全文获取类型
收费全文 | 173篇 |
免费 | 18篇 |
国内免费 | 16篇 |
专业分类
化学 | 55篇 |
力学 | 19篇 |
综合类 | 1篇 |
数学 | 74篇 |
物理学 | 58篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 2篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 11篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有207条查询结果,搜索用时 15 毫秒
101.
Dr. George Kleinhans Dr. Alan K.-W. Chan Dr. Ming-Yi Leung David C. Liles Prof. Dr. Manuel A. Fernandes Prof. Dr. Vivian W.-W. Yam Prof. Dr. Israel Fernández Prof. Dr. Daniela I. Bezuidenhout 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(31):6993-6998
The photophysical properties of a series of T-shaped coinage d10 metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored. The series includes a rare new example of a tridentate T-shaped AgI complex. Post-complexation modification of the AuI complex provides access to a linear cationic AuI complex following ligand alkylation, or the first example of a cationic square planar AuIII−F complex from electrophilic attack on the metal centre. Emissions ranging from blue (CuI) to orange (AgI) are obtained, with variable contributions of thermally-dependent fluorescence and phosphorescence to the observed photoluminescence. Green emissions are observed for all three gold complexes (neutral T-shaped AuI, cationic linear AuI and square planar cationic AuIII). The higher quantum yield and longer decay lifetime of the linear gold(I) complex are indicative of increased phosphorescence contribution. 相似文献
102.
We give new recursive constructions of complete caps in PG(n,2). We approach the problem of constructing caps with low dependency via the doubling construction and comparison to lower
bounds. We report results of the exhaustive classification (up to projective equivalence) of all caps in PG(n,2) for n≤ 6.
Research partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) 相似文献
103.
104.
We prove the existence of a rank three geometry admitting the Hall–Janko group J2 as flag-transitive automorphism group and Aut(J2) as full automorphism group. This geometry belongs to the diagram (c·L*) and its nontrivial residues are complete graphs of size 10 and dual Hermitian unitals of order 3. 相似文献
105.
W. S. Weiglhofer A. Lakhtakia 《International Journal of Infrared and Millimeter Waves》1996,17(8):1365-1376
We present some novel expressions for the depolarization dyadics in uniaxial dielectric-magnetic media. These expressions were obtained by generalizing the Fikioris approach for extracting the singular behaviour of integrals involving the dyadic Green functions and the source current density distributions. Cubical, cylindrical and spherical geometries serve as examples for a discussion of the depolarization dyadics' dependence on geometry and anisotropy. 相似文献
106.
Paul W. Vos 《Annals of the Institute of Statistical Mathematics》1995,47(1):49-64
When the variance is a known function of the mean, as in quasi-likelihood applications, the sample variance also contains information about the mean and extensions of quasi-likelihood functions have been suggested that incorporate this additional information. In order to be sure these extensions are an improvement, further assumptions are made typically on the higher moments of the data so that there is a trade-off between the greater robustness of the quasi-likelihood estimates and the potentially improved estimates based on the extended quasi-likelihood functions. Improvement is often measured by relative efficiency but more insight can be gained by considering optimality of estimating functions, information loss, and sufficiency. All these measures can be described using the dual geometries of the quasi- and extended quasi-likelihood estimators. For a substantial range of models, the extended estimates offer little improvement when the coefficient of variation is small. 相似文献
107.
In the present study, a high-order compact finite-difference lattice Boltzmann method is applied for accurately computing 3-D incompressible flows in the generalized curvilinear coordinates to handle practical and realistic geometries with curved boundaries and nonuniform grids. The incompressible form of the 3-D nineteen discrete velocity lattice Boltzmann method is transformed into the generalized curvilinear coordinates. Herein, a fourth-order compact finite-difference scheme and a fourth-order Runge-Kutta scheme are used for the discretization of the spatial derivatives and the temporal term, respectively, in the resulting 3-D nineteen discrete velocity lattice Boltzmann equation to provide an accurate 3-D incompressible flow solver. A high-order spectral-type low-pass compact filtering technique is applied to have a stable solution. All boundary conditions are implemented based on the solution of the governing equations in the 3-D generalized curvilinear coordinates. Numerical solutions of different 3-D benchmark and practical incompressible flow problems are performed to demonstrate the accuracy and performance of the solution methodology presented. Herein, the 2-D cylindrical Couette flow, the decay of a 3-D double shear wave, the cubic lid-driven cavity flow with nonuniform grids, the flow through a square duct with 90° bend and the flow past a sphere at different flow conditions are considered for validating the present computations. Numerical results obtained show the accuracy and robustness of the present solution methodology based on the implementation of the high-order compact finite-difference lattice Boltzman method in the generalized curvilinear coordinates for solving 3-D incompressible flows over practical and realistic geometries. 相似文献
108.
109.
We review a construction of quaternionic Kähler metrics starting from a rank 2 distribution in 5 dimensions. We relate it to a more general theory about Einstein deformations of symmetric metrics. Finally we ask some questions on complete metrics and relate them to a Zoll phenomenon. 相似文献
110.
A nonlocal continuum-based model is derived to simulate the dynamic behavior of bridged carbon nanotube-based nano-scale mass detectors. The carbon nanotube (CNT) is modeled as an elastic Euler-Bernoulli beam considering von-Kármán type geometric nonlinearity. In order to achieve better accuracy in characterization of the CNTs, the geometrical properties of an attached nano-scale particle are introduced into the model by its moment of inertia with respect to the central axis of the beam. The inter-atomic long-range interactions within the structure of the CNT are incorporated into the model using Eringen's nonlocal elastic field theory. In this model, the mass can be deposited along an arbitrary length of the CNT. After deriving the full nonlinear equations of motion, the natural frequencies and corresponding mode shapes are extracted based on a linear eigenvalue problem analysis. The results show that the geometry of the attached particle has a significant impact on the dynamic behavior of the CNT-based mechanical resonator, especially, for those with small aspect ratios. The developed model and analysis are beneficial for nano-scale mass identification when a CNT-based mechanical resonator is utilized as a small-scale bio-mass sensor and the deposited particles are those, such as proteins, enzymes, cancer cells, DNA and other nano-scale biological objects with different and complex shapes. 相似文献