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21.
Marcel Marchand Wouter T. De Groot 《The International journal of environmental studies》2013,70(1-2):31-43
Third World rural planning involves the transfer of First World technologies to the socially and ecologically vulnerable tropical environment. This transfer is guided by normative, “ideological” views concerning social and environmental issues which often remain implicit. To uncover these views, a content analysis of a series of papers has been carried out, focused on impoldering as a type of project with far reaching social and environmental impacts. Three types of “ideologies” could be distinguished, which have been labelled as sociocratic, eco‐sociocratic and technocratic. They differentiate significantly with regard to (1) values attached to ecological and cultural systems, (2) preferred pace and scale of projects, (3) envisaged project feasibility, (4) the range of feasible alternatives, as well as (5) the institutional background of their adherents. The latter separation, however, is not complete. This may stimulate the growth of insight in the normative background of the seemingly objective rationality of project design. 相似文献
22.
A new method is presented that enables sensitive measurement of free concentrations of radiolabeled ligands. Additionally, protein binding of radiochemicals in complex matrixes can be determined with this new technique that combines negligible depletion solid-phase microextraction (nd-SPME) with liquid scintillation counting (LSC) as detection. [3H]Estradiol was taken as an example compound. Possible matrix effects of protein on fiber uptake kinetics were studied. No matrix effect was found, either by fouling of the fiber, or by changed uptake kinetics. The validity of the method was shown in the determination of the affinity constant (Ka) of estradiol for human serum albumin (HSA). The Ka was estimated at 8.9 x 10(4) M(-1), which corresponds well with literature values. This study shows that nd-SPME is suitable to study the free concentration and protein binding of [3H]estradiol. The method described in this paper combines the advantages of nd-SPME with the advantages of radiolabeled analytes, creating a timesaving, simple, and sensitive analytical tool that will be particularly useful in complex matrixes containing many potential interferences for chromatographic methods. 相似文献
23.
Wouter R. A. Ryckaert Jozef A. L. Ghijselen Jan J. M. Desmet Alex P. M. Van den Bossche Jan A. A. Melkebeek David M. Van de Sype 《Electrical Engineering (Archiv fur Elektrotechnik)》2005,87(6):315-326
Although complete compensation is only possible using true active filters, resistive shunt harmonic impedances (SHI) have
been shown to provide a considerable reduction of the harmonic propagation.
In this paper, the harmonic mitigation potential of a resistive SHI is discussed concerning its influence on the voltage distortion
profile along a typical distribution feeder, with the location of the SHI along the feeder as a parameter. Although the distortion values
are dependent on the SHI location, it is shown that the end of the feeder is generally a good location to install the SHI,
especially when the power system parameters can vary or are unknown.
Calculations are performed on a typical radial distribution feeder. Both the power factor correction capacitors and the non-linear
loads are concentrated in single nodes. The linear loads are disconnected to obtain the worst case for the voltage distortion.
Also some measurements on a scale model of a typical distribution feeder are done and the experimental results confirm the
results obtained from simulations. 相似文献
24.
25.
Lopes da Silva FH Blanes W Kalitzin SN Parra J Suffczynski P Velis DN 《IEEE transactions on bio-medical engineering》2003,50(5):540-548
In this overview, we consider epilepsies as dynamical diseases of brain systems since they are manifestations of the property of neuronal networks to display multistable dynamics. To illustrate this concept we may assume that at least two states of the epileptic brain are possible: the interictal state characterized by a normal, apparently random, steady-state electroencephalography (EEG) ongoing activity, and the ictal state, that is characterized by paroxysmal occurrence of synchronous oscillations and is generally called, in neurology, a seizure. The transition between these two states can either occur: 1) as a continuous sequence of phases, like in some cases of mesial temporal lobe epilepsy (MTLE); or 2) as a sudden leap, like in most cases of absence seizures. In the mathematical terminology of nonlinear systems, we can say that in the first case the system's attractor gradually deforms from an interictal to an ictal attractor. The causes for such a deformation can be either endogenous or external. In this type of ictal transition, the seizure possibly may be anticipated in its early, preclinical phases. In the second case, where a sharp critical transition takes place, we can assume that the system has at least two simultaneous interictal and ictal attractors all the time. To which attractor the trajectories converge, depends on the initial conditions and the system's parameters. An essential question in this scenario is how the transition between the normal ongoing and the seizure activity takes place. Such a transition can occur either due to the influence of external or endogenous factors or due to a random perturbation and, thus, it will be unpredictable. These dynamical changes may not be detectable from the analysis of the ongoing EEG, but they may be observable only by measuring the system's response to externally administered stimuli. In the special cases of reflex epilepsy, the leap between the normal ongoing attractor and the ictal attractor is caused by a well-defined external perturbation. Examples from these different scenarios are presented and discussed. 相似文献
26.
