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71.
Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an 1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier. 相似文献
72.
Toshio Yamanaka Mitsuru Ohkubo Fumie Takahashi Masayuki Kato 《Tetrahedron letters》2004,45(13):2843-2845
An efficient synthesis of the orally-active GpIIb/IIIa antagonist FR184764 was achieved. The key intermediate, an optically active ethynyl β-amino ester, was synthesized efficiently by utilizing a lipase catalyzed kinetic resolution step. 相似文献
73.
Fukuji Higashi Yuko Mihara Ikuo Takahashi Wen-Hsin Chen Tech-Chou Chang 《Journal of polymer science. Part A, Polymer chemistry》1985,23(11):2851-2856
The reaction promoted by Vilsmeier adduct derived from tosyl chloride (TsCl) with N,N-dimethylformamide (DMF) was successfully applied to the preparation of copolyesteramides of high molecular weights directly from aromatic dicarboxylic acids, diamines, and bisphenols. The polycondensation was significantly affected by the reaction of activated dicarboxylic acids with bisphenols and diamines. Addition of a mixture of bisphenols and diamines likely caused gelation of the reaction mixtures, resulting in insoluble polymers, especially with high mol % diamines. Stepweise addition of them, however, gave the homogeneous reaction mixtures and copolymers of better solubility. These phenomena were studied in terms of sequence length distribution of polyester units, which was estimated by thermal analyses of the random copolymers prepared under various conditions for the initial reaction with bisphenols. 相似文献
74.
Kasai HF Tsubuki M Matsumoto Y Shirao M Takahashi K Honda T Ueda H 《Chemical & pharmaceutical bulletin》2004,52(3):311-315
Gas chromatographic separations of the stereoisomers of menthol derivatives, important intermediates in the synthesis of physiologically active natural products, were carried out on several substituted beta-cyclodextrin (CD) columns, including per-O-methyl-beta-cyclodextrin (PME-beta-CD), heptakis(2,3-di-O-acetyl-6-tert-butyldimethylsilyl)-beta-CD (DIAC-6-TBDS-beta-CD), and heptakis(2,3-di-O-methyl-6-tert-butyldimethylsilyl)-beta-CD (DIME-6-TBDS-beta-CD) as chiral stationary phases (CSPs). With the DIME-6-TBDS-beta-CD column, a separation of the Z- and E-isomers of methylidenementhol was accomplished; no separation was achieved with the other columns. The stereoisomers of methylidenementhol and the corresponding tert-butyldimethylsilyl (TBS) ether were separated on both the beta-CD and the heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TME-beta-CD) columns by high-performance liquid chromatography (HPLC) with a mobile phase involving acetonitrile and H(2)O. For the separation of the Z- and E-isomers of methylidenementhol, the TME-beta-CD column was superior. In contrast, the beta-CD column was preferable in the case of the corresponding TBS ether. 相似文献
75.
Tadahiro Kato Motoyuki Tanaka Shin‐suke Takagi Keita Nakanishi Masahiro Hoshikawa 《Helvetica chimica acta》2004,87(1):197-214
The synthesis of kempa‐6,8‐dien‐3β‐ol ( 4a ), as a synthetic leading model of the natural product 4b , was carried out starting from intermediate 12 , the synthetic route of which has been developed previously (Scheme 1). The conversion of 12 to the model compound 4a involved the elaboration of three structure modifications by three processes, Tasks A, B, and C (see Scheme 2). Task A was achieved by epoxy‐ring opening of 41 with Me3SiCl (Scheme 9), and Task B being performed by oxidation at the 13‐position, followed by hydrogenation, and then epimerization (Schemes 4 and 5). The removal of the 2‐OH group from 12 (Task C) was achieved via 30b according to Scheme 6, whereby 30b was formed exclusively from 30a / 31a 1 : 1 (Scheme 7). In addition, some useful reactions from the synthetic viewpoint were developed during the course of the present experiments. 相似文献
76.
