全文获取类型
收费全文 | 303篇 |
免费 | 34篇 |
国内免费 | 6篇 |
专业分类
化学 | 85篇 |
力学 | 14篇 |
综合类 | 1篇 |
数学 | 172篇 |
物理学 | 71篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 30篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 21篇 |
2006年 | 13篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1967年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有343条查询结果,搜索用时 594 毫秒
101.
Mihaela Monica Constantin Ctlina Gabriela Corbu Sorin Mocanu Elena Irina Popescu Marin Micutz Teodora Staicu Raluca omoghi Bogdan Tric Vlad Tudor Popa Aurica Precupas Iulia Matei Gabriela Ionita 《Molecules (Basel, Switzerland)》2022,27(1)
Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements. 相似文献
102.
Tudor Zamfirescu 《Set-Valued Analysis》2000,8(3):295-297
We introduce the notion of a starshaped set-valued function, and relate it to convex set-valued functions. We prove a theorem which, in the convex case, implies that single-valuedness is exceptional if the function is not everywhere single-valued. A second result shows a remarkable costantness of images for starshaped set-valued functions. Both theorems were inspired from a result of Deutsch and Singer, which they strengthen. 相似文献
103.
104.
105.
Tudor Zamfirescu 《Journal of Geometry》2008,88(1-2):194-199
This paper is about diameters of compact sets. These are chords of maximal length. On one hand we see that the sum of the
angles under which we see a diameter from two points of the set separated by the diameter is never smaller than 5π/6. On the other hand we describe cases in which the diameter of a point-symmetric set must join symmetric points.
相似文献
106.
107.
108.
Sheet metal forming processes often involve complex loading sequences. To improve the prediction of some undesirable phenomena, such as springback, physical behavior models should be considered. This paper investigates springback behavior predicted by advanced elastoplastic hardening models which combine isotropic and kinematic hardening and take strain-path changes into account. A dislocation-based microstructural hardening model formulated from physical observations and the more classical cyclic model of Chaboche have been considered in this work. Numerical implementation was carried out in the ABAQUS software using a return mapping algorithm with a combined backward Euler and semi-analytical integration scheme of the constitutive equations. The capability of each model to reproduce transient hardening phenomena at abrupt strain-path changes has been shown via simulations of sequential rheological tests. A springback analysis of strip drawing tests was performed in order to emphasize the impact of several influential parameters, namely: process, numerical and behavior parameters. The effect of the two hardening models with respect to the process parameters has been specifically highlighted. 相似文献
109.
We show that the strong-coupling physics inherent to the insulating Mott state in 2D leads to a jump in the chemical potential upon doping and the emergence of a pseudogap in the single-particle spectrum below a characteristic temperature. The pseudogap arises because any singly occupied site not immediately neighboring a hole experiences a maximum energy barrier for transport equal to t(2)/U, t the nearest-neighbor hopping integral and U the on-site repulsion. The resultant pseudogap cannot vanish before each lattice site, on average, has at least one hole as a near neighbor. The ubiquity of this effect in all doped Mott insulators suggests that the pseudogap in the cuprates has a simple origin. 相似文献
110.
Juan-Pablo Ortega Víctor Planas-Bielsa Tudor S. Ratiu 《Journal of Differential Equations》2005,214(1):92-127
This paper includes results centered around three topics, all of them related with the nonlinear stability of equilibria in constrained dynamical systems. First, we prove an energy-Casimir type sufficient condition for stability that uses functions that are not necessarily conserved by the flow and that takes into account the asymptotically stable behavior that may occur in certain constrained systems, such as Poisson and Leibniz dynamical systems. Second, this method is specifically adapted to Poisson systems obtained via a reduction procedure and we show in examples that the kind of stability that we propose is appropriate when dealing with the stability of the equilibria of some constrained mechanical systems. Finally, we discuss two situations in which the use of continuous Casimir functions in stability studies is equivalent to the topological stability methods introduced by Patrick et al. (Arch. Rational Mech. Anal., 2004, preprint arXiv:math.DS/0201239v1, to appear). 相似文献