全文获取类型
收费全文 | 1315篇 |
免费 | 25篇 |
国内免费 | 2篇 |
专业分类
化学 | 1044篇 |
晶体学 | 12篇 |
力学 | 17篇 |
数学 | 35篇 |
物理学 | 234篇 |
出版年
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 6篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 25篇 |
2013年 | 52篇 |
2012年 | 56篇 |
2011年 | 81篇 |
2010年 | 37篇 |
2009年 | 38篇 |
2008年 | 82篇 |
2007年 | 60篇 |
2006年 | 68篇 |
2005年 | 67篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 57篇 |
2001年 | 36篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 21篇 |
1992年 | 16篇 |
1991年 | 23篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 27篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 17篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 8篇 |
1968年 | 7篇 |
1967年 | 6篇 |
排序方式: 共有1342条查询结果,搜索用时 0 毫秒
101.
The resonant Raman scattering of polar optical phonons has been measured in trigonal γ-InSe at the E'1 exciton edge. The two-phonon scattering spectrum widely spreads over the frequency range of 50 cm-1 with an extremely asymmetric lineshape. This spectrum has been interpreted in terms of the directional dispersion of extraordinary LO and TO phonons. 相似文献
102.
Clean surfaces of GaAs and GaP were studied by field-ion microscope (FIM). Field-ion images with ordered surfaces were first obtained in pure hydrogen, neon-50% hydrogen and pure neon gases at 78 K, by using channeltron electron multiplier arrays (CEMA). The field-ion images of GaAs were quite similar to those of GaP with respect to the surface structure and the image contrast. They showed the anisotropies of the ion emission and the surface structure between the [111] and orientations. Ring steps expected from a spherical surface were observed on the (111) and {100} planes, but not on the and {110} planes. The regional brightness of the FIM patterns was discussed in terms of the Knor and Müller model and the atomic and electronic structures of the surface. The image field of these crystals was much lower than that of metals usually used in FIM. For example, the image field strength for the hydrogen and GaAs system was about 1.1 V/Å. The reduction of the field necessary to image was also discussed in terms of the field penetration effect. 相似文献
103.
H. Kuroda I. Ikemoto K. Asakura H. Ishii H. Shirakawa T. Kobayashi H. Oyanagi T. Matsushita 《Solid State Communications》1983,46(3):235-238
FeK absorption spectra of FeCl3-doped polyacetylene [CH(FeCl3)y]x having y values of 0.024, 0.087 and 0.13, were measured by use of synchrotron radiation. The analyses of observed EXAFS data showed that Fe atom is surrounded by about four Cl atoms with Fe-Cl distance of 2.18–2.20 Å. It is concluded that the dopant exists mainly in the form of FeCl4-, and the following reaction takes place in the FeCl3 doping process. 2FeCl3 + e- → FeCl4- + FeCl2 相似文献
104.
The inelastic leptoproduction of heavy resonances J (J = J/ψ, Ψ,…) is investigated in a model where γvg → Jg is assumed to be the dominant mechanism. Analytic expressions for the differential cross section as well as for the helicity amplitudes are presented. A detailed numerical analysis of the angular distribution of the muon pair arising from the decay of the heavy resonance in its rest frame is presented. 相似文献
105.
106.
We demonstrate the generation of up to the 63rd harmonic (lambda = 12.6 nm) of a Ti:sapphire laser pulse (150 fs, 10 mJ), using a prepulse- (210-ps,24-mJ) produced boron plasma as the nonlinear medium. The influence of various parameters on the harmonic conversion efficiency was analyzed. The steep decrease in intensity for low-order harmonics (up to 19th order) was followed by a plateau. Typical conversion efficiencies were evaluated to be 10(-4) (for a 3rd harmonic) to 10(-7) (within the plateau region). Harmonic generation appeared to be efficient for the plasma that comprised neutral atoms and singly ionized boron. 相似文献
107.
Sasaki K Sugou K Miyamoto K Hirai J Tsubouchi S Miyasaka H Itaya A Kuroda Y 《Organic & biomolecular chemistry》2004,2(19):2852-2860
The nonameric porphyrin assemblies constructed with the series of free base tetraphenylporphyrins Pn having four pyrazine moieties linked with alkyl chains of different lengths, (CH2)n (n = 1, 5, 9, 17, 30), and dimeric [meso-tetrakis(2-carboxy-4-nonylphenyl)porphyrinato]zinc(II), ZnP2, show the effective light-collection effect and the typical Forster-type energy transfer from ZnP2 to Pn. 相似文献
108.
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
109.
Nakano H Takahashi K Okuyama Y Senoo C Tsugawa N Suzuki Y Fujita R Sasaki K Kabuto C 《The Journal of organic chemistry》2004,69(21):7092-7100
Cationic palladium (Pd)- and platinum (Pt)-phosphinooxazolidine catalysts 13a-c, 15a-d, 17a-c, and 19a-c were prepared from phosphinooxazolidine ligands 1-3, MCl(2) (M = Pd and Pt), and counterions, and the activities of the catalysts in the asymmetric Diels-Alder (DA) reactions of cyclic or acyclic dienes with imide dienophiles were investigated. These catalysts demonstrated high levels of catalytic activity. The cationic Pd-POZ complex 13c provided particularly excellent enantioselectivity (98% ee) in the DA reactions of cyclopentadiene with acryloyl-, crotonyl-, and fumaroyl-1,3-oxazolidin-2-ones (20a-c). 相似文献
110.
Sadamoto R Niikura K Ueda T Monde K Fukuhara N Nishimura S 《Journal of the American Chemical Society》2004,126(12):3755-3761
UDP-MurNAc-pentapeptide derivative bacterial cell-wall precursors were synthesized as effective tools for surface display on living bacteria. Lactobacilli were incubated in the ketone-modified precursor-containing medium, and the ketone moiety was displayed on the bacterial surface through cell-wall biosynthesis. Oligomannose was coupled with the ketone moiety on the bacterial surface via a aminooxyl linker, thereby displaying this oligosaccharide on the surface of the bacteria. The increase in the adhesion of the sugar-displaying bacteria onto a concanavalin A-attached film compared to that of native bacteria was confirmed by microscopic observation and surface plasmon resonance measurement. The incorporation of the artificial cell-wall precursors was enhanced when incubated with fosfomycin, an inhibitor of cell-wall precursor biosynthesis. 相似文献