全文获取类型
收费全文 | 1376篇 |
免费 | 47篇 |
国内免费 | 4篇 |
专业分类
化学 | 1075篇 |
晶体学 | 15篇 |
力学 | 12篇 |
数学 | 81篇 |
物理学 | 244篇 |
出版年
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 20篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 26篇 |
2015年 | 25篇 |
2014年 | 41篇 |
2013年 | 67篇 |
2012年 | 85篇 |
2011年 | 81篇 |
2010年 | 51篇 |
2009年 | 57篇 |
2008年 | 78篇 |
2007年 | 86篇 |
2006年 | 93篇 |
2005年 | 89篇 |
2004年 | 60篇 |
2003年 | 58篇 |
2002年 | 67篇 |
2001年 | 20篇 |
2000年 | 27篇 |
1999年 | 19篇 |
1998年 | 19篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 6篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有1427条查询结果,搜索用时 15 毫秒
91.
Introduction of a hydrogen-bonding substituent to 1-cyanonaphthalene and alkene resulted in the selective formations of endo-photocycloadducs. Furthermore, the yield and selectivity were improved as the reaction temperature was lowered. 相似文献
92.
Kawase K Mizuno M Sohma S Takahashi H Taniuchi T Urata Y Wada S Tashiro H Ito H 《Optics letters》1999,24(15):1065-1067
Among nonlinear materials, the organic ionic salt crystal 4-dimethylamino- N -methyl-4-stilbazolium-tosylate (DAST) is known for its large nonlinearity. We generated a coherent terahertz (THz) wave, using DAST, from the difference frequency between two oscillating wavelengths of an electronically tuned Ti:sapphire laser. In LiNbO(3), LiTaO(3), KTiOPO(4), and GaP crystals, THz-wave generation was not observed under the same experimental conditions. This result proves the high efficiency of DAST crystals for generation of difference-frequency THz waves. 相似文献
93.
Masahiro Ueda Sanae Mizuno Akio Matsumura Fumio Tohjyo 《Optics and Lasers in Engineering》1996,24(4):339-350
An optical method for measuring the thickness of heterogeneous materials has been studied. The method is based on the light attenuation theory. A complete system has been constructed in order to demonstrate the applicability of the present method for industrial use. The experimental set-up consists of semiconductor lasers, focusing lenses, photo-diodes serving as a power meter and a personal computer with an A/D converter for data acquisition. Averaging of numerous measurements is required in the present method because the heterogeneous cell structure of the foam material yields large fluctuations in transmitted light levels. The fluctuations can be reduced to below 1% of the transmitted light power by 80 times averaging. The error of the measurement is considered to be a few tens of micrometers in thickness. The present system is capable of sampling data at a rate of 400 Hz and has been successfully applied to a manufacturing process. 相似文献
94.
95.
Photo-induced edge-shift affect in As2S3 film has been studies for different intensities of incident light. This process depends only on the total energy E of light. A simple experimental relationship between shift of edge Δλ and E has been obtained, which coincides with a theretical prediction deduced from a model based on a first-order reaction. 相似文献
96.
Nuclear magnetic relaxation times, T1 and T2 are measured in dilute Au-V alloys for 1–300 K. A value for T1T = 17.0 ± 0.5 msK is obtained. 相似文献
97.
Shigeyuki Mayama Toshikazu Tani Tamio Ueno Kazumasa Hirabayashi Tadakazu Nakashima Hiroshi Fukami Yukio Mizuno Hiroshi Irie 《Tetrahedron letters》1981,22(22):2103-2106
The major phytoalexin from oat leaves has been identified as 2-[2-(4-hydroxyphenyDethenyl] -6-hydroxy-4H-3,1-benzoxazin-4-one (). 相似文献
98.
A bent photonic crystal waveguide was fabricated by use of a lattice pattern of a circular photonic crystal that allowed high transmission for a broad band of wavelengths with a small radius of curvature at a bend. The waveguide was fabricated by use of alumina rods with a diameter of 3 mm. Windows of high transmission as a result of waveguiding were observed near 9 and 15 GHz. By measurement of the relative wave intensity [E]2 along the line defects, the propagation losses in the straight and the bent sections were estimated at 9.3 GHz to be 0.04 and 0.03 dB/mm, respectively. 相似文献
99.
Anisotropic optical properties of mechanically aligned single-walled carbon nanotubes in polymer 总被引:1,自引:0,他引:1
M.?IchidaEmail author S.?Mizuno H.?Kataura Y.?Achiba A.?Nakamura 《Applied Physics A: Materials Science & Processing》2004,78(8):1117-1120
We have prepared aligned single-walled carbon nanotubes in polymer by mechanical stretching. The polarized absorption and Raman spectra of the aligned samples have been investigated. The optical transitions in nanotubes strongly depend on the angle between the polarization of the incident light and the nanotube axis: the absorbance measured at the peak energy shows a maximum at =0°, and they are suppressed at =90°. Raman spectra also show strong polarization dependence, which is mainly determined by the dependence of the oscillator strength of optical transitions in nanotubes. PACS 71.35.Cc; 78.30.-j; 78.67.Ch; 73.22.-f 相似文献
100.
Hong FL Minoshima K Onae A Inaba H Takada H Hirai A Matsumoto H Sugiura T Yoshida M 《Optics letters》2003,28(17):1516-1518
A frequency comb spanning more than one octave has been achieved by injecting the second-harmonic generation (780 nm) of a mode-locked fiber laser (1.56 microm) into a photonic crystal fiber. We propose and realize a novel interferometric scheme for observing the carrier-envelope offset frequency of the frequency comb. Frequency noise has been observed on the measured carrier-envelope offset frequency, which has been confirmed to be generated in the photonic crystal fiber by comparing the measured beat frequencies between cw lasers and frequency combs before and after the photonic crystal fiber. The mode-locked fiber laser is considered to be an important candidate for the light source used in realizing a compact optical frequency measurement system including applications in the telecommunication bands. 相似文献