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51.
Two dimensional (2D) liquid chromatography (LC) separations of proteins can be obtained faster and more automated than traditional 2D gel electrophoresis. Previously we have described a 2D LC method for separation of native proteins with separation according to pI by pH-gradient strong anion exchange (SAX) chromatography in the first dimension, and according to hydrophobicity by reversed phase chromatography in the second dimension. Since there are few literature reports on the combination of reduced/alkylated proteins and modern LC, a basic study of the chromatographic properties of a few reduced /alkylated proteins was undertaken with a pH-gradient SAX chromatographic system. Proteins where the disulfide groups were reduced, but not alkylated, were also included. The conditions that separated native proteins according to pI could not be used for neither reduced nor reduced/alkylated proteins. High concentrations of urea (4–8 M) were needed in the mobile phase in order to obtain good peak shapes. Addition of urea had an undesired impact on both the retention of the proteins and the pH gradient profile, with the effect that little correlation between reported pI values and elution pH was found. The conclusion was that proteins should be separated in the native state if good pI–pH correlations are important, and in the alkylated state with urea if other considerations are more important. 相似文献
52.
Nedonchelle E Pitiot O Vijayalakshmi MA 《Applied biochemistry and biotechnology》2000,83(1-3):287-295
Catalytic autoimmune antibodies from the sera of lupus patients were purified using histidyl-aminohexyl-Sepharose gel and
compared with the antibodies purified with protein A and protein G affinity chromatography. The IgG preparations from the
histidine affinity column had a much higher catalytic activity in hydrolyzing the peptide substrate Pro-Phe-Arg-methyl-coumarinamide
compared to the antibodies obtained by the conventional protein A/G method. This preservation of catalytic activity is attributed
to the gentle buffer conditions used in the histidine ligand method that allowed the integrity of three-dimensional structure
of purified catalytic antibodies. Thus, histidine affinity offer a superior method for isolating autoimmune catalytic antibodies. 相似文献
53.
Wilson SR Boix F Holm A Molander P Lundanes E Greibrokk T 《Journal of separation science》2005,28(14):1751-1758
Quantification of bradykinin peptides in limited amounts of rat muscle tissue dialysate has been performed using a packed capillary LC-ESI-TOF-MS method. The micro dialysate samples (450 microL) with added internal standard were loaded onto a 1 mm x 5 mm loading column packed with 5 microm Kromasil C18 particles by a carrier solution of 0.1% formic acid in ACN/water (5:95, v/v) at a flow rate of 250 microL/min for online preconcentration of the analytes. Back-flushed elution onto a 150 mm x 0.5 mm Zorbax C18 column packed with 5 microm particles was conducted using a linear solvent ACN/H2O gradient containing 0.1% formic acid. (Tyr8)-bradykinin was used as an internal standard and was added to the dialysis sample prior to injection. Baseline separation of bradykinin, arg-bradykinin and (tyr8)-bradykinin was achieved within 10 min. Positive ESI was performed in the m/z range of 200-1300. The method was validated in the range 0.2-1.0 ng/mL dialysate, yielding correlation coefficients of 0.995 and 0.990 for bradykinin and arg-bradykinin, respectively. The within-assay and between-assay precisions were between 4.3-9.6% and 6.2-10.6%, respectively. Both arg-bradykinin and bradykinin were detected in dialysate from rat muscle tissue, at concentrations of 0.1 and 0.4 ng/mL for bradykinin and arg-bradykinin, respectively, confirming the presence of arg-bradykinin in rat muscles. 相似文献
54.
3-Methylimidazolium tribromide proves to be an alternative highly efficient reagent/solvent for the halogenation of non-activated aromatic compounds. 相似文献
55.
M. Ftima C. Guedes da Silva Elsa M. P. R. P. Branco Yu Wang Joo J. R. Fraústo da Silva Armando J. L. Pombeiro Roberta Bertani Rino A. Michelin Mirto Mozzon Franco Benetollo Gabriella Bombieri 《Journal of organometallic chemistry》1995,490(1-2)
Complexes trans-[PtX(L)(PPh3)2]A [1: X = CF3; A = BF4; L = NCNH2, NCNMe2, NCNEt2, or NCNC(NH2)2. 2: X = Cl; A = BPh4; L = NCNMe2 or NCNEt2] and cis-[PtCl(L)(PPh3)2][BPh4] [3: L = NCNH2 or NCNC(NH2)2], which appear to be the first cyanamide or cyanoguanidine complexes of platinum to be reported, have been prepared by treatment of trans-[PtBr(CF3)(PPh3)2] (in CH2Cl2/acetone and in the presence of Ag[BF4]) or of cis-[PtCl2(PPh3)2] (in THF and in the presence of Na[BPh4]), respectively, with the appropriate substrate. In KBr pellets or in solution 1 (L = NCNMe2 or NCNEt2) undergoes ready replacement of the organocyanamide (under the trans influence of CF3) by bromide to regenerate trans-(PtBr(CF3)(PPh3)2]. The X-ray structure of 1 (X = CF3, A = BF4, L = NCNEt2) is also reported, and shows the presence of two apical intramolecular contacts of the metal with two ortho-hydrogen atoms of the phosphines, whereas the amine N atom of the diethylcyanamide is trigonal planar in the linear NCN framework with a delocalized π system. 相似文献
56.
