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151.
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153.
Modeling the effectiveness of oil combating from an ecological perspective--a Bayesian network for the Gulf of Finland; the Baltic Sea 总被引:1,自引:0,他引:1
Maritime traffic poses a major threat to marine ecosystems in the form of oil spills. The Gulf of Finland, the easternmost part of the Baltic Sea, has witnessed a rapid increase in oil transportation during the last 15 years. Should a spill occur, the negative ecological impacts may be reduced by oil combating, the effectiveness of which is, however, strongly dependent on prevailing environmental conditions and available technical resources. This poses increased uncertainty related to ecological consequences of future spills. We developed a probabilistic Bayesian network model that can be used to assess the effectiveness of different oil combating strategies in minimizing the negative effects of oil on six species living in the Gulf of Finland. The model can be used for creating different accident scenarios and assessing the performance of various oil combating actions under uncertainty, which enables its use as a supportive tool in decision-making. While the model is confined to the western Gulf of Finland, the methodology is adaptable to other marine areas facing similar risks and challenges related to oil spills. 相似文献
154.
155.
Norrman A Setälä T Friberg AT 《Journal of the Optical Society of America. A, Optics, image science, and vision》2011,28(3):391-400
We consider partial spatial coherence and partial polarization of purely evanescent optical fields generated in total internal reflection at an interface of two dielectric (lossless) media. Making use of the electromagnetic degree of coherence, we show that, in such fields, the coherence length can be notably shorter than the light's vacuum wavelength, especially at a high-index-contrast interface. Physical explanation for this behavior, analogous to the generation of incoherent light in a multimode laser, is provided. We also analyze the degree of polarization by using a recent three-dimensional formulation and show that the field may be partially polarized at a subwavelength distance from the surface even though it is fully polarized farther away. The degree of polarization can assume values unattainable by beamlike fields, indicating that electromagnetic evanescent waves generally are genuine three-dimensional fields. The results can find applications in near-field optics and nanophotonics. 相似文献
156.
The extraction of yellow gentian root (Gentiana lutea L .) 总被引:1,自引:0,他引:1
Amaia Ariño Inés Arberas M. Jesús Leiton Mertxe de Renobales Juan B. Dominguez 《European Food Research and Technology》1997,205(4):295-299
Several solvents have been investigated for the preparation of bitter compounds of gentian roots (Gentiana lutea L.) for food applications. The highest concentrations of the bitter compounds, amarogentin and gentiopicroside, were obtained
with ethanol : water 55 : 45 (v/v), propylene glycol: water 30 : 70 (v/v) and ethanol: propylene glycol: water 20 : 20 : 60
(v/v/v). Enzyme treatment prior to solvent extraction gave a greater extract yield (3.5%) but the amarogentin and gentiopicroside
concentrations remained the same. The volatile fraction was affected by the solvent used through the formation of esters of
organic acids from the plant.
Received: 22 January 1997 / Revised version: 18 March 1997 相似文献
157.
The Liu and Jordan method of calculating long term average energy collection of flat plate collectors is simplified (by about a factor of 4), improved, and generalized to all collectors, concentrating and nonconcentrating. The only meteorological input needed are the long term average daily total hemispherical isolation
on a horizontal surface and, for thermal collectors the average ambient temperature. The collector is characterized by optical efficiency, heat loss (or U-value), heat extraction efficiency, concentration ratio and tracking mode. An average operating temperature is assumed. If the operating temperature is not known explicitly, the model will give adequate results when combined with the
, f-chart of Klein and Beckman.A conversion factor is presented which multiplies the daily total horizontal insolation
to yield the long term average useful energy
delivered by the collector. This factor depends on a large number of variables such as collector temperature, optical efficiency, tracking mode, concentration, latitude, clearness index, diffuse insolation etc., but it can be broken up into several component factors each of which depends only on two or three variables and can be presented in convenient graphical on analytical form. In general, the seasonal variability of the weather will necessitate a separate calculation for each month of the year; however, one calculation for the central day of each month will be adequate. The method is simple enough for hand calculation.Formulas and examples are presented for five collector types: flat plate, compound parabolic concentrator, concentrator with east-west tracking axis, concentrator with polar tracking axis, and concentrator with 2-axis tracking. The examples show that even for relatively low temperature applications and cloudy climates (50°C in New York in February), concentrating collectors can outperform the flat plate.The method has been validated against hourly weather data (with measurements of hemispherical and beam insolation), and has been found to have an average accuracy better than 3 per cent for the long term average radiation available to solar collectors. For the heat delivery of thermal collectors the average error has been 5 per cent. The excellent suitability of this method for comparison studies is illustrated by comparing in a location independent manner the radiation availability for several collector types or operating conditions: 2-axis tracking versus one axis tracking; polar tracking axis versus east-west tracking axis; fixed versus tracking flat plate; effect of ground reflectance; and acceptance for diffuse radiation as function of concentration ratio. 相似文献
158.
