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61.
Maria Kelly Venezuela Mônica Carneiro SandovalDenise Aparecida Botter 《Computational statistics & data analysis》2011,55(4):1867-1883
Local influence diagnostics based on estimating equations as the role of a gradient vector derived from any fit function are developed for repeated measures regression analysis. Our proposal generalizes tools used in other studies (
[Cook, 1986] and [Cadigan and Farrell, 2002]), considering herein local influence diagnostics for a statistical model where estimation involves an estimating equation in which all observations are not necessarily independent of each other. Moreover, the measures of local influence are illustrated with some simulated data sets to assess influential observations. Applications using real data are presented. 相似文献
62.
Johnson GP Calo VM Gaither KP 《IEEE transactions on visualization and computer graphics》2008,14(6):1420-1427
A stand-alone visualization application has been developed by a multi-disciplinary, collaborative team with the sole purpose of creating an interactive exploration environment allowing turbulent flow researchers to experiment and validate hypotheses using visualization. This system has specific optimizations made in data management, caching computations, and visualization allowing for the interactive exploration of datasets on the order of 1TB in size. Using this application, the user (co-author Calo) is able to interactively visualize and analyze all regions of a transitional flow volume, including the laminar, transitional and fully turbulent regions. The underlying goal of the visualizations produced from these transitional flow simulations is to localize turbulent spots in the laminar region of the boundary layer, determine under which conditions they form, and follow their evolution. The initiation of turbulent spots, which ultimately lead to full turbulence, was located via a proposed feature detection condition and verified by experimental results. The conditions under which these turbulent spots form and coalesce are validated and presented. 相似文献
63.
64.
Several authors have previously discussed the use of log-linear models, often called maximum entropy models, for analyzing spike train data to detect synchrony. The usual log-linear modeling techniques, however, do not allow time-varying firing rates that typically appear in stimulus-driven (or action-driven) neurons, nor do they incorporate non-Poisson history effects or covariate effects. We generalize the usual approach, combining point-process regression models of individual neuron activity with log-linear models of multiway synchronous interaction. The methods are illustrated with results found in spike trains recorded simultaneously from primary visual cortex. We then assess the amount of data needed to reliably detect multiway spiking. 相似文献
65.
66.
During 6 months of post-natal development in the laboratory, the weight of the adrenal gland relative to body weight decreases exponentially. In the 3 day-old duckling a single intravenous dose of labelled corticosterone becomes distributed in a very large apparent volume and an "extracellular" pool that is greater than the extracellular fluid volume and the pattern of disappearance of labelled hormone from plasma is biphasic. Later during development the volumes of distribution decrease and the biphasic pattern of disappearance becomes less distinct until at 6 months only one phase of disappearance can be detected with confidence. No significant change in plasma corticosterone concentration occurs during this period of development in the laboratory. Estimations of the corticosterone secretory rates, however, indicate that whereas the adrenal weight-specific rate os secretion increases during the first 3 weeks and declines therafter, the bodyf weight-specific secretory rate continues to decline throughtout the period of increasing body weight. 相似文献
67.
Chromium diboride thin films possess desirable combinations of properties (such as high hardness, wear resistance, chemical inertness, high thermal and electrical conductivity), which are attractive for a wide range of potential industrial applications. However, these properties depend strongly on the deposition process and parameters. Investigation of the resultant coating structures could explain certain differences between them, giving important information about the characteristics of the deposition process (which in this particular case is a recently developed method involving magnetron sputtering of loosely packed blended powder targets) and pointing out directions for improvement.In this paper, Cr-B coatings deposited by direct current (DC) and DC-pulse magnetron sputtering of loosely packed blended powder targets are characterised by transmission electron microscopy (TEM) techniques (electron diffraction and bright-field/dark-field imaging). The structures of the coatings deposited with different parameters are investigated and compared, and the effect of oxygen contamination on the structure is discussed.Coatings with an extremely fine, nanocolumnar structure were observed. DC sputter deposited (and generally non-stoichiometric) Cr-B coatings exhibit a short range ordered ‘zone T’ microstructure, while DC-pulse deposited stoichiometric CrB2 coatings are dense and defect-free, crystalline and show strong preferred orientation.A small amount of contamination by oxygen of the interfacial sub-layers (due to the target material being a powder) of the DC-pulse magnetron sputter deposited stoichiometric CrB2 (and near-stoichiometric CrB) coatings was found to affect the structure by suppressing nanocolumnar growth and promoting equiaxed, nanometer-sized grains, close to the coating/substrate interface. The majority of the coating however remained nanocolumnar. 相似文献
68.