Bioassay-guided fractionation allowed the isolation of two new cytotoxic ent-kaurene diterpenoids, licamichauxiioic-A and -B acids (1 and 2) from the root extract of Licania michauxii Prance (Chrysobalanaceae). They were characterized as ent-15-oxo-9(11),16-kauradien-19-oic acid (1) and ent-15-oxo-13(14),16-kauradien-19-oic acid (2) by various spectroscopic methods, in particular, 1D and 2D NMR spectra, and chemical evidence. 相似文献
57.
Werkema EL Messines E Perrin L Maron L Eisenstein O Andersen RA 《Journal of the American Chemical Society》2005,127(21):7781-7795
The monomeric metallocenecerium hydride, Cp'(2)CeH (Cp' = 1,2,4-tri-tert-butylcyclopentadienyl), reacts instantaneously with CH(3)F, but slower with CH(2)F(2), to give Cp'(2)CeF and CH(4) in each case, a net H for F exchange reaction. The hydride reacts very slowly with CHF(3), and not at all with CF(4), to give Cp'(2)CeF, H(2), and 1,2,4- and 1,3,5-tri-tert-butylbenzene. The substituted benzenes are postulated to result from trapping of a fluorocarbene fragment derived by alpha-fluoride abstraction from Cp'(2)CeCF(3). The fluoroalkyl, Cp'(2)CeCF(3), is generated by reaction of Cp'(2)CeH and Me(3)SiCF(3) or by reaction of the metallacycle, [(Cp')(Me(3)C)(2)C(5)H(2)C(Me(2))CH(2)]Ce, with CHF(3), and its existence is inferred from the products of decomposition, which are Cp'(2)CeF, the isomeric tri-tert-butylbenzenes and in the case of Me(3)SiCF(3), Me(3)SiH. The fluoroalkyls, Cp'(2)CeCH(2)F and Cp'(2)CeCHF(2), generated from the metallacycle and CH(3)F and CH(2)F(2), respectively, are also inferred by their decomposition products, which are Cp'(2)CeF, CH(2), and CHF, respectively, which are trapped. DFT(B3PW91) calculations have been carried out to examine several reaction paths that involve CH and CF bond activation. The calculations show that the CH activation by Cp(2)CeH proceeds with a low barrier. The carbene ejection and trapping by H(2) is the rate-determining step, and the barrier parallels that found for reaction of H(2) with CH(2), CHF, and CF(2). The barrier of the rate-determining step is raised as the number of fluorines increases, while that of the CH activation path is lowered as the number of fluorines increases, which parallels the acidity. 相似文献
58.
Chiral Phosphate in Rhodium‐Catalyzed Asymmetric [2+2+2] Cycloaddition: Ligand,Counterion, or Both?
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Dr. Marion Barbazanges Dr. Elsa Caytan Dr. Denis Lesage Dr. Corinne Aubert Prof. Louis Fensterbank Prof. Vincent Gandon Dr. Cyril Ollivier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8553-8558
Investigations based on NMR spectroscopy, mass spectrometry, and DFT calculations shed light on the metallic species generated in the rhodium‐catalyzed asymmetric [2+2+2] cycloaddition reaction between diynes and isocyanates with the chiral phosphate TRIP. The catalytic mixture comprising [{Rh(cod)Cl}2], 1,4‐diphenylphosphinobutane (dppb), and Ag(S)‐TRIP actually gives rise to two species, both having an effect on the stereoselectivity. One is a rhodium(I) complex in which TRIP is a weakly coordinating counterion, whereas the other is a bimetallic Rh/Ag complex in which TRIP is a strongly coordinating X‐type ligand. 相似文献
59.
Paolo Costa Iris Trosien Miguel Fernandez‐Oliva Elsa Sanchez‐Garcia Wolfram Sander 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(9):2694-2698
The fluorenyl cation is a textbook example for a 4π antiaromatic cation. However, contrasting results have been published on how the annelated benzene rings compensate the destabilizing effect of the 4π antiaromatic five‐membered ring in its core. Whereas previous attempts to synthesize this cation in superacidic media resulted in undefined polymeric material only, we herein report that it can be generated and isolated in amorphous water ice at temperatures below 30 K by photolysis of diazofluorene. Under these conditions, the fluorenylidene is protonated by water to give the fluorenyl cation, which could be characterized spectroscopically. Its absorption in the visible‐light range matches that previously obtained by ultrafast absorption spectroscopy, and furthermore, its IR spectrum could be recorded. The IR bands in amorphous ice very nicely match predictions from DFT and DFT/MM calculations, suggesting the absence of strong interactions between the cation and surrounding water molecules. 相似文献
60.
Youssef Belmabkhout Gerhard Pirngruber Elsa Jolimaitre Alain Methivier 《Adsorption》2007,13(3-4):341-349
In this work a combination of static gravimetric and inverse chromatographic techniques is used to study the adsorption and
separation of the main synthesis gas components, i.e. CO2, CO, CH4 and H2. The single component adsorption isotherms of CO2, CO, CH4 and H2 on faujasite NaX were measured from 303 K to 473 K and over a large range of pressures (from 0 to 1200 kPa). Breakthrough
curves of CO2 and CO and their mixtures were determined at 323 K and 373 K and 100 kPa as an illustrative example. A nice agreement was
noticed between the two above-mentioned techniques for single component adsorption. Binary mixture dynamics measurements were
compared to the predictions of ideal adsorption solution theory (IAST) via the previously cited single component adsorption
data. 相似文献