全文获取类型
收费全文 | 897篇 |
免费 | 15篇 |
专业分类
化学 | 666篇 |
晶体学 | 6篇 |
力学 | 25篇 |
数学 | 66篇 |
物理学 | 149篇 |
出版年
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 19篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 23篇 |
2014年 | 16篇 |
2013年 | 39篇 |
2012年 | 46篇 |
2011年 | 69篇 |
2010年 | 29篇 |
2009年 | 27篇 |
2008年 | 55篇 |
2007年 | 45篇 |
2006年 | 59篇 |
2005年 | 49篇 |
2004年 | 43篇 |
2003年 | 31篇 |
2002年 | 30篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1985年 | 5篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1967年 | 4篇 |
1958年 | 3篇 |
排序方式: 共有912条查询结果,搜索用时 17 毫秒
1.
Let
d−1{(x1,…,xd)
d:x21+···+x2d=1} be the unit sphere of the d-dimensional Euclidean space
d. For r>0, we denote by Brp (1p∞) the class of functions f on
d−1 representable in the formwhere dσ(y) denotes the usual Lebesgue measure on
d−1,
and Pλk(t) is the ultraspherical polynomial.For 1p,q∞, the Kolmogorov N-width of Brp in Lq(
d−1) is given bythe left-most infimum being taken over all N-dimensional subspaces XN of Lq(
d−1).The main result in this paper is that for r2(d−1)2,where ANBN means that there exists a positive constant C, independent of N, such that C−1ANBNCAN.This extends the well-known Kashin theorem on the asymptotic order of the Kolmogorov widths of the Sobolev class of the periodic functions. 相似文献
2.
3.
D. Chithrani R. L. Williams J. Lefebvre P. J. Poole G. C. Aers 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):290
We discuss the preparation and spectroscopic characterisation of a single InAs/InP quantum dot suitable for long-distance quantum key distribution applications around λ=1.55 μm. The dot is prepared using a site-selective growth technique which allows a single dot to be deposited in isolation at a controlled spatial location. Micro-photoluminescence measurements as a function of exciton occupation are used to determine the electronic structure of the dot. Biexciton emission, shell filling and many-body re-normalization effects are observed for the first time in single InAs/InP quantum dots. 相似文献
4.
A Monte-Carlo model is described which has been developed for calculation of multiply scattered LIDAR returns. Results are shown for the common problem selected by the MUSCLE (MUltiple SCattering LIDAR Experiments) group for intercomparison, which represents a typical ground-based cloud-sensing scenario. This is contrasted with returns from the same cloud sensed by a space-based LIDAR, where multiple-scattering effects are much greater. The magnitude of multiple-scattering effects is seen to be largely determined by the optical depth across the receiver field of view at the cloud. 相似文献
5.
6.
Summary Glass formation in nature and materials science is reviewed and the recent recognition of polymorphism within the glassy state,
polyamorphism, is discussed. The process by which the glassy state originates during the continuous cooling or viscous slowdown
process, is examined and the three canonical characteristics of relaxing liquids are correlated through the fragility. The
conversion of strong liquids to fragile liquids by pressure-induced coordination number increases is discussed, and then it
is shown that for the same type of system it is possible to have the same conversion accomplished via a first-order transition
within the liquid state. The systems in which this can happen are of the same type which exhibit polyamorphism, and the whole
phenomenology can be accounted for by a recent simple modification of the van der Waals model for tetrahedrally bonded liquids.
The concept of complex amorphous systems which can lose a significant number of degrees of freedom through weak first-order
transitions is then used to discuss the relation between native and denatured hydrated proteins, since the latter have much
in common with plasticized chain polymer systems. Finally, we close the circle by taking a short-time-scale phenomenon given
much attention by protein physicists,viz., the onset of an anomaly in the Debye-Waller factor with increasing temperature, and showing that for a wide variety of liquids,
including computer-simulated strong and fragile ionic liquids, this phenomenon is closely correlated with the experimental
glass transition temperature. This implies that the latter owes its origin to the onset of strong anharmonicity in certain
components of the vibrational density of states (evidently related to the boson peak) which then permits the system to gain
access to its configurational degrees of freedom. The more anharmonic these vibrational components, the closer to the Kauzmann
temperature will commence the exploration of configuration space and, for a given configurational microstate degeneracy, the
more fragile the liquid will be.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
7.
Gavin D. Henry Author Vitae 《Tetrahedron》2004,60(29):6043-6061
8.
We couple a morphological study of an immiscible binary AB mixture with a micromechanical simulation to determine how the spatial distribution of the A and B domains and the interfacial region (interphase) affects the mechanical behavior of the blend. The morphological studies are conducted through a three-dimensional Cahn-Hilliard (CH) simulation. Through the CH calculations, we obtain the size and structure of the domains for different blend compositions. The output of the CH model serves as the input to the Lattice Spring Model (LSM), which consists of a three-dimensional network of springs. In particular, the location of the different phases is mapped onto the LSM lattice and the appropriate force constants are assigned to the LSM sites. A stress is applied to the LSM lattice and we calculate the elastic response of the material. We find that the local stress and strain fields are highly dependent on the morphology of the system. By integrating the morphological and mechanical models, we can isolate how modifications in the composition of the mixture affect the macroscopic behavior. Thus, we can establish how choices made in the components affect the ultimate performance of the material. 相似文献
9.
10.
Using flow microcalorimetry, the ion association reaction M2+(aq)+Fe(CN)
6
4–
(aq)=MFe(CN)
6
2–
(aq) (M=Ca, Mg) has been studied at 25°C over the ionic strength range 0.02 to 0.08 mol-dm–3. Analyses of the data to obtain Ho, the enthalpy change at infinite dilution, are described. The value obtained for Ho is sensitive to the kind of functions used to correct for non-ideal behavior. 相似文献