The stress state in plates with circular holes made of orthotropic homogeneous material has no singularities and it can be
exactly determined. The numerical stress distribution calculation by the finite element method will be compared with those
obtained by the analytical equations developed by several authors. The goal of this work is to validate the finite element
method, in conjunction with in-plane and out of plane failure criteria, in order to calculate not only the stress distribution
for orthotropic plates with circular holes but also to determine their ultimate strength.The tool used has been a user subroutine
(UMAT) specially developed for this work that implements the features of the commercial FE program (ABAQUS). The code performs
an implicit analysis of the stress-state with progressive damage modelling.Finally, both of them, numerical and analytical
method, will be checked with experimental tests by means of strain gauges. 相似文献
159.
Ari‐Pekka Hameri Mikael Puittinen Mikko Syrjlahti 《International Journal of Communication Systems》2002,15(7):607-619
Research on complex adaptive systems has generated several conceptual parables to explain systems with emergent behaviour. One prominent use for terms such as self‐organization, evolutionary trajectories, co‐evolution and punctuated equilibrium has been in understanding human organizations. In such systems, emergent behaviour is demonstrated in novel structures, processes and spin‐offs that cannot be explained just by studying single components of the organization and the intelligence embedded in them. Instead of solely exploiting the qualitative explanatory power of the evolutionary concepts, this paper focuses also on quantitative methods to track emergent behaviour in a globally distributed, constantly fluctuating and highly networked project organization. The underlying case is that of CERN (CERN, the European Laboratory for Particle Physics, has its headquarters in Geneva. At present, its Member States are Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, Netherlands, Norway, Poland, Portugal, the Slovak Republic, Spain, Sweden, Switzerland and the United Kingdom. Israel, the Russian Federation, Turkey, Yugoslavia (status suspended after the UN embargo, June 1992), the European Commission and UNESCO have observer status.) and its decade long accelerator project, which strongly relies on electronic communication and networking to achieve its major objectives due to be accomplished by the year 2006. By using time series and self‐organizing maps to analyse the global interaction among project groups and individuals the paper provides new insight to the understanding of emergent behaviour in human organizations. The key result of the study concerns the rigid deep structure of each case organization that seems to remain intact for the duration of the whole project. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
160.
A case history in debris characterization is presented for oblique impacts of chunky tungsten projectiles against thin plates. The integrated approach of scaled experiments and hydrocode simulations led to a semi-analytic model of behind the plate debris fragment distributions. This debris distribution model agreed quite well with the experimental fragment distributions derived from witness plate measurements. The 1/4 scale test program included three projectile masses, two target geometries (single and dual plates), a velocity range of 4–7 km/s and a strike angle range of 15–55 degrees. Close correlation of measured and predicted fragment distributions encouraged the extension of the model to higher velocities not currently obtainable in the laboratory.
The paper also includes discussions of critical features of debris in oblique hypervelocity impact, the scalability of fragment data, and the utilization of the derived fragment models in semi-analytic damage assessment codes. 相似文献