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71.
Since the discovery of the hydrated electron in bulk water in 1962, the species has been the subject of intense research and speculation. For many decades even the basic features of the simplest of all chemical and biological transients and reactants--such as its structure, binding motifs, lifetimes, and binding energies--remained elusive. Recently, another milestone in the research of the hydrated electron was the determination of its vertical binding energy (VBE). Also a long-lived hydrated electron near the surface of liquid water has been discovered. The present Minireview discusses the implications and consequences of this and other new findings in addition to the emerging complex picture of a solvated electron in water. 相似文献
72.
Renner L Pompe T Salchert K Werner C 《Langmuir : the ACS journal of surfaces and colloids》2004,20(7):2928-2933
Desorption and exchange of preadsorbed fibronectin layers in pure buffer solution and solutions of human serum albumin or fibronectin, respectively, were studied in dependence on the physicochemical characteristics of maleic acid copolymer films used as substrates. Although the preadsorbed amount of fibronectin differed only slightly, the protein was found to exhibit a significantly enhanced anchorage at the more hydrophobic polymer surface as compared to the more hydrophilic and more negatively charged polymer surface. The preadsorbed fibronectin layer was most efficiently exchanged by fibronectin (i.e., in the homodisplacement process) while pure buffer solution and human serum albumin solutions induced desorption or exchange of fibronectin to lower and similar degrees. An increase of the total adsorbed amount of protein due to additional adsorption of fibronectin or human serum albumin accompanied the partial exchange of the preadsorbed fibronectin in the displacement experiments. Evaluation of the kinetics of desorption and exchange of fibronectin at any of the substrates revealed two kinds of surface-attached protein populations--a fast desorbing species and a species with a slow desorption and exchange rate. By a multivariate regression analysis the surface characteristics of the polymer substrate were confirmed to determine the degree of protein desorption and exchange while the dynamics of the layer alteration was found to solely depend on the diffusion behavior of the proteins. 相似文献
73.
74.
The objective of the study is an analysis of lung ventilation during breathing under rest conditions and for high frequency
ventilation (HFV). The measurements include investigations of the flow using an endotracheal tube. A transparent model of
the upper human lung airways down to the 6th generation was generated, and the oscillatory flow through the branching network
was studied by DPIV. The method of refractive index matching of the fluid (water/glycerin) and the model (silicone) allows
an unobstructed view into the internal flow network. The mass flow rate and the frequency were adapted to the characteristic
flow parameters, the Reynolds- and the Womersley-number. The comparison of the results for normal breathing and HFV shows
that a mass exchange occurs for higher frequencies known as Pendelluft, which could not be seen during normal breathing. This
mass exchange between the daughter tubes is a consequence of the asymmetric impedance in the successive daughter branches.
The lung topology determines the local pressure loss in the model and therefore the local mass flow direction of the Pendelluft.
At higher frequencies we observed an increase in exchange between the daughter branches. The transformation of the velocity
profiles between inspiration and expiration suggests a net mass flow which is created into the model along the centerline
and the inner walls of the bifurcations. This flow is compensated with a net mass outflow to the trachea along the outer walls
of the branches. 相似文献
75.
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78.
Schütz K Persike M Carle R Schieber A 《Analytical and bioanalytical chemistry》2006,384(7-8):1511-1517
The anthocyanin pattern of artichoke heads (Cynara scolymus L.) has been investigated by high-performance liquid chromatography–electrospray ionization mass spectrometry. For this purpose a suitable extraction and liquid chromatographic method was developed. Besides the main anthocyanins—cyanidin 3,5-diglucoside, cyanidin 3-glucoside, cyanidin 3,5-malonyldiglucoside, cyanidin 3-(3′′-malonyl)glucoside, and cyanidin 3-(6′′-malonyl)glucoside—several minor compounds were identified. Among these, two peonidin derivatives and one delphinidin derivative were characterized on the basis of their fragmentation patterns. To the best of our knowledge this is the first report on anthocyanins in artichoke heads consisting of aglycones other than those of cyanidin. Quantification of individual compounds was performed by external calibration. Cyanidin 3-(6′′-malonyl)glucoside was found to be the major anthocyanin in all the samples analyzed. Total anthocyanin content ranged from 8.4 to 1,705.4 mg kg−1 dry mass.
相似文献
79.
Katrin Petzold-Welcke Manuela Kötteritzsch Dominik Fenn Andreas Koschella Thomas Heinze 《Macromolecular Symposia》2010,294(2):133-140
The synthesis of hydroxyethyl celluloses with regioselective functionalization in position 2 and 3 starting from triphenylmethyl (trityl) cellulose is described. The effects of reaction conditions upon both the degree of substitution and the distribution of the hydroxyethyl moieties were investigated in detail. The interest was not only focused on regioselective functionalization within the anhydroglucose unit but also on the formation of oxyethylene side chains. To avoid the formation of oxyethylene side chains, 2-(2-bromoethoxy)tetrahydropyran was used as etherifying agent in comparison with 2-bromoethanol. By acidic hydrolysis, both protecting groups – trityl at 6 position and tetrahydropyran at the hydroxyethyl substituent – can be simultaneously cleaved off. The hydroxyethyl celluloses were characterized by one- and two-dimensional NMR spectroscopy in order to determine the substitution pattern. 相似文献
80.
Stephanie Hesse-Ertelt Thomas Heinze Birgit Kosan Katrin Schwikal Frank Meister 《Macromolecular Symposia》2010,294(2):75-89
The interactions of ionic liquids (IL) with solvents usually used in liquid-state nuclear magnetic resonance (NMR) spectroscopy are studied. The 1H- and 13C-NMR chemical shift values of 1-n-butyl-3-methyl (BM)- and 1-ethyl-3-methyl (EM)-substituted imidazolium (IM) -chlorides (Cl) and -acetates (Ac) are determined before and after diluting with deuterated solvents (DMSO-d6, D2O, CD3OD, and CDCl3). The dilution offers structural modifications of the IL due to the solvents capacity to ionization. For further investigation of highly viscous cellulose dopes made of imidazolium-based IL, solid-state NMR spectroscopy enables the reproducibility of liquid-state NMR data of pure IL. The correlation of liquid- and solid-state NMR is shown on EMIM-Ac and cellulose/EMIM-Ac dope (10 wt %). 相似文献