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101.
M Imuta H Itani H Ona Y Hamada S Uyeo T Yoshida 《Chemical & pharmaceutical bulletin》1991,39(3):663-671
The synthesis and antibacterial activity of the 1-methylcarbapenems, 2-heteroaromatic-thiomethyl and 2-carbamoyloxymethyl derivatives having a 6-[(R)-1-hydroxyethyl] side chain, are described. The introduction of a methyl substituent at the C-1 position was accomplished by a newly developed procedure using crotyl halides and zinc dust. The 2-hydroxymethyl carbapenems as key intermediates allowed an easy entry into the preparation of title carbapenems. 相似文献
102.
Asymmetric hydroxymethylation of silicon enolates with formaldehyde in aqueous media has been achieved using praseodymium triflate and a chiral crown ether. Formaldehyde aqueous solution can be directly used for the reactions, and a water/THF mixture was found to be the best solvent system. This is the first example of catalytic asymmetric hydroxymethylation of silicon enolates. 相似文献
103.
Ando K Tsuji E Ando Y Kunitomo J Kobayashi R Yokomizo T Shimizu T Yamashita M Ohta S Nabe T Kohno S Ohishi Y 《Organic & biomolecular chemistry》2005,3(11):2129-2139
Variable benzo[b]furan derivatives having (E)- and (Z)-2-alkylcarbamoyl-1-methylvinyl groups at the 2-, 4- and 5-positions and a carboxylpropoxy or (1-phenyl)ethoxy group at the 7-position were prepared to find novel and selective leukotriene B4(LTB4) receptor antagonists. (E)-2-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (4v) showed selective inhibition to the human BLT2 receptor (hBLT2). On the other hand, (E)-2-acetyl-4-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (7v) inhibited both human BLT(1) receptor (hBLT1) and hBLT2. The (E)-2-(2-diethylcarbamoyl-1-methylvinyl) group lay on approximately the same plane as the benzo[b]furan ring, whereas the (E)-4-(2-diethylcarbamoyl-1-methylvinyl) group had the torsion angle (45.7 degree) from the benzo[b]furan ring plane. However, the (Z)-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans were inactive. The inhibitory activity depended on the conformation of the 2-diethylcarbamoyl-1-methylvinyl group. 相似文献
104.
Masayuki Inoue 《Tetrahedron letters》2004,45(10):2053-2056
We report a new reaction for the direct construction of O,S-acetals, key intermediates in the assembly of fused polycyclic ethers. α-Fluorosulfides and secondary alcohols were coupled by the action of Yb(OTf)3 to generate O,S-acetals in high yield. The neutral and selective nature of the reaction should be useful for synthesizing natural and artificial polyethers with multisensitive functionalities. 相似文献
105.
A novel protocol for assembling polycyclic ethers was developed and successfully applied to the synthesis of the EFGH ring system of ciguatoxin CTX3C. A key transformation involves construction of an O,S-acetal through coupling of alpha-chlorosulfide and a secondary alcohol under mild conditions. The method is highly applicable to use with sensitive substrates and will enable the synthesis of various natural and artificial polycyclic ethers. [reaction: see text] 相似文献
106.
Keinosuke Hamada 《Journal of Molecular Structure》1978,48(2):191-197
The Raman and IR spectra of hexachlorodisilazane were measured, and the assignment carried out by comparison with those of the structurally related compounds, hexachlorodisiloxane, hexachlorodisilane and dimethylamine. The vibrational spectra of hexachlorodisilazane are very closely related to those of hexachlorodisiloxane, hexachlorodisilane and dimethylamine, and can be interpreted in terms of a non-rigid D3d symmetry with an internal rotation. 相似文献
107.
Miki Murata Hiyoruki Yamasaki Tsukasa Ueta Masayuki Nagata Masanori Ishikura Shinji Watanabe Yuzuru Masuda 《Tetrahedron》2007,63(19):4087-4094
The general and efficient silylation of aryl halides has been developed utilizing triethoxysilane and a rhodium catalyst. The substrate scope is broad and includes ortho-, meta-, and para-substituted electron-rich and -deficient aryl iodides. In addition, the silylation of aryl bromides and fluoroalkanesulfonates proceeded in the presence of tetra-n-butylammonium iodide. 相似文献
108.
The information of template DNA strands was converted into the specific sequences in a programmable way by following the mediation of cross-linked DNAs. 相似文献
109.
Masayuki Muroi Konomi Haibara Mitsuko Asai Kazuhide Kamiya Toyokazu Kishi 《Tetrahedron》1981,37(6):1123-1130
Macbecin I 1, C30H42N2O8, and macbecin II 2, C30H44N2O8, were shown to be 2,6-disubstituted benzoquinone and hydroquinone derivatives by an oxidation-reduction relationship, UV. 1H and 13C NMR spectra. Alkaline methanolysis of 1 gave a 2-aminobenzoquinone derivative 5, suggesting an ansa-structure for 1, and acid hydrolysis of 1 gave decarbamoyl products 9,10 and 11, indicative of the location of carbamoyloxy group in allylic position. Spin decoupling studies on 1,3 and 5clarified the partial structures [A], [B], [C] and [D]. From their mutual disposition two structures 1a and 1b, were proposed out of which 1a has been selected for the structure of 1 on the basis of the structure of oxidative degradation product 12. X-Ray analysis of the bromoacetyl derivative of 1 confirmed the above proposed structure and determined the absolute stereochemistry of 1 and 2. 相似文献
110.
The performance of a 160 keV slant hole collimator (160 keV SH) was compared with that of a 140 keV high resolution collimator (140 keV HR) for SPECT imaging of the head using 99mTc. The minimum radius of revolution was reduced from about 23 cm to 13 cm using 160 keV SH. Relative sensitivity of the 160 keV SH was 108% of that of the 140 keV HR. Compared with SPECT using 140 keV HR, 160 keV SH SPECT yielded approximately a 15% increase in resolution. The 160 keV SH SPECT images of phantom were superior in resolution and contrast to that of 140 keV HR SPECT. We concluded that high quality SPECT images of the head can be obtained from rotating gamma cameras equipped with slant hole collimators. 相似文献