全文获取类型
收费全文 | 3246篇 |
免费 | 68篇 |
国内免费 | 13篇 |
专业分类
化学 | 2227篇 |
晶体学 | 37篇 |
力学 | 45篇 |
数学 | 194篇 |
物理学 | 824篇 |
出版年
2023年 | 15篇 |
2021年 | 24篇 |
2020年 | 38篇 |
2019年 | 48篇 |
2018年 | 34篇 |
2017年 | 28篇 |
2016年 | 55篇 |
2015年 | 59篇 |
2014年 | 77篇 |
2013年 | 180篇 |
2012年 | 157篇 |
2011年 | 168篇 |
2010年 | 96篇 |
2009年 | 116篇 |
2008年 | 152篇 |
2007年 | 174篇 |
2006年 | 165篇 |
2005年 | 182篇 |
2004年 | 184篇 |
2003年 | 153篇 |
2002年 | 144篇 |
2001年 | 77篇 |
2000年 | 66篇 |
1999年 | 31篇 |
1998年 | 48篇 |
1997年 | 44篇 |
1996年 | 52篇 |
1995年 | 60篇 |
1994年 | 45篇 |
1993年 | 44篇 |
1992年 | 45篇 |
1991年 | 44篇 |
1990年 | 48篇 |
1989年 | 46篇 |
1988年 | 29篇 |
1987年 | 34篇 |
1986年 | 20篇 |
1985年 | 34篇 |
1984年 | 29篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 18篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1976年 | 19篇 |
1975年 | 14篇 |
1974年 | 18篇 |
1973年 | 26篇 |
排序方式: 共有3327条查询结果,搜索用时 711 毫秒
991.
992.
Makoto Yoshitake Naoko Sejima Hideyuki Yoshida Kenichiro Todoroki Hitoshi Nohta Masatoshi Yamaguchi 《Analytical sciences》2007,23(8):949-953
A selective and sensitive fluorometric determination method for native fluorescent peptides has been developed. This method is based on intramolecular fluorescence resonance energy transfer (FRET) detection in a liquid chromatography (LC) system following precolumn derivatization of the amino groups of tryptophan (Trp)-containing peptides. In this detection process, we monitored the FRET from the native fluorescent Trp moieties (donor) to the derivatized fluorophore (acceptor). From a screening study involving 10 fluorescent reagents, we found that o-phthalaldehyde (OPA) generated FRET most effectively. The OPA derivatives of the native fluorescent peptides emitted OPA fluorescence (445 nm) through an intramolecular FRET process when they were excited at the excitation maximum wavelength of the Trp-containing peptides (280 nm). The generation of FRET was confirmed through comparison with the analysis of a non-fluorescent peptide (C-reactive protein fragment (77 - 82)) performed using LC and a three-dimensional fluorescence detection system. We were able to separate the OPA derivatives of the Trp-containing peptides when performing LC on a reversed-phase column. The detection limits (signal-to-noise ratio = 3) for the Trp-containing peptides, at a 20-microL injection volume, were 41 - 180 fmol. The sensitivity of the intramolecular FRET-forming derivatization method is higher than that of the system that takes advantage of the conventional detection of OPA derivatives. Moreover, native non-fluorescent amines and peptides in the sample monitored at FRET detection are weaker than those of conventional fluorescence detection. 相似文献
993.
Vassiliev invariants of type two for a link 总被引:1,自引:0,他引:1
Hitoshi Murakami 《Proceedings of the American Mathematical Society》1996,124(12):3889-3896
We show that any type two Vassiliev invariant of a link can be expressed as a linear combination of the second coefficients of the Conway polynomials of its components and a quadratic expression of linking numbers.
994.
