全文获取类型
收费全文 | 1546篇 |
免费 | 37篇 |
国内免费 | 1篇 |
专业分类
化学 | 1148篇 |
晶体学 | 16篇 |
力学 | 51篇 |
数学 | 40篇 |
物理学 | 329篇 |
出版年
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 7篇 |
2019年 | 19篇 |
2018年 | 7篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 25篇 |
2014年 | 35篇 |
2013年 | 85篇 |
2012年 | 84篇 |
2011年 | 76篇 |
2010年 | 52篇 |
2009年 | 52篇 |
2008年 | 73篇 |
2007年 | 70篇 |
2006年 | 83篇 |
2005年 | 67篇 |
2004年 | 79篇 |
2003年 | 87篇 |
2002年 | 64篇 |
2001年 | 31篇 |
2000年 | 31篇 |
1999年 | 27篇 |
1998年 | 16篇 |
1997年 | 16篇 |
1996年 | 15篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 20篇 |
1984年 | 35篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有1584条查询结果,搜索用时 15 毫秒
31.
This paper describes the mapping of the spatiotemporal principal stress distribution evolved with time in an epoxy photoelastic sample. In the optical heterodyne polarimeter exploited, the signal beam of light transmitted by the sample under continuously loaded condition is photomixed with the local oscillator beam of light made up of orthogonal linearly polarized two-frequency components. Every pixel of a MOS video camera used generates a beat photocurrent that possesses the two orthogonal field components of the elliptically polarized signal beam. The spatiotemporal principal stress distributions can be uniquely determined simultaneously and independently from these two orthogonal field components, and are successfully mapped in a time-sequential form. The spatial and temporal resolutions in the maps are 0.18 mm and 2.9 ms, respectively. 相似文献
32.
33.
Takanari Yasui Takeshi Ohtsuka Tetsu Suzuki Shigeki Okajima Kazuya Nakayama Mitsuru Tomioka Katsuhiro Kamimura Takeo Namekata Hiroaki Minamide Hiromasa Ito 《International Journal of Infrared and Millimeter Waves》2006,27(2):199-210
A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic
cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity
of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical
mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement
in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities,
thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum
radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed
good agreements with classical antenna theory. 相似文献
34.
Letters in Mathematical Physics - While the argument by Zamolodchikov and Polchinski suggests global conformal invariance implies Virasoro invariance in two-dimensional unitary conformal field... 相似文献
35.
Multiple ionization process of a rare gas dimer BC collided with a slow highly charged ion Aq+ is investigated with the three-center Coulombic over-barrier model previously developed by the present authors. To reveal stereodynamical effects, we calculate asymmetric ion-pair formation cross sections σ(QB,QC) as a function of the orientation angle. We introduce a pair of atomic impact parameters bB and bC with which we distinguish the near and far sites. Furthermore, we distinguish the forward and backward emitted ions produced as a result of Coulomb explosion. Partial screening effects are also considered. 相似文献
36.
Seven organic dyes were adsorbed on photoconductive zinc oxide powder and their sensitizing efficiencies were examined. The adsorption of dye induced a change in the dark conductivity, the magnitude of which appeared to represent the sensitizing power of the dye. The initial slope of sensitized photocurrent was found to be an exponential function of σ0, the pre-exponential factor in the conductivity equation. A model is proposed, which is consistent with all the observations. In this model, the sensitized photoinjection of electrons is assumed to occur from surface states to the bulk, depending upon the population of the surface states. A critical surface level for the spectral sensitization is introduced to account for the observed temperature effect. Surface states located below the critical energy are assumed not to contribute for the sensitization. 相似文献
37.
Tomoko KANEKO-ISHINO Fumitoshi ISHINO 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2015,91(10):511-538
Mammals, including human beings, have evolved a unique viviparous reproductive system and a highly developed central nervous system. How did these unique characteristics emerge in mammalian evolution, and what kinds of changes did occur in the mammalian genomes as evolution proceeded? A key conceptual term in approaching these issues is “mammalian-specific genomic functions”, a concept covering both mammalian-specific epigenetics and genetics. Genomic imprinting and LTR retrotransposon-derived genes are reviewed as the representative, mammalian-specific genomic functions that are essential not only for the current mammalian developmental system, but also mammalian evolution itself. First, the essential roles of genomic imprinting in mammalian development, especially related to viviparous reproduction via placental function, as well as the emergence of genomic imprinting in mammalian evolution, are discussed. Second, we introduce the novel concept of “mammalian-specific traits generated by mammalian-specific genes from LTR retrotransposons”, based on the finding that LTR retrotransposons served as a critical driving force in the mammalian evolution via generating mammalian-specific genes. 相似文献
38.
Hisahiro Nakayama Jiro Kasahara Akiko Matsuo Ikkoh Funaki 《Proceedings of the Combustion Institute》2013,34(2):1939-1947
The propagation of curved detonation waves of gaseous explosives stabilized in rectangular-cross-section curved channels is investigated. Three types of stoichiometric test gases, C2H4 + 3O2, 2H2 + O2, and 2C2H2 + 5O2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel (ri) to the normal detonation cell width (λ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around ri/λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity (Dn)?curvature (κ) relations are evaluated. The Dn nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity (DCJ) is a function of the κ nondimensionalized by λ. The Dn/DCJ?λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the Dn/DCJ?λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same ri/λ, regardless of the curved channel and test gas. 相似文献
39.
40.
K. Nakayama H. Tazawa S. Okajima K. Kawahata K. Tanaka T. Tokuzawa Y. Ito 《International Journal of Infrared and Millimeter Waves》2003,24(9):1421-1430
A diagnostic system using short-wavelength far-infrared (FIR) lasers (40–70 m in wavelength) is now being developed for high density and large volume plasmas. In the wavelength region, a CVD-diamond is the excellent materials for optical windows of the laser and the plasma vessel and beam splitters of a multichannel interferometer. To design these optical elements, the optical constants (refractive index n, absorption coefficient and transmissivity T) of the CVD-diamond have been measured precisely by using FIR lasers of 48-, 57- and 71-m in wavelength. As an example, the result for 57.1511 m light is n = 2.383(1) ± 0.002, = 0.19 ± 0.05 cm-1 and T = 97.5 ± 1.5% at 1.023 mm in thickness. 相似文献