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71.
A Rank Encoder: Adaptive Analog to Digital Conversion Exploiting Time Domain Spike Signal Processing
Philipp Häfliger Elin Jørgensen Aasebø 《Analog Integrated Circuits and Signal Processing》2004,40(1):39-51
An electronic circuit is presented that encodes an array of analog input signals into a digital number. The digital output is a rank order code that reflects the relative strength of the inputs, but is independent of the absolute input intensities. In that sense, the circuit performs an adaptive analog to digital conversion, adapting to the average intensity of the inputs (i.e. effectively normalizing) and adapting the quantization levels to the spread of the inputs. Thus, it can convey essential information with a minimal amount of output bits over a huge range of input signals.As a first processing step the analog inputs are projected into the time domain, i.e. into voltage spikes. The latency of those spikes encodes the strength of the input. This conversion enables the circuit to conduct further analog processing steps by asynchronous logic. 相似文献
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Accuracy of delayed matching to sample was studied in 12 Silver King pigeons at different combinations of length of intertrial interval (ITI) and length of delay. When ITI and delay were varied between sessions in Exps I and II, accuracy increased monotonically with ITI and decreased monotonically with delay. Evidence was found for constancy of performance at equivalent ratios of ITI to delay, and percentage of correct choices was linearly related to the log of this ratio. In Exps III and IV, ITI was manipulated as a within-sessions variable. In contrast to the effect of this variable when manipulated between sessions, accuracy improved only from the shortest interval to the next shortest interval and remained constant at all longer intervals. In Exp IV, it was found that performance improved as a direct function of the mean ITI for sessions and that this relation was not affected by the degree of ITI variability within sessions. Findings resemble the effects of temporal variables on autoshaping, and the possibility that some common processes are involved in delayed matching and autoshaping is discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
Femtosecond broadband stimulated Raman: a new approach for high-performance vibrational spectroscopy
Femtosecond stimulated Raman spectroscopy (FSRS) is a new technique that produces high-quality vibrational spectra free from background fluorescence. FSRS combines a narrow-bandwidth picosecond Raman pump pulse with an approximately 80 fs continuum probe pulse to produce stimulated Raman spectra from the pump-induced gain in the probe spectrum. The high intensity of the Raman pump combined with the broad bandwidth of the probe produces high signal-to-noise vibrational spectra with very short data acquisition times. FSRS spectra of standard solutions and solvents such as aqueous Na2SO4, aqueous KNO3, methanol, isopropanol, and cyclohexane are collected in seconds. Furthermore, stimulated Raman spectra can be obtained using just a single pump-probe pulse pair that illuminates the sample for only approximately 1 ps. Fluorescence rejection is demonstrated by collecting FSRS spectra of dyes (rhodamine 6G, chlorophyll a, and DTTCI) with varying degrees of fluorescence background and resonance enhancement. The high signal-to-noise, short data acquisition time, fluorescence rejection, and high spectral and temporal resolution of femtosecond stimulated Raman spectroscopy make it a valuable new vibrational spectroscopic technique. 相似文献
75.
Greffet JJ De La Cruz-Gutierrez M Ignatovich PV Radunsky A 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(12):2315-2320
We analyze the effect of partial spatial coherence on the scattering of light by an arbitrary particle. We extend the definition of the extinction cross section to spatially partially coherent fields. We then discuss the effect of the partial coherence on the extinction scattering cross section by introducing the Wigner transform. It is shown that for rotationally invariant scatterers, the extinction cross section does not depend on the coherence of the incident field. The effect of partial coherence on the angular behavior of the scattered intensity is also discussed in the framework of the Wigner transform. The implications for practical applications are considered. 相似文献
76.
