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81.
The novel ring system, 6H-1,2,4-triazino[4,3—b]1,2,4-triazolo[3,4—f]-pyridazine was prepared either by ring closure of1-(1-ethoxycarbonylethylene)-2-(1,2,4-triazolo[4,3—b]pyridazinyl-6)-hydrazine derivatives (4, 5, 7) in polyphosphoric acid or of a hydrazine15 derived from pyridazino-1,2,4-triazine under the action of triethyl orthoformate. Compound8 showed a positive inotropic effect.
Über Pyridazinring enthaltende Verbindungen, 20. 6H-1,2,4-Triazino[4,3—b]1,2,4-triazolo[3,4—f]pyridazin, ein neues angulares Ringsystem
Zusammenfassung Das neue Ringsystem 6H-1,2,4-Triazino[4,3—b]1,2,4-triazolo[3,4—f]-pyridazin wurde entweder durch Ringschluß der1-(1-Ethoxycarbonylethylen)-2-(1,2,4-triazolo[4,3—b]pyridazinyl-6)-hydrazin-Derivate(4, 5, 7) 4, 5, 7 in Polyphosphorsäure, oder aus einem von Pyridazino-1,2,4-triazin abgeleiteten Hydrazin15 durch Ringschluß mit Orthoameisensäuretriethylester hergestellt. Verbindung8 zeigte einen positiven inotropen Effekt.
  相似文献   
82.
The rate constants of thermal (irreversible) damage of bacteriochlorin pigments (bacteriochlorophyll monomer [B], bacteriochlorophyll dimer [P] and bacteriopheophytine [H]) in reaction center [RC] protein from the photosynthetic bacterium Rhodobacter sphaeroides were studied in the dark and during intense (400 mW x cm(-2)) laser light excitation (wavelengths 488 and 515 nm) under deoxygenated conditions. While the kinetics of degradation of P and B were monoexponential, the decay kinetics of H were overlapped by an initial lag phase at elevated (>40 degrees C) temperature. This is explained by removal of the central metal ion from the bacteriochlorophylls as part of their degradation processes. At all temperatures, the rates of damage were very similar for all bacteriochlorin pigments and were larger in the light than in the dark. The logarithm of the rate constant of pigment degradation and loss of photochemistry as a function of reciprocal (absolute) temperature (Arrhenius/Eyring plot) showed single phase in the light and double phases in the dark. Below 20 degrees C, the rate of pigment degradation in the RC decreased so dramatically in the dark that it became limited by the natural degradation process of bacteriochlorophyll measured in solution. The function of loss of photochemistry in the dark was also biphasic and had a break point at 40 degrees C. The damage in the dark required high enthalpy change (DeltaH(++) = 64 kcal/mol for P and DeltaH(++) = 60 kcal/mol for B) and entropy increase (T x DeltaS(++) = 38 kcal/mol for P and T x DeltaS(++) = 34 kcal/mol for B at T = 300 K), whereas significantly smaller enthalpy change (DeltaH(++) = 21 kcal/mol for P and B and DeltaH(++) = 13 kcal/mol for H) and practically no (T x DeltaS(++) = -1 kcal/mol for P and B at T = 300 K) or small (T x DeltaS(++) = -9 kcal/mol for H at T = 300 K) entropy change was needed in the light. The thermodynamic parameters of activation reveal major steps common in the degradation of all bacteriochlorin pigments: ring opening reactions at C5 or C20 meso-bridges (or both) and breaking/removal of the phytyl chain. Their contribution in the degradation is probably reflected in the observed enthalpy/entropy compensation at an almost constant (DeltaG(++) = 22-26 kcal/mol at T = 300 K) free energy change of activation.  相似文献   
83.
