全文获取类型
收费全文 | 3325篇 |
免费 | 89篇 |
国内免费 | 12篇 |
专业分类
化学 | 2529篇 |
晶体学 | 35篇 |
力学 | 37篇 |
数学 | 145篇 |
物理学 | 680篇 |
出版年
2022年 | 14篇 |
2021年 | 19篇 |
2020年 | 38篇 |
2019年 | 53篇 |
2018年 | 41篇 |
2017年 | 20篇 |
2016年 | 62篇 |
2015年 | 50篇 |
2014年 | 67篇 |
2013年 | 168篇 |
2012年 | 152篇 |
2011年 | 176篇 |
2010年 | 109篇 |
2009年 | 95篇 |
2008年 | 156篇 |
2007年 | 156篇 |
2006年 | 151篇 |
2005年 | 159篇 |
2004年 | 137篇 |
2003年 | 155篇 |
2002年 | 135篇 |
2001年 | 87篇 |
2000年 | 87篇 |
1999年 | 58篇 |
1998年 | 34篇 |
1997年 | 44篇 |
1996年 | 45篇 |
1995年 | 30篇 |
1994年 | 33篇 |
1993年 | 43篇 |
1992年 | 40篇 |
1991年 | 50篇 |
1990年 | 53篇 |
1989年 | 36篇 |
1988年 | 46篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 70篇 |
1984年 | 49篇 |
1983年 | 24篇 |
1982年 | 45篇 |
1981年 | 39篇 |
1980年 | 25篇 |
1979年 | 39篇 |
1978年 | 36篇 |
1977年 | 44篇 |
1976年 | 35篇 |
1975年 | 25篇 |
1974年 | 22篇 |
1973年 | 25篇 |
排序方式: 共有3426条查询结果,搜索用时 140 毫秒
991.
Application of PSP to low density gas flows 总被引:1,自引:0,他引:1
Recently optical pressure measurement systems using pressure sensitive paints (PSP) have actively developed to measure continuous
pressure distributions on solid surfaces. However, the pressure range has been almost limited above 130 Pa (about 1 Torr)
and there is no application to lower pressure range because the pressure sensitivity seems to be not so high in that range.
In this study, we have applied three types of PSP [two types are composed by organic dye and polymer (luminophore/binder);
PtOEP/GP197 and PtTFPP/poly(TMSP), and another one is Bath-Ru adsorbed on anodized aluminum] to the rarefied gas flow mainly
lower than 130 Pa and examine those fundamental properties such as pressure sensitivity, leading to selection of the most
suitable PSP among them for the low-pressure range. Since PtTFPP/poly(TMSP) has the highest sensitivity, it is applied successfully
to the measurement of the two-dimensional pressure distribution on the surface interacting with a low density supersonic free
jet. 相似文献
992.
Yoshida T Zhou XJ Sasagawa T Yang WL Bogdanov PV Lanzara A Hussain Z Mizokawa T Fujimori A Eisaki H Shen ZX Kakeshita T Uchida S 《Physical review letters》2003,91(2):027001
Lightly doped La2-xSrxCuO4 in the so-called "insulating" spin-glass phase has been studied by angle-resolved photoemission spectroscopy. We have observed that a "quasiparticle" (QP) peak crosses the Fermi level in the node direction of the d-wave superconducting gap, forming an "arc" of Fermi surface, which explains the metallic behavior at high temperatures of the lightly doped materials. The QP spectral weight of the arc smoothly increases with hole doping, which we attribute to the n approximately x behavior of the carrier number in the underdoped and lightly doped regions. 相似文献
993.
Malek M Morii M Fukuda S Fukuda Y Ishitsuka M Itow Y Kajita T Kameda J Kaneyuki K Kobayashi K Koshio Y Miura M Moriyama S Nakahata M Nakayama S Namba T Okada A Ooyabu T Saji C Sakurai N Shiozawa M Suzuki Y Takeuchi H Takeuchi Y Totsuka Y Yamada S Desai S Earl M Kearns E Messier MD Stone JL Sulak LR Walter CW Goldhaber M Barszczak T Casper D Gajewski W Kropp WR Mine S Liu DW Smy MB Sobel HW Vagins MR Gago A Ganezer KS Keig WE Ellsworth RW Tasaka S Kibayashi A Learned JG Matsuno S Takemori D 《Physical review letters》2003,90(6):061101
A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to 130 macro nu(e) cm(-2) s(-1). Additionally, an upper bound of 1.2 macro nu(e) cm(-2) s(-1) was set for the supernova relic neutrino flux in the energy region E(nu)>19.3 MeV. 相似文献
994.
Kiriyama H Yamakawa K Nagai T Kageyama N Miyajima H Kan H Yoshida H Nakatsuka M 《Optics letters》2003,28(18):1671-1673
We report a high-average-power laser-diode-pumped Nd:YAG master oscillator power amplifier system that has a minimum number of elements in the single multipass zigzag-slab amplifier stage and is used to pump a high-peak-power and high-average-power Ti:sapphire laser system. This phase-conjugated system produces an average power of 362 W at 1 kHz in a 30-ns pulse with an optical-to-optical conversion efficiency of 14%. With an external KTP doubler this system generates 132 W of green average output power at 1 kHz with a conversion efficiency of 60% when pumped at a power level of 222 W. To the best of our knowledge these results represent the highest average output power at both infrared and green wavelengths achieved in a single amplifier stage. 相似文献
995.
