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31.
Many tools in production technology are nowadays coated to obtain a satisfactory lifetime and degradation resistance. Therefore, the main goal of this study is to investigate antiadhesive and wear resistant coatings made of ceramics, plastics and metals produced by High Power Pulsed Magnetron Sputtering (HPPMS) technique [1]. A cohesive zone element technique (CZ) is applied to model the interactions of the coatings and the substrate surfaces (see [2]). This goes along with the investigations of the delamination and failure behavior of the involved surfaces. To illustrate the applicability of the model, several structural simulations are performed. The developed CZ element model is capable of modeling the separation, the contact and also the irreversible reloading conditions in both normal and tangential directions [3]. The model is further developed to be applicable for different structures including different bonding behaviors, with a higher stability. The talk concludes with a detailed discussion of the numerical results of different material and interface properties. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
32.
Dr. Kilian Colas A. Catarina V. D. dos Santos Dr. Stefanie V. Kohlhepp Dr. Abraham Mendoza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(9):e202104053
The synthesis of ketones through addition of organometallic reagents to aliphatic carboxylic acids is a straightforward strategy that is limited to organolithium reagents. More desirable Grignard reagents can be activated and controlled with a bulky aniline-derived turbo-Hauser base. This operationally simple procedure allows the straightforward preparation of a variety of aliphatic and perfluoroalkyl ketones alike from functionalized alkyl, aryl and heteroaryl Grignard reagents. 相似文献
33.
Jannik Brückmann Dr. Carolin Müller Tamar Maisuradze Dr. Alexander K. Mengele Dr. Djawed Nauroozi Sven Fauth Andreas Gruber Prof. Dr. Stefanie Gräfe Prof. Dr. Kerstin Leopold Dr. Stephan Kupfer Prof. Dr. Benjamin Dietzek-Ivanšić Prof. Dr. Sven Rau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(51):e202200766
The synthesis and detailed characterization of a new Ru polypyridine complex containing a heteroditopic bridging ligand with previously unexplored metal-metal distances is presented. Due to the twisted geometry of the novel ligand, the resultant division of the ligand in two distinct subunits leads to steady state as well as excited state properties of the corresponding mononuclear Ru(II) polypyridine complex resembling those of prototype [Ru(bpy)3]2+ (bpy=2,2'-bipyridine). The localization of the initially optically excited and the nature of the long-lived excited states on the Ru-facing ligand spheres is evaluated by resonance Raman and fs-TA spectroscopy, respectively, and supported by DFT and TDDFT calculations. Coordination of a second metal (Zn or Rh) to the available bis-pyrimidyl-like coordination sphere strongly influences the frontier orbitals, apparent by, for example, luminescence quenching. Thus, the new bridging ligand motif offers electronic properties, which can be adjusted by the nature of the second metal center. Using the heterodinuclear Ru−Rh complex, visible light-driven reduction of NAD+ to NADH was achieved, highlighting the potential of this system for photocatalytic applications. 相似文献
34.
We propose a model to describe correlated two-electron dynamics in strong laser fields during laser-induced recollision between an electron and its parent ion. We derive an effective interaction potential which describes the effect of the laser-driven electron collision with an ion while retaining the correlation between the colliding and the bound electron. Using dissociative ionization of molecular hydrogen as an example, we analyze the dynamics of correlation-driven electron localization in a dissociating hydrogen molecular ion. 相似文献
35.
A novel dihydroazepine-bridged BIPHEP phosphoramidite ligand with an amino acid moiety in the backbone was synthesized and evaluated in the Rh-catalyzed asymmetric hydrogenation. The scorpion tail-like amino acid backbone is capable of hydrogen bond formation and able to shift the rotamer composition of the biphenyl axis with the two scissor-like arms. Pivaloyl-l -valine was studied as chiral selector unit and compared with pivaloylglycine as the achiral reference substance. The enantiomerization barrier of the pivaloylglycine-modified biphenylamide was determined to be ΔG≠=110 kJ/mol. In the case of pivaloyl-l -valine, the (Sax) isomer is thermodynamically favored. Due to the relatively high barrier, the ligand is atropisomeric at room temperature and allows the preparative separation of the stereoisomers. The obtained phosphoramidite ligands were separated by chiral HPLC. For the first eluting rotamer, Rh complex ([Rh(cod)(L)2]BF4) was generated in situ and examined in the enantioselective hydrogenation of 2-acetamidoacrylate and methyl 2-acetamido-3-phenylacrylate, achieving enantiomeric excesses of up to 94 %. 相似文献
36.
