全文获取类型
收费全文 | 1252篇 |
免费 | 23篇 |
国内免费 | 3篇 |
专业分类
化学 | 918篇 |
晶体学 | 5篇 |
力学 | 21篇 |
数学 | 66篇 |
物理学 | 268篇 |
出版年
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 70篇 |
2012年 | 57篇 |
2011年 | 60篇 |
2010年 | 28篇 |
2009年 | 30篇 |
2008年 | 68篇 |
2007年 | 54篇 |
2006年 | 68篇 |
2005年 | 63篇 |
2004年 | 49篇 |
2003年 | 58篇 |
2002年 | 47篇 |
2001年 | 44篇 |
2000年 | 29篇 |
1999年 | 19篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 7篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 32篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1969年 | 6篇 |
1968年 | 5篇 |
排序方式: 共有1278条查询结果,搜索用时 15 毫秒
71.
72.
We calculate scattering functions S(q-->,omega) of neutron Compton scattering (NCS) for a proton (deuteron) pair in the entangled state caused by the indistinguishability of particles. From the calculation, it is concluded that the effect of entanglement on the scattering intensity is undetectable in NCS experiments because of their high energy transfer and broad energy resolution. 相似文献
73.
Taniguchi J Yamaguchi A Ishimoto H Ikegami H Matsushita T Wada N Gatica SM Cole MW Ancilotto F Inagaki S Fukushima Y 《Physical review letters》2005,94(6):065301
Heat capacity measurements have been made down to 5 mK for 3He fluid films adsorbed in one-dimensional (1D) nanometer-scale pores, 28 A in diameter, preplated with 4He of 1.47 atomic layers. At low 3He density, the heat capacity shows a density-dependent, Schottky-like peak near 150 mK asymptoting to the value corresponding to a 2D Boltzmann gas at high temperatures. The peak behavior is attributed to the crossover from a 2D gas to a 1D state at low temperatures. The degenerate state of the 1D 3He fluid is indicated by a predominantly linear temperature dependence below about 30 mK. 相似文献
74.
R. A. Ganeev M. Baba M. Morita A. I. Ryasnyanskii M. Suzuki M. Turu H. Kuroda 《Optics and Spectroscopy》2004,97(5):735-745
The saturated nonlinear absorption and Kerr nonlinearities of an aqueous pseudoisocyanine solution are investigated at the wavelengths of 532 and 529 nm with the use of pulsed laser radiation of different duration (8 ns and 475 fs). The measured values of the nonlinear refractive indices amount to ?6×10?12 (t=8 ns) and ?8×10?14 cm2W?1 (t=475 fs). The change in self-action effects in pseudoisocyanine from self-defocusing to self-focusing revealed in the case of increasing intensity of femtosecond laser pulses is attributed to the effect of a fifth-order nonlinear optical process. The nonlinear refractive index responsible for this process amounts to 4×10?24 cm4 W?2. The imaginary part of the third-order nonlinear susceptibility, responsible for the induced transparency of the pseudoisocyanine solution, is Imχ (3)=?2×10?12 esu. Temporal changes in the shape of nanosecond laser pulses due to the nonlinear refraction induced by a thermal process are analyzed. 相似文献
75.
Shirakawa E Morita R Tsuchimoto T Kawakami Y 《Journal of the American Chemical Society》2004,126(42):13614-13615
Molecular hydrogen adds to aliphatic and aromatic alkynylstannanes in the presence of a ruthenium catalyst, pushing the stannyl group to the adjacent carbon atom to give alpha-substituted vinylstannanes. This is the first achievement of hydrogenation of alkynylstannanes, which is applicable also to the deuteration affording precursors for an important class of deuterium-labeled compounds. 相似文献
76.
Morita Y Nishida S Kobayashi T Fukui K Sato K Shiomi D Takui T Nakasuji K 《Organic letters》2004,6(9):1397-1400
[structure: see text] A bowl-shaped neutral radical with a corannulene system has been designed and synthesized for the first time as a stable solid in air. An unequivocal characterization of the electronic properties of the radical shows that an appreciable amount of spin delocalization extends onto the corannulene unit's curved surface. 相似文献
77.
We have measured the nuclear susceptibility of 3He in Grafoil filled with pure liquid 3He over the pressure region between 0.6 and 31.38 bars and at temperatures down to 0.5 mK with a cw NMR method. The nuclear magnetization corresponding to the adsorbed 3He layers on the Grafoil surface shows a strong ferromagnetic tendency with a periodic behavior as a function of liquid pressure. This observation is attributable to the growth of third and fourth solid 3He layers with the liquid pressure increase. The pressure dependence of the Weiss temperature indicates the third layer is completed at 19 bars and the fourth probably at 28 bars. The number of localized spins estimated from the solid magnetization is almost doubled from 0 to 28 bars, being consistent with this scenario. 相似文献
78.
Direct demagnetization has been made for two-dimensional solid 3He in both the paramagnetic and the antiferromagnetic phases. The lowest temperature is about 10 microK, judging from the observed magnetization for the paramagnetic solid 3He. The magnetization of the antiferromagnetic solid 3He shows a gradual increase to about 10 microK for the 4/7 phase adsorbed on both one layer of 4He and two layers of HD preplated graphite. This strongly suggests that the triangular antiferromagnet with the higher order multiple exchange has a quantum spin liquid ground state with nearly zero or extremely small spin gap less than 10 microK. 相似文献
79.
Zegers RG Sumihama M Ahn DS Ahn JK Akimune H Asano Y Chang WC Daté S Ejiri H Fujimura H Fujiwara M Hicks K Hotta T Imai K Ishikawa T Iwata T Kawai H Kim ZY Kino K Kohri H Kumagai N Makino S Matsumura T Matsuoka N Mibe T Miwa K Miyabe M Miyachi Y Morita M Muramatsu N Nakano T Niiyama M Nomachi M Ohashi Y Ooba T Ohkuma H Oshuev DS Rangacharyulu C Sakaguchi A Sasaki T Shagin PM Shiino Y Shimizu H Sugaya Y Toyokawa H Wakai A Wang CW Wang SC Yonehara K Yorita T Yoshimura M Yosoi M 《Physical review letters》2003,91(9):092001
Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6相似文献
80.
Otsuka H Kijima H Hirata E Shinzato T Takushi A Bando M Takeda Y 《Chemical & pharmaceutical bulletin》2003,51(3):286-290
Five megastigmane glucosides were isolated from the leaves of Glochidion zeylanicum. One of them was a known compound, blumenol C O-beta-D-glucopyranoside (1), and the structures of the four new compounds, glochidionionosides A-D (2-5), were mainly elucidated by spectroscopic methods, including a modified Mosher's method. The absolute configurations of the six-membered ring of glochidionionoside D (5) were deduced by beta-D-glucopyranosylation-induced shift trends in the (13)C-NMR spectra and confirmed by X-ray analysis as its p-bromobenzoate (5b), and the axis chirality of C-7 was determined to be R. 相似文献