全文获取类型
收费全文 | 196篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
化学 | 76篇 |
晶体学 | 4篇 |
力学 | 33篇 |
数学 | 48篇 |
物理学 | 42篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 11篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有203条查询结果,搜索用时 31 毫秒
21.
Shokrollah Salarian Sean Sather-Wagstaff Siamak Yassemi 《Journal of Pure and Applied Algebra》2006,207(1):99-108
Let (R,m) be a Noetherian local ring of depth d and C a semidualizing R-complex. Let M be a finite R-module and t an integer between 0 and d. If the GC-dimension of M/aM is finite for all ideals a generated by an R-regular sequence of length at most d−t then either the GC-dimension of M is at most t or C is a dualizing complex. Analogous results for other homological dimensions are also given. 相似文献
22.
In this paper we address the problem of the implementation of boundary conditions for the derived pressure Poisson equation of incompressible flow. It is shown that the direct Galerkin finite element formulation of the pressure Poisson equation automatically satisfies the inhomogeneous Neumann boundary conditions, thus avoiding the difficulty in specifying boundary conditions for pressure. This ensures that only physically meaningful pressure boundary conditions consistent with the Navier-Stokes equations are imposed. Since second derivatives appear in this formulation, the conforming finite element method requires C1 continuity. However, for many problems of practical interest (i.e. high Reynolds numbers) the second derivatives need not be included, thus allowing the use of more conventional C0 elements. Numerical results using this approach for a wall-driven contained flow within a square cavity verify the validity of the approach. Although the results were obtained for a two-dimensional problem using the p-version of the finite element method, the approach presented here is general and remains valid for the conventional h-version as well as three-dimensional problems. 相似文献
23.
We give a generalization of Eagon-Reiner’s theorem relating Betti numbers of the Stanley-Reisner ideal of a simplicial complex and the CMt property of its Alexander dual. Then we characterize bi-CMt bipartite graphs and bi-CMt chordal graphs. These are generalizations of recent results due to Herzog and Rahimi. 相似文献
24.
Irregularities are widespread in large databases and often lead to erroneous conclusions with respect to data mining and statistical
analysis. For example, considerable bias is often resulted from many parameter estimation procedures without properly handling
significant irregularities. Most data cleaning tools assume one known type of irregularity. This paper proposes a generic
Irregularity Enlightenment (IE) framework for dealing with the situation when multiple irregularities are hidden in large
volumes of data in general and cross sectional time series in particular. It develops an automatic data mining platform to
capture key irregularities and classify them based on their importance in a database. By decomposing time series data into
basic components, we propose to optimize a penalized least square loss function to aid the selection of key irregularities
in consecutive steps and cluster time series into different groups until an acceptable level of variation reduction is achieved.
Finally visualization tools are developed to help analysts interpret and understand the nature of data better and faster before
further data modeling and analysis. 相似文献
25.
Amir Babaei S. Reza Ghaffarian M. Mehdi Khorasani Siamak Baseghi 《Journal of Macromolecular Science: Physics》2013,52(3):481-495
High-density polyethylene/organoclay nanocomposites were prepared via melt intercalation in an internal mixer using both a direct mixing and master batching method. Two types of maleic anhydride grafted polyethylene, high-density polyethylene grafted maleic anhydride, and linear low-density polyethylene grafted maleic anhydride, (HDPE-g-MA, LLDPE-g-MA) were used as compatibilizers to enhance the dispersibility of nanoclay in HDPE. Dispersion of organoclay in the nanocomposites was characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and rheological mechanical spectroscopy (RMS). Effects of clay content and degree of clay dispersion on the rheological and tensile properties were also investigated. Furthermore, the effect of order of mixing on the dispersion and distribution of the clay layers was studied. The obtained results showed that organoclay in the nanocomposites were dispersed homogeneously and exfoliated better when HDPE-g-MA and the direct mixing route were used. Although in the master batching method clay intercalated better, clay layers chiefly remain in compatibilizer rich areas. On the other hand, direct mixing was observed to lead to clay particles being dispersed in the HDPE matrix or at the interface of the matrix and compatibilizer and, consequently, better improvement in the tensile modulus was achieved. It was determined that the compatibilizer with the higher miscibility with the matrix was the key factor for achieving better exfoliation of clay sheets. 相似文献
26.
27.
Let G be a finite simple graph on a vertex set V(G) = {x 11,…, x n1}. Also let m 1,…, m n ≥ 2 be integers and G 1,…, G n be connected simple graphs on the vertex sets V(G i ) = {x i1,…, x im i }. In this article, we provide necessary and sufficient conditions on G 1,…, G n for which the graph obtained by attaching the G i to G is unmixed or vertex decomposable. Then we characterize Cohen–Macaulay and sequentially Cohen–Macaulay graphs obtained by attaching the cycle graphs or connected chordal graphs to arbitrary graphs. 相似文献
28.
Siamak Shams Es-haghi Robert A. Weiss 《Journal of polymer science. Part A, Polymer chemistry》2022,60(16):2476-2487
A continuum damage model was developed to describe the finite tensile deformation of tough double-network (DN) hydrogels synthesized by polymerization of a water-soluble monomer inside a highly crosslinked rigid polyelectrolyte network. Damage evolution in DN hydrogels was characterized by performing loading-unloading tensile tests and oscillatory shear rheometry on DN hydrogels synthesized from 3-sulfopropyl acrylate potassium salt (SAPS) and acrylamide (AAm). The model can explain all the mechanical features of finite tensile deformation of DN hydrogels, including idealized Mullins effect and permanent set observed after unloading, qualitatively and quantitatively. The constitutive equation can describe the finite elasto-plastic tensile behavior of DN hydrogels without resorting to a yield function. It was showed that tensile mechanics of DN hydrogels in the model is controlled by two material parameters which are related to the elastic moduli of first and second networks. In effect, the ratio of these two parameters is a dimensionless number that controls the behavior of material. The model can capture the stable branch of material response during neck propagation where engineering stress becomes constant. Consistent with experimental data, by increasing the elastic modulus of the second network the finite tensile behavior of the DN hydrogel changes from necking to strain hardening. 相似文献
29.
A novel approach using Monte Carlo method applied to simulation of low‐density polyethylene (LDPE) polymerization in tubular reactor showing topological characteristics, and the comprehensive kinetic mechanism has been taken into consideration. The results show the precise details of the structure of a chain in the three levels of the backbone, the main branches, and branches on branch. The chain types include dead polymer, dead polymer with unsaturated end, and live polymer with primary radical, secondary radical, and tertiary radical. In this work, the branches on branch were identified in terms of number, length, and position of the branch. Sixty percent of branches on branch are 1 to 5 carbons long, and the longest branch on branch is about 50 carbons. Thus, this study provides a tool for more accurately mapping the polymer chains architecture, superior to determine the number, and position of long‐ and short‐chain branches in past researches. Finally, this approach will advance the prediction of microstructure‐related properties of polymer one step further. 相似文献
30.