A low-capacity cation-exchange HPLC method for the determination of UV-absorbing organic cations such as amino acids, histidine dipeptides, and creatinine was developed. A commercially available reversed-phase column was dynamically coated with hexadecylsulfonate, and was successfully used for the cation-exchange separation with ethylenediammonium eluting ion at pH 2.5. The coated column was enough stable for the specific use with a completely aqueous mobile phase at low and constant pH; and the day-to-day reproducibility for retention time was 0.9-1.7% of RSD (relative standard deviation). The linear relation between concentrations and detector responses (area) by using a photodiode-array UV detection at 210 nm ranged from 0.2 to 1000 microM (sample size 50 microl) for 1-methylhistidine, 3-methylhistidine, histidine, creatinine, anserine, carnosine, and homocarnosine, and from 0.5 to 2000 microM for creatine, tyrosine, and phenylalanine, with less than 5% of RSD. The UV spectrum (190-300 nm) obtained during chromatography was very indicative for each analyte. Overall recoveries were 97-104%. The developed HPLC method in conjunction with preliminary fractionation technique could be applied to the analysis of urine of patient with metabolic disorder such as phenylketonuria. 相似文献
77.
A convenient synthetic approach is established to prepare a new class of 1-l-α-amino acid derivatives of phospholene oxides by amination of (±)-1-chloro-2-phospholene-1-oxides with several optically pure l-α-amino acid esters. All compounds obtained as a diastereomeric mixture in good to high yields. The two diastereomers were successfully separated by column chromatography and structurally identified by their spectral analyses. 相似文献
78.
A novel enantiopure 1,2-diamine (5) having two phenolic hydroxy groups was attached into chloromethylated polystyrene through benzyl ether linkage, which was used as a chiral ligand of the catalyst in asymmetric hydrogenation of acetophenone. 相似文献
79.
Enzymatic transformations into cyclic oligomers were carried out with the objective of developing chemical recycling of poly(lactic acid)s, such as poly(D,L-lactic acid) (PDLLA), poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA), which are typical biodegradable polymers. They were degraded by lipase in an organic solvent to produce the corresponding cyclic oligomer with a molecular weight of several hundreds. PDLLA (with a Mw of 84,000) was quantitatively transformed into cyclic oligomers by lipase RM (Lipozyme RM IM) in chloroform/hexane at 60 degrees C. PLLA (with a Mw of 120,000) was transformed into cyclic oligomer by lipase CA (Novozym 435) at a higher temperature of 100 degrees C in o-xylene. The oligomer structure was identified by 1H and 13C NMR spectroscopy and MALDI-TOF (matrix assisted laser desorption/ionization-time-of-flight) mass spectrometry. 相似文献
80.
Taichi Sato Takato Nakamura Toru Takahashi 《Journal of Thermal Analysis and Calorimetry》1985,30(1):97-106
The complexes (R3NHVO(OH)Cl2)2 and (R3RNVO(OH)Cl2)2 prepared by drying in vacuo the organic solutions from the extraction into benzene of aqueous vanadyl chloride solution with trioctylamine (TOA, R3N) and trioctylmethylammonium chloride (TOMAC, R3RNCl), were studied by thermogravimetry and differential thermal analysis under an atmosphere of nitrogen, and the products of their thermal decomposition, such as volatile matter and residues, by gas chromatography. X-ray diffraction and infrared spectroscopy. It was found that the complexes with TOA and TOMAC thermally decompose to V2O3 at 200–300° by cracking of the compounds R3NHVO(OH)Cl2 and R3RNVO(OH)Cl2 formed via dissociation of the complexes at about 150°.
We wish to thank the Koei Chemical Co. Ltd. for samples of TOA and TOMAC. 相似文献
Zusammenfassung Die Komplexe (R3NHVO(OH)Cl2)2 und (R3RNVO(OH)Cl2)2 wurden hergestellt, indem benzolische und wässrige Vanadylchlorid-Lösungen mit Trioctylamin (TOA, R3N) und Trioctylmethylammoniumchlorid (TOMAC, R3RNCl) extrahiert und die erhaltenen Lösungen im Vakuum eingedampft wurden. Die Komplexen wurden in Stickstoffatmosphäre mittels TG und DTA untersucht und die thermischen Zersetzungsprodukte, und zwar sowohl die flüchtigen Verbindungen als auch die Rückstände, gaschromatographisch bzw. röntgendiffraktometrisch und IR-spektroskopisch bestimmt. Es wurde festgestellt, daß die Komplexe mit TOA und TOMAC bei 150° in die Verbindungen R3NHVO(OH)Cl2 und R3RNVO(OH)Cl2 dissoziieren, die bei 200–300° thermisch zu V2O3 zersetzt werden.
(R3NHVO(OH)Cl2)2 (R3RNVO(OH)Cl2)2 (R3,) ( , R3RNCl). , , . , 200–300° V23 R3NV()l2 R3RNVO(OH)Cl2, 150°.
We wish to thank the Koei Chemical Co. Ltd. for samples of TOA and TOMAC. 相似文献