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481.
Observation of superconductivity in a single layer of Pb on the (111) surface of bulk silicon has renewed interest in a longstanding question; can superconductivity persist to the ultimate atomic limit? Using first-principles techniques, we investigate the total electron-phonon coupling in monolayer Pb supported by a Si(111) substrate. Our ultra-fine sampling of the electronic structure, lattice dynamics and electron-phonon matrix elements in the nearly two-dimensional Brillouin zone yields a total electron-phonon coupling parameter which explains the experimentally observed superconducting transition temperature of 1.83 K [T. Zhang, et al., Nat. Phys. 6 (2010) 104]. The observed suppression of the superconducting transition temperature from the bulk value of 7.2 K is found to arise from the interplay of reduced electron-phonon matrix elements and a modification of the lattice dynamics resulting from the Pb-Si bonding. 相似文献
482.
Brian R. Hirshman Jesse St. Charles Kathleen M. Carley 《Computational & Mathematical Organization Theory》2011,17(4):318-343
Substantial evidence indicates that our social networks are divided into tiers in which people have a few very close social
support group, a larger set of friends, and a much larger number of relatively distant acquaintances. Because homophily—the
principle that like seeks like—has been suggested as a mechanism by which people interact, it may also provide a mechanism
that generates such frequencies and distributions. However, our multi-agent simulation tool, Construct, suggests that a slight
supplement to a knowledge homophily model—the inclusion of several highly salient personal facts that are infrequently shared—can
more successfully lead to the tiering behavior often observed in human networks than a simplistic homophily model. Our findings
imply that homophily on both general and personal facts is necessary in order to achieve realistic frequencies of interaction
and distributions of interaction partners. Implications of the model are discussed, and recommendations are provided for simulation
designers seeking to use homophily models to explain human interaction patterns. 相似文献
483.
Walvoort MT de Witte W van Dijk J Dinkelaar J Lodder G Overkleeft HS Codée JD van der Marel GA 《Organic letters》2011,13(16):4360-4363
The reactivity of a variety of mannopyranosyl uronic acid donors was assessed in a set of competition experiments, in which two (S)-tolyl mannosyl donors were made to compete for a limited amount of promoter (NIS/TfOH). These experiments revealed that the reactivity of mannuronic acid donors is significantly higher than expected based on the electron-withdrawing capacity of the C-5 carboxylic acid ester function. A 4-O-acetyl-β-(S)-tolyl mannuronic acid donor was found to have similar reactivity as per-O-benzyl-α-(S)-tolyl mannose. 相似文献
484.
We report gas-phase electronic photodissociation spectra of the undercoordinated bromoiridate complexes IrBr(4)(-) and IrBr(5)(-) at photon energies from 1 to 5.6 eV. Both ions have open-shell ground states with low-symmetry structures. The fragmentation is characterized by thresholds for the loss of one Br atom for IrBr(4)(-) and one or two Br atoms for IrBr(5)(-). The experimental spectra consist of ligand-to-metal charge transfer transitions and reveal a large density of electronic states that can be recovered by time-dependent density functional theory. 相似文献
485.
Dr. Jesse J. Sabatini Dr. Jared D. Moretti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12839-12845
Prototype testing of perchlorate‐free hand‐held signal illuminants for the US Army’s M126 A1 red‐star and M195 green‐star parachute illuminants are described. Although previous perchlorate‐free variants for these items have been developed based on high‐nitrogen compounds that are not readily available, the new formulations consist of anhydrous 5‐aminotetrazole as the suitable perchlorate replacement. Compared to the perchlorate‐containing control, the disclosed illuminants exhibited excellent stabilities toward various ignition stimuli and had excellent pyrotechnic performance. The illuminants are important from both military and civil fireworks perspectives, as the perchlorate‐free nature of the illuminants adequately address environmental concerns associated with perchlorate‐containing red‐ and green‐light‐emitting illuminants. 相似文献
486.
Manuel J. Llansola‐Portoles Jesse J. Bergkamp John Tomlin Thomas A. Moore Gerdenis Kodis Ana L. Moore Gonzalo Cosa Rodrigo E. Palacios 《Photochemistry and photobiology》2013,89(6):1375-1382
The photosensitization effect of three perylene dye derivatives on titanium dioxide nanoparticles (TiO2 NPs) has been investigated. The dyes used, 1,7‐dibromoperylene‐3,4,9,10‐tetracarboxy dianhydride (1), 1,7‐dipyrrolidinylperylene‐3,4,9,10‐tetracarboxy dianhydride (2) and 1,7‐bis(4‐tert‐butylphenyloxy)perylene‐3,4,9,10‐tetracarboxy dianhydride (3) have in common bisanhydride groups that convert into TiO2 binding groups upon hydrolysis. The different substituents on the bay position of the dyes enable tuning of their redox properties to yield significantly different driving forces for photoinduced electron transfer (PeT). Recently developed TiO2 NPs having a small average size and a narrow distribution (4 ± 1 nm) are used in this work to prepare the dye‐TiO2 systems under study. Whereas successful sensitization was obtained with 1 and 2 as evidenced by steady‐state spectral shifts and transient absorption results, no evidence for the attachment of 3 to TiO2 was observed. The comparison of the rates of PeT (kPeT) for 1‐ and 2‐TiO2 systems studied in this work with those obtained for previously reported analogous systems, having TiO2 NPs covered by a surfactant layer (Hernandez et al. [2012] J. Phys. Chem. B., 117, 4568–4581), indicates that kPeT for the former systems is slower than that for the later. These results are interpreted in terms of the different energy values of the conduction band edge in each system. 相似文献
487.
