全文获取类型
收费全文 | 219篇 |
免费 | 12篇 |
国内免费 | 21篇 |
专业分类
化学 | 104篇 |
晶体学 | 1篇 |
力学 | 7篇 |
数学 | 51篇 |
物理学 | 89篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 11篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 21篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 13篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有252条查询结果,搜索用时 15 毫秒
21.
H. B. Zhou X. H. Zhou Y. H. Zhang Y. Zheng M. L. Liu N. T. Zhang L. Chen S. T. Wang G. S. Li H. X. Wang B. Ding X. G. Lei Y. X. Guo G. X. Dong F. R. Xu M. Oshima Y. Toh M. Koizumi A. Osa Y. Hatsukawa 《The European Physical Journal A - Hadrons and Nuclei》2011,47(9):1-7
High-spin states in 101Pd have been investigated by means of in-beam γ-ray spectroscopic techniques via the 76Ge(28Si, 3n) reaction at beam energies of 85 and 95 MeV. The previously known d 5/2 and 1/2?[550] bands were extended to higher spins, and the unfavored signature branch of the 1/2?[550] band was built. The band crossings observed experimentally are explained by the alignment of g 9/2 protons. The band properties in 101Pd are compared with those in the neighboring nuclei and are discussed within the framework of the cranked shell model (CSM). 相似文献
22.
Let ${\mathcal{A}}$ be a collection of n linear hyperplanes in ${\mathbb{k}^\ell}$ , where ${\mathbb{k}}$ is an algebraically closed field. The Orlik-Terao algebra of ${\mathcal{A}}$ is the subalgebra ${{\rm R}(\mathcal{A})}$ of the rational functions generated by reciprocals of linear forms vanishing on hyperplanes of ${\mathcal{A}}$ . It determines an irreducible subvariety ${Y (\mathcal{A})}$ of ${\mathbb{P}^{n-1}}$ . We show that a flat X of ${\mathcal{A}}$ is modular if and only if ${{\rm R}(\mathcal{A})}$ is a split extension of the Orlik-Terao algebra of the subarrangement ${\mathcal{A}_X}$ . This provides another refinement of Stanley’s modular factorization theorem [34] and a new characterization of modularity, similar in spirit to the fibration theorem of [27]. We deduce that if ${\mathcal{A}}$ is supersolvable, then its Orlik-Terao algebra is Koszul. In certain cases, the algebra is also a complete intersection, and we characterize when this happens. 相似文献
23.
Polynomiality of an inexact infeasible interior point algorithm for semidefinite programming 总被引:3,自引:0,他引:3
In this paper we present a primal-dual inexact infeasible interior-point algorithm for semidefinite programming problems (SDP). This algorithm allows the use of search directions that are calculated from the defining linear system with only moderate accuracy, and does not require feasibility to be maintained even if the initial iterate happened to be a feasible solution of the problem. Under a mild assumption on the inexactness, we show that the algorithm can find an -approximate solution of an SDP in O(n2ln(1/)) iterations. This bound of our algorithm is the same as that of the exact infeasible interior point algorithms proposed by Y. Zhang.Research supported in part by the Singapore-MIT alliance, and NUS Academic Research Grant R-146-000-032-112.Mathematics Subject Classification (1991): 90C05, 90C30, 65K05 相似文献
24.
Yew Hoong Leong Eng Guan Tay Tin Lam Toh Khiok Seng Quek Jaguthsing Dindyal 《The Journal of Mathematical Behavior》2011,30(3):181-193
This study is based on the stance that Pólya's “Look Back,” though understudied, remains relevant to Mathematics curricula that place emphasis on problem solving. Although the Singapore Mathematics curriculum adopts the goal of teaching Look Back, research about how it is carried out in actual classroom practice is rare. In our project, we focus on a redesign of a teacher development programme that is targeted to help teachers realize Pólya's original vision of Look Back in the classroom. We report the cases of two teachers who have participated in the teacher development programme: their thinking about Look Back (through interview records) and their interpretation of Look Back in their classroom practice (through video records). By bringing these two spheres of data together, we discuss their degree of ‘buy-in’ to Look Back in the overall problem solving enterprise. 相似文献
25.
Z. B. Yan F. Duan T. N. Wong K. C. Toh K. F. Choo P. K. Chan Y. S. Chua L. W. Lee 《Heat and Mass Transfer》2013,49(7):985-990
An inclined spray chamber with four multiple nozzles to cool a 1 kW 6U electronic test card has been designed and tested in this study. The multiple inclined sprays can cover the same heated surface area as that with the multiple normal sprays but halve the volume of the spray chamber. The spray cooling system used R134a as a working fluid in a modified refrigeration cycle. It is observed that increasing mass flow rate and pressure drop across the nozzles improved the heat transfer coefficient with a maximum enhancement of 117 %, and reduced the maximum temperature difference at the heated surface from 13.8 to 8.4 °C in the inclined spray chamber with a heat flux of 5.25 W/cm2, while the heat transfer coefficient of the normal spray increased with a maximum enhancement of 215 % and the maximum temperature difference decreased from 10.8 to 5.4 °C under similar operating conditions. We conclude that the multiple inclined sprays could produce a higher heat transfer coefficient but with an increase in non-uniformity of the surface temperature compared with the multiple normal sprays. 相似文献
26.
27.
Summary.
It is well known that the zeros of a polynomial are equal to
the
eigenvalues of the associated companion matrix . In this paper
we take a
geometric view of the conditioning of these two problems and of the stability of
algorithms for polynomial zerofinding. The
is the set of zeros of all polynomials obtained by
coefficientwise perturbations of of size ;
this is a subset of the
complex plane considered earlier by Mosier, and is bounded by a
certain generalized lemniscate. The
is another subset of
defined as the set of eigenvalues of matrices
with ; it is bounded by a
level curve of the resolvent
of $A$. We find that if $A$ is first balanced in the usual EISPACK sense, then
and
are usually quite close to one another. It follows that the Matlab
ROOTS algorithm of balancing the companion matrix, then computing its eigenvalues, is a stable
algorithm for polynomial zerofinding. Experimental comparisons with the
Jenkins-Traub (IMSL) and
Madsen-Reid (Harwell) Fortran codes confirm that these three algorithms have roughly
similar stability properties.
Received June 15, 1993 相似文献
28.
We study four measures of problem instance behavior that might account for the observed differences in interior-point method
(IPM) iterations when these methods are used to solve semidefinite programming (SDP) problem instances: (i) an aggregate geometry
measure related to the primal and dual feasible regions (aspect ratios) and norms of the optimal solutions, (ii) the (Renegar-)
condition measure C(d) of the data instance, (iii) a measure of the near-absence of strict complementarity of the optimal solution, and (iv) the
level of degeneracy of the optimal solution. We compute these measures for the SDPLIB suite problem instances and measure
the sample correlation (CORR) between these measures and IPM iteration counts (solved using the software SDPT3) when these
measures have finite values. Our conclusions are roughly as follows: the aggregate geometry measure is highly correlated with
IPM iterations (CORR = 0.901), and provides a very good explanation of IPM iterations, particularly for problem instances
with solutions of small norm and aspect ratio. The condition measure C(d) is also correlated with IPM iterations, but less so than the aggregate geometry measure (CORR = 0.630). The near-absence
of strict complementarity is weakly correlated with IPM iterations (CORR = 0.423). The level of degeneracy of the optimal
solution is essentially uncorrelated with IPM iterations.
This research has been partially supported through the MIT-Singapore Alliance. 相似文献
29.
30.