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41.
KM Varier AM Vinodkumar NVSV Prasad PV Madhusudhana Rao DL Sastry Lagy T Baby MC Radhakrishna NG Puttaswamy JJ Das P Sugathan N Madhavan AK Sinha DO Kataria 《Pramana》1999,53(3):529-533
Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies.
Coupled channel calculations incorporating couplings to 2+ and 3− states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements
had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer
were carried out for 46,48Ti+61Ni systems. The present paper gives the results of these studies. 相似文献
42.
Arne Johansen Randi Midtkandal Heidi Roggen Carl Henrik Grbitz 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):o198-o200
The valine side chains in the crystal structure of the title compound [systematic name: 2‐(2‐ammonio‐3‐methylbutanamido)‐3‐hydroxypropanoate trihydrate], C8H16N2O4·3H2O, stack along an a axis of 4.77 Å to form hydrophobic columns surrounded by remarkable water/hydroxyl shells. The peptide main chains are connected by hydrogen bonds in two‐dimensional layers. The peptide molecules in each layer are related only by translation, and generate a very rare pattern. This is rendered possible through the formation of the shortest Cα—H·O(carboxylate) interaction ever recorded. 相似文献
43.
In view of different patterns of π-electron density currents in benzenoid aromatic compounds it is of interest to investigate the pattern of ring currents in various classes of compounds. Recently such a study using a graph theoretical approach to calculating CC bond currents was reported for fully benzenoid hydrocarbons, that is, benzenoid hydrocarbons which have either π-sextets rings or “empty” rings in the terminology of Clar. In this contribution we consider π-electron currents in benzenoid hydrocarbons which have π-electron sextets and C=C bonds fully fixed. Our approach assumes that currents arise from contributions of individual conjugated circuits within the set of Kekulé valence structures of these molecules. 相似文献
44.
Milan Randić Damir Vukičević Marjana Novič Dejan Plavšić 《International journal of quantum chemistry》2012,112(12):2456-2462
Recently, we have reported on calculation of π‐electron ring currents in several smaller fully benzenoid hydrocarbons having up to eight fused benzene rings and five Clar π‐aromatic sextets. In contrast to early HMO ring current calculations and more recent ab initio calculations of π‐electron density, our current calculations are based on a graph theoretical model in which contributions to ring currents comes from currents associated with individual conjugated circuits. In this contribution, we consider several larger fully benzenoid hydrocarbons having from 9 to 13 fused rings and from six or seven π‐aromatic sextets. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
45.
When regions of three-phase flow arise in an oil reservoir, each of the flow parameters, i.e. capillary pressures and relative
permeabilities, are generally functions of two phase saturations and depend on the wettability state. The idea of this work
is to generate consistent pore-scale based three-phase capillary pressures and relative permeabilities. These are then used
as input to a 1-D continuum core- or reservoir-scale simulator. The pore-scale model comprises a bundle of cylindrical capillary
tubes, which has a distribution of radii and a prescribed wettability state. Contrary to a full pore-network model, the bundle
model allows us to obtain the flow functions for the saturations produced at the continuum-scale iteratively. Hence, the complex
dependencies of relative permeability and capillary pressure on saturation are directly taken care of. Simulations of gas
injection are performed for different initial water and oil saturations, with and without capillary pressures, to demonstrate
how the wettability state, incorporated in the pore-scale based flow functions, affects the continuum-scale displacement patterns
and saturation profiles. In general, wettability has a major impact on the displacements, even when capillary pressure is
suppressed. Moreover, displacement paths produced at the pore-scale and at the continuum-scale models are similar, but they
never completely coincide. 相似文献
46.
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48.