Badwaik VD Bartonojo JJ Evans JW Sahi SV Willis CB Dakshinamurthy R 《Langmuir : the ACS journal of surfaces and colloids》2011,27(9):5549-5554
There is an increased interest in understanding the toxicity and rational design of gold nanoparticles (GNPs) for biomedical applications in recent years. Such efforts warrant reliable, viable, and biofriendly synthetic methodology for GNPs with homogeneous sizes and shapes, particularly sizes above 30 nm, which is currently challenging. In the present study, an environmentally benign, biofriendly, single-step/single-phase synthetic method using dextrose as a reducing and capping agent in a buffered aqueous solution at moderate temperature is introduced. The resulting GNPs are near-spherical, stable, catalytically active, place exchangeable, and water-soluble within the size range of 10-120 nm. The added advantage of the biologically friendly reaction medium employed in this new synthetic approach provides a method for the direct embedment/integration of GNPs into biological systems such as the E. coli bacterium without additional capping ligand or surface modification processes. 相似文献
488.
The paper presents an experimental study and a 0D dynamic modeling of a biomass boiler based on the Bond Graph formalism from mass and energy balance. The biomass boiler investigated in this study is an automatic pellet boiler with a nominal power of 30 kW with a fixed bed. The balances allow to model as time function the flue gas enthalpy flux variation and the thermal transfers between the flue gas and the walls of the boiler subsystems. The main objective is to build a model to represent the dynamic thermal behavior of the boiler. Indeed, small domestic boilers have discontinuous operating phases when the set temperature is reached. The global thermal transfer coefficients for the boiler subsystems are obtained according to an iterative calculation by inverse method. The boiler has an average efficiency of 67.5% under our operating conditions and the radiation is the dominant thermal transfer by reaching 97.6% of the total thermal transfers inside the combustion chamber. The understanding of the dynamic behavior of the boiler during the operating phases allows to evaluate its energy performances. The proposed model is both stimulated and validated using experimental results carried out on the boiler. 相似文献
489.
Clark AJ Calvillo JL Roosa MS Green DB Ganske JA 《Analytical and bioanalytical chemistry》2011,399(10):3589-3600
Volatile organic compounds emitted from a several decade series of bound periodicals (1859–1939) printed on ground wood paper,
as well as historical books dating from the 1500s to early 1800s made from cotton/linen rag, were studied using an improved
headspace SPME/GC–MS method. The headspace over the naturally aging books, stored upright in glass chambers, was monitored
over a 24-h period, enabling the identification of a wide range of organic compounds emanating from the whole of the book.
The detection of particular straight chain aldehydes, as well as characteristic alcohols, alkenes and ketones is correlated
with oxidative degradation of the C18 fatty acid constituency of paper. The relative importance of hydrolytic and oxidative chemistry involved in paper aging in
books published between 1560 and 1939 was examined by comparing the relative abundances of furfural (FUR) a known cellulose
hydrolysis product, and straight chain aldehydes (SCA) produced from the oxidation of fatty acids in paper. The relative abundance
of furfural is shown to increase across the 379-year publication time span. A comparison of relative SCA peak areas across
the series of books examined reveals that SCA emission is more important in the cotton/linen rag books than in the ground
wood books. 相似文献
490.
Dr. Zhicheng Jin Yi Li Dr. Ke Li Dr. Jiajing Zhou Justin Yeung Chuxuan Ling Wonjun Yim Tengyu He Dr. Yong Cheng Dr. Ming Xu Matthew N. Creyer Yu-Ci Chang Dr. Pavla Fajtová Dr. Maurice Retout Baiyan Qi Prof. Shuzhou Li Prof. Anthony J. O'Donoghue Prof. Jesse V. Jokerst 《Angewandte Chemie (International ed. in English)》2023,62(4):e202214394
Aromatic interactions are commonly involved in the assembly of naturally occurring building blocks, and these interactions can be replicated in an artificial setting to produce functional materials. Here we describe a colorimetric biosensor using co-assembly experiments with plasmonic gold and surfactant-like peptides (SLPs) spanning a wide range of aromatic residues, polar stretches, and interfacial affinities. The SLPs programmed in DDD−(ZZ)x−FFPC self-assemble into higher-order structures in response to a protease and subsequently modulate the colloidal dispersity of gold leading to a colorimetric readout. Results show the strong aggregation propensity of the FFPC tail without polar DDD head. The SLPs were specific to the target protease, i.e., Mpro, a biomarker for SARS-CoV-2. This system is a simple and visual tool that senses Mpro in phosphate buffer, exhaled breath condensate, and saliva with detection limits of 15.7, 20.8, and 26.1 nM, respectively. These results may have value in designing other protease testing methods. 相似文献