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561.
Tackett BS Li Y Clouthier DJ Pacheco KL Schick GA Judge RH 《The Journal of chemical physics》2006,125(11):114301
Single vibronic level dispersed fluorescence spectra of jet-cooled HGeBr, DGeBr, HGeI, and DGeI have been obtained by laser excitation of selected bands of the A (1)A(")-X (1)A(') electronic transition. The measured ground state vibrational intervals were assigned and fitted to anharmonicity expressions, which allowed the harmonic frequencies to be determined for both isotopomers. In some cases, lack of a suitable range of emission data necessitated that some of the anharmonicity constants and vibrational frequencies be estimated from those of HGeClDGeCl and the corresponding silylenes (HSiX). Harmonic force fields were obtained for both molecules, although only four of the six force constants could be determined. The ground state effective rotational constants and force field data were combined to calculate average (r(z)) and approximate equilibrium (r(e) (z)) structures. For HGeBr r(e) (z)(GeH)=1.593(9) A, r(e) (z)(GeBr)=2.325(21) A, and the bond angle was fixed at our CCSD(T)/aug-cc-pVTZ ab initio value of 93.6 degrees . For HGeI we obtained r(e) (z)(GeH)=1.589(1) A, r(e) (z)(GeI)=2.525(5) A, and bond angle=93.2 degrees . Franck-Condon simulations of the emission spectra using ab initio Cartesian displacement coordinates reproduce the observed intensity distributions satisfactorily. The trends in structural parameters in the halogermylenes and halosilylenes can be readily understood based on the electronegativity of the halogen substituent. 相似文献
562.
A new reaction for the preparation of enaminones has been discovered. This method employs beta-amino acids as starting materials to allow diversification as well as incorporation of chirality. The beta-amino acids, once converted to ynones, are readily cyclized to the desired six-membered enaminone via a two-step, one-pot protocol. Although disguised as a 6-endo-dig cyclization, the reagents employed in the transformation play a direct role in bond making and bond breaking, thus changing the mode of addition. 相似文献
563.
Jian-Bo Yang Brandon Y.H. Wong Dong-Ling Xu Theodor J. Stewart 《European Journal of Operational Research》2009
Data envelopment analysis (DEA) and multiple objective linear programming (MOLP) are tools that can be used in management control and planning. Whilst these two types of model are similar in structure, DEA is directed to assessing past performances as part of management control function and MOLP to planning future performance targets. This paper is devoted to investigating equivalence models and interactive tradeoff analysis procedures in MOLP, such that DEA-oriented performance assessment and target setting can be integrated in a way that the decision makers’ preferences can be taken into account in an interactive fashion. Three equivalence models are investigated between the output-oriented dual DEA model and the minimax reference point formulations, namely the super-ideal point model, the ideal point model and the shortest distance model. These models can be used to support efficiency analysis in the same way as the conventional DEA model does and also support tradeoff analysis for setting target values by individuals or groups. A case study is conducted to illustrate how DEA-oriented efficiency analysis can be conducted using the MOLP methods and how such performance assessment can be integrated into an interactive procedure for setting realistic target values. 相似文献
564.
Course of Action analysis and Resource Management are concerned with the allocation of resources over time to effect desired
actions as a result of the perceived situation awareness. Decision Support Systems provide automated recommended courses of
action to decision makers, considering relevant resource capabilities and constraints. Incorporating potential adversary actions
and reactions to the current course of action decision (and the resources effecting the actions) in the decision making process
will make the decision support system more robust and increase confidence that the recommended decisions are appropriate responses
to the unfolding situations. We discuss research results from the inclusion of possible adversary actions and reactions into
the course of action/resource allocation decision making framework. The overall decision problem is formulated as a multi-stage
mathematical program. As the problem is NP-hard, an heuristic is developed through a natural problem decomposition. Simulated results show the effectiveness of the
heuristic in producing good-quality solutions in an efficient manner. 相似文献
565.
Influence of atmospheric turbulence on states of light carrying orbital angular momentum 总被引:2,自引:0,他引:2
B Rodenburg MP Lavery M Malik MN O'Sullivan M Mirhosseini DJ Robertson M Padgett RW Boyd 《Optics letters》2012,37(17):3735-3737
We have experimentally studied the degradation of mode purity for light beams carrying orbital angular momentum (OAM) propagating through simulated atmospheric turbulence. The turbulence is modeled as a randomly varying phase aberration, which obeys statistics postulated by Kolmogorov turbulence theory. We introduce this simulated turbulence through the use of a phase-only spatial light modulator. Once the turbulence is introduced, the degradation in mode quality results in crosstalk between OAM modes. We study this crosstalk in OAM for 11 modes, showing that turbulence uniformly degrades the purity of all the modes within this range, irrespective of mode number. 相似文献
566.
