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101.
Sengmany S Léonel E Polissaint F Nédélec JY Pipelier M Thobie-Gautier C Dubreuil D 《The Journal of organic chemistry》2007,72(15):5631-5636
A general efficient electrochemical method for the preparation of aryl- and heteroarylpyridazines in a nickel-catalyzed cross-coupling reaction of 3-chloro-6-methoxypyridazine and 3-chloro-6-methylpyridazine with a range of functionalized aryl or heteroaryl halides is reported. 相似文献
102.
12/14/14‐Helix Formation in 2:1 α/β‐Hybrid Peptides Containing Bicyclo[2.2.2]octane Ring Constraints
Dr. Baptiste Legrand Dr. Christophe André Laure Moulat Dr. Claude Didierjean Dr. Patrick Hermet Prof. Jean‐Louis Bantignies Prof. Jean Martinez Dr. Muriel Amblard Dr. Monique Calmès 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11986-11990
The highly constrained β‐amino acid ABOC induces different types of helices in β urea and 1:1 α/β amide oligomers. The latter can adopt 11/9‐ and 18/16‐helical folds depending on the chain length in solution. Short peptides alternating proteinogenic α‐amino acids and ABOC in a 2:1 α/β repeat pattern adopted an unprecedented and stable 12/14/14‐helix. The structure was established through extensive NMR, molecular dynamics, and IR studies. While the 1:1 α‐AA/ABOC helices diverged from the canonical α‐helix, the helix formed by the 9‐mer 2:1 α/β‐peptide allowed the projection of the α‐amino acid side chains in a spatial arrangement according to the α‐helix. Such a finding constitutes an important step toward the conception of functional tools that use the ABOC residue as a potent helix inducer for biological applications. 相似文献
103.
104.
Dr. Elisabet Öberg Dr. Andreas Orthaber Dr. Christophe Lescop Prof. Régis Réau Prof. Muriel Hissler Prof. Sascha Ott 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8421-8432
Phosphole‐substituted phosphaalkenes (PPAs) of the general formula Mes*P?C(CH3)?(C4H2P(Ph))?R 5 a – c (Mes*=2,4,6‐tBu3Ph; R=2‐pyridyl ( a ), 2‐thienyl ( b ), phenyl ( c )) have been prepared from octa‐1,7‐diyne‐substituted phosphaalkenes by utilizing the Fagan–Nugent route. The presence of two differently hybridized phosphorus centers (σ2,λ3 and σ3,λ3) in 5 offers the possibility to selectively tune the HOMO–LUMO gap of the compounds by utilizing the different reactivity of the two phosphorus heteroatoms. Oxidation of 5 a – c by sulfur proceeds exclusively at the σ3,λ3‐phosphorus atom, thus giving rise to the corresponding thioxophospholes 6 a – c . Similarly, 5 a is selectively coordinated by AuCl at the σ3,λ3‐phosphorus atom. Subsequent second AuCl coordination at the σ2,λ3‐phosphorus heteroatom results in a dimetallic species that is characterized by a gold–gold interaction that provokes a change in π conjugation. Spectroscopic, electrochemical, and theoretical investigations show that the phosphaalkene and the phosphole both have a sizable impact on the electronic properties of the compounds. The presence of the phosphaalkene unit induces a decrease of the HOMO–LUMO gap relative to reference phosphole‐containing π systems that lack a P?C substituent. 相似文献
105.
106.
Caillet-Saguy C Delepierre M Lecroisey A Bertini I Piccioli M Turano P 《Journal of the American Chemical Society》2006,128(1):150-158
Hemophore HasA is a 19 kDa iron(III) hemoprotein that participates in the shuttling of heme to a specific membrane receptor. In HasA, heme iron has an original coordination environment with a His/Tyr pair as axial ligands. Recently developed two-dimensional protonless (13)C-detected experiments provide the sequence-specific assignment of all but three protein residues in the close proximity of the paramagnetic center, thus overcoming limitations due to the short relaxation times induced by the presence of the iron(III) center. Mono-dimensional (13)C and (15)N experiments tailored for the detection of paramagnetic signals allow the identification of resonances of the axial ligands. These experiments are used to characterize the conformational features and the electronic structure of the heme iron(III) environment. The good complementarity among (1)H-, (13)C-, and (15)N-detected experiments is highlighted. A thermal high-spin/low-spin equilibrium is observed and is related to a modulation of the strength of the coordination bond between the iron and the Tyr74 axial ligand. The key role of a neighboring residue, His82, for the stability of the axial coordination and its involvement in the heme delivery to the receptor is discussed. 相似文献
107.
The degree of polarization (DOP) is an important tool in many optical measurement and imaging applications. We address the problem of its estimation in images that are perturbed with both speckle and photon noise, by determining the Cramer-Rao lower bounds (CRLBs) when the illuminated materials are purely depolarizing. We demonstrate that the CRLBs are simply the sum of the CRLBs due to speckle noise and Poisson noise. We use this result to analyze the influence of different optical parameters on DOP estimation. 相似文献
108.
The problem of storing permutations in a distributed manner arises in several common scenarios, such as efficient updates of a large, encrypted, or compressed data set. This problem may be addressed in either a combinatorial or a coding approach. The former approach boils down to presenting large sets of permutations with locality, that is, any symbol of the permutation can be computed from a small set of other symbols. In the latter approach, a permutation may be coded in order to achieve locality. Both approaches must present low query complexity to allow the user to find an element efficiently. We discuss both approaches, and give a particular focus to the combinatorial one. In the combinatorial approach, we provide upper and lower bounds for the maximal size of a set of permutations with locality, and provide several simple constructions which attain the upper bound. In cases where the upper bound is not attained, we provide alternative constructions using a variety of tools, such as Reed-Solomon codes, permutation polynomials, and multi-permutations. In addition, several low-rate constructions of particular interest are discussed. In the coding approach we discuss an alternative representation of permutations, present a paradigm for supporting arbitrary powers of the stored permutation, and conclude with a proof of concept that permutations may be stored more efficiently than ordinary strings over the same alphabet. 相似文献
109.
Dorian Sonet Mattéo Cayla Dr. Raphaël Méreau Estelle Morvan Aline Lacoudre Dr. Nicolas Vanthuyne Muriel Albalat Dr. Dario M. Bassani Dr. Antoine Scalabre Dr. Emilie Pouget Prof. Dr. Brigitte Bibal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202202695
Chiral trifluoromethyl alcohol groups were introduced at the hindered ortho positions of 9,10-diphenylanthracenes to investigate their effects on the physical properties and reactivity towards oxidative dearomatization. In such compact structures, the position in different quadrants and the preferred orientation of the −CH(OH)CF3 groups were determined by the relative and absolute configurations of each stereoisomer, respectively. As a consequence, the stereochemistry governs the organization of the H-bonded molecules in single crystals (homochiral dimers vs ribbon), whereas in chlorinated solvents, they all behave as discrete compounds. Concerning their reactivity, the stereospecific dearomative oxidation of these molecules leads to 9,10-bis-spiro-isobenzofuran-anthracenes, when using organic single-electron transfer oxidants. The chiroptical properties of the alcohols and the corresponding dearomatized products were compared and showed an important modulation of the intensity. 相似文献
110.