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排序方式: 共有329条查询结果,搜索用时 15 毫秒
31.
Mügge C Rothenburger C Beyer A Görls H Gabbiani C Casini A Michelucci E Landini I Nobili S Mini E Messori L Weigand W 《Dalton transactions (Cambridge, England : 2003)》2011,40(9):2006-2016
Twelve Pt(II) complexes with cis-PtP(2)S(2) pharmacophores (where P(2) refers to two monodentate or one bidentate phosphane ligand and S(2) is a dithiolato ligand) were prepared, characterized and evaluated as potential antiproliferative agents. The various compounds were first studied from the structural point of view; afterward, their solubility properties as well as their solution behaviour were analyzed in detail. Antiproliferative properties were specifically evaluated against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin. For comparison purposes similar studies were carried out on four parent cis-dichloro bisphosphane Pt(II)complexes. On the whole, the cis-PtP(2)S(2) compounds displayed significant antiproliferative properties while the cis-PtP(2)Cl(2) (cis-dichloro bisphosphane Pt(II)) compounds revealed quite poor biological performances. To gain further insight into the molecular mechanisms of these bisphosphane Pt(II) compounds, the reactions of selected complexes against the model protein cytochrome c were investigated by ESI-MS and their adduct formation explored. A relevant reactivity with cyt c was obtained only for cis-PtP(2)Cl(2) compounds, whereas cis-PtP(2)S(2) compounds turned out to be nearly unreactive. The obtained results are interpreted and discussed in the frame of the current knowledge of anticancer platinum compounds and their structure-activity-relationships. The observation of appreciable antiproliferative effects for the relatively inert cis-PtP(2)S(2) compounds strongly suggests that these compounds will undergo specific activation within the cellular environment. 相似文献
32.
L-Carnosine (β-alanyl-L-histidine, LCar) is the most widely and abundantly distributed copper(II)-coordinating endogenous dipeptide. Though its physiological role has not been completely understood yet, many functions have been proposed for this compound. LCar might be crucial in the potential reduction or prevention of several pathologies in which the metal ions are thought to be involved. The potential therapeutic applications of LCar are drastically limited because of hydrolysis by specific dipeptidases (carnosinases). D-Carnosine (DCar), the enantiomer of the naturally occurring dipeptide, shows the same properties as those of LCar, but it is not hydrolyzed by carnosinases. Chemical modification of LCar has been proposed as a promising strategy to reduce its enzymatic hydrolysis; conjugation of a carbohydrate moiety may also improve site-specific transport to different tissues, which would enhance the peptide bioavailability. On this basis, we have functionalized DCar with β-cyclodextrin (CDDCar) and characterized the compound via NMR. The copper(II) binding properties of the new DCar derivative were investigated by spectroscopic techniques (UV-vis, circular dichroism, electron paramagnetic resonance) and potentiometric measurements. The results surprisingly revealed a pronounced difference from the analogous LCar derivative (CDLCar), especially concerning the dimeric species. The spectroscopic data show that this stereoselectivity is driven by noncovalent interactions, namely, hydrogen bonds, CH-π interactions, and steric and hydrophobic effects of the cyclodextrin cavity. 相似文献
33.
Ida A Cohen B Asaka T Kawai A Organero JA Shibuya K Douhal A 《Physical chemistry chemical physics : PCCP》2011,13(45):20318-20325
Photoinduced isomerization of a novel photochromic cation, [2PA-Mmim](+) (2-phenylazo-1,3-dimethylimidazolium cation), was studied by optical spectroscopic methods. The UV-Vis absorption spectra of the [2PA-Mmim](+) cation show two prominent bands starting around 410 and 520 nm, corresponding to the S(0)-S(2) (π, π*) and S(0)-S(1) (n, π*) transitions, respectively. The photoisomerization mechanism is studied by femtosecond time-resolved transient absorption experiments performed after S(0)-S(2) (π, π*) excitation in several solvents with different viscosity, including ionic liquids. The transient absorption signals at two representative wavelengths were fitted by bi-exponential functions, which yield four decay components. The photoisomerization mechanism is discussed in light of the relaxation schemes available for azobenzene. Only one of the components depends on the solvent viscosity and it changes from 1.2 ps (dichloromethane, 0.4 cP) to 5.6 ps ([Bmim][BF(4)], 93 cP). This component is assigned to a molecule at the S(1) state, which is responsible for the "rotational" isomerization. The weak dependence on the solvent viscosity of this component is explained in terms of local change in the viscosity as a result of local heating due to excess energy released at S(2)-S(1) internal conversion. The other three components of ~0.4, 1.0 and 10 ps are attributed to relaxation processes of the molecule at S(2), S(1) and S(0) states, respectively. The quantum yields for the forward E-Z photoisomerization are ~0.15 after S(2) excitation. The backward Z-E isomerization is slow with a lifetime of 1 hour and an activation energy of 91 kJ mol(-1) through an "inversion" mechanism. 相似文献
34.
