全文获取类型
收费全文 | 3264篇 |
免费 | 86篇 |
国内免费 | 16篇 |
专业分类
化学 | 2319篇 |
晶体学 | 35篇 |
力学 | 32篇 |
数学 | 126篇 |
物理学 | 854篇 |
出版年
2021年 | 17篇 |
2020年 | 29篇 |
2019年 | 45篇 |
2018年 | 21篇 |
2017年 | 25篇 |
2016年 | 51篇 |
2015年 | 52篇 |
2014年 | 59篇 |
2013年 | 138篇 |
2012年 | 143篇 |
2011年 | 158篇 |
2010年 | 95篇 |
2009年 | 93篇 |
2008年 | 163篇 |
2007年 | 147篇 |
2006年 | 176篇 |
2005年 | 147篇 |
2004年 | 155篇 |
2003年 | 127篇 |
2002年 | 110篇 |
2001年 | 90篇 |
2000年 | 66篇 |
1999年 | 42篇 |
1998年 | 32篇 |
1997年 | 31篇 |
1996年 | 47篇 |
1995年 | 48篇 |
1994年 | 33篇 |
1993年 | 51篇 |
1992年 | 58篇 |
1991年 | 40篇 |
1990年 | 30篇 |
1989年 | 39篇 |
1988年 | 45篇 |
1987年 | 37篇 |
1986年 | 26篇 |
1985年 | 77篇 |
1984年 | 61篇 |
1983年 | 43篇 |
1982年 | 51篇 |
1981年 | 44篇 |
1980年 | 42篇 |
1979年 | 37篇 |
1978年 | 38篇 |
1977年 | 43篇 |
1976年 | 40篇 |
1975年 | 37篇 |
1974年 | 20篇 |
1973年 | 35篇 |
1966年 | 18篇 |
排序方式: 共有3366条查询结果,搜索用时 312 毫秒
991.
Yamada TK Bischoff MM Heijnen GM Mizoguchi T Van Kempen H 《Physical review letters》2003,90(5):056803
We report the observation of a magnetic contrast of up to 20% in the scanning tunneling spectroscopy dI/dV maps obtained with Fe-coated tips on Mn(001) layers grown on an Fe(001) whisker at 370 K. These nanometer resolution microscopy results show that the layers couple antiferromagnetically. By normalizing the dI/dV curves by tunneling probability functions, we found a spin-dependent peak on the body-centered-tetragonal (bct) Mn(001) surface at +0.8 V, whose high spin polarization gives rise to the dI/dV map contrast. Band structure calculations allow one to identify the +0.8 V peak as due to two spin-polarized d(z(2)) surface states. 相似文献
992.
Wavelength division with three-dimensional couplers fabricated by filamentation of femtosecond laser pulses 总被引:1,自引:0,他引:1
Refractive-index changes can be induced by filamentation of 800-nm, 1-kHz femtosecond laser pulses in silica glass. Two-dimensional translation of a 40-microm-long filament leads to the formation of a curved waveguide because of bending by the previously induced refractive-index change. The fabrication of 2-mm directional couplers to split the coupled beam into 1:1 at a wavelength of 632.8 nm is demonstrated. The realization of three-dimensional directional couplers and wavelength division in the output from the couplers is also demonstrated. 相似文献
993.
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
994.
Yamada K Kurokawa T Tokuyama H Fukuyama T 《Journal of the American Chemical Society》2003,125(22):6630-6631
The total synthesis of (+)-duocarmycin A and SA through a common indoline intermediate is described. The key reactions include selective lithiation of a 2,6-dibromoiodobenzene derivative and diastereoselective addition to a chiral nitroalkene, copper-mediated aryl amination, and addition of aryllithium to azlactones. 相似文献
995.
Yamada K Nomura Y Citterio D Iwasawa N Suzuki K 《Journal of the American Chemical Society》2005,127(19):6956-6957
A non-PET and non-PCT fluoroionophore has been designed and synthesized based on the combination of a biaryl boron-dipyrromethene fluorophore with an oligoethyleneglycol bridge. A specific red-shift response of absorption for NaClO4 in acetonitrile was demonstrated based on conformational restriction triggered by cation recognition at the bridge. The concentration of Na+ can be determined accurately using fluorescence due to a high extinction coefficient (epsilon = 50 000), a high fluorescence quantum yield (Phif = 0.68), and the sharpness of absorption and emission peaks of the boron-dipyrromethene derivative. 相似文献
996.
