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排序方式: 共有372条查询结果,搜索用时 671 毫秒
1.
Microencapsulation of DNA Within alginate microspheres and crosslinked chitosan membranes for in vivo application 总被引:4,自引:0,他引:4
T. Alexakis D. K. Boadi D. Quong A. Groboillot I. O’Neill D. Poncelet R. J. Neufeld 《Applied biochemistry and biotechnology》1995,50(1):93-106
Calf thymus DNA was microencapsulated within crosslinked chitosan membranes, or immobilized within chitosan-coated alginate
microspheres. Microcapsules were prepared by interfacial polymerization of chitosan, and alginate microspheres formed by emulsification/
internal gelation. Diameters ranged from 20 to 500 Μm, depending on the formulation conditions. Encapsulated DNA was quantifiedin situ by direct spectrophotometry (260 nm) and ethidium bromide fluorimetry, and compared to DNA measurements on the fractions
following disruption and dissolution of the microspheres. Approximately 84% of the DNA was released upon core dissolution
and membrane disruption, with 12% membrane bound. The yield of encapsulation was 96%. Leakage of DNA from intact microspheres/capsules
was not observed. DNA microcapsules and microspheres were recovered intact from rat feces following gavage and gastrointestinal
transit. Higher recoveries (60%) and reduced shrinkage during transit were obtained with the alginate microspheres. DNA was
recovered and purified from the microcapsules and microspheres by chromatography and differential precipitation with ethanol.
This is the first report of microcapsules or microspheres containing biologically active material (DNA) being passed through
the gastrointestinal tract, with the potential for substantial recovery. 相似文献
2.
The determination of the enantiomeric purity of 2 or 3-substituted cyclanones, particularly cyclohexanones, is conveniently achieved by derivatisation into cyclic aminals with commercially available (R, R)-1,2-diphenylethylenediamine. The derivatisation procedure is directly done into the NMR tube, instantaneously, and 13C NMR allows an accurate measure of the ee. 相似文献
3.
4.
The influence of the nature of acylating reagents, solvents and ligands on the preparation of ketones by acylation of organomanganous reagents is studied. Thus acid chlorides in ether, symmetrical acid anhydrides in ether or THF and mixed carboxylic-carbonic anhydrides (R'COOCOOEt) in ether are compared, they lead to the corresponding ketones with good or excellent yields. Some problems of reproductibility are encountered and discussed when mixed anhydrides R'COOCOOEt are used in THF. The addition of a great variety of cosolvents (e.g. C6H6, AcOEt, CO3Et2, CH2CN, CH2CL2, . .) to the reaction mixture before addition of the acylating reagent does not affect the yield of ketones. In comparison the complexation of organomanganous reagents by several ligands (e.g. Me2S or Ph3P) has no subsequent effect on their acylation. The main limitation for the choice of solvents or ligands is the use of amino derivatives which generally lead to a very low yield of ketones (e.g. C5H5N, TMEDA, Et3N) or unreproducible yields (e.g. HMPA). Two applications of these studies are described:The stabilization of s or t-alkyl manganous derivatives by complexation which leads to the best yield of the corresponding ketonesThe use of a cosolvent in order to increase the yield when mixed anhydrides R'COOCOOEt are used in THF. 相似文献
5.
Various oxazolidines were prepared from ephedrine. It was shown that their formation is not general, the reaction is not always stereoselective and can lead to isomerization of the double bond of α,β-unsaturated aldehydes. Some of these oxazolidines were used in stereoselective preparation of β-alkyl aldehydes. 相似文献
6.
Koulouri S Malamidou-Xenikaki E Spyroudis S Tsanakopoulou M 《The Journal of organic chemistry》2005,70(22):8780-8784
[reaction: see text] Thermal decomposition of phenyliodonium ylide of 2-hydroxy-1,4-naphthoquinone (lawsone) in the presence of indole derivatives affords 3-acylated indoles existing in their enol forms, through a ring contraction and alpha,alpha'-dioxoketene formation reaction. The same reactants afford 3-(3-indolyl)-2-hydroxy-1,4-naphthoquinones in a copper-catalyzed reaction. Enamines, among other C-nucleophiles tested, give analogous results. 相似文献
7.
