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131.
James T. Snow Shu Murakami Satoru Masamune David J. Williams 《Tetrahedron letters》1984,25(38):4191-4194
Tetrakis(2,6-diethylphenyl)digermene (1b) has been synthesized and its molecular structure determined: (1) the GeGe bond length is 2.213(2) Å and (2) the molecule has a twist angle of 11° about the GeGe bond and an out-of-plane bending angle of 15° at the germanium atoms. 相似文献
132.
A direct approach to syn-3-hydroxy-2-vinylcarbonyl compounds via a boron-mediated aldol reaction with()-1-cyclohexyl-1-triethylsilyloxypenta-3(-en-2-one (6c) is described. 相似文献
133.
Fukuyama Y Kubo M Minami H Yuasa H Matsuo A Fujii T Morisaki M Harada K 《Chemical & pharmaceutical bulletin》2005,53(1):72-80
Nine new diterpenes, neovibsanin D (1), 7-epi-neovibsanin D (2), 15-O-methylneovibsanin F (3), 14-epi-15-O-methylneovibsanin F (4), 15-O-methyl-18-oxoneovibsanin F (5), 2-O-methylneovibsanin H (6), 2-O-methylneovibsanin I (7), neovibsanin G (8), and 14-epi-neovibsanin G (9), were isolated from a methanol extract of the leaves of Viburnum awabuki. Their structures were elucidated to be uniquely rearranged vibsane-type diterpenes by spectroscopic analyses and comparison of NMR data with those of previously reported vibsane-type diterpenes. In addition, irradiation of vibsanin B (12) in methanol with a high-pressure Hg lump led to the direct formation of neovibsanins A (14) and B (15). These results gave a clue to understanding of the biogenetic interconversion of 11-membered vibsanins into neovibsanins. 相似文献
134.
Ho Sik Kim Tong Eun Kim Seong Uk Lee Dong Il Kim Sung Wook Han Yoshihisa Okamoto Takako Mitomi Yoshihisa Kurasawa 《Journal of heterocyclic chemistry》1998,35(6):1515-1520
The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 5 with a 2-fold molar amount of ethyl chloroglyoxalate gave ethyl 8-chloro-4-methyl-4H-1,3,4-oxadiazino[5,6-b]quinoxaline-2-carboxylate 6 , whose reaction with hydrazine hydrate afforded the C2-hydrazinocarbonyl derivative 7 . The reaction of compound 7 with nitrous acid provided the C2-acylazide derivative 8 , which was converted into the C2-amino 9 , C2-carbamate 11a-c, 12a,b , and C2-ureido 13a-c, 14 derivatives. The mass spectral fragmentation patterns were examined for compounds 10–14 , wherein the molecular ion peak did not appear in the mass spectra of compounds 10c, 11a-c, 12a,b, 13c , and 14. 相似文献
135.
Jiang ZH Tanaka T Sakamoto T Kouno I Duan JA Zhou RH 《Chemical & pharmaceutical bulletin》2002,50(1):137-139
A new biflavanone (1) with a C-3/C-3" linkage, a new daphnane-type diterpene (2) acylated by an unsaturated fatty acid, and a new coumarin glycoside (3), along with six lignans, two phenylpropanoids, five flavonoids, two diterpenes, and three coumarins were isolated from the roots of Stellera chamaejasme L. (Thymelaeaceae). Elucidation of these secondary metabolites of S. chamaejasme L. supplied strong chemical verification of the close taxonomic relationships among the genera Stellera, Daphne, and Wikstroemia, all of which belong to the family Thymelaeaceae. 相似文献
136.