Yanxing Wang Brandon Duane Walker Chengwen Liu Pengyu Ren 《Molecules (Basel, Switzerland)》2022,27(23)
Accurate conformational energetics of molecules are of great significance to understand maby chemical properties. They are also fundamental for high-quality parameterization of force fields. Traditionally, accurate conformational profiles are obtained with density functional theory (DFT) methods. However, obtaining a reliable energy profile can be time-consuming when the molecular sizes are relatively large or when there are many molecules of interest. Furthermore, incorporation of data-driven deep learning methods into force field development has great requirements for high-quality geometry and energy data. To this end, we compared several possible alternatives to the traditional DFT methods for conformational scans, including the semi-empirical method GFN2-xTB and the neural network potential ANI-2x. It was found that a sequential protocol of geometry optimization with the semi-empirical method and single-point energy calculation with high-level DFT methods can provide satisfactory conformational energy profiles hundreds of times faster in terms of optimization. 相似文献
567.
Hannah J. Dokken Brandon L. Frenette Dr. Michael J. Ferguson Prof. Dr. Eric Rivard 《欧洲无机化学杂志》2023,26(26):e202300202
We report the synthesis and reactivity of the geminal-linked fluorene-derived P/B frustrated Lewis pair (FLP) iPr2P(C13H8)BCy2 ( 1 ). Compound 1 displays anomalous behavior towards small molecules, acting as a “masked” FLP. This behavior stems from significant polarization of the B−C(fluorene) bond in 1 , as identified by density functional theory (DFT) computations. We exploit this B−C bond polarity through reactions with PhPCl2, H3N ⋅ BH3, and iPrNH2, demonstrating P−Cl and N−H bond activation, respectively. 相似文献
568.
Brandon L. Frenette Jonathan Trach Dr. Michael J. Ferguson Prof. Dr. Eric Rivard 《Angewandte Chemie (International ed. in English)》2023,62(10):e202218587
We report phosphinidenes (PR) stabilized by an intramolecular frustrated Lewis pair (FLP) chelate. These adducts include the parent phosphinidene, PH, which is accessed via thermolysis of coordinated HPCO. The reported FLP-PH species acts as a springboard to other phosphorus-containing compounds, such as FLP-adducts of diphosphorus (P2) and InP3. Our new adducts participate in thermal- or light-induced phosphinidene elimination (of both PH and PR, R=organic group), transfer P2 units to an organic substrate, and yield the useful semiconductor InP at only 110 °C from solution. 相似文献
569.
Dr. Cristin E. Juda Claire E. Casaday Dr. Ryan M. Clarke Nicholas P. Litak Brandon M. Campbell Tieyan Chang Dr. Shao-Liang Zheng Dr. Yu-Sheng Chen Dr. Theodore A. Betley 《Angewandte Chemie (International ed. in English)》2023,62(50):e202313156
Metalation of the polynucleating ligand F,tbsLH6 (1,3,5-C6H9(NC6H3−4-F−2-NSiMe2tBu)3) with two equivalents of Zn(N(SiMe3)2)2 affords the dinuclear product (F,tbsLH2)Zn2 ( 1 ), which can be further deprotonated to yield (F,tbsL)Zn2Li2(OEt2)4 ( 2 ). Transmetalation of 2 with NiCl2(py)2 yields the heterometallic, trinuclear cluster (F,tbsL)Zn2Ni(py) ( 3 ). Reduction of 3 with KC8 affords [KC222][(F,tbsL)Zn2Ni] ( 4 ) which features a monovalent Ni centre. Addition of 1-adamantyl azide to 4 generates the bridging μ3-nitrenoid adduct [K(THF)3][(F,tbsL)Zn2Ni(μ3-NAd)] ( 5 ). EPR spectroscopy reveals that the anionic cluster possesses a doublet ground state (S = ). Cyclic voltammetry of 5 reveals two fully reversible redox events. The dianionic nitrenoid [K2(THF)9][(F,tbsL)Zn2Ni(μ3-NAd)] ( 6 ) was isolated and characterized while the neutral redox isomer was observed to undergo both intra- and intermolecular H-atom abstraction processes. Ni K-edge XAS studies suggest a divalent oxidation state for the Ni centres in both the monoanionic and dianionic [Zn2Ni] nitrenoid complexes. However, DFT analysis suggests Ni-borne oxidation for 5 . 相似文献
570.
Cécile Bousch Brandon Vreulz Kartikey Kansal Ali El-Husseini Dr. Samy Cecioni 《Angewandte Chemie (International ed. in English)》2023,62(49):e202314248
Glycan recognition by glycan-binding proteins is central to the biology of all living organisms. The efficient capture and characterization of relatively weak non-covalent interactions remains an important challenge in various fields of research. Photoaffinity labeling strategies can create covalent bonds between interacting partners, and photoactive scaffolds such as benzophenone, diazirines and aryl azides have proved widely useful. Since their first introduction, relatively few improvements have been advanced and products of photoaffinity labeling remain difficult to detect. We report a fluorinated azido-coumarin scaffold which enables photolabeling under fast and mild activation, and which can leave a fluorescent tag on crosslinked species. Coupling this scaffold to an α-fucoside, we demonstrate fluorogenic photolabeling of glycan-protein interactions over a wide range of affinities. We expect this strategy to be broadly applicable to other chromophores and we envision that such “fluoro-crosslinkers” could become important tools for the traceable capture of non-covalent binding events. 相似文献