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61.
Fused silica capillaries deactivated with D4 and coated with OV-1 were subjected to cobalt-60 gamma radiation in order to elucidate the effect of incident radiation on column performance. The chromatographic performance of these open tubular columns in which OV-1 was polymerized in situ was found to be dependent on the dosage of radiation and was evaluated before and after the irradiated columns were rinsed with solvent. Of the radiation dosages employed, 3 MRad produced superior chromatographic performance coupled with very favorable residual surface activity. 相似文献
62.
Summary The separation of poly(styrene-co-acrylonitrile) is presented in open tubular stainless steel columns and columns packed with
non-porous glass beads. Furthermore separation on a short silica packed column proved to be better than on a similar longer
column. A definition of the term high performance precipitation liquid chromatography is suggested for gradient elution with
sample injection into a starting eluent which is a nonsolvent for the copolymer under investigation. The choice of a suitable
solvent-nonsolvent combination is of essential importance. 相似文献
63.
K. Jones 《Chromatographia》1988,25(7):577-581
Summary The flexibility of process scale high performance liquid chromatography is demonstrated by three examples of reversed-phase
separations (a) a standard purification (b) isolation of trace compounds, and (c) recovery from crystallisation mother liquors.
It was shown that a material, thought to be acceptably pure, contained a toxic impurity, and a remaining impurity, a previously
unseen component of potential therapeutic interest. Favourable cost data were indicated for example (3).
This work was conducted in the Chemical Technology Unit, University of Manchester Institute of Science and Technology, PO
Box 88, Manchester M6O 1OD, UK. 相似文献
64.
Summary The measurement of flow constancy and pulsation amplitudes of HPLC pump based on the photoconversion of malachite green leucocyanide is described. The irradiation time and hence the degree of conversion of the leucocyanide is correlated to flow fluctuations of piston driven HPLC pumps. It is possible to measure the amplitude of pulsations and determine the constancy of the flow rate. Most of the pumps show a flow stability better than ±1% measured as relative standard deviation of the flow rate under HPLC conditions (pressure drop 100 bar at 1 ml/min flow rate). The most expensive pump of those tested showed less than ±0.5% flow instability, however, this result was achieved by installation of a large-volume pulsation damper. The method described also allows flow rate measurements under FIA conditions where there is little or no pressure drop at the pump outlet. 相似文献
65.
Summary The interaction of some benzene and naphthalene derivatives with sodium dodecyl sulphate, hexadecyltrimethylmmonium bromide and polyoxyethylene [23] dodecanol micelles has been evaluated by high operformance liquid chromatography using micellar mobile phases. The micelle-solute association constants have been obtained for the compounds investigated. Good correlation between free energy of transfer for water-micelles and for octanol-water has been observed. 相似文献
66.
Summary The chromatographic behaviour of some porphyrins and their complexes with zinc has been studied by HPLC on 150×3.9 mm and
300×3.9 mm columns packed with Nova-Pak C18 and μ-Bondapak C18, respectively, and on a microcolumn (64×2 mm) packed with Nucleosil C18. The effect of the nature and the arrangement of side substituents in the porphyrin molecules on retention is considered.
It is demonstrated that HPLC can be used for the separation ofcis-andtrans-isomers (atropisomers) of the zinc complex of 5,15-di(phenyl-2-CH3O)-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrin and other porphyrins with a similar structure. The efficiency of separation
has been compared on different columns. 相似文献
67.
Masoud Zabet‐Moghaddam Aarif L. Shaikh Satomi Niwayama 《Journal of mass spectrometry : JMS》2012,47(12):1546-1553
Two cysteine‐specific modifiers we reported previously, N‐ethyl maleimide (NEM) and iodoacetanilide (IAA), have been applied to the labeling of cysteine residues of peptides for the purpose of examining the enhancement of ionization efficiencies in combination with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS). The peak intensities of the peptides as a result of modification with these modifiers were compared with the peak intensities of peptides modified with a commercially available cysteine‐specific modifier, iodoacetamide (IA). Our experiments show significant enhancement in the peak intensities of three cysteine‐containing synthetic peptides modified with IAA compared to those modified with IA. The results showed a 4.5–6‐fold increase as a result of modification with IAA compared to modification with IA. Furthermore, it was found that IAA modification also significantly enhanced the peak intensities of many peptides of a commercially available proteins, bovine serum albumin (BSA), compared to those modified with IA. This significant enhancement helped identify a greater number of peptides of these proteins, leading to a higher sequence coverage with greater confidence scores in identification of proteins with the use of IAA. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
68.
Summary A multiresidue method has been developed for identification and quantitation of the herbicides most commonly used in cultivation
of maize and grain, and of their transformation products, in soil samples. The analytes were isolated by soil column extraction
(SCE) and the extracts were purified by use of a Carbograph-1 cartridge. Analysis was performed by liquid chromatography coupled
with tandem mass spectrometric detection (LC-TISP-MS-MS) in negative-ion mode. To optimize the extraction conditions affecting
the performance of SCE, e.g. the extracting solvent used, temperature, extracting volume, and solvent flow rate, were studied.
To evaluate the matrix effect in SCE, recovery experiments were performed on soil samples, with different physical and chemical
characteristics, fortified with the 100 ng g−1 of the target compounds. Recovery data were satisfactory and the method detection limits were between 3 and 100 ng g−1, depending on the compound. 相似文献
69.
Summary The combination affinity chromatography-mass spectrometry can be drastically improved by introducing a reversed phase column
prior to the mass spectrometric detection. The interactions of the macrocyclic antibiotic vancomycin with oligopeptides were
used to illustrate the performance of the technique. A library of 36 peptides was successfully screened and the active compounds
identified by electrospray MS(n). The strong affinity of compounds ending with (D)-alanine and with (D)-alanine or an aromatic (D)-amino acid in the penultimate
position with vancomycin was confirmed. 相似文献
70.
Summary A chromatographic method has been developed for enrichment of methionine-bound sulfur in casein, for stable-isotope analysis.
Casein is precipitated from milk samples and cleaved by acid hydrolysis in 6m hydrochloric acid at 95 °C. The amino acids released are converted into theirN-acetyl derivatives by addition of acetic acid anhydride. After lyophilization,N-acetylmethionine is separated from the accompanying components on octadecylsilica by use of a gradient prepared from 0.02m formic acid and methanol. The fractions containingN-acetylmethionine are pooled and freeze dried. Procedures for hydrolysis and derivatization were optimized to furnish the
highest yields. The influence of the abundance ratio on the chromatographic separation is shown and discussed. From 1.0 g
casein 16.5 mgN-acetylmethionine were isolated. 相似文献