Spiessens B Lesaffre E Verbeke G Kim K DeMets DL 《Statistical methods in medical research》2000,9(5):497-515
During the last decade, several papers have been published on group sequential methods in general and on sequential longitudinal clinical trials in particular. This paper gives an overview of the proposed methods, emphasizing longitudinal clinical trials. Furthermore, it tries to answer some practical questions that may arise during the conduct of interim analyses in longitudinal trials. Simulations have been carried out to obtain insight in these practical considerations. 相似文献
27.
Wouter Bracke Patrick Merken Robert Puers Chris Van Hoof 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(1):130-140
Traditionally, most of the sensor interfaces must be tailored towards a specific application. This approach results in a high recurrent design cost and time to market. On the other hand, generic sensor interface design reduces the costs and offers a handy solution for multisensor applications. This paper presents a generic sensor interface chip (GSIC), which can read out a broad range of capacitive sensors. It contains capacitance-to-voltage converters, a switched-capacitor amplifier, an analog-to-digital converter, oscillators, clock generation circuits and a reference circuit. The system combines a very low-power design with a smart energy management, which adapts the current consumption according to the accuracy and speed requirements of the application. The GSIC is used in a pressure and an acceleration monitoring system. The pressure monitoring system achieves a current drain of 2.3 muA for a 10-Hz sample frequency and an 8-bit accuracy. In the acceleration monitoring system, we measured a current of 3.3 muA for a sample frequency of 10 Hz and an accuracy of 9 bits 相似文献
28.
L. P. C. Verbeke Corresponding author F. M. B. Vancoillie R. R. De wulf 《International journal of remote sensing》2013,34(14):2747-2771
This paper focuses on a method to overcome some of the disadvantages that are related with the use of artificial neural networks (ANNs) as supervised classifiers. The proposed method aims at speeding up network learning, improving classification accuracies and reducing variability on classification performance due to random weight initialization. This can be realized by transferring implicit knowledge from a previously learned source task to a new target task using the proposed algorithm, Discriminality Based Transfer (DBT). The presented approach is compared with conventional network training and a literal transfer method in a 13-class tropical savannah classification experiment using Landsat Thematic Mapper (TM) data. Knowledge was extracted from a network trained on the Kara experimental site in Togo. This information was used to classify the Savanes-L'Oti area which differs in terms of geographical position, image acquisition date, climatological condition and land cover. It was possible to speed up network learning 5.2, 4.3 and 1.8 times using, respectively, 5-, 10- and 20-pixels-per-class training sets. Larger training sets showed less speed improvement. After applying DBT, average classification accuracies were not significantly different from accuracies obtained after training random initialized networks, although DBT tended to show better performance on smaller training sets. It was possible to explain differences in individual class accuracies by analysing Bhattacharyya (BH) distances calculated between all Kara and Savanes-L'Oti classes. Finally, variability on classification performance decreased significantly when training with 5-, 10- and 20-pixels-per-class training sets after DBT application. 相似文献
29.
Oytun Akman Ronald Poelman Wouter Caarls Pieter Jonker 《Machine Vision and Applications》2013,24(5):931-946
With the recent developments in wearable augmented reality (AR), the role of natural human–computer interaction is becoming more important. Utilization of auxiliary hardware for interaction introduces extra complexity, weight and cost to wearable AR systems and natural means of interaction such as gestures are therefore more desirable. In this paper, we present a novel multi-cue hand detection and tracking method for head-mounted AR systems which combines depth, color, intensity and curvilinearity. The combination of different cues increases the detection rate, eliminates the background regions and therefore increases the tracking performance under challenging conditions. Detected hand positions and the trajectories are used to perform actions such as click, select, etc. Moreover, the 6 DOF poses of the hands are calculated by approximating the segmented regions with planes in order to render a planar menu (interface) around the hand and use the hand as a planar selection tool. The proposed system is tested on different scenarios (including markers for reference) and the results show that our system can detect and track the hands successfully in challenging conditions such as cluttered and dynamic environments and illumination variance. The proposed hand tracker outperforms other well-known hand trackers under these conditions. 相似文献
30.
Maarten Overdijk Wouter van Diggelen 《International Journal of Computer-Supported Collaborative Learning》2008,3(2):165-192
The use and effects of a CSCL-tool are not always predictable from the properties of the tool alone, but depend on how that
tool is appropriated. This paper presents the findings from a case study about the appropriation of a graphical shared workspace.
When students are presented with a new tool they may encounter competing constraints and multiple possibilities for interacting
with it. We argue that during critical events the students make choices, and in order to collaborate, coordinate these choices
as a group. We study appropriation by looking into the ways in which small groups organize their contributions during a computer-mediated
argumentative discussion. The results of our study illustrate how certain principles for organization emerge from an implicit
negotiation of conventions, with mutual influence between the students and the tool. 相似文献