Decomposition of carbon tetrachloride was studied in an inductively coupled thermal plasma reactor and in a low temperature, non-equilibrium plasma reactor, in neutral and oxidative conditions, respectively. In neutral conditions formation of solid soot, aliphatic- and cyclodienes was observed in equilibrium, and products, such as Cl2 and C2Cl6 were detected in non-equilibrium plasma. Feeding of oxygen into the thermal plasma reactor depressed both soot and dienes formation and induced the formation of oxygen containing intermediates and products. GC-MS analyses of the gaseous products and the extract of the soot referred to as complex decomposition and recombination mechanism at given conditions. Presence of oxygen in the low temperature plasma reactor results in the formation of carbonyl compounds as intermediers. CO2 and Cl2 revealed as final products of CCl4 decomposition in cold plasma.  相似文献   
84.
Fast atom bombardment and collision-induced dissociation tandem mass spectrometry were used to study the fragmentation of quaternary pyridinium salt-type amides of tryptophan (α-amino-3-indolepropionic acid) esters and their analogs which incorporate the α-nitrogen into the quaternary pyridinium structure. By cleavage directly at the pyridine nitrogen, the 1-alkyl-substituted nicotinamides decompose exclusively to a carbocation, which then becomes the intermediate to further fragments. Rearrangement of the 3-indolepropionate-2-yl carbocations may involve a five- to seven-membered ring expansion, which generates alternative fragmentation pathways; the formation of an even-electron and a radical cation, respectively. In trigonellyl amide-type tryptophan derivatives, fragmentation of the pyridinium ion proceeds on multiple pathways induced by the positive charge which may not be localized on the quaternary nitrogen, and isomerization to a dihydropyridinyl structure is probably involved. Besides the formation of protonated nicotinamide and alkene from tryptophan amides that contain methylene or ethylene units between the amino and the quaternary pyridinium nitrogens, a fragmentation route leading to the carbocation identical with that of the 1-alkyl-substituted nicotinamides has also been revealed.  相似文献   
85.
Summary The chromatographic characteristics of the thiazolidine carboxylic acids formed by the reaction of D- and L-penicillamine with various substituted benzaldehydes and heterocyclic aldehydes have been studied on Chiralplate layers. It has been found that the nature and position of substituents strongly affect the RF values and resolution factors (RS) of the isomers. An unambiguous relationship has been established between the RS values of the L- and D-enantiomers and the dipole moment of the aldehydes. The transformation to thiazolidine carboxylic acids with benzaldehyde and substituted benzaldehydes, however, is not complete, thus the reaction with formaldehyde is still more suitable for quantitative determination of penicillamine isomers.  相似文献   
86.
Two ferric-ion-based total antioxidant capacity methods: 1,10-phenanthroline (Phen) and ferric reducing antioxidant power (FRAP) were used for determination of antioxidant capacities (AC) of the acetonic and methanolic extracts of vegetable oils. The obtained mean Phen and FRAP values for acetonic extracts of olive oils, rapeseed, rice and four sunflower oils (39.3–336.5 and 39.5–339.6 μmol Fe/100 g) were higher than for methanolic extracts (22.8–307.3 and 23.5–300.1 μmol Fe/100 g). However, antioxidant capacities of methanolic extracts of corn oil, blended oils and two sunflower oils with garden green flowers (56.5–312.9 and 53.9–306.5 μmol Fe/100 g for Phen and FRAP methods, respectively) were higher than for acetonic extracts of these oils (54.2–249.2 and 52.9–244.7 μmol Fe/100 g for Phen and FRAP methods, respectively). There is a linear and significant correlation between these two analytical methods (r = 0.9989 and 0.9986 for acetonic and methanolic extracts). Also, total phenolic compounds (TPC) in the studied oils correlated with their antioxidant capacities determined by Phen and FRAP methods (r = 0.9012, 0.7818 and 0.8947, 0.7830 for acetonic and methanolic extracts, respectively). The comparable precision (R.S.D. = 0.8–4.6%, 0.9–4.9% and 0.7–4.0%, 0.6–4.0% for acetonic and methanolic extracts, respectively) and sensitivity ( = 1.27 × 104, 1.11 × 104 and 2.62 × 104 dm3 mol−1 cm−1) for the proposed Phen and the modified FRAP methods, demonstrate the benefit of the Phen method in the routine analysis of antioxidant capacities of vegetable oils.  相似文献   
87.
