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41.
A p‐Hydroxyphenacyl–Benzothiazole–Chlorambucil Conjugate as a Real‐Time‐Monitoring Drug‐Delivery System Assisted by Excited‐State Intramolecular Proton Transfer
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Shrabani Barman Sourav K. Mukhopadhyay Sandipan Biswas Surajit Nandi Moumita Gangopadhyay Satyahari Dey Anakuthil Anoop N. D. Pradeep Singh 《Angewandte Chemie (International ed. in English)》2016,55(13):4194-4198
Among the well‐known phototriggers, the p‐hydroxyphenacyl (pHP) group has consistently enabled the very fast, efficient, and high‐conversion release of active molecules. Despite this unique behavior, the pHP group has been ignored as a delivery agent, particularly in the area of theranostics, because of two major limitations: Its excitation wavelength is below 400 nm, and it is nonfluorescent. We have overcome these limitations by incorporating a 2‐(2′‐hydroxyphenyl)benzothiazole (HBT) appendage capable of rapid excited‐state intramolecular proton transfer (ESIPT). The ESIPT effect also provided two unique advantages: It assisted the deprotonation of the pHP group for faster release, and it was accompanied by a distinct fluorescence color change upon photorelease. In vitro studies showed that the p‐hydroxyphenacyl–benzothiazole–chlorambucil conjugate presents excellent properties, such as real‐time monitoring, photoregulated drug delivery, and biocompatibility. 相似文献
42.
T. Pradeep B. Feng T. Ast J. S. Patrick R. G. Cooks S. J. Pachuta 《Journal of the American Society for Mass Spectrometry》1995,6(3):187-194
Reactive collisions of low energy (<100-eV) mass-selected ions are used to chemically modify fluorinated self-assembled monolayer surfaces comprised of alkanethiolate chains CF3(CF2)11(CH2)2S— bound to Au. Typical experiments were done by using 1-nA/cm2 beams and submonolayer doses of reactant ions. Characterization of the modified surface was achieved by in situ chemical sputtering (60-eV Xe+·) and by independent high mass resolution time-of-flight-secondary ionization mass spectrometry (TOF-SIMS) (15–25-keV, Ga+) experiments. Treatment with Si35C1 4 +· produced a surface from which Xe+ sputtering liberated CF2 35C1+ ions, which suggested Cl-for-F halogen exchange at the surface. Isotopic labeling studies that used Si35Cl2 37Cl 2 +· ; and experiments with bromine-containing and iodine-containing projectiles, confirmed this reaction. High mass resolution TOF-SIMS spectra, as well as high spatial resolution images, provided further evidence as to the existence of halogen-exchanged species at the bombarded surface. Analogous Cl-for-F halogen substitution was observed in a model gas-phase reaction. The ion-surface reaction is suggested to proceed through an intermediate fluoronium ion in which the projectile is bonded to the target molecule. The most significant conclusion of the study is that selective chemical modification of monolayer surfaces can be achieved by using reactive ion beams, which lead to new covalent bonds at the surface and in the scattered ions. 相似文献
43.
Pradeep R. Varadwaj Arpita Varadwaj Helder M. Marques Koichi Yamashita 《Molecules (Basel, Switzerland)》2022,27(5)
The phosphorus bond in chemical systems, which is an inter- or intramolecular noncovalent interaction, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a covalently or coordinately bonded phosphorus atom in a molecular entity and a nucleophile in another, or the same, molecular entity. It is the second member of the family of pnictogen bonds, formed by the second member of the pnictogen family of the periodic table. In this overview, we provide the reader with a snapshot of the nature, and possible occurrences, of phosphorus-centered pnictogen bonding in illustrative chemical crystal systems drawn from the ICSD (Inorganic Crystal Structure Database) and CSD (Cambridge Structural Database) databases, some of which date back to the latter part of the last century. The illustrative systems discussed are expected to assist as a guide to researchers in rationalizing phosphorus-centered pnictogen bonding in the rational design of molecular complexes, crystals, and materials and their subsequent characterization. 相似文献
44.
45.