Muhammad Zada Liwei Guo Randi Zhang Wenjuan Zhang Yanping Ma Gregory A. Solan Yang Sun Wen‐Hua Sun 《应用有机金属化学》2019,33(5)
Five examples of unsymmetrical 1,2‐bis (arylimino) acenaphthene ( L1 – L5 ), each containing one N‐2,4‐bis (dibenzocycloheptyl)‐6‐methylphenyl group and one sterically and electronically variable N‐aryl group, have been used to prepare the N,N′‐nickel (II) halide complexes, [1‐[2,4‐{(C15H13}2–6‐MeC6H2N]‐2‐(ArN)C2C10H6]NiX2 (X = Br: Ar = 2,6‐Me2C6H3 Ni1 , 2,6‐Et2C6H3 Ni2 , 2,6‐i‐Pr2C6H3 Ni3 , 2,4,6‐Me3C6H2 Ni4 , 2,6‐Et2–4‐MeC6H2 Ni5 ) and (X = Cl: Ar = 2,6‐Me2C6H3 Ni6 , 2,6‐Et2C6H3 Ni7 , 2,6‐i‐Pr2C6H3 Ni8 , 2,4,6‐Me3C6H2 Ni9 , 2,6‐Et2–4‐MeC6H2 Ni10 ), in high yield. The molecular structures Ni3 and Ni7 highlight the extensive steric protection imparted by the ortho‐dibenzocycloheptyl group and the distorted tetrahedral geometry conferred to the nickel center. On activation with either Et2AlCl or MAO, Ni1 – Ni10 exhibited very high activities for ethylene polymerization with the least bulky Ni1 the most active (up to 1.06 × 107 g PE mol?1(Ni) h?1 with MAO). Notably, these sterically bulky catalysts have a propensity towards generating very high molecular weight polyethylene with moderate levels of branching and narrow dispersities with the most hindered Ni3 and Ni8 affording ultra‐high molecular weight material (up to 1.5 × 106 g mol?1). Indeed, both the activity and molecular weights of the resulting polyethylene are among the highest to be reported for this class of unsymmetrical 1,2‐bis (imino)acenaphthene‐nickel catalyst. 相似文献
49.
Milan Randić 《Theoretical chemistry accounts》1985,67(2):137-155
Isomerization mode defines the process of interconversion of one isomer into another. Several mechanisms are conceivable for degenerate rearrangements and, in general, lead to a distinctive network of relations between participating isomers. Here we consider selected modes which are complementary in the sense that if mode 1 transforms an isomer A into B, C, D etc., then mode 2 transforms the same isomer A into X, Y, Z, etc., which includes all isomers not comprised by the first mode. Physico-chemical complementarity can be translated into mathematical complementarity of associated chemical graphs. This allows us to use the tool of Graph Theory. One example of graph theoretical use is the theorem that graph G and its complement G have the same automorphism group (i.e., the same symmetry). We have shown that a close examination of a graph and its complement and their components allows us to recognize the automorphism group in some complex cases without resorting to canonical numbering or other involved procedures, and even allows us to determine isomorphism of different processes.Dedicated to Professor Kurt Mislow of Princeton UniversityOperated for the U.S. Department of Energy by Iowa State University under contract W-7405-Eng-82. Supported in part by the Office of the Director. 相似文献
50.
Milan Randić 《Journal of mathematical chemistry》1996,19(3):375-392
We present a refinement of recently proposed characterization of molecules based on a sequence of powers of interatomic separations referred to as molecular profiles. The molecular profiles and closely related shape profiles were based on the averaging contributions arising from different powers of interatomic distances for atoms in a molecule or atoms at the molecular periphery, respectively. Consequently, molecular models in which atoms have the same set of coordinates but different bonding patterns will result in identical molecular profiles. In this article we outline a refinement of molecular profiles in which the bonding pattern in a molecule is fully acknowledged. This is accomplished by adding ghost sites along chemical bonds. The distance-based invariants of the augmented matrix reflect the bonding pattern of a structure giving different molecular profiles for molecules having the same atomic coordinates but different bondings. The procedure is general and applies to two-dimensional and three-dimensional molecular skeletons. Equally, the approach can be applied to van der Waals-type molecular surfaces and molecular contours of equal electron densities in order to obtain characterization of more realistic molecular models.Dedicated to a leading graph theorist, Professor R. C. Read, for sharing his mathematical talents on chemical structures. 相似文献