Philipp Andrea M.; Jolicoeur Pierre; Falkenstein Michael; Koch Iring 《Canadian Metallurgical Quarterly》2007,33(6):1062
The present study used a go/no-go signal delay (GSD) to explore the role of response-related processes in task switching. A go/no-go signal was presented at either 100 ms or 1,500 ms after the stimulus. Participants were encouraged to use the GSD for response selection and preparation. The data indicate that the opportunity to select and prepare a response (i.e., long GSD) resulted in a substantial reduction of task-shift costs (Experiment 1) and n-2 task-repetition costs (i.e., backward inhibition; Experiment 2) in the current trial. These results suggest that interference from the preceding trial can be resolved during response selection and preparation. Furthermore, the shift costs and the n-2 repetition costs after no-go trials with long GSD (i.e., response selection but no execution) were markedly smaller than after go trials. These findings suggest that the interference that gives rise to shift costs and n-2 repetition costs is related not solely to response selection but also to response execution. Thus, the present study demonstrates dissociable contributions of response selection and response execution to interference effects in task switching. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
Singer Philipp; Boison Detlev; M?hler Hanns; Feldon Joram; Yee Benjamin K. 《Canadian Metallurgical Quarterly》2007,121(5):815
Selective deletion of glycine transporter 1 (GlyT1) in forebrain neurons enhances N-methyl-D-aspartate receptor (NMDAR)-dependent neurotransmission and facilitates associative learning. These effects are attributable to increases in extracellular glycine availability in forebrain neurons due to reduced glycine re-uptake. Using a forebrain- and neuron-specific GlyT1-knockout mouse line (CamKIIαCre; GlyT1tm1.2fl/fI), the authors investigated whether this molecular intervention can affect recognition memory. In a spontaneous object recognition memory test, enhanced preference for a novel object was demonstrated in mutant mice relative to littermate control subjects at a retention interval of 2 hr, but not at 2 min. Furthermore, mutants were responsive to a switch in the relative spatial positions of objects, whereas control subjects were not. These potential procognitive effects were demonstrated against a lack of difference in contextual novelty detection: Mutant and control subjects showed equivalent preference for a novel over a familiar context. Results therefore extend the possible range of potential promnesic effects of specific forebrain neuronal GlyT1 deletion from associative learning to recognition memory and further support the possibility that mnemonic functions can be enhanced by reducing GlyT1 function. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
Modern computer systems become increasingly distributed and heterogeneous by comprising multi-core CPUs, GPUs, and other accelerators. Current programming approaches for such systems usually require the application developer to use a combination of several programming models (e.g., MPI with OpenCL or CUDA) in order to exploit the system’s full performance potential. In this paper, we present dOpenCL (distributed OpenCL)—a uniform approach to programming distributed heterogeneous systems with accelerators. dOpenCL allows the user to run unmodified existing OpenCL applications in a heterogeneous distributed environment. We describe the challenges of implementing the OpenCL programming model for distributed systems, as well as its extension for running multiple applications concurrently. Using several example applications, we compare the performance of dOpenCL with MPI + OpenCL and standard OpenCL implementations. 相似文献
79.
Microsystems technology is an emerging technology that is used in ever more technical systems, such as inkjet nozzles or accelerometers. 3D micromechanical structures became feasible by miniaturizing macromechanical elements. One big challenge in downsizing mechanical elements is to adapt conventional manufacturing technologies to the conditions of microtechnology. Integrated design and production processes must be suited to the new requirements, in-depth knowledge of production technology is required to design micromechanical components. Since 2000, the Collaborative Research Center 499 “Design, Production and Quality Assurance of Molded Microcomponents made of Metallic and Ceramic Materials” has been focusing on a continuous and stable process chain for molded micro components (Albers et al. 2005, Microsyst Technol). The aim of prior funding periods was to develop the knowledge about how components, such as gearwheels, and systems, such as micro gears, can be designed. Present research is focused on how to design functional elements, i.e. shaft-hub joints to transmit torque. This paper will introduce an approach that generates know-how via testing several plain bearings and shaft-hub joints in order to derive the necessary know-how to develop simulation tools later on. 相似文献
80.
Philipp WollmannMatthias Leistner Wulf GrählertOliver Throl Frieder DreisbachStefan Kaskel 《Microporous and mesoporous materials》2012,149(1):86-94
The demand for fast screening methods in modern materials chemistry led to the development of a room temperature operated high-throughput tool for adsorption screening. Within five minutes a porosity screening of a large sample pool can be realized. Using a variety of different porous materials (activated carbons, porous polymers, metal-organic frameworks, zeolites) and the test gas n-butane, the reliability of the new instrument is shown. Furthermore, possible applications in the determination of n-butane capacities and BET surface areas are given as well as the application in synthesis or product control.The presented data exhibit high quality factors for the correlation of integrated signal intensity (heat of adsorption) and specific surface areas (above 0.97). As an example for the applicability of other gases that can be used with this tool, screening measurements using cyclohexane as test gas are also presented. The developed automated screening tool is an important step to overcome the bottle-neck between high-throughput syntheses technologies developed in the last decades and measurement of adsorption properties. 相似文献