全文获取类型
收费全文 | 406篇 |
免费 | 7篇 |
专业分类
化学 | 319篇 |
晶体学 | 2篇 |
力学 | 21篇 |
数学 | 16篇 |
物理学 | 55篇 |
出版年
2020年 | 3篇 |
2019年 | 7篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 21篇 |
2007年 | 33篇 |
2006年 | 17篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有413条查询结果,搜索用时 15 毫秒
121.
Oki Hisaya 《Thermochimica Acta》1979,31(1):55-59
The solid reaction between [Cr(NH3)6]X3(X? = Cl, I, SCN and NO3) and L-α-alanine was studied under continuous rise in temperature and isothermal heating. Under continuous rise in temperature, the main products were [Cr(NCS)3-(NH3)3] (X? = NCS) and [Cr(L-ala)3] (X? = NO3), when [Cr(NH3)6]Cl3 and [Cr(NH3)6]I3 as starting complexes were used; in both cases only the decomposition proceeds. Under isothermal heating at 150°C the main products were [CrCl(NH3)5]-Cl2 (X? = Cl), [Cr(NH3)6]I2 (X? = I), [Cr(NCS)3(NH3)3] (X? = SCN) and [Cr(L-ala)3] (X? = NO3). In those matrix reactions, the ease of anion coordination was: SCN? > Cl? > I? > alanine. For the synthesis of tris(alaninato)chromium(III) complex the most desirable starting complex was [Cr(NH3)6](NO3)3.The solid state reaction between [Cr(en)3]X3 type complexes and NH4X (X? = F, Cl, Br, I and SCN), KX (X? = Cl, Br and I), and NaSCN have been reported by Wendlandt and Stembridge1. They reported that the reaction product in most cases, was cis-[Cr(en)2Y2]X, where Y and X are the same or different anions, depending upon the matrix material employed and the thermal matrix method appears to be a useful new route for the synthesis of bis(ethylendiamine(chromium(III) complexes.In the previous paper2, the solid state reaction between [Cr(NH3)6](NO3)3 and L-amino acids has been utilized in the preparation of tris(amino acidato)chromium(III) complexes. The preparation of [Cr(L-ala)3] by the solid state reaction between [Cr(NH3)6](NO3)3 and L-alanine have been reported. No studies on the effect of the counter-ion have been reported.In this paper, various hexaamminechromium(III) complexes, [Cr(NH3)6]X3 (X? = Cl, I, SCN and NO3), were heated with L-α-alanine under continuous rise in temperature and under isothermal heating at 150°C for studies on the ease of anion coordination. It will seen that the anion which replaces the ammonia in the hexaamminechromium(III) complex comes from either the alanine or counter-ion. 相似文献
122.
Nobutoshi Kiba Ayumi Koga Masaki Tachibana Kazue Tani Hitoshi Koizumi Tetsuo Koyama Akira Yamamura Kunio Matsumoto Tohru Okuda Koki Yokotsuka 《Analytical sciences》2006,22(1):95-98
A chemiluminometric flow injection analytical system for the quantitation of L-histidine is described. Histidine oxidase (EC 1.4.3.-) from Brevibacillus borstelensis KAIT-B-022 was immobilized on tresylated poly(vinyl alcohol) beads and packed into a stainless-steel column. The hydrogen peroxide produced was detected chemiluminometrically by a flowthrough sensor containing immobilized peroxidase (EC 1.1 1.1.7). The maximum sample throughput was 10 h(-1). The calibration graph was linear from 0.05 to 5 mM; the detection limit (signal to noise ratio = 3) was 0.01 mM. The activity of immobilized histidine oxidase reduced to 65% of the initial value after 350 injections. The system was applied to the determination of L-histidine in fish meat, such as salmon, tunny, bonito, and mackerel. 相似文献
123.
