全文获取类型
收费全文 | 418篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
化学 | 276篇 |
晶体学 | 9篇 |
力学 | 9篇 |
数学 | 60篇 |
物理学 | 79篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 17篇 |
2014年 | 14篇 |
2013年 | 16篇 |
2012年 | 32篇 |
2011年 | 31篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 34篇 |
2007年 | 27篇 |
2006年 | 23篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 19篇 |
2002年 | 10篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 16篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1972年 | 1篇 |
1930年 | 2篇 |
排序方式: 共有433条查询结果,搜索用时 31 毫秒
61.
62.
63.
A set D of vertices of a graph G = (V, E) is called a dominating set if every vertex of V not in D is adjacent to a vertex of D. In 1996, Reed proved that every graph of order n with minimum degree at least 3 has a dominating set of cardinality at most 3n/8. In this paper we generalize Reed's result. We show that every graph G of order n with minimum degree at least 2 has a dominating set of cardinality at most (3n +IV21)/8, where V2 denotes the set of vertices of degree 2 in G. As an application of the above result, we show that for k ≥ 1, the k-restricted domination number rk (G, γ) ≤ (3n+5k)/8 for all graphs of order n with minimum degree at least 3. 相似文献
64.
Anti-biofouling properties of comblike block copolymers with amphiphilic side chains 总被引:1,自引:0,他引:1
Krishnan S Ayothi R Hexemer A Finlay JA Sohn KE Perry R Ober CK Kramer EJ Callow ME Callow JA Fischer DA 《Langmuir : the ACS journal of surfaces and colloids》2006,22(11):5075-5086
Surfaces of novel block copolymers with amphiphilic side chains were studied for their ability to influence the adhesion of marine organisms. The surface-active polymer, obtained by grafting fluorinated molecules with hydrophobic and hydrophilic blocks to a block copolymer precursor, showed interesting bioadhesion properties. Two different algal species, one of which adhered strongly to hydrophobic surfaces, and the other, to hydrophilic surfaces, showed notably weak adhesion to the amphiphilic surfaces. Both organisms are known to secrete adhesive macromolecules, with apparently different wetting characteristics, to attach to underwater surfaces. The ability of the amphiphilic surface to undergo an environment-dependent transformation in surface chemistry when in contact with the extracellular polymeric substances is a possible reason for its antifouling nature. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) was used, in a new approach based on angle-resolved X-ray photoelectron spectroscopy (XPS), to determine the variation in chemical composition within the top few nanometers of the surface and also to study the surface segregation of the amphiphilic block. A mathematical model to extract depth-profile information from the normalized NEXAFS partial electron yield is developed. 相似文献
65.
Jinho Oh Heedo Na In-Su Mok Jonggi Kim Kyumin Lee Hyunchul Sohn 《Applied Physics A: Materials Science & Processing》2012,108(3):679-684
In our study, the physical properties of (TiO2) x (SiO2)1?x , including band-gap, band-offset, and thermal stability and the electrical properties of band-engineered SiO2/(TiO2) x (SiO2)1?x tunnel barrier stacks, including the tunneling current and charge-trapping characteristics for applications to nonvolatile memory devices were investigated. It was observed that the band-gap and band-offset of (TiO2) x (SiO2)1?x can be controlled by adjustment in the composition of the (TiO2) x (SiO2)1?x films. Ti-silicate film with TiO2:SiO2 cycle ratio of 1:5 was maintained in an amorphous phase, even after annealing at 950 °C. The tunneling current of the band-engineered SiO2/(TiO2) x (SiO2)1?x stacked tunnel barrier was larger than that of a single SiO2 barrier under a higher external bias, while the tunneling current of a SiO2/(TiO2) x (SiO2)1?x stacked tunnel barrier under a lower external bias was smaller. Charge-trapping tests showed that the voltage shift for SiO2/(TiO2) x (SiO2)1?x is slightly larger than that for single SiO2. 相似文献
66.
Xue-gang Chen Shinya Fujita Michitaka Furuya Moo Young Sohn 《Discrete Applied Mathematics》2012,160(4-5):488-493
A graph is said to be bicritical if the removal of any pair of vertices decreases the domination number of . For a bicritical graph with the domination number , we say that is -bicritical. Let denote the edge-connectivity of . In [2], Brigham et al. (2005) posed the following question: If is a connected bicritical graph, is it true that In this paper, we give a negative answer toward this question; namely, we give a construction of infinitely many connected -bicritical graphs with edge-connectivity for every integer . Furthermore, we give some sufficient conditions for a connected -bicritical graph to have . 相似文献
67.
