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1.
In this paper, we present a new method to solve the Plateau-Bézier problem. A new energy functional called weak-area functional is proposed as the objective functional to obtain the approximate minimal Bézier surface from given boundaries. This functional is constructed based on Dirichlet energy and weak isothermal parameterization condition. Experimental comparisons of the weak-area functional method with existing Dirichlet, quasi-harmonic, the strain energy-minimizing, harmonic and biharmonic masks are performed which show that the weak-area functional method are among the best by choosing appropriate parameters.  相似文献   
2.
The goal of the paper is to automatize the construction and parameterization of kinetic reaction mechanisms that can describe a set of experimentally measured concentration versus time curves. Using the framework and theorems of formal reaction kinetics, first, we build a set of possible mechanisms with a given number of measured and unmeasured (real or fictitious) species and reaction steps that fulfill some chemically reasonable requirements. Then we fit all the corresponding mass-action kinetic models and offer the best one to the chemist to help explain the underlying chemical phenomenon or to use it for predictions. We demonstrate the use of the method via two simple examples: on an artificial, simulated set of data and on a small real-life data set. The method can also be used to do a kind of lumping to generate a model that can reproduce the simulation results of a detailed mechanism with less species and thereby can largely accelerate spatially inhomogeneous simulations.  相似文献   
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The inability to rapidly generate accurate and robust parameters for novel chemical matter continues to severely limit the application of molecular dynamics simulations to many biological systems of interest, especially in fields such as drug discovery. Although the release of generalized versions of common classical force fields, for example, General Amber Force Field and CHARMM General Force Field, have posited guidelines for parameterization of small molecules, many technical challenges remain that have hampered their wide‐scale extension. The Force Field Toolkit (ffTK), described herein, minimizes common barriers to ligand parameterization through algorithm and method development, automation of tedious and error‐prone tasks, and graphical user interface design. Distributed as a VMD plugin, ffTK facilitates the traversal of a clear and organized workflow resulting in a complete set of CHARMM‐compatible parameters. A variety of tools are provided to generate quantum mechanical target data, setup multidimensional optimization routines, and analyze parameter performance. Parameters developed for a small test set of molecules using ffTK were comparable to existing CGenFF parameters in their ability to reproduce experimentally measured values for pure‐solvent properties (<15% error from experiment) and free energy of solvation (±0.5 kcal/mol from experiment). © 2013 Wiley Periodicals, Inc.  相似文献   
5.
《Optimization》2012,61(7):961-973
In this article, we present and compare three mean-variance optimal portfolio approaches in a continuous-time market setting. These methods are the L 2-projection as presented in Schweizer [M. Schweizer, Approximation of random variables by stochastic integrals, Ann. Prob. 22 (1995), pp. 1536–1575], the Lagrangian function approach of Korn and Trautmann [R. Korn and S. Trautmann, Continuous-time portfolio optimization under terminal wealth constraints, ZOR-Math. Methods Oper. Res. 42 (1995), pp. 69–92] and the direct deterministic approach of Lindberg [C. Lindberg, Portfolio optimization when expected stock returns are determined by exposure to risk, Bernoulli 15 (2009), pp. 464–474]. As the underlying model, we choose the recent innovative market parameterization introduced by Lindberg (2009) that has the particular aim to overcome the estimation problems of the stock price drift parameters. We derive some new results for the Lagrangian function approach, in particular explicit representations for the optimal portfolio process. Further, we compare the different optimization frameworks in detail and highlight their attractive and not so attractive features by numerical examples.  相似文献   
6.
利用TRMM(热带测雨雷达)搭载的TMI(微波成像仪)反演廓线资料,分析“菲特”台风登陆前、后云团内部水凝物的分布种类,依此选择WRF区域中尺度模式下符合条件的6个云微物理过程参数化方案(Lin,WSM6,Godgce,WDM6,Morrison以及Thompson方案),模拟2013年10月6~8日的台风过程.从降水落区、强度,水凝物及风场垂直分布,台风路径及强度等方面对预报性能进行对比,结果表明,选用的6个云微物理方案都较好地模拟了浙江暴雨的范围和强度.结合Ts评分,降水量级越大,模拟效果对云微物理方案选择越敏感,其中,Lin方案效果最佳,尤其对极端降水的模拟,其次为WSM6、WDM6及Thompson方案,Morrison和Godgce方案相对较差.结合水凝物平均值廓线分布发现,除WDM6方案外,其他方案对暖雨过程的模拟基本一致,而对冰相过程的模拟6个方案差别较大;同时,各方案对风分量的模拟结果较水凝物廓线差别小,说明对于动力因素模拟不敏感.另外,6个方案对于台风强度的模拟整体偏弱,相较之下,Lin方案较好地模拟了强度变化趋势.  相似文献   
7.
In this paper, we discuss an inverse problem, i.e., the reconstruction of a linear differential dynamic system from the given discrete data of the solution. We propose a model and a corresponding algorithm to recover the coefficient matrix of the differential system based on the normal vectors from the given discrete points, in order to avoid the problem of parameterization in curve fitting and approximation. We also give some theoretical analysis on our algorithm. When the data points are taken from the solution curve and the set composed of these data points is not degenerate, the coefficient matrix $A$ reconstructed by our algorithm is unique from the given discrete and noisefree data. We discuss the error bounds for the approximate coefficient matrix and the solution which are reconstructed by our algorithm. Numerical examples demonstrate the effectiveness of the algorithm.  相似文献   
8.
Chondroitin‐6‐sulfate (C6S) is a glycosaminoglycan (GAG) constituent in the extracellular matrix, which participates actively in crucial biological processes, as well as in various pathological conditions, such as atherosclerosis and cancer. Molecular interactions involving the C6S chain are therefore of considerable interest. A computational model for atomistic simulation was built. This work describes the design and validation of a force field for a C6S dodecasaccharide chain. The results of an extensive molecular dynamics simulation performed with the new force field provide a novel insight into the structure and dynamics of the C6S chain. The intramolecular H‐bonds in the disaccharide linkage region are suggested to play a major role in determining the chain structural dynamics. Moreover, the unravelling of an additional H‐bond involving the sulfate groups in C6S is interesting as changes in sulfation have been claimed to be an important factor in several diseases. The force field will prove useful for future studies of crucial interactions between C6S and various nanoassemblies. It can also be used as a basis for modeling of other GAGs. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   
9.
In our previous work, we have given an algorithm for segmenting a simplex in the n-dimensional space into rt n+ 1 polyhedrons and provided map F which maps the n-dimensional unit cube to these polyhedrons. In this paper, we prove that the map F is a one to one correspondence at least in lower dimensional spaces (n _〈 3). Moreover, we propose the approximating subdivision and the interpolatory subdivision schemes and the estimation of computational complexity for triangular Bézier patches on a 2-dimensional space. Finally, we compare our schemes with Goldman's in computational complexity and speed.  相似文献   
10.
We investigate the one-parametric set of projective subspaces that is generated by a set of rational curves in projective relation. The main theorem connects the algebraic degree of , the number of degenerate subspaces in and the dimension of the variety of all rational curves that can be used to generate . It generalizes classical results and is related to recent investigations on projective motions with trajectories in proper subspaces of the fixed space. Received 9 May 2001.  相似文献   
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