Nakahara R Fujimoto T Doi M Morita K Yamaguchi T Fujita Y 《Chemical & pharmaceutical bulletin》2008,56(7):977-981
Methods for the fluorophotometric determination of hydrogen peroxide (H(2)O(2)) and other reactive oxygen species (ROS) were proposed by using the fluorescence reaction between H(2)O(2) or other ROS and fluorescein hydrazide (FH). In the determination of H(2)O(2), the calibration curve exhibited linearity over the H(2)O(2) concentration range of 2.1-460 ng ml(-1) at an emission wavelength of 527 nm with an excitation of 460 nm and with the relative standard deviations (n=6) of 4.06%, 1.78%, and 2.21% for 3.1 ng ml(-1), 30.8 ng ml(-1), and for 308 ng ml(-1) of H(2)O(2), respectively. The detection limit for H(2)O(2) was 0.7 ng ml(-1) due to three blank determinations (rho=3). The calibration curves for ROS-related compounds were also constructed under the optimum conditions. This method was successfully applied in the assay of H(2)O(2) in human urine. In addition, we performed the characterization of FH, and interesting information was obtained with regard to the relationship between the chemical structure and fluorescence. 相似文献
137.
In an attempt to explore the mechanism for the synthesis of silsesquioxanes (POSS), the entire reaction processes from HSi(OH)3 to T8, one of the most common and stable POSS was investigated with electronic structure theory calculations, including electron correlation effects. In addition, the effect of some controlling factors, which play important roles in the reaction mechanism, is discussed. 相似文献
138.
Takako Ishiguro Yukichi Sakata Hidetoshi Arima Daisuke Iohara Makoto Anraku Kaneto Uekama Fumitoshi Hirayama 《Journal of inclusion phenomena and macrocyclic chemistry》2018,92(1-2):147-155
The release control of fragrances, benzyl acetate (BA), citral (CR), linalool (LL), citronellol (CL) and linalyl acetate (LA), was conducted using β-cyclodextrin (β-CyD), 2-hydroxypropyl-β-CyD (HP-β-CyD) and 2,6-di-O-methyl β-CyD (DM-β-CyD). The release rate of the fragrances from 30% ethanol/water solution was significantly suppressed by the complexation with these CyDs, and the suppressing effect increased in the order of β-CyD?<?HP-β-CyD?<?DM-β-CyD. The concentration-dependent change of the release rate was quantitatively analyzed to obtain the stability constant (Kc) of the fragrance-CyD complexes. These Kc values were in good agreement with those determined by the solubility method. The results suggest that the release of fragrances can be prolonged by the complexation with β-CyDs and their effects can be controlled by choosing appropriate CyD derivatives with higher Kc values and by setting proper concentrations of the host molecules. 相似文献
139.
Masahiro Hirama David S. Garvey Linda D.-L. Lu Satoru Masamune 《Tetrahedron letters》1979,20(41):3937-3940
The -vinyloxyborane (), prepared from S-phenyl propanethioate, 9-BBN triflate, and diisopropylethylamine, reacts stereoselectively with aldehydes to provide -β-hydroxy-α-methylcarboxylic acid thiol esters. This reaction has been applied to a synthesis of Prelog-Djerassi lactonic acid (). 相似文献
140.
Determination of acrolein in serum by high‐performance liquid chromatography with fluorescence detection after pre‐column fluorogenic derivatization using 1,2‐diamino‐4,5‐dimethoxybenzene
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Takahiro Imazato Mariko Kanematsu Naoya Kishikawa Kaname Ohyama Takako Hino Yukitaka Ueki Eisuke Maehata Naotaka Kuroda 《Biomedical chromatography : BMC》2015,29(9):1304-1308
Acrolein is a major unsaturated aldehyde that is generated during the lipid peroxidation process. The measurement of acrolein in biological samples should be useful to estimate the degree of lipid peroxidation and to evaluate the effect of hazardous properties of acrolein on human health. In this study, a highly sensitive and selective high‐performance liquid chromatography with fluorescence detection method was developed for the determination of acrolein in human serum. The proposed method involves the pre‐column fluorogenic derivatization of acrolein with 1,2‐diamino‐4,5‐dimethoxybenzene (DDB) as a reagent. The fluorescent derivative of acrolein could be detected clearly without any interfering reagent blank peaks because DDB does not have intrinsic fluorescence itself, and the detection limit was 10 nM (signal‐to‐noise ratio = 3). The proposed method could selectively detect acrolein in human serum with a simple protein precipitation treatment. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献