Yong-Seok Choi Kyung-Won Seo Myong-Hwan Sohn Sang-Joon Lee 《Optics and Lasers in Engineering》2012,50(1):39-45
The accurate three-dimensional (3D) velocity field measurement technique has been receiving large attention in the study of microfluidics. DHM-PTV technique was developed by combining the digital holographic microscopy and particle tracking velocimetry technique. DHM-PTV is an ideal method for measuring three-component-three-dimensional (3C-3D) velocity field in a microscale flow with a fairly good spatial resolution. The advances in the DHM-PTV technique enable the measurement of various microscale flows, such as transport of red blood cells in a microtube and 3D flows in microfluidic devices. DHM-PTV is also applied in studying the motile behavior of swimming microorganisms. DHM-PTV would play an important role in ascertaining the undiscovered basic physics in various microscale and biofluid flow phenomena. In the current study, the basic principle of the DHM-PTV technique and its typical applications to microscale flows are introduced and discussed. 相似文献
68.
Understanding a time reversal process in Lamb wave propagation 总被引:2,自引:0,他引:2
This study investigates the time reversal process (TRP) of Lamb wave signals which are transmitted and received by piezoelectric transducers bonded on plate-like structures. A number of previous studies have paid attention to spatial and temporal refocusing capability of an original excitation through the TRP in highly dispersive and complex media. However, when the TRP is applied to Lamb waves in a homogeneous regular waveguide, the refocusing capability is limited due to permanent residual side bands even if the duration of the time reversed signal increases. Based on the reciprocity of elastodynamics and linear piezoelectricity, theoretical interpretation is conducted for the main and residual side bands of the reconstructed signal in the time domain. In particular, the interpretation includes the temporal effect of velocity and amplitude dispersions, the existence of multimodes, and the reflections from boundaries during the TRP. Then, numerical and experimental tests are conducted to validate the theoretical findings of this paper. Practical issues for the successful implementation of the TRP of Lamb waves are briefly addressed as well. 相似文献
69.
Myong Hwan Sohn 《Experiments in fluids》2010,48(4):565-575
The vortex flow characteristics of a sharp-edged delta wing with an apex strake was investigated through the visualization
and particle image velocimetry (PIV) measurement of the wing-leeward flow region, and the wing-surface pressure measurement.
The wing model was a flat-plate, and 65°-sweep cropped-delta wing with sharp leading edges. The apex strake was also a flat-plate
wing with a cropped-delta shape of 65°/90° sweep, and it can change its incidence angle. The flow Reynolds number was 2.2 × 105 for the flow visualization and 8.2 × 105 for the PIV and wing-surface pressure measurements. The physics of the vortex flow in the wing-leeward flow region and the
suction-pressure distribution on the wing upper-surface were interrelated and analyzed. The effect of a positive (negative)
strake incidence-angle was the upward movement of the strake and wing vortices away from (downward movement of the strake
and wing vortices toward) the wing-upper surface and the delayed (enhanced) coiling interaction between them. This change
of vortex flow characteristics projected directly on the suction pressure distribution on the wing upper-surface. 相似文献
70.
Yang Sung Sohn Anat losub-Amir Alfredo E. Cardenas Ola Karmi Merav Darash Yahana Tal Gruman Linda Rowland Henri-Baptiste Marjault Lauren J. Webb Ron Mittler Ron Elber Assaf Friedler Rachel Nechushtai 《Chemical science》2022,13(23):6929
An effective anti-cancer therapy should exclusively target cancer cells and trigger in them a broad spectrum of cell death pathways that will prevent avoidance. Here, we present a new approach in cancer therapy that specifically targets the mitochondria and ER of cancer cells. We developed a peptide derived from the flexible and transmembrane domains of the human protein NAF-1/CISD2. This peptide (NAF-144-67) specifically permeates through the plasma membranes of human epithelial breast cancer cells, abolishes their mitochondria and ER, and triggers cell death with characteristics of apoptosis, ferroptosis and necroptosis. In vivo analysis revealed that the peptide significantly decreases tumor growth in mice carrying xenograft human tumors. Computational simulations of cancer vs. normal cell membranes reveal that the specificity of the peptide to cancer cells is due to its selective recognition of their membrane composition. NAF-144-67 represents a promising anti-cancer lead compound that acts via a unique mechanism.An effective anti-cancer therapy should exclusively target cancer cells and trigger in them a broad spectrum of cell death pathways that will prevent avoidance. 相似文献