全文获取类型
收费全文 | 437篇 |
免费 | 12篇 |
专业分类
化学 | 329篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 19篇 |
物理学 | 95篇 |
出版年
2023年 | 4篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 12篇 |
2013年 | 15篇 |
2012年 | 19篇 |
2011年 | 27篇 |
2010年 | 9篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 40篇 |
2006年 | 30篇 |
2005年 | 31篇 |
2004年 | 23篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1973年 | 12篇 |
1972年 | 5篇 |
1970年 | 3篇 |
1968年 | 8篇 |
1967年 | 2篇 |
1961年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有449条查询结果,搜索用时 28 毫秒
221.
Ceperley proposed a concept of a traveling wave heat engine ["A pistonless Stirling engine-The traveling wave heat engine," J. Acoust. Soc. Am. 66, 1508-1513 (1979).] that provided a starting point of thermoacoustics today. This paper verifies experimentally his idea through observation of amplification and strong damping of a plane acoustic traveling wave as it passes through axial temperature gradients. The acoustic power gain is shown to obey a universal curve specified by a dimensionless parameter ωτα; ω is the angular frequency and τα is the relaxation time for the gas to thermally equilibrate with channel walls. As an application of his idea, a three-stage acoustic power amplifier is developed, which attains the gain up to 10 with a moderate temperature ratio of 2.3. 相似文献
222.
Matsuoka T Fujihisa H Hirao N Ohishi Y Mitsui T Masuda R Seto M Yoda Y Shimizu K Machida A Aoki K 《Physical review letters》2011,107(2):025501
Europium hydride EuH(x), when exposed to high-pressure H?, has been found to exhibit the following structural and valence changes: Pnma(x = 2, divalent) → P6?/mmc(x = 2, 7.2-8.7 GPa) → I4/m(x > 2, 8.7-9.7 GPa) → I4/mmm(x > 2, 9.7 GPa-,trivalent). With a trivalent character and a distorted cubic fcc structure, the I4/mmm structure is the β phase commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH(x) is no longer an irregular member of the rare-earth metal hydrides. 相似文献
223.
We present an investigation of the interquark potential determined from the q ?q Bethe-Salpeter (BS) amplitude for heavy quarkonia in lattice QCD. The q ?q potential at finite quark mass m(q) can be calculated from the equal-time and Coulomb gauge BS amplitude through the effective Schr?dinger equation. The definition of the potential itself requires information about a kinetic mass of the quark. We then propose a self-consistent determination of the quark kinetic mass on the same footing. To verify the proposed method, we perform quenched lattice QCD simulations with a relativistic heavy-quark action at a lattice cutoff of 1/a≈2.1 GeV in a range 1.0≤m(q)≤3.6 GeV. Our numerical results show that the q ?q potential in the m(q)→∞ limit is fairly consistent with the conventional one obtained from Wilson loops. The quark-mass dependence of the q ?q potential and the spin-spin potential are also examined. 相似文献
224.
Yonggang Jiang Takayuki Fujita Minoru UeharaYuki Iga Taichi HashimotoXiuchun Hao Kohei HiguchiKazusuke Maenaka 《Journal of magnetism and magnetic materials》2011,323(21):2696-2700
The silicon molding technique is described for patterning of NdFeB/Ta multilayered magnetic films and NdFeB magnetic powder at the micron scale. Silicon trenches are seamlessly filled by 12-μm-thick NdFeB/Ta multilayered magnetic films with a magnetic retentivity of 1.3 T. The topography image and magnetic field distribution image are measured using an atomic force microscope and a magnetic force microscope, respectively. Using a silicon molding technique complemented by a lift-off process, NdFeB magnetic powder is utilized to fabricate magnetic microstructures. Silicon trenches as narrow as 20 μm are filled by a mixture of magnetic powder and wax powder. The B-H hysteresis loop of the patterned magnetic powder is characterized using a vibrating sample magnetometer, which shows a magnetic retentivity of approximately 0.37 T. 相似文献
225.
Ko Mibu Makoto Seto Takaya Mitsui Yoshitaka Yoda Ryo Masuda Shinji Kitao Yasuhiro Kobayashi Edi Suharyadi Masaaki Tanaka Masakiyo Tsunoda Hideto Yanagihara Eiji Kita 《Hyperfine Interactions》2013,217(1-3):127-135
Applications of synchrotron-radiation-based Mössbauer spectroscopy in the “energy domain” to the studies on magnetism of thin films are introduced on the basis of the experiments recently performed at SPring-8, Japan. The measured samples are spintronics-related thin films, such as Co2MnSn films, layered Fe/Cr films, layered Fe/Fe3O4 films, and Fe4N films. The validity of the energy domain measurements is demonstrated in the light of industrial applications of magnetic thin films. 相似文献
226.
227.
Kentaro Mitsui 《Mathematische Zeitschrift》2014,276(1-2):237-242
We give a new method to construct unirational surfaces which may be applied to the following question posed by Zariski in his studies on unirational surfaces. Is any Zariski surface with geometric genus zero rational? Our main result is a negative answer to this question in any characteristic case. 相似文献
228.
Cheng Peng Dr. Taichi Kusakabe Shoko Kikkawa Prof. Dr. Tomoyuki Mochida Prof. Dr. Isao Azumaya Dr. Yogesh Daulat Dhage Dr. Keisuke Takahashi Prof. Dr. Hiroaki Sasai Prof. Dr. Keisuke Kato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):733-737
The first example of an asymmetric cyclization–dimerization of (ortho-alkynyl phenyl) (methoxymethyl) sulfides with a palladium(II) bisoxazoline (box) catalyst has been developed. The box ligand enhances the alkynophilicity of benzothienyl palladium(II) intermediate A and thus promotes coordination of the second alkyne substrate, leading to the dimerization. The characteristic properties of the box ligand were supported by density functional theory (DFT) calculations of the intermediate. Axially chiral bibenzothiophenes were obtained in good yields with good enantioselectivities. 相似文献
229.
Fukuzawa K Shimuta T Yoshida T Mitsuya Y Zhang H 《Langmuir : the ACS journal of surfaces and colloids》2006,22(16):6951-6955
The effect of the surface energy gamma, disjoining pressure, Pi, and roughness on the dewetting of molecularly thin liquid lubricant films on magnetic disks, which have sub-nanometer surface topography, has been investigated by visualizing the dewetting process directly using ellipsometric microscopy. The dewetting process of thin liquids on the rough surface is determined not only by the well-known instability of films, which is determined by the sign of dPi/dh, but also by the sign of Pi and the surface topography of the substrate even if its roughness is of the sub-nanometer order. The dewetting film formed small droplets, which were not along the surface topography of the substrate, when Pi < 0. On the other hand, it formed grooves along the surface topography with a sub-nanometer roughness when Pi > 0. Moreover, the sub-nanometer roughness initiated the dewetting of the metastable liquid thin films. 相似文献
230.
We demonstrate the formation of nanoscale volcano-like structures induced by ion-beam irradiation of nanoscale pores in freestanding silicon nitride membranes. Accreted matter is delivered to the volcanoes from micrometer distances along the surface. Volcano formation accompanies nanopore shrinking and depends on geometrical factors and the presence of a conducting layer on the membrane's back surface. We argue that surface electric fields play an important role in accounting for the experimental observations. 相似文献