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181.
Dr. Andrew M. White Dr. Simon J. de Veer Guojie Wu Dr. Peta J. Harvey Kuok Yap Dr. Gordon J. King Dr. Joakim E. Swedberg Dr. Conan K. Wang Dr. Ruby H. P. Law Dr. Thomas Durek Prof. David J. Craik 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11369-11373
Ruthenium-catalysed azide–alkyne cycloaddition (RuAAC) provides access to 1,5-disubstituted 1,2,3-triazole motifs in peptide engineering applications. However, investigation of this motif as a disulfide mimetic in cyclic peptides has been limited, and the structural consequences remain to be studied. We report synthetic strategies to install various triazole linkages into cyclic peptides through backbone cyclisation and RuAAC cross-linking reactions. These linkages were evaluated in four serine protease inhibitors based on sunflower trypsin inhibitor-1. NMR and X-ray crystallography revealed exceptional consensus of bridging distance and backbone conformations (RMSD<0.5 Å) of the triazole linkages compared to the parent disulfide molecules. The triazole-bridged peptides also displayed superior half-lives in liver S9 stability assays compared to disulfide-bridged peptides. This work establishes a foundation for the application of 1,5-disubstituted 1,2,3-triazoles as disulfide mimetics. 相似文献
182.
183.
Expanding reaction fronts are central to many terrestrial processes as well as such cosmic phenomena as the thermonuclear combustion in supernovae. While in terrestrial conditions the effect of intrinsic flamefront instabilities is generally believed to be supplementary to, say, external turbulence and chamber dynamics, at the astrophysical scale the role of flamefront instabilities in the flame acceleration is presumably dominant. Moreover, while in terrestrial systems we focus mainly on the hydrodynamic, Darrieus–Landau (DL) instability, the Rayleigh–Taylor (RT), body-force instability could be a key issue for astrophysical flames because of the enormous gravity and the associated large scales. Consequently, if RT effects dominate over DL effects, the globally-spherical flamefront can be replaced by an expanding bubble with a non-spherical shape, possibly that of digit “8”. In the present work we have developed a self-similar formulation describing a globally-spherical expanding flamefront corrugated due to the DL instability in a central gravitation field. The associated scenario of the flame acceleration, the evolution of the upstream flow, and the instant when a gas parcel ahead of the flamefront first explodes, hence initiating the deflagration-to-detonation transition (DDT), as well as the radial coordinate of this parcel, are determined. We have also compared the effects of DL and RT instabilities, estimating whether a globally-spherical, DL-corrugated flamefront is subsequently terminated by the formation of RT bubbles. It is shown how the instant of such a transition and the relevant global flame radius are coupled to various flame and flow parameters. 相似文献
184.
He S Li H Yip YW Yeung CT Fung YO Kong HK Yeung HL Law GL Wong KL Lee CS Lam MH Murphy MB Lam PK Wong WT 《Organic letters》2011,13(19):5036-5039
A water-soluble europium(III) complex (1) has been synthesized and demonstrated to be a specific fluorescence probe for the paralytic shellfish toxin saxitoxin, a neurotoxin that blocks the voltage-gated sodium channels on cell membranes. Saxitoxin binds to the europium complex (K(B) = 6.1 × 10(4) M(-1)) and triggers a two-photon induced f-f emission enhancement by over 100% and increases the two-photon absorption cross-section from 9 to 36 GM. 相似文献
185.
Fung YO Wu W Yeung CT Kong HK Wong KK Lo WS Law GL Wong KL Lau CK Lee CS Wong WT 《Inorganic chemistry》2011,50(12):5517-5525
Two series of dimeric DO3A (1,4,7,10-tetraazacyclodecane-1,4,7-triacetate) lanthanide complexes (LnL(1)-LnL(2), Ln = Eu, Gd, and Tb) have been synthesized with two different bridged chromophores. The X-ray structures of dimeric LnL(1) (Ln = Gd and Tb) complexes show that each metal ion has nine coordination numbers with eight directly bound donor atoms of the ligand and one oxygen donor from the water molecule. Photophysical measurements indicate that the bridged antenna in LnL(2) gives a higher efficiency than that of LnL(1) and is responsive to the protein Human Serum Albumin (HSA), giving an f-f luminescence signal enhancement with a binding constant log K = 4.84. In vitro imaging of EuL(1) and EuL(2) in HeLa cells has been recorded, and EuL(2) has demonstrated a higher rate of cellular uptake and low cytotoxicity (IC(50) = 3 mM). 相似文献
186.