Taku Matsushita Ryuji Nomura Harvey H. Hensley Hitoshi Shiga Takao Mizusaki 《Czechoslovak Journal of Physics》1996,46(6):2995-3002
Pulsed NMR was used to investigate nuclear spin dynamics of nuclear-ordered solid3He in the low field phase. The nuclear spin motion became unstable under certain conditions. Under stable conditions the spin motion can be described by the OCF equations. The tipping-angle-dependent frequency shift and multiple spin echoes were observed, which are similar to the case of superfluid3He. The onset of the instability of spin motion is attributed to the stimulated emission mechanism through the three-magnon relaxation process, which is similar to the Suhl instability in electronic magnetism. We derived the magnon life time from the analysis of the instability. During the instability, a largenegative frequency shift was observed. This negative shift is explained by the extension of Fomin-Ohmi's theory to include the state of decayed magnon and this explanation is consistent with the instability model. 相似文献
995.
996.
997.
Takashi Abe Eiji Hayashi Hajime Baba Shunji Nagase 《Journal of fluorine chemistry》1984,26(3):295-312
Perfluorobicyclic ethers and perfluorospiroethers, all containing an oxolane skeleton, were treated with AlCl3 in a heterogeneous manner to give the corresponding α,α,α′-trichlorinated and α,α-dichlorinated products, respectively. From perfluoroacetal compounds, for example, perfluoro(8-methoxy-7-oxabicyclo- [4.3.0]nonane), mono- and di-chlorinated products, i.e. perfluoro- (8-chloro-8-methoxy-7-oxabicyclo[4.3.0]nonane) and perfluoro- (8,8-dichloro-7-oxabicyclo[4.3.0]nonane) were obtained in good yields. The action of fuming sulfuric acid on these polychlorinated products led to the formation of the corresponding lactones. Perfluoro(6-chloro-7-oxa-8-oxobicyclo[4.3.0]nonane) was treated with (CH3)2NLi to give N,N-dimethylundecafluoro-2-oxocyclohexyl- acetamide. 相似文献
998.
Microemulsions in separation sciences 总被引:9,自引:0,他引:9
Hitoshi Watarai 《Journal of chromatography. A》1997,780(1-2):93-102
Fundamental properties of microemulsions in relation to their utilization in liquid state separation methods of ionic and non-ionic compounds are briefly reviewed. Discussions are focused on some characteristics functions of o/w (L1) and w/o (L2) single-phase microemulsions and the two-phase microemulsion systems of Winsor I and Winsor II from the viewpoint of their use as separation media in solvent extraction, liquid chromatography and capillary electrophoresis. Through reviewing, practical advantages of the microemulsion media in the separation of metal ions and biological compounds are assessed. 相似文献
999.
T.T. John C.S. Kartha K.P. Vijayakumar T. Abe Y. Kashiwaba 《Applied Physics A: Materials Science & Processing》2006,82(4):703-707
We report a new structure for CuInS2/In2S3 solar cell, in which both absorber and buffer layers were deposited using chemical spray pyrolysis (CSP) technique. The usual
superstrate structure, having buffer layer just above ITO, was not functioning mainly due to diffusion of Cu into In2S3 layer as seen from X-ray photoelectron spectroscopy (XPS) results. However, when the configuration of the cell was ITO/CuInS2/In2S3/Ag, cell parameters obtained were Voc=0.45 V, Jsc=44.03 mA/cm2, fill factor (FF) = 29.5% and η=5.87%. Good results could be obtained by using indium sulfide thin films having maximum photosensitivity.
The cell was characterized using X-ray diffraction, optical absorption, current–voltage and spectral response measurements.
PACS 81.15.Rs; 82.45.Mp; 84.60.Jt 相似文献
1000.
The interfacial adsorption and dimerization behavior of tetraphenylporphinatomanganese(III)chroride (Mn(TPP)Cl) in the toluene/water two phase system was studied. The absorption spectra of the porphyrin complex in the organic phase were blue shifted with increasing of pH in the aqueous phase, suggesting the formation of the mu-oxo dimer. The interfacial species in these systems were examined by means of UV/vis external reflection (ER) spectrophotometry. ER spectral maxima were also blue shifted with the increase in pH, whereas the shape of the ER spectra in the basic conditions was different from that of the mu-oxo dimer. The observed results suggest that the hydroxide-coordinated monomer, Mn(TPP)OH, was generated from the Mn(TPP)(H2O)+ at the interface under the basic conditions and that was further converted to the mu-oxo dimer, which was soluble into the toluene phase. 相似文献