insights into the AIEE of 1,8‐Naphthalimides (NPIs): Inverse Effects of Intermolecular Interactions in Solution and Aggregates
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Sanjoy Mukherjee Prof. Dr. Pakkirisamy Thilagar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8012-8023
Systematic structural perturbation has been used to fine‐tune and understand the luminescence properties of three new 1,8‐naphthalimides (NPIs) in solution and aggregates. The NPIs show blue emission in the solution state and their fluorescence quantum yields are dependent upon their molecular rigidity. In concentrated solutions of the NPIs, intermolecular interactions were found to quench the fluorescence due to the formation of excimers. In contrast, upon aggregation (in THF / H2O mixtures), the NPIs show aggregation‐induced emission enhancement (AIEE). The NPIs also show moderately high solid‐state emission quantum yields (ca. 10–12.7 %). The AIEE behaviour of the NPIs depends on their molecular rigidity and the nature of their intermolecular interactions. The NPIs 1 – 3 show different extents of intermolecular (π–π and C?H???O) interactions in their solid‐state crystal structures depending on their substituents. Detailed photophysical, computational and structural investigations suggest that an optimal balance of structural flexibility and intermolecular communication is necessary for achieving AIEE characteristics in these NPIs. 相似文献
122.
Sanjoy Mukherjee Prof. Dr. Pakkirisamy Thilagar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):9052-9062
Three new NPI–BODIPY dyads 1 – 3 (NPI=1,8‐naphthalimide, BODIPY=boron‐dipyrromethene) were synthesized, characterized, and studied. The NPI and BODIPY moieties in these dyads are electronically separated by oxoaryl bridges, and the compounds only differ structurally with respect to methyl substituents on the BODIPY fluorophore. The NPI and BODIPY moieties retain their optical features in molecular dyads 1 – 3 . Dyads 1–3 show dual emission in solution originating from the two separate fluorescent units. The variations of the dual emission in these compounds are controlled by the structural flexibilities of the systems. Dyads 1 – 3 , depending on their molecular flexibilities, show considerably different spectral shapes and dissimilar intensity ratios of the two emission bands. The dyads also show significant aggregation‐induced emission switching (AIES) on formation of nano‐aggregates in THF/H2O with changes in emission color from green to red. Whereas the flexible and aggregation‐prone compound 1 shows AIES, rigid systems with less favorable intermolecular interactions (i.e., 2 and 3 ) show aggregation‐induced quenching of emission. Correlations of the emission intensity and structural flexibility were found to be reversed in solution and aggregated states. Photophysical and structural investigations suggested that intermolecular interactions (e.g., π–π stacking) play a major role in controlling the emission of these compounds in the aggregated state. 相似文献
123.
Rational Design and Identification of a Non‐Peptidic Aggregation Inhibitor of Amyloid‐β Based on a Pharmacophore Motif Obtained from cyclo[‐Lys‐Leu‐Val‐Phe‐Phe‐]
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Tadamasa Arai Takushi Araya Dr. Daisuke Sasaki Dr. Atsuhiko Taniguchi Dr. Takeshi Sato Dr. Youhei Sohma Prof. Motomu Kanai 《Angewandte Chemie (International ed. in English)》2014,53(31):8236-8239
Inhibition of pathogenic protein aggregation may be an important and straightforward therapeutic strategy for curing amyloid diseases. Small‐molecule aggregation inhibitors of Alzheimer’s amyloid‐β (Aβ) are extremely scarce, however, and are mainly restricted to dye‐ and polyphenol‐type compounds that lack drug‐likeness. Based on the structure‐activity relationship of cyclic Aβ16–20 (cyclo‐[KLVFF]), we identified unique pharmacophore motifs comprising side‐chains of Leu2, Val3, Phe4, and Phe5 residues without involvement of the backbone amide bonds to inhibit Aβ aggregation. This finding allowed us to design non‐peptidic, small‐molecule aggregation inhibitors that possess potent activity. These molecules are the first successful non‐peptidic, small‐molecule aggregation inhibitors of amyloids based on rational molecular design. 相似文献
124.
Joseph J. Chen Dr. Martin Hürlimann Dr. Jeffrey Paulsen Dr. Denise Freed Dr. Soumyajit Mandal Dr. Yi‐Qiao Song 《Chemphyschem》2014,15(13):2676-2681
Crude oils, which are complex mixtures of hydrocarbons, can be characterized by nuclear magnetic resonace diffusion and relaxation methods to yield physical properties and chemical compositions. In particular, the field dependence, or dispersion, of T1 relaxation can be used to investigate the presence and dynamics of asphaltenes, the large molecules primarily responsible for the high viscosity in heavy crudes. However, the T2 relaxation dispersion of crude oils, which provides additional insight when measured alongside T1, has yet to be investigated systematically. Here we present the field dependence of T1‐T2 correlations of several crude oils with disparate densities. While asphaltene and resin‐containing crude oils exhibit significant T1 dispersion, minimal T2 dispersion is seen in all oils. This contrasting behavior between T1 and T2 cannot result from random molecular motions, and thus, we attribute our dispersion results to highly correlated molecular dynamics in asphaltene‐containing crude oils. 相似文献
125.
