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排序方式: 共有445条查询结果,搜索用时 15 毫秒
101.
Cui-Lian Liu Eduard O. Bobylev Yang Fu David A. Poole III Dr. Koen Robeyns Prof. Dr. Charles-André Fustin Prof. Dr. Yann Garcia Prof. Dr. Joost N. H. Reek Prof. Dr. Michael L. Singleton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(52):11960-11965
Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal–organic cages. Two ligands, the bend angles of which are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions, were synthesized and used for self-assembly with Pd2+. As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M2( L1 )4, M6( L2 )12, and M12( L2 )24 cages. By controlling the self-assembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydrogen-bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests. 相似文献
102.
103.
József Lörinczi Christian Maes Koen Vande Velde 《Probability Theory and Related Fields》1998,112(1):121-147
We study local transformations of Gibbs measures. We establish sufficient conditions for the quasilocality of the images
and obtain results on the existence and continuity properties of their relative energies. General results are illustrated
by simple examples.
Received: 11 November 1997 / Revised version: 20 February 1998 相似文献
104.
In this paper, we classify the generalized quadrangles of order (s,t), s ≠ 1 ≠ t, which admit the natural action of PSL(2,s) × PSL(2,s) on a subGQ of order (s,1). This generalizes a recent result of J. De Kaey and H. Van Maldeghem 3 , by whom the classification was obtained for the case s = t. © 2005 Wiley Periodicals, Inc. J Combin Designs. 相似文献
105.
Capturing the Genesis of an Active Fischer–Tropsch Synthesis Catalyst with Operando X‐ray Nanospectroscopy
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Ilse K. van Ravenhorst Charlotte Vogt Heiko Oosterbeek Koen W. Bossers José G. Moya‐Cancino Dr. Ir. Alexander P. van Bavel Ad M. J. van der Eerden Dr. David Vine Prof. Dr. Frank M. F. de Groot Dr. Florian Meirer Prof. Dr. Ir. Bert M. Weckhuysen 《Angewandte Chemie (International ed. in English)》2018,57(37):11957-11962
A state‐of‐the‐art operando spectroscopic technique is applied to Co/TiO2 catalysts, which account for nearly half of the world's transportation fuels produced by Fischer–Tropsch catalysis. This allows determination of, at a spatial resolution of approximately 50 nm, the interdependence of formed hydrocarbon species in the inorganic catalyst. Observed trends show intra‐ and interparticular heterogeneities previously believed not to occur in particles under 200 μm. These heterogeneities are strongly dependent on changes in H2/CO ratio, but also on changes thereby induced on the Co and Ti valence states. We have captured the genesis of an active FTS particle over its propagation to steady‐state operation, in which microgradients lead to the gradual saturation of the Co/TiO2 catalyst surface with long chain hydrocarbons (i.e., organic film formation). 相似文献
106.
De Smet K Pleysier A Vankelecom IF Jacobs PA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(1):334-338
Although transition-metal complexes are very attractive as homogeneous catalysts in fine chemistry, their high prices often limit their applications. A means to recycle those catalysts would solve this problem and would simultaneously facilitate the downstream purification of the product. This is now realized in a new concept in which homogeneous catalysis is coupled to dialysis. The advantages of homogeneous catalysis (off-the-shelf catalysts, high activities and selectivities) are thus combined with those of heterogeneous catalysis (easy catalyst separation from product solution, reuse of catalyst, and possibility for continuous operation). Since the heart of the process is the membrane, self-prepared membranes were preferred as they allow a better control and understanding of the separation characteristics. Rhodamine B was used as a probe molecule to define the working conditions of the membrane. The concept is proven to work for two relevant chiral reactions: a hydrogenation with Ru-BINAP and a hydrogen transfer reaction with Ru-TsDPEN [BINAP=(1,1'-binaphthalene)-2,2'-diylbis(diphenylphosphine); TsDPEN= tosyl-N,N'-diphenyl-1,2-ethanediamine]. 相似文献
107.
