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91.
Efficient real-time trajectory tracking 总被引:1,自引:0,他引:1
Ralph Lange Frank Dürr Kurt Rothermel 《The VLDB Journal The International Journal on Very Large Data Bases》2011,20(5):671-694
Moving objects databases (MOD) manage trajectory information of vehicles, animals, and other mobile objects. A crucial problem
is how to efficiently track an object’s trajectory in real-time, in particular if the trajectory data is sensed at the mobile
object and thus has to be communicated over a wireless network. We propose a family of tracking protocols that allow trading
the communication cost and the amount of trajectory data stored at a MOD off against the spatial accuracy. With each of these
protocols, the MOD manages a simplified trajectory that does not deviate by more than a certain accuracy bound from the actual
movement. Moreover, the different protocols enable several trade-offs between computational costs, communication cost, and
the reduction in the trajectory data: Connection-Preserving Dead Reckoning minimizes the communication cost using dead reckoning, a technique originally designed for tracking an object’s current position.
Generic Remote Trajectory Simplification (GRTS) further separates between tracking of the current position and simplification of the past trajectory and can be realized
with different line simplification algorithms. For both protocols, we discuss how to bound the space consumption and computing
time at the moving object and thereby present an effective compression technique to optimize the reduction performance of
real-time line simplification in general. Our evaluations with hundreds of real GPS traces show that a realization of GRTS
with a simple simplification heuristic reaches 85–90% of the best possible reduction rate, given by retrospective offline
simplification. A realization with the optimal line simplification algorithm by Imai and Iri even reaches more than 97% of
the best possible reduction rate. 相似文献
92.
Improving classroom learning by collaboratively observing human tutoring videos while problem solving. 总被引:1,自引:0,他引:1
Craig Scotty D.; Chi Michelene T. H.; VanLehn Kurt 《Canadian Metallurgical Quarterly》2009,101(4):779
Collaboratively observing tutoring is a promising method for observational learning (also referred to as vicarious learning). This method was tested in the Pittsburgh Science of Learning Center’s Physics LearnLab, where students were introduced to physics topics by observing videos while problem solving in Andes, a physics tutoring system. Students were randomly assigned to three groups: (a) pairs collaboratively observing videos of an expert human tutoring session, (b) pairs observing videos of expert problem solving, or (c) individuals observing expert problem solving. Immediate learning measures did not display group differences; however, long-term retention and transfer measures showed consistent differences favoring collaboratively observing tutoring. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
Daniel E. Canfield Jr Darren J. Pecora Kurt W. Larson Jesse Stephens Mark V. Hoyer 《Lakes & Reservoirs: Research and Management》2013,18(3):239-245
Stocking of largemouth bass is an important management tool for fish management. The stocking of hatchery‐produced fingerling or advanced‐fingerling bass to supplement bass year‐classes, however, has exhibited varying success. Utilizing a different approach, a multiyear stocking programme using wild adult largemouth bass was initiated at the Harris Chain of Lakes (3800 ha Lake Griffin; 1811 ha Lake Dora) in central Florida. Wild adult bass (24 781 fish), ranging in size from 200 mm total length (TL) to over 600 mm TL, were stocked in Lake Griffin (13 932 fish) and Lake Dora (10 849 fish). One month after stocking, the number of stocked bass caught in electrofishing catches in Lake Griffin and Lake Dora was ~10% and 22%, respectively. Estimates of mortality were similar to the native largemouth bass, although the movement of stocked fish into other connecting water bodies was extensive. For the Lake Griffin/Lake Dora stocking programme, bass were transferred at a cost of $10.09–19.89 per fish, depending on how the costs of the project are calculated ($250 000 for just the capture and transport of the fish vs. $492 775 for the total project). Considering only capture and transport costs, conservative benefit/cost ratio estimates would be $1.77/$1.00 spent for replacement and $1.85/$1.00 spent recreational costs, although the benefit/cost ratios could exceed $10/$1. Based on the present study, stocking wild adult largemouth bass is a cost‐effective tool for managing largemouth bass. 相似文献
94.
Kurt Kornbluth Zach McCaffrey Paul A. Erickson 《International Journal of Hydrogen Energy》2009,34(22):9248-9257
A 0.745 L 2-cylinder spark-ignition engine was operated with compressed natural gas and with simulated landfill gas (60% CH4 and 40% CO2 by volume) containing hydrogen concentrations of 0, 30%, 40%, and 50% (by volume of the CH4 in the fuel) at constant rpm. This empirical data was compared with predictions from three existing semi-empirical engine models, using a first-law-based finite heat release model to correlate measured in-cylinder pressure data and burn rate for each fuel mixture. Of the three models only a two zone model incorporating thermal and prompt NOx came within 25% of predicting the measured NOx emissions. 相似文献
95.