César R. García-Jacas Yovani Marrero-Ponce Ricardo Vivas-Reyes José Suárez-Lezcano Felix Martinez-Rios Julio E. Terán Longendri Aguilera-Mendoza 《Journal of computational chemistry》2020,41(12):1209-1227
Advances to the distributed, multi-core and fully cross-platform QuBiLS-MIDAS software v2.0 ( http://tomocomd.com/qubils-midas ) are reported in this article since the v1.0 release. The QuBiLS-MIDAS software is the only one that computes atom-pair and alignment-free geometrical MDs (3D-MDs) from several distance metrics other than the Euclidean distance, as well as alignment-free 3D-MDs that codify structural information regarding the relations among three and four atoms of a molecule. The most recent features added to the QuBiLS-MIDAS software v2.0 are related (a) to the calculation of atomic weightings from indices based on the vertex-degree invariant (e.g., Alikhanidi index); (b) to consider central chirality during the molecular encoding; (c) to use measures based on clustering methods and statistical functions to codify structural information among more than two atoms; (d) to the use of a novel method based on fuzzy membership functions to spherically truncate inter-atomic relations; and (e) to the use of weighted and fuzzy aggregation operators to compute global 3D-MDs according to the importance and/or interrelation of the atoms of a molecule during the molecular encoding. Moreover, a novel module to compute QuBiLS-MIDAS 3D-MDs from their headings was also developed. This module can be used either by the graphical user interface or by means of the software library. By using the library, both the predictive models built with the QuBiLS-MIDAS 3D-MDs and the QuBiLS-MIDAS 3D-MDs calculation can be embedded in other tools. A set of predefined QuBiLS-MIDAS 3D-MDs with high information content and low redundancy on a set comprised of 20,469 compounds is also provided to be employed in further cheminformatics tasks. This set of predefined 3D-MDs evidenced better performance than all the universe of Dragon (v5.5) and PaDEL 0D-to-3D MDs in variability studies, whereas a linear independence study proved that these QuBiLS-MIDAS 3D-MDs codify chemical information orthogonal to the Dragon 0D-to-3D MDs. This set of predefined 3D-MDs would be periodically updated as long as new results be achieved. In general, this report highlights our continued efforts to provide a better tool for a most suitable characterization of compounds, and in this way, to contribute to obtaining better outcomes in future applications. 相似文献
126.
127.
Bart W. H. Saes Dr. Martijn M. Wienk Prof. René A. J. Janssen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(62):14221-14228
Introducing solubilizing α-branched alkyl chains on a poly(diketopyrrolopyrrole-alt-terthiophene) results in a dramatic change of the structural, optical, and electronic properties compared to the isomeric polymer carrying β-branched alkyl side chains. When branched at the α-position the alkyl substituent creates a steric hindrance that reduces the tendency of the polymer to π–π stack and endows the material with a much higher solubility in common organic solvents. The wider π–π stacking and reduced tendency to crystallize, evidenced from grazing-incidence wide-angle X-ray scattering, result in a wider optical band gap in the solid state. In solar cells with a fullerene acceptor, the α-branched isomer affords a higher open-circuit voltage, but an overall lower power conversion efficiency as a result of a too well-mixed nanomorphology. Due its reduced π–π stacking, the α-branched isomer fluoresces and affords near-infrared light-emitting diodes emitting at 820 nm. 相似文献
128.
Mengmeng Li Haijun Bin Xuechen Jiao Martijn M. Wienk He Yan Ren A. J. Janssen 《Angewandte Chemie (International ed. in English)》2020,59(2):846-852
It remains a challenge to precisely tailor the morphology of polymer monolayers to control charge transport. Herein, the effect of the dissolution temperature (Tdis) is investigated as a powerful strategy for morphology control. Low Tdis values cause extended polymer aggregation in solution and induce larger nanofibrils in a monolayer network with more pronounced π–π stacking. The field‐effect mobility of the corresponding monolayer transistors is significantly enhanced by a factor of four compared to devices obtained from high Tdis with a value approaching 1 cm2 V?1 s?1. Besides that, the solution kinetics reveal a higher growth rate of aggregates at low Tdis, and filtration experiments further confirm that the dependence of the fibril width in monolayers on Tdis is consistent with the aggregate size in solution. The generalizability of the Tdis effect on polymer aggregation is demonstrated using three other conjugated polymer systems. These results open new avenues for the precise control of polymer aggregation for high‐mobility monolayer transistors. 相似文献
129.
Yunyu Sun Mingcheng Yang Yutong Guo Mengjiao Cheng Bin Dong Feng Shi 《Angewandte Chemie (International ed. in English)》2020,59(3):1098-1102
Light‐driven micropumps, which are based on electro‐osmosis with the electric field generated by photocatalytic reactions, are among most attractive research topics in chemical micromotors. Until now, research in this field has mainly been focused on the directional motion or collective behavior of microparticles, which lack practical applications. In this study, we have developed a photowelding strategy for repeated photoinduced conductivity recovery of cracked flexible circuits. We immersed the circuit in a suspension of conductive healing particles and applied photoillumination to the crack; photocatalysis of a predeposited pentacene (PEN) layer triggered electro‐osmotic effects to gather conductive particles at the crack, thus leading to conductivity recovery of the circuit. This photowelding strategy is a novel application of light‐driven micropumps and photocatalysis for conductivity restoration. 相似文献
130.
Marco Deiana Karam Chand Jan Jamroskovic Ikenna Obi Erik Chorell Nasim Sabouri 《Angewandte Chemie (International ed. in English)》2020,59(2):896-902
The design of turn‐on dyes with optical signals sensitive to the formation of supramolecular structures provides fascinating and underexplored opportunities for G‐quadruplex (G4) DNA detection and characterization. Here, we show a new switching mechanism that relies on the recognition‐driven disaggregation (on‐signal) of an ultrabright coumarin‐quinazoline conjugate. The synthesized probe selectively lights‐up parallel G4 DNA structures via the disassembly of its supramolecular state, demonstrating outputs that are easily integrable into a label‐free molecular logic system. Finally, our molecule preferentially stains the G4‐rich nucleoli of cancer cells. 相似文献