We prove part of a conjecture by Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28.) regarding threshold functions for the existence of an H‐factor in a random graph . We prove that the conjectured threshold function is correct for any graph H which is not covered by its densest subgraphs. We also demonstrate that the main result of Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28) generalizes to multigraphs, digraphs, and a multipartite model. 相似文献
37.
Dipl.‐Chem. Günther Thiele Thomas Krüger Prof. Dr. Stefanie Dehnen 《Angewandte Chemie (International ed. in English)》2014,53(18):4699-4703
The first inorganic lead(IV) compound without oxygen, nitrogen or halogen ligands attached to the lead atom was obtained as the potassium salt of the tetraselenidoplumbate(IV) anion [PbIVSe4]4?. It is stable under inert conditions which may enable the transfer of the chemistry of chalcogenidogermanate(IV) or chalcogenidostannate(IV) materials, to the lead homologues. 相似文献
38.
Coverage‐ and Temperature‐Dependent Metalation and Dehydrogenation of Tetraphenylporphyrin on Cu(111) 下载免费PDF全文
Michael Röckert Matthias Franke Quratulain Tariq Stefanie Ditze Michael Stark Patrick Uffinger Daniel Wechsler Upendra Singh Dr. Jie Xiao Dr. Hubertus Marbach Prof. Dr. Hans‐Peter Steinrück Dr. Ole Lytken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):8948-8953
Using temperature‐programmed desorption, supported by X‐ray photoelectron spectroscopy and scanning tunneling microscopy, a comprehensive overview of the main reactions of 5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin (2HTPP) on Cu(111) as a function of coverage and temperature is obtained. Three reactions were identified: metalation with Cu substrate atoms, stepwise partial dehydrogenation, and finally complete dehydrogenation. At low coverage the reactions are independent of coverage, but at higher coverage metalation becomes faster and partial dehydrogenation slower. This behavior is explained by a weaker interaction between the iminic nitrogen atoms and the Cu(111) surface in the high‐coverage checkerboard structure, leading to faster metalation, and the stabilizing effect of T‐type interactions in the CuTPP islands formed at high coverage after metalation, leading to slower dehydrogenation. Based on the amount of hydrogen released and the appearance in STM, a structure of the partially dehydrogenated molecule is suggested. 相似文献
39.
Organotin–Oxido Cluster‐Based Multiferrocenyl Complexes Obtained by Hydrolysis of Ferrocenyl‐Functionalized Organotin Chlorides 下载免费PDF全文
Zhiliang You Robert Möckel Jakob Bergunde Prof. Dr. Stefanie Dehnen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13491-13496
Three organotin–oxido clusters were formed by hydrolysis of ferrocenyl‐functionalized organotin chloride precursors in the presence of NaEPh (E=S, Se). [RFcSnCl3?HCl] ( C ; RFc = CMe2CH2C(Me)?N?N?C(Me)Fc) and [SnCl6]2? formed {(RFcSnCl2)3[Sn(OH)6]}[SnCl3] ( 3 a ) and {(RFcSnCl2)3[Sn(OH)6]}[PhSeO3] ( 3 b ), bearing an unprecedented [Sn4O6] unit, in a one‐pot synthesis or stepwise through [(RFcSnCl2)2Se] ( 1 ) plus [(RFcSnCl2)SePh] ( 2 ). A one‐pot reaction starting out from FcSnCl3 gave [(FcSn)9(OH)6O8Cl5] ( 4 ), which represents the largest Fc‐decorated Sn/O cluster reported to date. 相似文献
40.
Determination of the Absolute Configuration of Perylene Quinone‐Derived Mycotoxins by Measurement and Calculation of Electronic Circular Dichroism Spectra and Specific Rotations 下载免费PDF全文
Prof. Dr. Joachim Podlech Dr. Stefanie C. Fleck Prof. Dr. Manfred Metzler Dr. Jochen Bürck Prof. Dr. Anne S. Ulrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11463-11470
Altertoxins I–III, alterlosins I and II, alteichin (alterperylenol), stemphyltoxins I–IV, stemphyperylenol, stemphytriol, 7‐epi‐8‐hydroxyaltertoxin I, and 6‐epi‐stemphytriol are mycotoxins derived from perylene quinone, for which the absolute configuration was not known. Electronic circular dichroism (ECD) spectra were calculated for these compounds and compared with measured spectra of altertoxins I–III, alteichin, and stemphyltoxin III and with reported Cotton effects. Specific rotations were calculated and compared with reported specific rotations. The absolute configuration of all the toxins, except for stemphyltoxin IV, could thus be determined. The validity of the assignment was high whenever reported ECD data were available for comparison, and the validity was lower when the assignment was based only on the comparison of calculated and reported specific rotations. ECD spectra are intrinsically different for toxins with a biphenyl substructure and for toxins derived from dihydroanthracene. 相似文献