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71.
72.
Okumura T Nakazono M Otsuka M Takayama K 《Colloids and surfaces. B, Biointerfaces》2006,49(2):153-157
Measurement precision based on homogeneous and accurate standard samples has been reported to result in significant improvement in the sensitivity and accuracy of the quantitative analysis of polymorphic mixtures. The purpose of this study was to further improve the accuracy of the quantitation based on data processing by artificial neural networks (ANNs), using such high quality standard samples. Homogeneous powder mixtures of - and γ-forms of indomethacin (IMC) at various ratios (0–50% -form content) were subjected to X-ray powder diffractometry. The two diffraction peaks selected as the best combination in multiple linear regression (MLR) were used in the ANN with an extended Kalman filter as a training algorithm. The results obtained by ANN had better predictive accuracy at lower contents (0–5%) compared to those of MLR. ANNs for the diffraction data based on high quality standard samples provide an extremely precise and accurate quantification for polymorphic mixtures. 相似文献
73.
Nishizawa S Sankaran NB Seino T Cui YY Dai Q Xu CY Yoshimoto K Teramae N 《Analytica chimica acta》2006,556(1):133-139
In combination with abasic site (AP site)-containing DNAs, potential use of a biotic fluorescence compound, Vitamin B2 (riboflavin), is demonstrated for the fluorescence detection of the thymine (T)-related single-nucleotide polymorphisms. Our method is based on construction of the AP site in DNA duplexes, which allows small ligands to bind to target nucleotides accompanied by fluorescence signaling: an AP site-containing probe DNA is hybridized with a target DNA so as to place the AP site toward a target nucleobase, by which hydrophobic microenvironments are provided for ligands to recognize target nucleotides through stacking and hydrogen-bonding interactions. In 10 mM sodium cacodylate buffer solutions (pH 7.0) containing 100 mM NaCl and 1.0 mM EDTA, Vitamin B2 is found to selectively bind to T (K11 = 1.8 × 106 M−1 at 5 °C) over other nucleobases, and this is accompanied by significant quenching of its fluorescence. While the sensing functions depend on the flanking sequences to the AP site, Vitamin B2 is applicable to the detection of T/C (cytosine), T/G (guanine) and T/A (adenine) mutation sequences of the CYP2A6 gene, where the flanking nucleobases are guanines in both positions (-GXG-, X = AP site). 相似文献
74.
Ken-ichiro Yamamoto Masayo Hayama Masato Matsuda Taiji Yakushiji Makoto Fukuda Takehiro Miyasaka Kiyotaka Sakai 《Journal of membrane science》2007
The tortuous capillary pore diffusion model (TCPDM) has been used for estimating diffusive and pure water permeability from simple structure parameters such as pore diameter, surface porosity, wall thickness and tortuosity. The validity of this model for evaluation of homogeneous membrane has been already confirmed. Recently, there is a trend toward the use of asymmetrical dialysis membranes made of synthetic polymer such as poly(acrylonitrile) (PAN), polysulfone (PS) and a polyethersulfone polyarylate (PEPA) blend polymer. The purpose of the present study is to apply the TCPDM to evaluation of commercially available hollow-fiber dialysis membranes with asymmetrical structures by simplifying them to a double-layer membrane. The TCPDM is capable of estimating pore tortuosity of asymmetrical dialysis membranes having skin and supporting layers from data on membrane thickness, pore diameter, pure water permeability and water content. Values for diffusive permeability obtained by the TCPDM are in a good agreement with experimental data. This TCPDM model is useful for evaluation of not only homogeneous membrane but also asymmetrical membrane. 相似文献
75.
76.
Toshio Kinoshita Tomoko Okunaka Takehiro Ohwada Hiroyuki Kawanaka Sunao Furukawa 《Journal of heterocyclic chemistry》1991,28(8):1901-1909
The following bromo-2,4(1H,3H)-pyrimidinediones possessing a bromo substituent at the 5-position and side chains at the 1- and 6-positions were prepared. The three types of mono-bromo derivatives are: 1-(bromoalkyl)-3,6-dimethyl- 3a-d , 5-bromo-3,6-dimethyl-1-(hydroxyalkyl)- 4a-d , and 1-(acetoxyalkyl)-5-bromo-3,6-dimethyl-2,4(1H,3H)-pyrimidinediones 11a-d . The three types of dibromo derivatives are: 5-bromo-1-(bromoalkyl)-3,6-dimethyl- Sa-d , 1-(acetoxyalkyl)-5-bromo-6-bromomethyl- 8a, 8c , and 8d , and 5-bromo-6-bromomethyl 1-(hydroxyalkyl)-2,4(1H,3H)-pyrimidinediones 9a, 9c , and 9d . Likewise one group of tribromo and one group of tetrabromo derivatives are: 5-bromo-1-(bromoalkyl)-6-bromomethyl -7a-d and 5-bromo-1-(bromoalkyl)-6-dibromomethyl-2,4(1H,3H)-pyrimidinediones 6a-d . 相似文献
77.
