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151.
During processing of recycled ABS and ABS/HIPS blends, voiding defects can occur within the resulting material which can result in deterioration of mechanical properties. The voids were previously thought to be caused by the evolution of volatile substances during processing. This study investigated the recycling of post-consumer ABS from a variety of types of WEEE. The mechanical properties of the processed material were assessed and a combination of visual observation during processing and optical microscopy was used to identify the extent of voiding. It was found that flexural strength and ductility in particular decreased with increased levels of voids. The gases emitted during heating and processing were analysed using Gas Chromatography with Mass Spectroscopy (GCMS) and were found to be breakdown products of the original polymers. These seem to be present in the WEEE, either as polymerization residuals or as products of degradation during the initial service life rather than degradation products from reprocessing. The amounts of volatiles liberated were quantified, which showed that the volatile emissions from post-consumer material were of a similar magnitude to those seen with virgin material. More intensive or longer processing led to a reduction in the emissions and voiding and an improvement in strength, suggesting that there is a finite potential for volatile liberation, and that the problem could be overcome by the use of suitable processing conditions.  相似文献   
152.
As shown by angle-resolved photoemission (PE), hybridization of bulk Yb 4f(2+) states with a shallow-lying valence band of the same symmetry leads in YbRh2Si2 to dispersion of a 4f PE signal in the region of the Kondo resonance with a Fermi-energy crossing close to Gamma[over ]. Additionally, renormalization of the valence state results in the formation of a heavy band that disperses parallel to the 4f originating signal. The symmetry and character of the states are probed by circular dichroism and the photon-energy dependence of the PE cross sections.  相似文献   
153.
We report an approach to conducting the hydroaminomethylation of diverse α‐olefins with a wide range of alkyl, aryl, and heteroarylamines at relatively low temperatures (70–80 °C) and pressures (1.0–3.4 bar) of synthesis gas. This approach is based on simultaneously using two distinct catalysts that are mutually compatible. The hydroformylation step is catalyzed by a rhodium diphosphine complex, and the reductive amination step, which is conducted as a transfer hydrogenation with aqueous, buffered sodium formate as the reducing agent, is catalyzed by a cyclometallated iridium complex. By adjusting the ratio of CO to H2, we conducted the reaction at one atmosphere of gas with little change in yield. A diverse array of olefins and amines, including hetreroarylamines that do not react under more conventional conditions with a single catalyst, underwent hydroaminomethylation with this new system, and the pharmaceutical ibutilide was prepared in higher yield and under milder conditions than with a single catalyst.  相似文献   
154.
We present a measurement of the total cross section σt in proton-proton collisions at the CERN ISR. The method involves determination of the total interaction rate and machine luminosity. A two-arm scintillation hodoscope observes ~ 90% of the total interaction rate, while a streamer chamber is employed for event topologies missed by the main trigger. An increase of about 10% in σt is observed in the energy range √s = 23.6 to √s = 62.8 GeV/c in agreement with previous experiments.  相似文献   
155.

Announcement

Joint European Stable Isotope Users group Meeting. JESIUM 2004  相似文献   
156.
The first hydrodynamic experiments were performed on the National Ignition Facility. A supersonic jet was formed via the interaction of a laser driven shock ( approximately 40 Mbar) with 2D and 3D density perturbations. The temporal evolution of the jet's spatial scales and ejected mass were measured with point-projection x-ray radiography. Measurements of the large-scale features and mass are in good agreement with 2D and 3D numerical simulations. These experiments provide quantitative data on the evolution of 3D supersonic jets and provide insight into their 3D behavior.  相似文献   
157.
Improved interactive tutoring capabilities in educational software for chemistry problem solving is an important need that has been clearly articulated by teachers and students. The purpose of this work is to examine the incorporation of new concepts from the field of artificial intelligence (AI) as a route to meaningful individualized tutoring. The basic shift is to replace specific foreknowledge of problems with a direct representation of chemical and pedagogical principles and then simulate reasoning using these principles to tutor students. To assess the potential of an AI-based approach, we have developed a prototype tutorial program for balancing chemical equations that contains two important advances. First, the system can create a worked-out solution with detailed explanations for any equation entered by the student or teacher. Unlike a conventional tutorial, this is done dynamically, without the equation being stored ahead of time. Second, the program can interactively answer a variety of detailed questions about its work at each step. Studying worked-out examples plays an important role in learning, and this approach to supporting interactive student inquiry is being investigated as a method of cognitive modeling and apprenticeship intended to foster the students own self-explanation and question-asking abilities.  相似文献   
158.
159.
The chloro bridges in di-μ-chloro-4-methoxy- and di-μ-chloro-4-acetoxy-2-methyl-but-2-enylchloropalladium are split by Group V donor ligands Ph3E (where E = P, As and Sb) to give [(η)3-H2CC(CH3)CHCH2X) PdCl · EPh3], (where X = OCH3, OCOCH3). These complexes are readily decomposed by dilute ethanolic hydrogen chloride yielding [Ph3E · PdCl]2 and isoprene. The structures of the compounds are discussed in the light of their 1H NMR spectra.  相似文献   
160.
A three-phase simulation written in Pascal and using a suite of procedures developed by Lancaster University and the London School of Economics is developed to model a group of ships subject to submarine and air attacks during an extended period of conflict. The simulation collects statistics on weapon usage by the ship group in order to study the impact of attrition, including the effects of preferential targeting, and correlation between the usages of different weapon systems, on war arsenal requirements.  相似文献   
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