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The synthesis and liquid crystalline properties of two novel series of triphenylenes with 4 or 5 pentafuoropentyloxy tails and 1 or 2 alkoxy tails of varying length are reported. All compounds form wide-range hexagonal columnar phases. The isotropisation temperatures and the corresponding enthalpy changes for the compounds with 4 or 5 fluorinated tails are higher than for the compounds with 6 alkoxy tails, and also higher than for compounds with 6 fluorinated tails. These results indicate that the best ordering is obtained for compounds with a mix of fluorinated and non-fluorinated tails. With increasing length of the alkyl tails in HAT compounds with 4 or 5 fluoroalkoxy tails, the isotropisation temperatures decrease and the d-spacings as observed by XRD increase. All fluoro-containing compounds have a strong tendency for spontaneous homeotropic alignment on surfaces, both hydrophilic and hydrophobic. 相似文献
105.
Aditi Saraswat Dr. K. Pramoda Koyendrila Debnath Swaraj Servottam Prof. Umesh V. Waghmare Prof. C. N. R. Rao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6499-6503
The recently discovered twisted graphene has attracted considerable interest. A simple chemical route was found to prepare twisted graphene by covalently linking layers of exfoliated graphene containing surface carboxyl groups with an amine-containing linker (trans-1,4-diaminocyclohexane). The twisted graphene shows the expected selected area electron diffraction pattern with sets of diffraction spots out with different angular spacings, unlike graphene, which shows a hexagonal pattern. Twisted multilayer graphene oxide could be prepared by the above procedure. Twisted boron nitride, prepared by cross-linking layers of boron nitride (BN) containing surface amino groups with oxalic acid linker, exhibited a diffraction pattern comparable to that of twisted graphene. First-principles DFT calculations threw light on the structures and the nature of interactions associated with twisted graphene/BN obtained by covalent linking of layers. 相似文献
106.
An induction machine is one of the most convenient devices for conversion of electrical energy to mechanical rotational energy. Induction machine is a typical member of a multi-domain, nonlinear, high-order dynamic system. To reduce its complexity, the mathematical models used for designing their control have several assumptions built into them. The most striking of these assumptions is that of linear magnetics. Bond graph is a convenient tool for modelling nonlinear elements. This paper proposes the use of the bond graph methodology to develop a model of an induction machine that includes the nonlinearities due to magnetics. 相似文献
107.
Anand Roy Anjali Singh S. Assa Aravindh Swaraj Servottam Umesh V. Waghmare C. N. R. Rao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7000-7005
We have carried out a combined experimental and theoretical investigation of the structures and properties of a family of cadmium phosphochlorides with varying Cl/Cd and P/Cd ratios, Cd2P3Cl, Cd4P2Cl3, Cd3PCl3, and Cd7P4Cl6. Their optical band gaps are in the visible region and the values are sensitive to the Cl/Cd and P/Cd ratios, leading to an increase and decrease, respectively. First‐principles calculations were used to understand the bonding and electronic structures. All phosphochlorides except Cd2P3Cl possess direct band gaps. The calculated dielectric constants and Born effective charges illustrate the bonding, hybridization, and ionic character in these compounds. The band positions indicate the thermodynamic feasibility to perform water splitting. All systems can be used in the hydrogen evolution reaction (HER), where Cd7P4Cl6 has the highest activity and Cd3PCl3 the lowest. The apparent quantum yield is highest in Cd7P4Cl6 (20.1 %) even without the assistance of a co‐catalyst. The HER activity can be understood on the basis of photoelectrochemical measurements. 相似文献
108.
Sepay Nayim Sepay Nadir Al Hoque Ashique Mondal Rina Halder Umesh Chandra Muddassir Mohd. 《Structural chemistry》2020,31(5):1831-1840
Structural Chemistry - Novel coronavirus, 2019-nCoV is a danger to the world and is spreading rapidly. Very little structural information about 2019-nCoV make this situation more difficult for drug... 相似文献
109.
Wojciech Pulawski Umesh Ghoshdastider Vincenza Andrisano Slawomir Filipek 《Applied biochemistry and biotechnology》2012,166(7):1626-1643
The common view of amyloids and prion proteins is that they are associated with many currently incurable diseases and present
a great danger to an organism. This danger comes from the fact that not only prion proteins, but also the infectious form(s)
of amyloids, as it has been shown recently, are able to transmit the disease. On the other hand, organisms take advantage
of the strength and durability of specific forms of amyloids. Such forms do not spread any disease. Also, in nanotechnology
there is a constantly growing need to employ amyloid fibrils in many industrial applications. With increasing knowledge about
amyloids and prion proteins we are aware that the amyloidal state is inherent to any protein, making the problem of amyloid
formation a central one in aging-related diseases. However, the “good” amyloids can be beneficial and even necessary for our
health. Furthermore, because of their mechanical properties, the amyloids are of great interest to engineers. 相似文献
110.
Umesh Fegade Shivaji Tayade G. Krishna Chaitanya Sanjay Attarde Anil Kuwar 《Journal of fluorescence》2014,24(3):675-681
The noncyclic 2,2′-[ethane-1,2-diylbis (iminomethanediyl)]diphenol (4) fluorescent receptor bearing two amine and hydroxyl groups have been designed and investigated for their binding properties towards various cations. The fluorescent spectral measurements revealed that receptor 4 is a selective fluorescent sensor for Fe3+ ions but not for metal ions such as Cr3+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ and Bi3+. The binding ability was confirmed with spectroscopic methods and density functional theory calculation (DFT). This straightforward and cost effective receptor provides rapid detection of Fe3+ ions at concentrations as low as 2.5 μM and expected to be useful to design efficient chemically and biological sensor. 相似文献