全文获取类型
收费全文 | 1016篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
化学 | 640篇 |
晶体学 | 13篇 |
力学 | 51篇 |
数学 | 35篇 |
物理学 | 298篇 |
出版年
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 58篇 |
2012年 | 49篇 |
2011年 | 44篇 |
2010年 | 34篇 |
2009年 | 28篇 |
2008年 | 43篇 |
2007年 | 39篇 |
2006年 | 42篇 |
2005年 | 35篇 |
2004年 | 43篇 |
2003年 | 41篇 |
2002年 | 31篇 |
2001年 | 27篇 |
2000年 | 27篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 32篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1970年 | 4篇 |
排序方式: 共有1037条查询结果,搜索用时 328 毫秒
71.
K.?MizoguchiEmail author S.?Fujita M.?Nakayama 《Applied Physics A: Materials Science & Processing》2004,78(4):461-464
We report the first observation of coherent phonons in crystalline lead phthalocyanine (PbPc) films grown on a (0001) sapphire substrate by using a pump–probe technique. Coherent phonon oscillations corresponding to intermolecular (lattice) vibrations in the PbPc film are observed in the frequency region from 1 to 5 THz. It is found that the intensities of coherent phonons are resonantly enhanced at the exciton energies of the Q band observed in the absorption spectrum. PACS 78.47.+p; 78.66.-w; 82.53.Xa; 78.40.Me 相似文献
72.
A layered nanocomposite with poly(diallyldimethylammonium), PDDA, intercalated between manganese oxide layers can be formed on a platinum electrode in a thin film form through a direct electrochemical route. The process involves a potentiostatic oxidation of aqueous Mn(2+) precursors in the presence of PDDA by applying a constant potential (+1.0 V vs Ag/AgCl). 相似文献
73.
Endonuclease BamHI mutants having an azophenylalanine residue in the dimer interface (azoAla-BamHI) were synthesized; while the activity was almost suppressed using trans-azoAla-BamHI, the cis-isomer generated with photoirradiation recovered its intrinsic activity. 相似文献
74.
In previous work on polarization-mode dispersion (PMD) measurement with an optical time-domain reflectometer with polarimetry (p-OTDR), scatterers were assumed to be a cloud of small spherical particles in a fiber. We have found that the p-OTDR waveforms were fitted well by modified Mueller matrices, assuming scattering by a cloud of nonspherical particles. We realized a PMD measurement based on the p-OTDR Jones matrix eigenanalysis (JME) method. The measured PMD was consistent with that of JME standard measurement with transmission-type polarimetry. 相似文献
75.
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
76.
Zegers RG Abend H Akimune H van den Berg AM Fujimura H Fujita H Fujita Y Fujiwara M Galès S Hara K Harakeh MN Ishikawa T Kawabata T Kawase K Mibe T Nakanishi K Nakayama S Toyokawa H Uchida M Yamagata T Yamasaki K Yosoi M 《Physical review letters》2003,90(20):202501
The excitation and subsequent proton decay of the isovector spin-flip giant monopole resonance (IVSGMR) is studied via the 208Pb(3He,t) reaction at 410 MeV. In the inclusive spectrum (60+/-5)% of the non-energy-weighted sum-rule strength for this 2 variant Planck's over 2h omega resonance was found in the region 29相似文献
77.
Suzuki M Waraksa CC Nakayama H Hanabusa K Kimura M Shirai H 《Chemical communications (Cambridge, England)》2001,(19):2012-2013
L-Lysine derivatives of viologens form supramolecular assemblies of fibers and ribbons in some aromatic solvents, and the charge separation reaction in these self-assembling systems proceeds with a similar efficiency to the MV2+ system. 相似文献
78.
Ishii A Kawai T Tekura K Oshida H Nakayama J 《Angewandte Chemie (International ed. in English)》2001,40(10):1924-1926
79.
M. Andachi T. Nakayama M. Kawasaki S. Kurokawa H.-P. Loock 《Applied physics. B, Lasers and optics》2007,88(1):131-135
Visible and near-infrared laser light pulses were coupled into two different types of optical fiber cavities. One cavity consisted
of a short strand of fiber waveguide that contained two identical fiber Bragg gratings. Another cavity was made using a loop
of optical fiber. In either cavity ∼40 ps laser pulses, which were generated using a custom-built gain-switched diode laser,
circulated for a large number of round trips. The optical loss of either cavity was determined from the ring-down times. Cavity
ring-down spectroscopy was performed on 200 pL volumes of liquid samples that were injected into the cavities using a 100 μm
gap in the fiber loop. A detection limit of 20 ppm of methylene blue dye in aqueous solution, corresponding to a minimum absorptivity
of εC<6 cm-1, was realized.
PACS 42.62.Fi; 42.81.-i 相似文献
80.
M.-W. Chu Y. Shingaya T. Nakayama 《Applied Physics A: Materials Science & Processing》2007,86(1):101-106
A combined transmission electron microscopy (TEM) and Raman spectroscopy study has been performed on nanocrystalline Ba0.9Sr0.1TiO3 (BST) crystals and tubes. TEM investigations revealed the existence of 90 deg ferroelastic twins in the materials. Raman spectra showed an obvious shoulder (∼750 cm-1) from the broad band at ∼720 cm-1 that nominally represents the quasimode of E(LO4) and A1(LO3). The intensity of this shoulder increases with the twin population in the nanocrystalline materials, suggesting a correlation between the lattice dynamical characteristics and the long-range ferroelastic strain of the twin wall. The ferroelastic strain is mainly constrained along the c-axis of the BST unit cell, and the effect of this constraint is more pronounced in nanocrystalline materials than in bulks due to a significant wall volume ratio in twinned nano-materials. A1 phonons showing collective ion dynamics along the c-direction could be then hardened by the strain, while E symmetry exhibiting vibrations perpendicular to the c-axis would be less affected. The theoretically predicted giant LO–TO coupling in tetragonal ferroelectric perovskites [18] suggests that the hardening of the softest A1(TO1) mode in A1 symmetry is accompanied by that of the hardest A1(LO3) phonon. Consequently, the shoulder could be ascribed to the ferroelastic strain induced hardening of the quasimode with a considerable contribution from the A1(LO3) phonon. PACS 61.72.Ff; 63.22.+m; 77.80.Bh; 77.80.Dj 相似文献