Masaru Oda Atsushi Hasegawa Ken Nishiura Akira Nishiyama Toshiro Tani 《Journal of luminescence》2007,127(1):198-203
We report here the distinctive modifications of photoluminescence (PL) behaviors in single CdSe/ZnS/TOPO nanocrystals depending on their environments. Long-time traces of PL intensity from single nanocrystals have been obtained in both vacuum and a wet nitrogen atmosphere. While all of the nanocrystals in both environments exhibit PL blinking behaviors, i.e. on-off intermittency of PL intensity, as usual, some of the nanocrystals in the wet nitrogen atmosphere show significant increase in duration time of on-events. As for the duration time of blinking off-events, it is for the moment associated with the occasional events of carrier capturing at trap sites on or near the nanocrystal surfaces. We propose a model in which adsorbed water molecules at the trap sites on the nanocrystal surfaces transform them under light irradiation, which eventually decreases the occurrence of the trapping events due to their inactivation. It in turn increases the PL on-times. In addition to the drastic modification of the blinking profile, we also found that in the PL time traces some kinds of undulated behaviors, i.e. continuous and rather low frequency fluctuation of PL intensity, appear during each on-event in vacuum while they disappear totally in the wet nitrogen atmosphere. These results are also described on the basis of the inactivation model of the trap sites introduced above. 相似文献
124.
Hiroko Tani Shunya Takahashi Keiko Hasumi Tomoki Tatefuji Yayoi Hongo Hiroyuki Koshino 《Tetrahedron: Asymmetry》2009,20(4):457-460
(E)-9,10-Dihydroxy-2-decenoic acid 1 was isolated as a new compound from royal jelly. The planar structure was deduced by spectroscopic analyses, whereas the absolute configuration was established by chemical synthesis of both enantiomers of 1. The natural product was revealed to be ca. 3.5:1 mixture of (R)- and (S)-acids by comparison of 1 with authentic samples. 相似文献
125.
Chishiro T Shimazaki Y Tani F Naruta Y 《Chemical communications (Cambridge, England)》2005,(8):1079-1081
An oxo-bridged ferric heme-copper(II) complex, obtained by thermal transformation of the corresponding peroxo-bridged complex, was reacted with an equimolar amount of H2O2 to regenerate the micro-peroxo complex by a ligand exchange from oxo to peroxo, without the formation of a ferryl-oxo species or heme degradation as are observed in general ferric heme-H2O2 reactions. 相似文献
126.
We report a molecular dynamics simulation study on an ensemble of rod-like particles, each composed of nine soft spheres held rigidly along a line. We have calculated translational mean square displacements and velocity autocorrelation functions in the fluid phases exhibited by the model, i.e., smectic A, nematic and isotropic. These quantities have then been used to compute diffusion coefficients. In addition, we have calculated viscosities in the nematic and isotropic phases. Despite its crude nature, the model is capable of providing a faithful reproduction of many features of the transport behavior observed in real liquid-crystalline materials. The simulation results have been compared with the predictions of the modified affine transformation theory, finding only a fair agreement. 相似文献
127.
128.
129.
130.
Bertolini D Cinacchi G De Gaetani L Tani A 《The journal of physical chemistry. B》2005,109(51):24480-24488
We report a molecular dynamics simulation study on the isotropic phase of an idealized calamitic liquid crystal model with a length-to-width ratio of approximately 5-6. The study focuses on the characterization of single-particle and collective orientational dynamics on approaching the phase transition to the nematic phase. Recent experimental and simulation works have suggested that a power law behavior exists at relatively short times in the decay of the time derivative of the orientational correlation functions. Qualitatively, our simulation data are consistent with these findings. Both single-particle and collective time correlation function derivatives possess, in their respective log-log plots, a linear region at very short times, whose slope is essentially independent from the thermodynamic state. Nevertheless, the single-particle orientational correlation functions are better described by a function which is the sum of a fast exponential, an intermediate stretched-exponential and a slow exponential, while the collective orientational correlation functions are satisfactorily described by a sum of two exponentials, at higher density, or by just one exponential, at lower density. 相似文献