The marshland upwelling system (MUS) was installed on private camps in the Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi. The system was evaluated for its effectiveness in removing fecal coliforms from settled, raw wastewater. A suite of studies was performed at flow rates of 1.9, 2.8, and 5.5 L/min and an injection frequency of 30 min every 3 h to investigate fecal coliform removal. An additional study was performed at a flow rate of 2.8 L/min and an injection frequency of 15 min every hour. Overall, the MUS consistently maintained fecal concentrations below effluent regulatory standards for shellfish harvesting waters (14 most probable number of colonies per 100 mL). Mean influent concentrations of 55,269±2,218,016 colony forming units (CFU)/100 mL were reduced to effluent counts of 2.7±14.07 CFU/100 mL (observed in the 1.5 m wells). Three- to four-log reductions in influent counts were observed over the initial 1.4 vector?m from the injection well. The overall removal followed a first-order decay relationship with respect to vector distance, resulting in removal rate constants ranging from 5.6 to 6.6/m and predicted surface concentrations approaching 0 CFU/100 mL. The 2.8 L/min for 30 min every 3 h treatment provided the best effluent quality. 相似文献
69.
Hanson William E.; Creswell John W.; Clark Vicki L. Plano; Petska Kelly S.; Creswell J. David 《Canadian Metallurgical Quarterly》2005,52(2):224
With the increased popularity of qualitative research, researchers in counseling psychology are expanding their methodologies to include mixed methods designs. These designs involve the collection, analysis, and integration of quantitative and qualitative data in a single or multiphase study. This article presents an overview of mixed methods research designs. It defines mixed methods research, discusses its origins and philosophical basis, advances steps and procedures used in these designs, and identifies 6 different types of designs. Important design features are illustrated using studies published in the counseling literature. Finally, the article ends with recommendations for designing, implementing, and reporting mixed methods studies in the literature and for discussing their viability and continued usefulness in the field of counseling psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
Static tests and ultrasonic measurements (2.25 MHz) have been carried out on a series of composite laminates of glass fibres
in a polypropylene matrix. A range of angle ply laminates were prepared for this study, with laminate angles θ of ±0, 10,
20, 30 and 40^∘. The high frequency measurements were made using the ultrasonic immersion technique, which allows the determination
of a complete set of the elastic constants of a material. The relationship between the ultrasonically determined elastic constants
of the angle ply laminates was found to be in excellent agreement with theoretical predictions, as previously validated for
carbon fibre/epoxy angle ply laminates.
A comparison between the ultrasonic and statically measured values was made for two of the angle ply laminates (θ = 0 and
20^∘). It was found that the static values were lower than those measured at ultrasonic frequency, particularly those constants
that were more matrix dominated (for example the transverse moduli of the laminates). Measurements on a pure polypropylene
sample at both testing frequencies confirmed that the change in matrix properties with frequency was the cause of this difference.
The change in properties with test frequency is likely to be much larger in this system than in other composite materials
because the glass transition temperature of polypropylene is close to ambient temperature. Dynamic mechanical tests (1 Hz)
were carried out on a sample of pure polypropylene to assess this effect. We also give an appropriate method of estimating
the dependence of glass transition temperature on frequency. The results for polypropylene are compared with those for other
commonly used polymer matrix materials: epoxy resin, nylon and polyetheretherketone (PEEK): DMTA measurements were also made
on these samples.
The effect of test frequency on matrix properties, for the glass/PP laminates, was further investigated by examining the relationship
of the Poisson's ratios with laminate angle using a mixture of ultrasonic experiments and theoretical predictions. Previously
we have shown that the degree of anisotropy between the reinforcing fibre and the matrix phase is paramount in determining
whether the material will show a negative Poisson's ratio at a critical laminate angle. The ultrasonic measurements carried
out in this study on the glass/PP laminates showed a minimum in one of the Poisson's ratio at a laminate angle of 32°, but
the value did not become negative. However, theoretical predictions showed that for a static frequency measurement (1 Hz),
where the matrix is softer and hence the anisotropy of each laminate ply is higher, the laminate will show a negative Poisson's
ratio with a minimum at a laminate angle of around 28°. 相似文献