Small-angle X-ray scattering (SAXS) measurements using contrast variation are reported for activated carbons prepared from poly(ethyleneterephthalate). The carbon surfaces are functionalized to different degrees by cold and hot nitric acid treatment. The latter treatment reduces the surface area by 75%, but the pore size distribution in the micropore range is hardly affected. Seven liquids, n-hexane, i-octane, i-propanol, cyclohexane, toluene, alpha-pinene, and nitrobenzene, in addition to water vapor, were used as contrast modifiers. Although the values of the specific surface area S(X) deduced from these measurements are relatively insensitive to the solvent, the detailed SAXS spectra reveal interactions occurring on different spatial scales that depend on the surface chemistry of the carbon and on the physicochemical properties of the solvent. In the most heavily oxidized sample, the amphiphilic molecule i-propanol stabilizes the surface structure, whereas nonpolar molecules make the rough surface smoother. In the untreated and the lightly functionalized carbons, water vapor at 50% relative humidity condenses only partially in the micropores at room temperature, whereas in the heavily treated sample condensation in the micropores is practically complete.  相似文献   
88.
Since the introduction of RDCs in high-resolution NMR studies of macromolecules, there is a growing interest in the development of accurate, and sensitive methods for determining coupling constants. Most methods for extracting these couplings are based on the measurement of the splitting between multiplet components in J-coupled spectra. However, these methods are often unreliable since undesired multiple-bond couplings can considerably broaden the multiplet components and consequently make accurate determination of their position difficult. To demonstrate one approach to this problem, G-BIRD((r)) decoupled TROSY sequences are proposed for the measurement of (1)J(NH) and (1)J(NC') coupling constants. Resolved or unresolved splittings due to remote protons are removed by a G-BIRD((r)) module employed during t(1) and as a result, spectra with narrow, well-resolved peaks are obtained from which heteronuclear one-bond couplings can be accurately measured. Moreover, introduction of a spin-state-selective alpha/beta-filter in the TROSY sequence allows the separation of the (1)J(NC') doublet components into two subspectra which contain the same number of peaks as the regular TROSY spectrum. The (1)J(NC') couplings are obtained from the displacement between the corresponding peaks in the subspectra.  相似文献   
89.
The 2(1H)-pyrazinones have been demonstrated to be versatile building blocks for the synthesis of biologically active compounds. Here, an efficient method is described for the decoration of these interesting scaffolds. Microwave-assisted palladium catalyzed reactions allow the easy introduction of different substituents at the C3- and even at the rather unreactive C5-position of the pyrazinones. Stille, Suzuki, Heck, Sonogashira reactions, in addition to reductive dechlorinations, and cyanation reactions are investigated.  相似文献   
90.
We describe a new NMR experiment, (1)H-detected double-J-modulated (DJM)-INEPT-INADEQUATE, for tracing out the carbon skeleton of molecules. This experiment allows simultaneous correlation of directly bonded carbon atoms and those separated by multiple bonds, while at the same time also providing the values of all J(CC) coupling constants. This is achieved by replacing both fixed carbon-carbon coupling evolution intervals of the INEPT-INADEQUATE experiment by variable time intervals, which are incremented in concert with the DQ evolution period (t(1)). We show that the analysis of the fine structure of cross-peaks in DJM-INEPT-INADEQUATE spectra leads to accurate values of coupling constants and give guidelines for the proper usage of the method. The proposed experiment is two times less sensitive that the original INEPT-INADEQUATE experiment. We show that, using a 600-MHz cryoprobe and 20 mg of a monosaccharide, spectra that are suitable for the analysis of coupling constants as small as 2 Hz can be obtained within 24 h. Instead of performing multiple experiments, a single DJM-INEPT-INADEQUATE experiment can thus provide a wealth of information for the structural analysis of small molecules.  相似文献   
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