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91.
André Fiebach Annegret Glitzky Alexander Linke 《Numerical Methods for Partial Differential Equations》2016,32(1):141-174
We investigate the convergence of an implicit Voronoi finite volume method for reaction–diffusion problems including nonlinear diffusion in two space dimensions. The model allows to handle heterogeneous materials and uses the chemical activities of the involved species as primary variables. The numerical scheme works with boundary conforming Delaunay meshes and preserves positivity and the dissipative property of the continuous system. Starting from a result on the global stability of the scheme (uniform, mesh‐independent global upper, and lower bounds), we prove strong convergence of the chemical activities and their gradients to a weak solution of the continuous problem. To illustrate the preservation of qualitative properties by the numerical scheme, we present a long‐term simulation of the Michaelis–Menten–Henri system. Especially, we investigate the decay properties of the relative free energy over several magnitudes of time, and obtain experimental orders of convergence for this quantity. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 141–174, 2016 相似文献
92.
Hollmann D Bähn S Tillack A Beller M 《Chemical communications (Cambridge, England)》2008,(27):3199-3201
Highly selective alkyl transfer processes of mono-, di- and trialkyl amines in the presence of the Shvo catalyst have been realized; in addition, a general method for N-alkylation of aniline with di- and trialkyl amines is presented. 相似文献
93.
Pews-Davtyan A Tillack A Ortinau S Rolfs A Beller M 《Organic & biomolecular chemistry》2008,6(6):992-997
Improved palladium catalysts for the Suzuki coupling of 3-bromo-1-methyl-4-(2-methyl-3-indolyl)maleimide have been developed. The coupling of both aryl- and heteroarylboronic acids proceeds smoothly in good to excellent yields at low catalyst loading. 相似文献
94.
Annegret Wagler 《Discrete Applied Mathematics》2008,156(17):3329-3338
Normal graphs can be considered as weaker perfect graphs in several ways. However, only few graphs are known yet to be normal, apart from perfect graphs, odd holes, and odd antiholes of length ≥ 9. Körner and de Simone [J. Körner, C. de Simone, On the odd cycles of normal graphs, Discrete Appl. Math. 94 (1999) 161-169] conjectured that every ()-free graph is normal. As there exist normal graphs containing C5, C7, or , it is worth looking for other ways to construct or detect normal graphs. For that, we treat the behavior of normal graphs under certain construction techniques (substitution, composition, and clique identification), providing several ways to construct new normal graphs from normal and even not normal ones, and consider the corresponding structural decompositions (homogeneous sets, skew partitions, and clique cutsets). Our results imply that normal graphs cannot be characterized by means of decomposition techniques as well as by forbidden subgraphs. We address negative consequences for the algorithmic behavior of normal graphs, reflected by the fact that neither the imperfection ratio can be bounded for normal graphs nor a χ-binding function exists. The latter is even true for the class of ()-free graphs and related classes. We conclude that normal graphs are indeed only “normal”. 相似文献
95.
We present an algorithm for computing the cardinality of the Jacobian of a random Picard curve over a finite field. If the underlying field is a prime field , the algorithm has complexity .
96.
A graph G is called preperfect if each induced subgraph G
′⊆G of order at least 2 has two vertices x, y such that either all maximum cliques of G
′ containing x contain y, or all maximum independent sets of G
′ containing y contain x, too. Giving a partial answer to a problem of Hammer and Maffray [Combinatorica 13 (1993), 199–208], we describe new classes
of minimally non-preperfect graphs, and prove the following characterizations:
(i) A graph of maximum degree 4 is minimally non-preperfect if and only if it is an odd cycle of length at least 5, or the
complement of a cycle of length 7, or the line graph of a 3-regular 3-connected bipartite graph.
(ii) If a graph G is not an odd cycle and has no isolated vertices, then its line graph is minimally non-preperfect if and only if G is bipartite, 3-edge-connected, regular of degree d for some d≥3, and contains no 3-edge-connected d
′-regular subgraph for any 3≤d
′<d.
Received: March 4, 1998 Final version received: August 14, 1999 相似文献
97.
Dr. Oldamur Hollóczki Zsolt Kelemen László Könczöl Dr. Dénes Szieberth Prof. Dr. László Nyulászi Dr. Annegret Stark Prof. Dr. Barbara Kirchner 《Chemphyschem》2013,14(2):315-320
Carbon dioxide–ionic liquid systems are of great current interest, and significant efforts have been made lately to understand the intermolecular interactions in these systems. In general, all the experimental and theoretical studies have concluded so far that the main solute–solvent interaction takes effect through the anion, and the cation has no, or only a secondary role in solvation. In this theoretical approach it is shown that this view is unfounded, and evidence is provided that, similarly to the benzene–CO2 system, dispersion interactions are present between the solute and the cation. Therefore, this defines a novel site for tailoring solvents to tune CO2 solubility. 相似文献
98.
We study the evolution of a self-gravitating compressible fluid in spherical symmetry and we prove the existence of weak solutions with bounded variation for the Einstein–Euler equations of general relativity. We formulate the initial value problem in Eddington–Finkelstein coordinates and prescribe spherically symmetric data on a characteristic initial hypersurface. We introduce here a broad class of initial data which contain no trapped surfaces, and we then prove that their Cauchy development contains trapped surfaces. We therefore establish the formation of trapped surfaces in weak solutions to the Einstein equations. This result generalizes a theorem by Christodoulou for regular vacuum spacetimes (but without symmetry restriction). Our method of proof relies on a generalization of the “random choice” method for nonlinear hyperbolic systems and on a detailed analysis of the nonlinear coupling between the Einstein equations and the relativistic Euler equations in spherical symmetry. 相似文献
99.