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111.
In this paper, a supervised neural network training technique based on constrained optimization is developed for preserving prior knowledge of an input-output mapping during repeated incremental training sessions. The prior knowledge, referred to as long-term memory (LTM), is expressed in the form of equality constraints obtained by means of an algebraic training technique. Incremental training, which may be used to learn new short-term memories (STMs) online, is then formulated as an error minimization problem subject to equality constraints. The solution of this problem is simplified by implementing an adjoined error gradient that circumvents direct substitution and exploits classical backpropagation. A target application is neural network function approximation in adaptive critic designs. For illustrative purposes, constrained training is implemented to update an adaptive critic flight controller, while preserving prior knowledge of an established performance baseline that consists of classical gain-scheduled controllers. It is shown both analytically and numerically that the LTM is accurately preserved while the controller is repeatedly trained over time to assimilate new STMs. 相似文献
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For the first time, a simulation has been carried out of lossy and dispersive nonlinear transmission lines (NLTLs) used for pulse compression, by two different time-domain approaches: SPICE and a full wave 3D finite difference time domain method. Results show good agreement between the two approaches. The output pulse risetime is strongly affected by DC and skin-effect losses 相似文献
115.
The luminescence of Cr3+ ions in cordierite glass nucleating MgAl2O4 nanocrystallites has been investigated. The time resolved fluorescence line narrowing measurements and the temperature dependence of the homogeneous line width show that most Cr3+ ions are inside the nanocrystallites. Cr3+ ions occupy non-equivalent crystal sites, due to the Mg2+–Al3+ inversion effect. The values of the homogeneous line width compare well with those of previous studies in crystals. No surface effect has been observed due to the large size of the crystals. 相似文献
116.
Paola Milla Franca Viola Maurizio Ceruti Flavio Rocco Luigi Cattel Gianni Balliano 《Lipids》1999,34(7):681-688
19-Azasqualene-2,3-epoxide was more inhibitory than the corresponding N-oxide against 2,3-oxidosqualene cyclase (OSC) solubilized from Saccharomyces cerevisiae (IC50 7±2 and 25±5 μM, respectively). Both compounds showed a reversible, noncompetitive-type inhibition on solubilized OSC. Different
inhibitory properties between the compounds were especially evident when measuring [14C]acetate incorporation into nonsaponifiable lipids extracted from treated cells. In cells treated with 19-azasqualene-2,3-epoxide
at 30 μM, the radioactivity associated with the oxidosqualene fraction, which was negligible in the controls, rose to over
40% of the nonsaponifiable lipids, whereas it remained at a slightly appreciable level in cells treated with the N-oxide derivative under the same conditions. 19-Azasqualene-2,3-epoxide was also more effective than the N-oxide as a cell growth inhibitor (minimal concentration of compound needed to inhibit yeast growth: 45 and >100 μM, respectively).
The two inhibitors underwent different metabolic fates in the yeast: while 19-azasqualene-2,3-epoxide did not undergo any
transformation, its N-oxide was actively reduced to the corresponding amine in whole and in “ultrasonically stimulated” cells. The N-oxide reductases responsible for this transformation appear to be largely confined within the microsomal fractions and require
NADPH for their activity. A possible relationship between the inhibitory properties of the two compounds and their metabolic
fates is discussed. 相似文献
117.
Among the multitude of concrete structure pathologies, corrosion of rebars is one of the most important problems of concrete durability. In the context of sustainable development, it appears of primary importance to develop new means to protect the rebars against corrosion. This study aims to develop a new eco‐friendly and corrosion‐inhibiting admixture based on EPS 180 exopolysaccharides, biopolymers used in coatings already studied for the corrosion inhibition on steel in seawater. C15 rebars embedded in CEMI and CEMV cement paste containing EPS 180 were immersed in natural seawater and their electrochemical behaviour was studied using open circuit potential measurements and electrochemical impedance spectroscopy. These tests highlight the decrease of the cathodic reaction kinetics due to the EPS 180 action at the rebars surface, and the absence of effect on the passive layer. Capillary imbibition tests carried out on cement paste and mortars showed that although limiting the imbibition kinetics for cement pastes, the EPS 180 did not influence the water imbibition of mortars. Tests comparing capillary imbibition of soaked cement pastes and mortars with EPS 180 solution and the same samples containing the EPS 180 admixture highlight that the corrosion inhibition induced by EPS 180 admixture is more due to the modification of the cement – rebars interface than to the clogging of the cement porous network. 相似文献
118.
Gislaine M. Bragagnolo Zehbour Panossian Neusvaldo Lira de Almeida Márcio Bispo de Almeida Jean V. Ferrari Mário Carlos Andreoli Fernando de L. Fragata 《Journal of Coatings Technology and Research》2011,8(5):629-638
The influences of the chromate quenching step and the surface chloride contamination levels of galvanized steel on the performance
of duplex systems were studied. Steel panels were galvanized in a commercial steel bath adopting three different postdipping
procedures. A comparative study of the galvanized steel, both painted and nonpainted, was performed by electrochemical techniques.
It was verified that the chloride contamination level of the galvanized steel surfaces is the main cause of duplex system
failures. An explanation for the influence of the chromate quenching on the performance of duplex systems was presented. 相似文献
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