全文获取类型
收费全文 | 574篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 421篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 29篇 |
物理学 | 135篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 20篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 28篇 |
2007年 | 42篇 |
2006年 | 19篇 |
2005年 | 20篇 |
2004年 | 30篇 |
2003年 | 25篇 |
2002年 | 17篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 13篇 |
1975年 | 16篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有590条查询结果,搜索用时 542 毫秒
101.
-Nitrophenylhydrazones, unsusceptible to autoxidation, are readily oxygenated in the presence of a five-coordinate cobalt(II)-Schiff base complex, Co(II)(MeOSalen) (Py) leading to quantitative formation of novel 1-(-nitrophenylazo)-1-peroxy Co(III) complexes 2, which were isolated as crystals. A plausible mechanism involving hydrogen abstraction by Co(III)(O2?.) from the substrate followed by formation of a substrate anion Co(III) complex intermediate is proposed. 相似文献
102.
This paper describes the results of hint-effect experiments, and analyses the human decision-making process from fuzzy-theoretic and concept-formational viewpoints. To begin with, we discuss the problem of the decision-making process subject to a specific and newly given information. In other words, the fuzzy-theoretic experiment concerning with some hints in the estimation and decision processes of the card arrangement is conducted. Next, the concept-formational process is analysed clearly by means of the introduction of both the cusp-curved surface in catastrophe theory and fuzziness concept in fuzzy set theory. Finally, we show the hint effect in the estimation and decision processes. 相似文献
103.
104.
Three allylbenzenes from Asiasarum heterotropoides, methyleugenol (1), elemicin (2) and gamma-asaron (3) showed suppressive effects on umu gene expression of the SOS response in the Salmonella typhimurium OY1001/1A2 umu test against the mutagen 2-amino-3,4-dimethylimidazo[4,5-f ]quinoline (MeIQ). Gene expression was suppressed 70.0, 75.9 and 81.7% at a concentration of 0.4 mM, respectively. The ID50 values (50% inhibition dose) of these compounds were 0.125, 0.098 and 0.059 mM, respectively. On the other hand, compounds 1-3 showed weak suppressive effects of the SOS-inducing activity on activated MeIQ. 相似文献
105.
Masahito Katto Kazuyoshi Oda Atsushi Yokotani Noriaki Miyanaga 《Optics Communications》2010,283(3):414-416
Subpicosecond vacuum ultraviolet (VUV) pulses at the wavelength of 126 nm have been generated in rare gases as a result of the 7th harmonic radiation of a subpicosecond Ti:Sapphire laser oscillating at 882 nm. The VUV harmonic intensity was optimized in Xe at the pressure of 1.2 Torr. The behavior of the harmonic emission was qualitatively reproduced by the classical nonlinear optics. The increase of the harmonic intensity was limited by multiphoton ionization of Xe. 相似文献
106.
Ishioka J Liu YH Shimatake K Kurosawa T Ichimura K Toda Y Oda M Tanda S 《Physical review letters》2010,105(17):176401
We discovered the chirality of charge-density waves (CDW) in 1T-TiSe? by using STM and time-domain optical polarimetry. We found that the CDW intensity becomes Ia?∶Ia?∶Ia? = 1∶0.7 ± 0.1∶0.5 ± 0.1, where Ia(i) (i=1,2,3) is the amplitude of the tunneling current contributed by the CDWs. There were two states, in which the three intensity peaks of the CDW decrease clockwise and anticlockwise. The chirality in CDW results in the threefold symmetry breaking. Macroscopically, twofold symmetry was indeed observed in optical measurement. We propose the new generalized CDW chirality H(CDW) ≡ q?·(q?×q?), where q(i) are the CDW q vectors, which is independent of the symmetry of components. The nonzero H(CDW)-the triple-q vectors do not exist in an identical plane in the reciprocal space-should induce a real-space chirality in CDW system. 相似文献
107.
Atsumu Sasaki 《Geometriae Dedicata》2010,145(1):151-158
Let G/K be an irreducible Hermitian symmetric space of non-compact type, and
G\mathbbC/K\mathbbC{G_{\mathbb{C}}/K_{\mathbb{C}}} its complexification by forgetting the original complex structure. Then,
D :=G\mathbbC/[K\mathbbC, K\mathbbC]{D :=G_{\mathbb{C}}/[K_{\mathbb{C}}, K_{\mathbb{C}}]} is a non-symmetric Stein manifold. We prove that a maximal compact subgroup of
G\mathbbC{G_{\mathbb{C}}} acts on D in a strongly visible fashion in the sense of Kobayashi (Publ Res Inst Math Sci 41:497–549, 2005) if and only if G/K is of non-tube type. Our proof uses the theory of multiplicity-free representations and a construction of a slice and an
anti-holomorphic involution on D. 相似文献
108.
A high-concentration in-situ phosphorus-doping technique for silicon low-temperature epitaxial growth with Si2H6 has been developed. Growth temperature has an impact on the crystal quality and on lattice strain of phosphorus-doped silicon layers. Resistivity, micro-Raman spectroscopy, and high-resolution X-ray diffraction indicated that good crystal quality was achieved at a growth temperature of 525 °C. On the other hand, growth pressure has little influence on crystal quality or on lattice strain except for surface morphology. By optimizing epitaxial growth conditions, an extremely high concentration of phosphorous doping was achieved without a high-temperature activation annealing, and the resultant good crystal quality of the phosphorus-doped silicon layer gave a very low resistivity. Accordingly, the high-concentration in-situ phosphorus doping is a powerful technique to fabricate future ultra-high-speed SiGe HBTs. 相似文献
109.
Takeshi Maeda Jin Zhou Yuya Oda Hiroyuki Nakazumi Shigeyuki Yagi 《Research on Chemical Intermediates》2018,44(8):4783-4795
Naphthalene diimides (NDIs) are promising candidate for electron acceptors due to their low-lying HOMOs and LUMOs. The functinalization of soluble NDIs at the 2,6-position affects the absorption and electrochemical properties. In this study, NDI-based hybrid dyes NDI-SQ-A, B fused with squaraine chromophore were designed and synthesized in order to elucidate the effects of the substitution on their optical and electrochemical properties. These dyes were successfully synthesized by Stille coupling reactions using 3-stannylcyclobutenediones and brominated NDI derivative, followed by a condensation reaction. DFT calculation predicts that the present dyes adopt distorted structures coming from a steric hindrance between semisquaraine and NDI moieties. The hybrid dyes show low-lying LUMOs due to the introduction of electron-deficient NDI moiety and broad absorption spectra in the far-red region. The absorption spectra of their thin films were bathochromically shifted relative to those in solution, indicating that hybrid dyes formed J aggregates. 相似文献
110.
K. Oda Y. Kikawada T. Oi T. Honda 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(2):475-478
A total of 19 elements in the samples of atmospheric deposition collected in Kawasaki, Japan, were determined by neutron activation
analysis, ICPAES and flame photometry. The amounts of soil dust depositions were larger in springs and those of Sb and Zn
depositions were larger in summers than in the other seasons. The values of the enrichment factors were higher for Sb and
Zn than for the other elements determined throughout the sampling period. A factor analysis showed that the two elements were
characterized as industrial components. Rubber products like tires that contain noncombustibles and rubber accelerators were
a possible origin of high concentrations of Sb and Zn in the present samples. 相似文献