C2-Symmetric bicyclo[2.2.1]hepta-2,5-dienes with various substituents (R=Bn, i-Bu, c-Hex, allyl) are prepared starting from the corresponding enantiomerically pure bis-triflate (R=OTf). These chiral ligands are tested and compared in rhodium(I)-catalyzed 1,4- and 1,2-addition of phenylboronic acid to cyclic enones and aryl aldehydes, respectively. Some interesting reactivity and selectivity effects due to the introduction of sterically demanding or olefinic substituents are reported. Moreover, remarkably high catalytic activity is observed for the rhodium(I)-catalyzed 1,2-addition. 相似文献
108.
Liquid Nickel Salts: Synthesis,Crystal Structure Determination,and Electrochemical Synthesis of Nickel Nanoparticles
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Jeroen Sniekers Ken Verguts Dr. Neil R. Brooks Dr. Stijn Schaltin Dr. Thanh Hai Phan Dr. Thi Mien Trung Huynh Prof. Luc Van Meervelt Prof. Steven De Feyter Prof. Jin Won Seo Prof. Jan Fransaer Prof. Koen Binnemans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):1010-1020
New nickel‐containing ionic liquids were synthesized, characterized and their electrochemistry was investigated. In addition, a mechanism for the electrochemical synthesis of nanoparticles from these compounds is proposed. In these so‐called liquid metal salts, the nickel(II) cation is octahedrally coordinated by six N‐alkylimidazole ligands. The different counter anions that were used are bis(trifluoromethanesulfonyl)imide (Tf2N?), trifluoromethanesulfonate (OTf?) and methanesulfonate (OMs?). Several different N‐alkylimidazoles were considered, with the alkyl sidechain ranging in length from methyl to dodecyl. The newly synthesized liquid metal salts were characterized by CHN analysis, FTIR, DSC, TGA and viscosity measurements. An odd‐even effect was observed for the melting temperatures and viscosities of the ionic liquids, with the complexes with an even number of carbon atoms in the alkyl chain of the imidazole having a higher melting temperature and a lower viscosity than the complexes with an odd number of carbons. The crystal structures of several of the nickel(II) complexes that are not liquid at room temperature were determined. The electrochemistry of the compounds with the lowest viscosities was investigated. The nickel(II) cation could be reduced but surprisingly no nickel deposits were obtained on the electrode. Instead, nickel nanoparticles were formed at 100 % selectivity, as confirmed by TEM. The magnetic properties of these nanoparticles were investigated by SQUID measurements. 相似文献
109.
Ana Sánchez-Grande Dr. José I. Urgel Aleš Cahlík Dr. José Santos Shayan Edalatmanesh Eider Rodríguez-Sánchez Dr. Koen Lauwaet Dr. Pingo Mutombo Prof. Dana Nachtigallová Reed Nieman Prof. Hans Lischka Dr. Bruno de la Torre Prof. Rodolfo Miranda Dr. Oliver Gröning Prof. Nazario Martín Prof. Pavel Jelínek Prof. David Écija 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17747-17752
We report on the synthesis and characterization of atomically precise one-dimensional diradical peripentacene polymers on a Au(111) surface. By means of high-resolution scanning probe microscopy complemented by theoretical simulations, we provide evidence of their magnetic properties, which arise from the presence of two unpaired spins at their termini. Additionally, we probe a transition of their magnetic properties related to the length of the polymer. Peripentacene dimers exhibit an antiferromagnetic (S=0) singlet ground state. They are characterized by singlet–triplet spin-flip inelastic excitations with an effective exchange coupling (Jeff) of 2.5 meV, whereas trimers and longer peripentacene polymers reveal a paramagnetic nature and feature Kondo fingerprints at each terminus due to the unpaired spin. Our work provides access to the precise fabrication of polymers featuring diradical character which are potentially useful in carbon-based optoelectronics and spintronics. 相似文献