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101.
Judith Zilberstein Avraham Bromberg Anatol Frantz Varda Rosenbach-Belkin Amnon Kritzmann Reuven Pfefermann Yoram Salomon Avigdor Scherz 《Photochemistry and photobiology》1997,65(6):1012-1019
Successful application of anticancer therapy, and especially photodynamic therapy (PDT) mediated by type II (PDTII) processes, depends on the oxygen content within the tumor before, during and after treatment. The high consumption of oxygen during type II PDT imposes constraints on therapy strategies. Although rates of oxygen consumption and repletion during PDTII were suggested by theoretical studies, direct measurements have not been reported. Application of a novel oxygen sensor allowed continuous and direct in situ measurements (up to a depth of 8–9 mm from the tumor surface and for several hours) of temporal variations in the oxygen partial pressure (pO2) during PDT. Highly pigmented M2R mouse melanoma tumors implanted in CD1 nude mice were treated with bacteriochlorophyll-serine (Bchl-Ser; a new photodynamic reagent) and were subjected to fractionated illumination (700 < λ. < 900 nm) at a fluence rate of 12 mW cm-2. This illumination led to total oxygen depletion with an average consumption rate of 7.2 uAf(O2) s-1. Spontaneous reoxygenation (at an average rate of 2.5 µM(O2)/s) was observed during the following dark period. These rates are in good agreement with theoretical considerations (Foster et al., Radiat. Res. 126, 296,1991 and Henning et al, Radiat. Res. 142, 221, 1995). The observed patterns of oxygen consumption and recovery during prolonged periods of light/dark cycles were interpreted in terms of vasculature damage and sensitizer clearance. The presented data support the previously suggested advantages of fractionated illumination for type II photodynamic processes. 相似文献
102.
Neta Uritsky Prof. Michael Shokhen Prof. Amnon Albeck 《Angewandte Chemie (International ed. in English)》2016,55(5):1680-1684
General‐base catalysis in serine proteases still poses mechanistic challenges despite decades of research. Whether proton transfer from the catalytic Ser to His and nucleophilic attack on the substrate are concerted or stepwise is still under debate, even for the classical Asp‐His‐Ser catalytic triad. To address these key catalytic steps, the transformation of the Michaelis complex to tetrahedral complex in the covalent inhibition of two prototype serine proteases was studied: chymotrypsin (with the catalytic triad) inhibition by a peptidyl trifluoromethane and GlpG rhomboid (with Ser‐His dyad) inhibition by an isocoumarin derivative. The sampled MD trajectories of averaged pKa values of catalytic residues were QM calculated by the MD‐QM/SCRF(VS) method on molecular clusters simulating the active site. Differences between concerted and stepwise mechanisms are controlled by the dynamically changing pKa values of the catalytic residues as a function of their progressively reduced water exposure, caused by the incoming ligand. 相似文献
103.
104.
[reaction: see text] A series of new adamantyl-oligoethyleneglycol-fullerene hybrids was prepared via Bingel-Hirsch functionalization of the C60 fullerene with various adamantyl-oligoethyleneglycol malonates. As NMDA-targeted antioxidants, these compounds may have the potential to be developed as therapeutic agents for the treatment of neurological disorders. 相似文献
105.
The formulation of phase conjugation via nondegenerate four-wave mixing in a Doppler-broadened resonant medium is generalized to include nondegenerate pump frequencies. This process is shown capable of yielding a tunable optical band-pass filter whose central frequency can be tuned over the entire Doppler profile with only a small degradation of the filter efficiency while still maintaining a bandwidth limited by the homogeneous linewidth. 相似文献
106.
An infinite number of effectively infinite clusters are predicted at the percolation threshold, if effectively infinite means that a cluster's mass increases with a positive power of the lattice size L. All these cluster masses increase as L
D with the fractal dimension D = d – /v, while the mass of the rth largest cluster for fixed L decreases as 1/r
, with = D/d in d dimensions. These predictions are confirmed by computer simulations for the square lattice, where D = 91/48 and = 91/96. 相似文献
107.
The dissociation of protonated alkyl benzoates (para H, CN, OMe and NO(2)) into protonated benzoic acids and alkyl cations was studied in the gas phase. It was found that the product ratio depends on the substituent at the para position of the phenyl ring. The substituent effect is probably the result of the formation of an ion-neutral complex intermediate that decomposes to an ion and a neutral, according to the relative proton affinities of the two moieties. The experimental results and theoretical calculations indicate that the favored protonation site in these compounds is the ester's carbonyl and that proton transfer from the phenyl ring to the ester group is very likely to occur under chemical ionization conditions. It is most probable that the carbonyl protonated form is a common intermediate in the fragmentation process, regardless of the protonation site. 相似文献
108.
Locust swarms hit subsistence-staple-crop-growing households at random and are not privately controllable. An aerial-spraying optimal control model that supports the said households’ livelihood at least expected cost is therefore developed. The qualitative properties of the model are analysed under economically plausible but mild assumptions. The steady state comparative statics reveal that the locust swarm size and the probability of a household’s crop being destroyed by a swarm decrease with the number of households, yield per household, and the staple crop’s replacement price, and increase with the marginal cost of spraying and the planner’s discount rate. A local comparative dynamics analysis is also conducted, as it provides the necessary economic intuition behind other ostensibly anomalous steady-state comparative statics results. 相似文献
109.
110.
Chagit Denekamp Alexander Etinger Walter Amrein Amnon Stanger Mihaiela Stuparu A Dieter Schlüter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(5):1628-1637
The two compounds, 1 and 5, are investigated by means of collision-induced dissociation experiments by using ion cyclotron resonance mass spectrometry and other mass spectrometric techniques as to their ability to act as precursors for the fully unsaturated double-stranded target compound 2. These experiments are complemented by flask-type pyrolyses of 5, the products of which are analyzed by mass spectrometry. For 1, no conditions were found under which the expected molecular ion of 2 at m/z 932 appeared, however, for its derivative 5 this was possible. This interesting finding is not in contradiction with the chemical structure of the long sought for compound 2 but calculations suggest that this compound may have isomerized into one where the conjugation is interrupted by hydrogen shift from the solubilizing alkyl chains into the cycle's perimeter. The key driving force for such an isomerization would be the considerable relief of strain energy. 相似文献