Towards cognitive evaluation of computer-drawn sketches 总被引:1,自引:0,他引:1
This paper seeks to raise visual comparisons beyond subjective opinions into evidence-based visual reasoning. It provides
an informal deductive analysis of the marks in sketches derived with two competing line-filtering algorithms. This prompted
the novel speculation that the visual system might be placing some types of anomalies in the foreground of mental 3D space,
where they can be ignored. A brief survey is provided to encourage informed debate. Although the proposed cognitive computation
was not automated, it justified the rejection of the Douglas–Peucker algorithm in favour of Visvalingam's algorithm in subsequent
research within the Cartographic Information Systems Research Group (CISRG). 相似文献
96.
Stuart Crozier Ph.D. Stephen Dodd Kurt Luescher James Field David M. Doddrell 《Magma (New York, N.Y.)》1995,3(1):49-55
By extending the formalism previously developed for the design of unshielded, biplanar gradient coils, shielded biplanarB
0 coils optimized for homogeneity and either minimum energy or minimum power may be designed. We present results from an integrated
approach to shielded biplanar coil design, the results of which are also applicable to gradient coils, enabling the design
of shielded coils with a concomitant decrease in total inductance of the coil. Length constraints are also included in the
integrated minimization procedure. Results from a preliminary design indicate that high-homogeneity, low-impedance, well-shielded
coils result from this design approach. 相似文献
97.
Newsted JL Nakanishi J Cousins I Werner K Giesy JP 《Environmental science & technology》2002,36(22):4761-4769
An assessment of HFE-7500, a 'segregated' hydrofluoroether, was conducted to evaluate the potential for exposure to and subsequent effects on humans and wildlife in Japan. The segregated hydrofluoroethers belong to a class of fluorochemicals currently being proposed as replacements for traditional fluorochemicals (CFCs and PFCs) that are currently being used in several industries, in particular, the semiconductor industry. These traditional compounds have been implicated as ozone-depleting or potent "greenhouse gases". The segregated hydrofluoroethers have useful physical and chemical properties, but do not contribute to ozone depletion and have lower "global warming potential" (GWP) indices. Although the physical properties of these materials (low H2O solubility and high vapor pressure) suggest there would be a very low level of risk to aquatic systems, a thorough analysis had not been previously performed. Predicted environmental concentrations (PECs) of HFE-7500 in Japan were determined with the Higashino model, a Gausian puff and plume model that used an approximation of environmental releases to the atmosphere as input to the model. Allowable concentrations to protect aquatic life, wildlife, and humans from noncancer effects were determined as detailed in USEPA's final Water Quality Guidance for the Great Lakes Systems. Potential risk to ecological receptors and humans was determined by calculating hazard quotients and margins of safety. The results of the risk assessment indicate that HFE-7500 poses no significant risk to either aquatic or terrestrial wildlife species or humans living in the Japanese environment. The least margin of safety for any ecological receptor was 100,000, and a margin of safety greater than 100,000,000 for most receptors indicated that HFE-7500 poses no threat to human health. Because of a scarcity of toxicity and exposure data, the risk assessment was based on very conservative assumptions. Therefore, the actual margins of safety for both humans and wildlife could have been 100- to 1,000-fold greater if additional data were available such that less stringent uncertainty factors could be applied. These results suggest that the environmental impact of HFE-7500 should be inconsequential based on the marked improvement in its atmospheric properties relative to the traditional compounds currently in use. Given the short atmospheric lifetime and low global warming potential of this material, its replacement of CFCs and PFCs would result in a net improvement of environmental health and safety. 相似文献
98.
Kurt P. Judmann 《e & i Elektrotechnik und Informationstechnik》2002,119(11):a16-a16
Sciencenews10-Jahr-Feier
Institut für Maschinelles Sehen und Darstellen 相似文献99.
Leith EN Mills KD Grannell S Dilworth DS Athey BD Lopez J 《Journal of the Optical Society of America. A, Optics, image science, and vision》2002,19(3):532-536
The method of Fourier optics is applied to the problem of time-gated imaging through scattering media. Tb adapt the problem to this treatment, appropriate alterations are made: The continuous medium is replaced by a cascade of thin scatterers, and a spatial filtering process is substituted for the conventional gating processes. Closed-form solutions are derived. 相似文献
100.
Cylindrical stand-alone tubes of plasma-sprayed alumina were tested in uniaxial compression at room temperature, using strain gages to monitor axial strains. The effect of lamella size on the mechanical response was investigated by employing different starting powders to fabricate samples. The average powder sizes investigated included 9 m, 19 m and 32 m alumina; the resulting effective lamella diameters were 10 m, 28 m, and 55 m, respectively. Similar stress-strain hysteresis was observed on unloading in all tubes, independent of lamella size. A strong correlation between the failure stress and the cumulative strain at failure was also observed for tubes fabricated from the three powders. For samples with approximately constant densities, tubes plasma sprayed with the 9 m powder exhibited greater moduli than tubes sprayed from either 19 or 32 m powders. This difference was attributed to the greater percentage of unmelted -Al2O3 in the coating. 相似文献