187.
Song T Hao Q Law CH Siu CK Chu IK 《Journal of the American Society for Mass Spectrometry》2012,23(2):264-273
In this study, we observed unprecedented cleavages of the Cβ–Cγ bonds of tryptophan residue side chains in a series of hydrogen-deficient tryptophan-containing peptide radical cations (M•+) during low-energy collision-induced dissociation (CID). We used CID experiments and theoretical density functional theory
(DFT) calculations to study the mechanism of this bond cleavage, which forms [M – 116]+ ions. The formation of an α-carbon radical intermediate at the tryptophan residue for the subsequent Cβ–Cγ bond cleavage is analogous to that occurring at leucine residues, producing the same product ions; this hypothesis was supported
by the identical product ion spectra of [LGGGH – 43]+ and [WGGGH – 116]+, obtained from the CID of [LGGGH]•+ and [WGGGH]•+, respectively. Elimination of the neutral 116-Da radical requires inevitable dehydrogenation of the indole nitrogen atom,
leaving the radical centered formally on the indole nitrogen atom ([Ind]•-2), in agreement with the CID data for [WGGGH]•+ and [W1-CH3GGGH]•+; replacing the tryptophan residue with a 1-methyltryptophan residue results in a change of the base peak from that arising
from a neutral radical loss (116 Da) to that arising from a molecule loss (131 Da), both originating from Cβ–Cγ bond cleavage. Hydrogen atom transfer or proton transfer to the γ-carbon atom of the tryptophan residue weakens the Cβ–Cγ bond and, therefore, decreases the dissociation energy barrier dramatically. 相似文献
188.
Diabetes is an increasing public health problem that is expected to escalate in the future due to the growing incidence of obesity in the western world. While this disease is well known for its devastating effects on the kidneys and vascular system, diabetic individuals can develop cardiac dysfunction, termed diabetic cardiomyopathy, in the absence of other cardiovascular risk factors such as hypertension or atherosclerosis. While much effort has gone into understanding the effects of elevated glucose or altered insulin sensitivity on cellular components within the heart, significant changes in the cardiac extracellular matrix (ECM) have also been noted. In this review article we highlight what is currently known regarding the effects diabetes has on both the expression and chemical modification of proteins within the ECM and how the fibrotic response often observed as a consequence of this disease can contribute to reduced cardiac function. 相似文献
189.
The formation of a C‐N bond via the cross‐couplings of aryl iodides with azoles, aryl amine, and amides can be successfully achieved in decent yield by the utilization of both [Cu 8(H){S2P(OiPr)2}6]+ and [Cu8{S2P(OEt)2}6]2+ as the pre‐catalysts. 相似文献
190.
Beric?SkewsEmail author Craig?Law Adam?Muritala Sebastian?Bode 《Experiments in fluids》2012,52(2):417-424
All previous studies on shock wave diffraction in shock tubes have spatial and temporal limitations due to the size of the
test sections. These limitations result from either the reflection of the expansion wave, generated at the corner, from the
top wall and/or of the reflection of the incident diffracted shock from the bottom wall of the test section passing back through
the region of interest. This has limited the study of the evolution of the shear layer and its associated vortex, which forms
a relatively small region of the flow behind the shock with an extent of only a few centimeters, and yet is a region of significant
interest. A special shock tube is used in the current tests which allow evolution of the flow to be examined at a scale about
an order of magnitude larger than in previously published results, with shear layer lengths of up to 250 mm being achieved
without interference from adjacent walls. Tests are presented for incident shock wave Mach numbers of nominally 1.3–1.5. Studies
have been undertaken with wall angles of 10, 20, 30 and 90°. Significant changes are noted as the spatial and temporal scale
of the experiment increases. For a given wall angle, the flow behind the incident shock is not self-similar as is usually
assumed. Both shear layer instability and the development of turbulent patches become evident, neither of which have been
noted in previous tests. 相似文献