BM Wong D Lacina IM Nielsen J Graetz MD Allendorf 《The journal of physical chemistry. C, Nanomaterials and interfaces》2011,115(15):7778-7786
Knowledge of the relative stabilities of alane (AlH(3)) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for 38 alane complexes with NH(3-n)R(n) (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH(2-n)R(n) (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine-alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine and obtaining upper limits of ΔG° for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. On the basis of this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system. 相似文献
35.
K Kakiuchi M Ue M Takeda T Tadaki Y Kato T Nagashima Y Tobe H Koike N Ida Y Odaira 《Chemical & pharmaceutical bulletin》1987,35(2):617-631
36.
37.
Determination of reduced and total ubiquinones in biological materials by liquid chromatography with electrochemical detection 总被引:2,自引:0,他引:2
A convenient and reliable liquid chromatographic (LC) method with electrochemical detection (ED) was developed for the determination of reduced (ubiquinol) and total ubiquinones in biological materials. After extraction of samples with n-hexane, ubiquinol was separated on a reversed-phase column and assayed directly by ED. In order to determine the total amount of a ubiquinone in biological samples, the unbiquinone was converted into the corresponding reduced form by treatment with sodium borohydride. No significant interfering peak (plastoquinol-9, ubichromenol-9, etc.) was observed in the elution areas of ubiquinol-7 to -11. This LC-ED method was about 70 times more sensitive than the previous LC-UV method and was able to detect 150 pg of ubiquinol-10. The method was applied satisfactorily to the determination of the contents of ubiquinol homologues in biological materials. The content of ubiquinols is a major component of the total ubiquinones in human plasma and urine and rat plasma and liver, but a minor component in rat heart and kidney. 相似文献
38.
Klaus Konitzer Ida Körner und Siegkried Voigt 《Fresenius' Journal of Analytical Chemistry》1966,223(6):426-434
Zusammenfassung Die Reaktion von Aminosäuren mit Ninhydrin wurde bei pH 5, 4 und 2,5 auf -NH2-Spezifität überprüft.Allein die mit vereinfachter Verfahrenstechnik durchgeführte Messung des ninhydrinlabilen NH3 bei pH 2,5 erwies sich als brauchbar für eine Messung des nicht konjugierten Total--NH2.
Unter technischer Mitarbeit von D. Fabian u. K. Michalke. 相似文献
Summary The reaction of amino-acids with ninhydrin was tested for specifity on -NH2 at pH 5.0; 4.0 and 2.5.Only the measurement of ninhydrin-labile NH3 at pH 2.5 proved to be useful for the determination of non-conjugated total -NH2.The procedure of Sobel et al. was modified by extracting ninhydrin with isoamyl alcohol/isopropyl ether. The colorimetric measurement of NH3 directly in an aliquot of the desaminated sample by the phenol-hypochlorite reaction allows the determination of -NH2 in the micromole and submicromole range.In extracts of biological material the specificity is slightly diminished by a nonquantitative evolution of NH3 from CyS- (70%NH3-yield) and Try (50%), as well as co-reaction of glycine-N-terminal and -glutamyl-terminal -NH2 (50–90%) and proline (11%).
Unter technischer Mitarbeit von D. Fabian u. K. Michalke. 相似文献
39.
40.
Ida Cattaneo Gasparini 《Annali di Matematica Pura ed Applicata》1960,50(1):467-473
Sunto Esame delle connessioni infinitesimali nello spazio fibrato dei riferimenti proiettivi di una Vn. Definizione di connessione proiettiva regolare Geodetiche di una Vn secondo una connessione proiettiva con speciale riguardo alle connessioni regolari.
Ad Antonio Signorini nel suo 70mo compleanno. 相似文献