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51.
Dynamics following electron photodetachment in a complex of a chloride anion with ammonia is explored by a combination of electronic structure and quantum dynamical methods. This system serves as a prototype for investigating a hitherto unexplored class of chemical reactions-nonadiabatic proton transfer triggered by a detachment of an electron. All the reactive and nonreactive channels of this process are characterized and the respective quantum yields are presented.  相似文献   
52.
We measured the long term spontaneous electrical activity of neuronal networks with different sizes, grown on lithographically prepared substrates and recorded with multi-electrode-array technology. The time sequences of synchronized bursting events were used to characterize network dynamics. All networks exhibit scale-invariant Lévy distributions and long-range correlations. These observations suggest that different-size networks self-organize to adjust their activities over many time scales. As predictions of current models differ from our observations, this calls for revised models.  相似文献   
53.
In this article, a rapid, simple method of electrochemically predicting a given phenolic substrate’s ability to be detected via amperometric laccase biosensors is proposed. Ten selected substrates were analysed by cyclic voltammetry and the relevant electrochemical parameters compared to biosensor kinetic parameters produced through amperometric detection of these substrates. The two major findings of this study were that biosensor detection sensitivities were found to correlate to: (1) peak oxidation potential of a substrate at unmodified electrodes and (2) the apparent Michaelis? Menten constant, Km, of the biosensor‐substrate system, once corrections accounting for the relative differences in electroreducible product yield are made.  相似文献   
54.
55.
SnS and SnS2 are layered semiconductors, with potential promising properties for electro- and photocatalytic hydrogen (H2) production. The vast knowledge in preparation and modification of layered structures was still not employed successfully in this system to fully maximize its potential. Here, the first report of structural transformation of SnS2 into SnS with Mo-doping as a bifunctional catalyst for the hydrogen evolution reaction (HER) is reported. The structural phase transition optimized the properties of the material, providing a more delicate morphology with additional catalytic sites. The electrochemical studies showed overpotential of 377 mV at 10 mA cm−2 for HER with Tafel slopes of 100 mV dec−1 in 0.5 m H2SO4 for 10 % Mo-SnS. The same structure acts as an efficient photocatalyst in the generation of H2 from water under visible illumination with rate of 0.136 mmol g−1 h−1 of H2, which is 20 times higher than pristine SnS2 under visible light.  相似文献   
56.
We show that there is no algorithm which, provided a polynomial number of random points uniformly distributed over a convex body in ℝ n , can approximate the volume of the body up to a constant factor with high probability.  相似文献   
57.
Abstract

Large amounts of aromatic compounds are produced by various industries and two thirds of these are heterocyclic chemicals. Compared with the extensive information available on microbial degradation of homocyclic aromatic compounds, relatively little is known on the transformation and biodegradation of heterocyclic chemicals in soil. Recent concerns about the persistence of hazardous pollutants have led to a renewed interest in the biodegradation of heterocyclic compounds. Hence, we investigated the microbial degradation of pyridine and some of its alkylated derivatives under aerobic and anaerobic conditions in groundwater, subsurface sediment, and soil. Results of the investigation revealed that these compounds were degraded predominantly under aerobic conditions and, to a lesser extent, under anaerobic conditions, with nitrate or sulfate serving as electron acceptors. In groundwater polluted with various pyridine derivatives, biodegradation was limited by the absence of oxygen. Therefore, we conclude that, under appropriate conditions, bioremediation is a potentially feasible method for the clean-up of environments contaminated with heterocyclic chemicals and, in particular, pyridine derivatives.  相似文献   
58.
A new analytical method is presented for the compound-specific carbon and nitrogen isotope ratio analysis of a thermo-labile nitramine explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS). Two main approaches were used to minimise thermal decomposition of the compound during gas chromatographic separation: programmed temperature vaporisation (PTV) as an injection technique and a high-temperature ramp rate during the GC run. δ15N and δ13C values of RDX measured by GC-IRMS and elemental analyser (EA)-IRMS were in good agreement within a standard deviation of 0.3‰ and 0.4‰ for nitrogen and carbon, respectively. Application of the method for the isotope analysis of RDX during alkaline hydrolysis at 50°C revealed isotope fractionation factors ε carbon?=??7.8‰ and ε nitrogen?=??5.3‰.  相似文献   
59.
In this Letter we suggest a method to observe remote interactions of spatially separated dipolar quantum fluids, and in particular, of dipolar excitons in GaAs bilayer based devices. The method utilizes the static electric dipole moment of trapped dipolar fluids to induce a local potential change on spatially separated test dipoles. We show that such an interaction can be used for model-independent, objective fluid density measurements, an outstanding problem in this field of research, as well as for interfluid exciton flow control and trapping. For a demonstration of the effects on realistic devices, we use a full two-dimensional hydrodynamical model.  相似文献   
60.

Background  

Rats treated chronically with the D2–3 dopamine agonist quinpirole were previously proposed as an animal model of obsessive-compulsive disorder (OCD) since their behavior is based on repeated, compulsive-like persistent traveling between a few places in the open field. The aim of the present study was to determine properties of the physical environment that shape such behavior. For this, quinpirole-treated rats were first exposed to an arena with an array of objects (landmarks) and after the development of compulsive-like behavior, the arena was manipulated by multiplying the number of objects, changing their spacing, relocating object array, or removing the objects.  相似文献   
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