首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   616篇
  免费   39篇
  国内免费   1篇
化学   503篇
晶体学   16篇
力学   3篇
数学   32篇
物理学   102篇
  2023年   7篇
  2022年   7篇
  2021年   16篇
  2020年   20篇
  2019年   20篇
  2018年   13篇
  2017年   10篇
  2016年   20篇
  2015年   18篇
  2014年   22篇
  2013年   38篇
  2012年   61篇
  2011年   65篇
  2010年   33篇
  2009年   27篇
  2008年   41篇
  2007年   34篇
  2006年   30篇
  2005年   21篇
  2004年   26篇
  2003年   8篇
  2002年   6篇
  2000年   2篇
  1999年   6篇
  1998年   5篇
  1995年   6篇
  1993年   2篇
  1992年   8篇
  1991年   8篇
  1990年   5篇
  1989年   4篇
  1987年   4篇
  1986年   2篇
  1985年   4篇
  1984年   2篇
  1983年   4篇
  1982年   4篇
  1981年   2篇
  1980年   4篇
  1979年   4篇
  1978年   2篇
  1976年   4篇
  1975年   2篇
  1974年   3篇
  1973年   6篇
  1972年   7篇
  1970年   2篇
  1968年   1篇
  1967年   1篇
  1932年   1篇
排序方式: 共有656条查询结果,搜索用时 15 毫秒
581.
The internal behavior of fast ions interacting with magnetohydrodynamic bursts excited by energetic ions has been experimentally investigated in the compact helical system. The resonant convective oscillation of fast ions was identified inside the last closed-flux surface during an energetic-particle mode (EPM) burst. The phase difference between the fast-ion oscillation and the EPM, indicating the coupling strength between them, remains a certain value during the EPM burst and drives an anomalous transport of fast ions.  相似文献   
582.
Resonant strengths have been measured for dielectronic recombination of Li-like iodine, holmium, and bismuth using an electron beam ion trap. By observing the atomic number dependence of the state-resolved resonant strength, clear experimental evidence has been obtained that the importance of the generalized Breit interaction (GBI) effect on dielectronic recombination increases as the atomic number increases. In particular, it has been shown that the GBI effect is exceptionally strong for the recombination through the resonant state [1s2s(2)2p(1/2)](1).  相似文献   
583.
The speckle interferometer based on multi-camera technologies using two cameras is applied to a dynamic measurement. The new speckle interferometer is constructed by a prism array and two cameras. A phenomenon, which a bearing-ball collides against a thin polymer film, is investigated by the proposed interferometer. Then, it is shown that the local maximum deformation of the thin film by the collision is about 1.0 μm. Such a deformation process can precisely be analyzed by this method without any troubles of optical dislocations. In the results, it is confirmed that a large deformation process can be analyzed by accumulating measured results of small deformation in every small continuous analysis. Furthermore, it is estimated that the measurement precision of this method is about 5 nm as experimental results.  相似文献   
584.
Sliding behavior of water droplets on line-patterned hydrophobic surfaces   总被引:1,自引:0,他引:1  
We prepared line-patterned hydrophobic surfaces using fluoroalkylsilane (FAS) and octadecyltrimethoxysilane (ODS) then investigated the effect of line direction on sliding behavior of water droplets by direct observation of the actual droplet motion during sliding. Water droplets slide down with a periodic large deformation of the contact line and sliding velocity fluctuation that occurred when they crossed over the 500-μm ODS line regions in FAS regions on a Si surface tilted at 35°. These behaviors are less marked for motion on a 100-μm line surface, or on lines oriented parallel to the slope direction. Smaller droplets slide down with greater displacement in the line direction on 500-μm line patterning when the lines were rotated at 13° in-plane for the slope direction. This sliding behavior depended on the droplet size and rotation angle, and is accountable by the balance between gravitational and retentive forces.  相似文献   
585.
We deposited 0.01-0.16 ML (monolayer) of potassium on stepped (7 5 5) [=6(1 1 1) × (1 0 0)] surface of nickel in order to fabricate and to understand the growth process of one-dimensional (1D) potassium atomic-chain structure by observing the low-energy-electron-diffraction (LEED) patterns. The LEED patterns from potassium adsorbates exhibit a distinct coverage dependence that 1× streaks first appeared at low coverages up to 0.04 ML and later 2× streaks appeared at around 0.09 ML. The streaks become spotty at the higher coverage. We explained these coverage-dependent changes in LEED patterns in a thorough comparison with kinematically calculated LEED patterns constructing a reasonable growth model.  相似文献   
586.
This study reports the synthesis of a methoxy-substituted 2,6-di(1,8-naphthyridin-2-yl)pyridine using Friedländer methodology. The functionalization at the 4-carbon of the methoxy-substituted derivative was confirmed by X-ray structural analysis. Finally, the methyl ether protecting group was cleaved to obtain 2,6-di(1,8-naphthyridin-2-yl)pyridine-4-ol. Using the compounds, coordination behavior to ruthenium(II) center was also examined.  相似文献   
587.
An enantiomeric pair of C2-chiral bifunctionalised spin labels having a pyrrolidine nitroxide moiety, whose configurations were determined by X-ray crystal diffraction analysis, was prepared and applied to troponin C whose binding mode of double disulfide linkage was proved by EPR spectroscopy.  相似文献   
588.
Trans-polyacetylene with a degenerate ground state has a nonlinear excitation of soliton after photoexcitation, due to the electron-phonon coupling. The excess energy of an excited electron-hole pair over a soliton pair creation induces a breather oscillation characterized by collective stretching vibration of the carbon-carbon bonds. A time-frequency analysis of pump probe signal shows that instantaneous frequencies of stretching modes are modulated for approximately 50 fs after excitation and the modulation period is 44+/-3 fs consistent with the theoretical expectation, clearly verifying the breather.  相似文献   
589.
We report on the development of a cantilever-based scanning near-field optical microscope (SNOM) working in an extreme environment, at cryogenic temperature around 10 K and under strong magnetic field up to 7 T. We designed a new optical system based on an infinite conjugate microscope, which extracts the near-field signal from a small aperture through a narrow chamber into free space as collimated light. Using this system, we successfully measured near-field and topographical images of a metal-hole sample simultaneously. Combining the local optical accessing technique with the external control of the electronic state, this SNOM system will be a powerful tool to study optical properties of semiconductor nanostructures.  相似文献   
590.
An acidic polysaccharide, named glycyrrhizan GA, was isolated from the stolon of Glycyrrhiza glabra L. var. glandulifera Reg. et Herd. It produced a single band on electrophoresis and a single peak on gel chromatography, and its molecular mass was estimated to be 85,000. Glycyrrhizan GA is composed of L-arabinose: D-galactose: L-rhamnose: D-galacturonic acid: D-glucuronic acid in the molar ratio of 22:10:1:2:1, in addition to small amounts of O-acetyl groups. Part of the hexuronic acid residues exist as methyl esters. Methylation analysis, carbon-13 nuclear magnetic resonance and periodate oxidation studies indicated that its structural features include mainly alpha-arabino-beta-3,6-galactan type structural units. Glycyrrhizan GA showed remarkable reticuloendothelial system-potentiating activity in a carbon clearance test.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号