Yasuyuki Takeda Takehiro Iwasaki Yoshihiro Kudo Hiroaki Matsuda 《Journal of inclusion phenomena and macrocyclic chemistry》1992,14(3-4):303-309
Thermodynamic parameters (H
ex
0
and S
ex
0
) for the overall extractions of monovalent metal (Na, K, Rb, and Tl) picrates with benzo-18-crown-6 (B18C6), and those (H
D,L
0
and S
D,L
0
) for the distribution of B18C6 were determined between chloroform and water. All the extracted B18C6 complexes were l:1:1 complexes (B18C6:metal ion: picrate anion). The H
ex
0
and S
ex
0
values for all the metals are negative. Every extraction of the metal picrate with B18C6 is completely enthalpy driven. The H
D,L
0
and S
D,L
0
values of B18C6 are both positive, and the partition of B18C6 is entirely entropy driven. Enthalpy (H
ex,ip
0
) and entropy changes (S
ex,ip
0
) for ion-pair extractions of B18C6-metal ion complexes with picrate anions were calculated. All the H
ex,ip
0
and S
ex,ip
0
values are negative, and the ion-pair extractions are completely enthalpy driven. 相似文献
78.
Hirobumi Takahashi Takehiro Fukami Hisaki Kojima Takeru Yamakawa Hiroyuki Takahashi Toshihiro Sakamoto Teruyuki Nishimura Masayuki Nakamura Takashi Yosizumi Kenji Niiyama Norikazu Ohtake Takashi Hayama 《Tetrahedron》2005,61(14):3473-3481
A robust synthetic method for 2-alkylamino-6-carboxy-5,7-diarylcyclopenteno[1,2-b]pyridines via acylamination at the alpha position of the functionalized pyridine system has been developed. The key step in this method was achieved by treatment of the corresponding pyridine N-oxides with 2.5 equiv of imidoyl chlorides in the presence of triethylamine, thus producing the desired 2-acylaminopyridines in good yields (74-96%). 相似文献
79.
S. Kitoh H. Senda K.‐K. Kunimoto S. Maeda A. Kuwae K. Hanai 《Crystal Research and Technology》2004,39(4):375-381
Crystal structures of (R)‐ and (rac)‐4‐phenyl‐1,3‐oxazolidin‐2‐one (4‐POO) have been determined by X‐ray diffraction and characterized by the solid state 13C NMR and IR spectra. Molecular geometries and intermolecular interactions in (R)‐ and (rac)‐4‐POO crystals are very similar to each other; 4‐POO molecules are linked via the N‐H…O intermolecular hydrogen bonds to form the chained structure. Chemical shifts of the solid state 13C NMR spectra are very similar to each other, whereas the 1H spin‐lattice relaxation times (T1H) value for (R)‐4‐POO is five times as large as that for (rac)‐4‐POO, reflecting the more restricted mobility of the (R)‐4‐POO chain. Although both crystals contain an unique molecule in the asymmetric unit, a doublet feature is observed for the C=O stretching mode in the IR spectra of (R)‐ and (rac)‐4‐POO crystals. The frequency gap of the C=O bands are correlated with the strength of the dipole‐dipole interactions between the neighboring C=O groups. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
80.
Takehiro Kohara Yukihiko Hashimoto Rieko Shioya Kazuhiko Saigo 《Tetrahedron: Asymmetry》1999,10(24):485-4840
1-Mesitylethylamine was designed as a new non-natural chiral auxiliary. Racemic 1-mesitylethylamine could be synthesized in two steps from mesityl cyanide and could be resolved via separation of diastereomeric carbamates derived from (−)-menthyl chloroformate, followed by reduction with DIBAL and acidic hydrolysis. Imines, prepared from enantiopure 1-mesitylethylamine and aromatic aldehydes, reacted with Danishefsky’s diene in the presence of a Lewis acid to give cycloaddition products, 4-pyridone derivatives, with high diastereoselectivity. 相似文献