Y. Kojima M. Shibata A. Taniguchi T. Hanafusa E. Yoshida K. Shizuma Y. Kawase S. Yamada 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):331-336
The β--decay of 151Pr produced by the thermal neutron-induced fission of 235U has been studied using an on-line isotope separator. From an internal-conversion electron measurement with a Si(Li) detector,
K-conversion coefficients were obtained for 20 γ-transitions. Spins and parities of 6 excited levels in 151Nd were newly determined from the deduced multipolarities: even parities for the 543 and 627 keV levels, odd parities for
250 and 599 keV, (3/2, 5/2)+ for 685 keV, and (1/2, 3/2)+ for 880 keV. The level structure was compared with the rotation-vibration coupling Nilsson model.
Received: 28 June 2002 / Accepted: 31 October 2002 / Published online: 25 February 2003
RID="a"
ID="a"e-mail: ykojima@hiroshima-u.ac.jp
Communicated by J. ?yst? 相似文献
996.
Mohri K Watanabe Y Yoshida Y Satoh M Isobe K Sugimoto N Tsuda Y 《Chemical & pharmaceutical bulletin》2003,51(11):1268-1272
Condensation of glycosylated arylaldehyde with acetylacetone-B(2)O(3) complex gave a corresponding diglycosylcurcuminoid, and a similar reaction using a mixture of arylaldehyde and glycosylarylaldehyde gave an unsymmetrical monoglycosylcurcuminoid, both as boron-complexes. The boron was removed from the complexes by heating in methanol, thus achieving the synthesis of di- and mono-glycosylcurcuminoids. 相似文献
997.
Hjelte I Karlsson L Svensson S De Fanis A Carravetta V Saito N Kitajima M Tanaka H Yoshida H Hiraya A Koyano I Ueda K Piancastelli MN 《The Journal of chemical physics》2005,122(8):84306
Vibrationally resolved spectra have been obtained for the lowest-lying cationic states X (2)B(1), A (2)A(1), and B (2)B(2) of the water molecule reached after participator resonant Auger decay of core-excited states. The angular distribution has been measured of the first four vibrational components of the X state in the photon energy regions including the O 1s-->4a(1) and the O 1s-->2b(2) core excitations, and for different portions of the vibrational envelope of the B state in the photon energy region including the O 1s-->2b(2) core excitation. For the X state, a large relative spread in beta values of the different vibrational components is observed across both resonances. For the B state, a very different trend is observed for the high binding energy side and the low binding energy side of the related spectral feature as a function of photon energy. A theoretical method based on the scattering K matrix has been used to calculate both the photoabsorption spectrum and the beta values, by taking both interference between direct and resonant photoemission and vibrational/lifetime interference into account. The numerical results show qualitative agreement with the trends detected in the experimental values and explain the conspicuous variations of the beta values primarily in terms of coupling between direct and resonant photoemission by interaction terms of different sign for different final vibrational states. 相似文献
998.
Yoshida M Shiraki K Okubo S Ohta H Ito T Takagi H Kaburagi M Ajiro Y 《Physical review letters》2005,95(11):117202
This Letter presents the fine structure of energy levels for the edge states of a Haldane chain. In order to investigate the edge states, we have performed high field and multifrequency electron spin resonance (ESR) measurements of finite length S=1 antiferromagnetic chains in Y2BaNi0.96Mg0.04O5. Owing to the high spectral resolution by high fields and high frequencies, observed ESR signals can be separated into the contributions of the finite chains with various chain lengths. Our results clearly show that the edge spins actually interact with each other through the quantum spin chain and the interaction depends on the chain length N. This N dependence has been obtained experimentally for the first time, and shows that the correlation length xi in the real system is somewhat larger than that calculated by a simple Heisenberg model. 相似文献
999.
We constrain energy spectra of supernova neutrinos through the avoidance of an overproduction of the 11B abundance during Galactic chemical evolution. In supernova nucleosynthesis calculations with a parametrized neutrino spectrum as a function of temperature of nu(mu,tau) and nu(mu,tau) and total neutrino energy, we find a strong neutrino temperature dependence of the 11B yield. When the yield is combined with observed abundances, the acceptable range of the nu(mu,tau) and nu(mu,tau) temperature is found to be 4.8 to 6.6 MeV. Nonzero neutrino chemical potentials would reduce this temperature range by about 10% for a degeneracy parameter eta(nu) = mu(nu)/kT(nu) smaller than 3. 相似文献
1000.
The longitudinal linewidth and corresponding relative intensity noise (RIN) of 10- and 40-GHz mode-locked laser diodes are measured for the first time to our knowledge. It is shown that the cavity Q value is a dominant parameter of the linewidth. It is also shown that the linewidth of the individual modes is almost constant. This means that the phase noise of each mode is almost the same in the mode-locked condition. The RIN value is larger for modes that are distant from the center longitudinal mode. This mode dependence is a consequence of the mode partition noise. 相似文献