Tetranuclear europium(III) complexes, [Eu4(μ-O)(L1)10] (L1=2-hydroxy-4-octyloxybenzophenone,1) and [Eu4(μ-O)(L2)10] (L2=2-hydroxy-4-dodecyloxybenzophenone,2) were synthesized by the reaction of lanthanide nitrates with L1 or L2 in the presence of triethylamine in methanol. The photosensitized emission bands of the both Eu(III) complexes in THF-d8 were observed around 579, 590, 615, 653, and 699 nm by the excitation of the ligands at 380 nm, whereas the emission from the mononuclear complex 3 containing ethanol molecules was almost quenched. The emission efficiencies were determined to be 3.1±0.1% for 1 and 3.9±0.1% for 2, respectively. The differential scanning calorimetry (DSC) measurements demonstrated that the decomposition points of 1 and 2 were 309 °C and 320 °C, respectively, indicating high thermostability of these complexes compared to the mononuclear Eu(III) complex 3 (250 °C). New strategy for designing stable rare earth compounds giving strong emission would be emphasized by introducing polynuclear complexes. Polynuclear complexes should open a wide range of molecular design for photosensitized luminescence and thermal stability. 相似文献
997.
Matsui H Terashima K Sato T Takahashi T Wang SC Yang HB Ding H Uefuji T Yamada K 《Physical review letters》2005,94(4):047005
We performed high-resolution angle-resolved photoemission spectroscopy on Nd1.87Ce0.13CuO4, which is located at the boundary of the antiferromagnetic (AF) and the superconducting phase. We observed that the quasiparticle (QP) effective mass around (pi,0) is strongly enhanced due to the opening of the AF gap. The QP mass and the AF gap are found to be anisotropic, with the largest value near the intersecting point of the Fermi surface and the AF zone boundary. In addition, we observed that the QP peak disappears around the Néel temperature (TN) while the AF pseudogap is gradually filled up at much higher temperatures, possibly due to the short-range AF correlation. 相似文献
998.
999.
Recent progress on time-division multiplexed (TDM) and wavelength-division multiplexed (WDM) soliton transmission is described, in which dispersion management plays an important role in increasing the power margin and the dispersion tolerance. The characteristics of the dispersion-managed soliton are compared with those of return to zero and nonreturn to zero pulses. With a small dispersion swing, the system can still be described as an average soliton using the nonlinear Schrodinger equation, while with a large dispersion swing, the solitonlike steady-state pulse becomes a chirped Gaussian pulse, in which the governing equation is closer to a linear Schrodinger equation with a parabolic potential well. We describe an in-line modulation scheme for up to 80 Gbit/s per channel and its two channel WDM transmission over 10 000 km. Finally, we describe 640 Gbit/s (40 Gbit/sx16 channels) WDM soliton transmission over 1000 km with a dispersion-managed single-mode fiber. (c) 2000 American Institute of Physics. 相似文献
1000.
Mizokawa T Kim C Shen ZX Ino A Yoshida T Fujimori A Goto M Eisaki H Uchida S Tagami M Yoshida K Rykov AI Siohara Y Tomimoto K Tajima S Yamada Y Horii S Yamada N Yamada Y Hirabayashi I 《Physical review letters》2000,85(22):4779-4782
We compare the angle-resolved photoemission spectra of the hole-doped Cu-O chains in PrBa2Cu3O7 (Pr123) and in PrBa2Cu4O8 (Pr124). While, in Pr123, a dispersive feature from the chain takes a band maximum at k(b) (momentum along the chain) approximately pi/4 and loses its spectral weight around the Fermi level, it reaches the Fermi level at k(b) approximately pi/4 in Pr124. Although the chains in Pr123 and Pr124 are approximately 1/4 filled, they show contrasting behaviors: While the chains in Pr123 have an instability to charge ordering, those in Pr124 avoid it and show an interesting spectral feature of a metallic coupled-chain system. 相似文献