Magafa Vassiliki Perlepes Spyros P. Stavropoulos George 《Transition Metal Chemistry》1997,23(1):105-107
It is becoming increasingly apparent that the coordination chemistry of oligopeptides with Cys-X-Y-Cys and His-X-Y-Cys sequences
(X, Y = variable amino acid residues) is an important theme in transition metal and bioinorganic chemistry(1,2). The Cys-X-Y-Cys
sequence is often encountered in the metal binding site of several metalloproteins, such as iron–sulfur proteins, e.g. rubredoxins(3)
and ferrodoxins(4), high potential iron–sulfur proteins(5), metallothioneins(6), zinc proteins(7) etc. The amino acid sequence
His-X-Y-Cys is also of bioinorganic importance since it has been found in the active site of copper(8), iron–sulfur(9) and
zinc(10) proteins. We are currently seeking to develop the area of transition metal/Cys-X-Y-Cys and His-X-Y-Cys peptide interactions(11,12);
our goals are: (i) to elucidate the role of these sequences in the biological activity and mechanism of action of the above
metallobiomolecules, and (ii) to find possible new and more effective agents for the elimination of heavy metals from the
human organism or from contaminated waste waters. Here we report the preparation and preliminary characterization of copper(II)
complexes of tetrapeptide ligands containing the Cys-X-Y-Cys and His-X-Y-Cys sequences.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Boudalis AK Lalioti N Spyroulias GA Raptopoulou CP Terzis A Bousseksou A Tangoulis V Tuchagues JP Perlepes SP 《Inorganic chemistry》2002,41(24):6474-6487
The preparations, X-ray structures, and detailed physical characterizations are presented for three new tetranuclear Fe(III)/RCO(2)(-)/phen complexes, where phen = 1,10-phenanthroline: [Fe(4)(OHO)(OH)(2)(O(2)CMe)(4)(phen)(4)](ClO(4))(3).4.4MeCN.H(2)O (1.4.4MeCN.H(2)O); [Fe(4)O(2)(O(2)CPh)(7)(phen)(2)](ClO(4)).2MeCN (2.2MeCN); [Fe(4)O(2)(O(2)CPh)(8)(phen)(2)].2H(2)O (3.2H(2)O). Complex 1.4.4MeCN.H(2)O crystallizes in space group P2(1)/n, with a = 18.162(9) A, b = 39.016(19) A, c = 13.054(7) A, beta = 104.29(2) degrees, Z = 4, and V = 8963.7 A(3). Complex 2.2MeCN crystallizes in space group P2(1)/n, with a = 18.532(2) A, b = 35.908(3) A, c = 11.591(1) A, beta = 96.42(1) degrees, Z = 4, and V = 7665(1) A(3). Complex 3.2H(2)O crystallizes in space group I2/a, with a = 18.79(1) A, b = 22.80(1) A, c = 20.74(1) A, beta = 113.21(2) degrees, Z = 4, and V = 8166(1) A(3). The cation of 1 contains the novel [Fe(4)(mu(4)-OHO)(mu-OH)(2)](7+) core. The core structure of 2 and 3 consists of a tetranuclear bis(mu(3)-O) cluster disposed in a "butterfly" arrangement. Magnetic susceptibility data were collected on 1-3 in the 2-300 K range. For the rectangular complex 1, fitting the data to the appropriate theoretical chi(M) vs T expression gave J(1) = -75.4 cm(-1), J(2) = -21.4 cm(-1), and g = 2.0(1), where J(1) and J(2) refer to the Fe(III)O(O(2)CMe)(2)Fe(III) and Fe(III)(OH)Fe(III) pairwise exchange interactions, respectively. The S = 0 ground state of 1 was confirmed by 2 K magnetization data. The data for 2 and 3 reveal a diamagnetic ground state with antiferromagnetic exchange interactions among the four high-spin Fe(III) ions. The exchange coupling constant J(bb) ("body-body" interaction) is indeterminate due to prevailing spin frustration, but the "wing-body" antiferromagnetic interaction (J(wb)) was evaluated to be -77.6 and -65.7 cm(-1) for 2 and 3, respectively, using the appropriate spin Hamiltonian approach. M?ssbauer spectra of 1-3 are consistent with high-spin Fe(III) ions. The data indicated asymmetry of the Fe(4) core of 1 at 80 K, which is not detected at room temperature due to thermal motion of the core. The spectra of 2 and 3 analyze as two quadrupole-split doublets which were assigned to the body and wing-tip pairs of metal ions. (1)H NMR spectra are reported for 1-3 with assignment of the main resonances. 相似文献
9.
Andreas G. Galinos Spyros P. Perlepes Theodore F. Zafiropoulos Panayiotis V. Ioannou John K. Kouinis 《Monatshefte für Chemie / Chemical Monthly》1981,112(10):1113-1121
The preparation and some properties of the cobalt(II) complexes Co(LH2)Cl2·2H2O, Co(LH2(NCS)2 and CoL·H2O (whereLH2=N,N-(dipicolyl)-1,8-naphthylenediamine) are reported. On the basis of magnetic moments, visible reflectance and IR data, the structure is proposed to be pseudo-octahedral for Co(LH2)Cl2·2 H2O, pseudo-tetrahedral for Co(LH2)(NCS)2 and square planar for CoL·H2O.
Deprotonierte und Nicht-deprotonierte Co(II)-Komplexe des vierzähnigen Bisamid-Liganden N,N-(Dipicolyl)-1,8-naphthyldiamin. Drei verschiedene Koordinationstypen
Zusammenfassung Es werden die Darstellung und einige Eigenschaften der Kobalt(II)-Komplexe Co(LH2)Cl2·2 H2O, Co(LH2)(NCS)2 und CoL·H2O [LH2=N,N-(dipicolyl)-1,8-naphthylendiamin] diskutiert. Auf der Grundlage von magnetischen Momenten, von Daten der sichtbaren Reflektions-und IR-Spektren wird eine pseudooctaedrische Struktur für Co(LH2)Cl2·2H2O, eine pseudotetraedrische für Co(LH2)(NCS)2 und eine planar-quadratische für CoL·H2O vorgeschlagen.相似文献
10.
Dimitrios V. Stergiou Spyros C. Karkabounas Panayotis G. Veltsistas Nicholaos P. Evmiridis Athanasios G. Vlessidis 《Mikrochimica acta》2007,158(1-2):59-64
A kinetic-potentiometric method is described for the quantitative assay of formaldehyde (HCHO) in pharmaceutical and industrial
preparations. It is based on the reaction of HCHO with (ethylenediamine)-Cu(II)-sulfate [Cu(CH2NH2)2(H2O)2] · SO4. The changes in potential, resulting from the release of the Cu(II) cations, are monitored with a Cu(II)-ion selective electrode.
The calibration curve for the HCHO is linear in the concentration range 50–250 mg L−1, with a limit of detection of 8.5 mg L−1. The method shows very good reproducibility with an RSD of 2.6% for successive injections (n = 5) of 150 mg L−1 HCHO primary solution, while it is interference free. The method was successfully tested in various industrial and pharmaceutical
preparations. 相似文献