Manohar Mahato Gaurav Rana Pradeep Kumar Ashwani Kumar Sharma 《Journal of polymer science. Part A, Polymer chemistry》2012,50(12):2344-2355
Highly toxic polyallylamine (PA) was reacted with a varying amount of a novel linker, 6‐(N,N,N′,N′‐tetramethylguanidinium chloride) hexanoic acid (Tmg‐HA), to prepare a series of tetramethylguanidinium‐PA (Tmg‐PA) polymers, which were used as vectors for gene transfection. The extent of attachment of the linker, Tmg‐HA, to the PA backbone was determined by 2,4,6‐trinitrobenzene sulfonic acid assay. The modified polymers (Tmg‐PAs), when complexed with pDNA, exhibited good condensation ability. The nanoparticles, so formed, were characterized by their size and zeta potential and were subsequently evaluated for their toxicity and transfection ability on various mammalian cells, viz., HeLa, CHO, and HEK 293 cells. Mobility shift assay revealed that on increasing the percent substitution of Tmg‐HA onto PA (from Tmg‐PA1 to Tmg‐PA6), relatively higher amounts of modified polymers were required to retard the mobility of a fixed amount of DNA. Besides, Tmg‐PA polymers provided sufficient protection (ca. 84–88%) to bound DNA against nucleases and one of the formulations, Tmg‐PA2 (ca. 15% substitution) displayed the highest transfection efficiency outcompeting the commercial transfection reagent, Lipofectamine? with minimal cytotoxicity. More impressively, the transfection efficiency increased despite recording a decrease in the buffering capacity of the grafted polymers suggesting that buffering capacity is not the sole parameter in determining the gene delivery efficiency of a vector system. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
46.
New metal-carbon clusters, M4C9
+ (M = Ti, V), generated using a combined thermal arc discharge evaporation set-up, have been studied with quadrupole mass
spectrometry. Reactivities of these clusters have been investigated by means of association reactions with H2O. Metal-carbon clusters of other compositions have also been studied. We speculate on the mechanism of formation of larger
metal-carbon clusters. 相似文献
47.
In this paper we explore the relation between information patterns and Nash Equilibria in extensive games. By information we mean what players know about moves made by others, as well as by chance. For the most part we confine ourselves to pure strategies. But in Section 2 behavioral strategies are also examined. It turns out that they can be modeled as pure strategies of an appropriately enlarged game. Our results, applied to the enlarged game, can then be reinterpreted in terms of the behavioral strategies of the original game. 相似文献
48.
We report an optical tweezers based approach for efficient and controlled manipulation of neuronal growth cones. The approach exploits asymmetric transverse gradient force created in a line optical tweezers to transport actin monomers in the desired growth direction. With this approach induction of artificial growth cones from the neuronal cell body and enhancement of the growth rate of the natural growth cones have been achieved. The use of this approach to bring two growth cones into close proximity for establishing a neuronal connection is also discussed. 相似文献
49.
Superlubricity of graphite 总被引:1,自引:0,他引:1
Dienwiebel M Verhoeven GS Pradeep N Frenken JW Heimberg JA Zandbergen HW 《Physical review letters》2004,92(12):126101
Using a home-built frictional force microscope that is able to detect forces in three dimensions with a lateral force resolution down to 15 pN, we have studied the energy dissipation between a tungsten tip sliding over a graphite surface in dry contact. By measuring atomic-scale friction as a function of the rotational angle between two contacting bodies, we show that the origin of the ultralow friction of graphite lies in the incommensurability between rotated graphite layers, an effect proposed under the name of "superlubricity" [Phys. Rev. B 41, 11 837 (1990)]]. 相似文献
50.
Model for heat conduction in nanofluids 总被引:1,自引:0,他引:1
Kumar DH Patel HE Kumar VR Sundararajan T Pradeep T Das SK 《Physical review letters》2004,93(14):144301
A comprehensive model has been proposed to account for the large enhancement of thermal conductivity in nanofluids and its strong temperature dependence, which the classical Maxwellian theory has been unable to explain. The dependence of thermal conductivity on particle size, concentration, and temperature has been taken care of simultaneously in our treatment. While the geometrical effect of an increase in surface area with a decrease in particle size, rationalized using a stationary particle model, accounts for the conductivity enhancement, a moving particle model developed from the Stokes-Einstein formula explains the temperature effect. Predictions from the combined model agree with the experimentally observed values of conductivity enhancement of nanofluids. 相似文献