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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
John Stachurski 《Computational Economics》2008,31(2):141-160
This paper studies fitted value iteration for continuous state numerical dynamic programming using nonexpansive function approximators.
A number of approximation schemes are discussed. The main contribution is to provide error bounds for approximate optimal
policies generated by the value iteration algorithm.
相似文献
952.
Multi-core CPUs,Clusters, and Grid Computing: A Tutorial 总被引:1,自引:0,他引:1
The nature of computing is changing and it poses both challenges and opportunities for economists. Instead of increasing clock
speed, future microprocessors will have “multi-cores” with separate execution units. “Threads” or other multi-processing techniques
that are rarely used today are required to take full advantage of them. Beyond one machine, it has become easy to harness
multiple computers to work in clusters. Besides dedicated clusters, they can be made up of unused lab computers or even your
colleagues’ machines. Finally, grids of computers spanning the Internet are now becoming a reality. 相似文献
953.
Differencing and merging of architectural views 总被引:1,自引:0,他引:1
Marwan Abi-Antoun Jonathan Aldrich Nagi Nahas Bradley Schmerl David Garlan 《Automated Software Engineering》2008,15(1):35-74
Differencing and merging architectural views is an important activity in software engineering. However, existing approaches
are still based on restrictive assumptions, such as requiring view elements to have unique identifiers or exactly matching
types, which is often not the case in many application domains.
We propose an approach based on structural information. We generalize a published polynomial-time tree-to-tree correction
algorithm that detects inserts, renames and deletes, into a novel algorithm that additionally detects restricted moves. Our
algorithm also supports forcing and preventing matches between view elements.
We incorporate the algorithm into tools to compare and merge Component-and-Connector (C&C) architectural views. We provide
an empirical evaluation of the algorithm. We illustrate the tools using extended examples, and use them to detect and reconcile
interesting differences between real architectural views.
This article is an expanded version of the following paper: Abi-Antoun, M., Aldrich, J., Nahas, N., Schmerl, B., and Garlan, D:
2006, ‘Differencing and Merging of Architectural Views’. In: Proceedings of the 21st IEEE International Conference on Automated Software Engineering, pp. 47–58. 相似文献
954.
Testing Forecast Accuracy of Foreign Exchange Rates: Predictions from Feed Forward and Various Recurrent Neural Network Architectures 总被引:3,自引:1,他引:2
In this research, we work with data of futures contracts on foreign exchange rates for British pound (BP), Canadian dollar
(CD), and Japanese yen (JY) that are traded at the Chicago Mercantile Exchange (CME) against US dollars. We model relationships
between exchange rates in these currencies using linear models, feed forward artificial neural networks (ANN), and three versions
of recurrent neural networks (RNN1, RNN2 and RNN3) for predicting exchange rates in these currencies against the US dollar.
Our results on forecast evaluations based on AGS test the tests of forecast equivalence between any two competing models among
the entire models employed for each of the series show that ANN and the three versions of RNN models offer superior forecasts
for predicting BP, CD and JY exchange rates although the forecast evaluations based on MGN test are in sharp contrast. On
the other hand forecast based on SIGN test shows that ANN and all the versions of RNN models offer superior forecasts for
BP and CD in exception of JY exchange rates. The results for forecast evaluation for all the models for each of the series
based on summary measures of forecast evaluations show that RNN3 model appears to offer the most accurate predictions of BP
and RNN1 for JP exchange rates. However, none of the RNN models appear to be statistically superior to the benchmark (i.e.,
linear model) for predicting CD exchange rates.
相似文献
955.
956.
A new approach to the design of a neural network (NN) based navigator is proposed in which the mobile robot travels to a pre-defined
goal position safely and efficiently without any prior map of the environment. This navigator can be optimized for any user-defined
objective function through the use of an evolutionary algorithm. The motivation of this research is to develop an efficient
methodology for general goal-directed navigation in generic indoor environments as opposed to learning specialized primitive
behaviors in a limited environment. To this end, a modular NN has been employed to achieve the necessary generalization capability
across a variety of indoor environments. Herein, each NN module takes charge of navigating in a specialized local environment,
which is the result of decomposing the whole path into a sequence of local paths through clustering of all the possible environments.
We verify the efficacy of the proposed algorithm over a variety of both simulated and real unstructured indoor environments
using our autonomous mobile robot platform. 相似文献
957.
An automatic road sign recognition system first locates road signs within images captured by an imaging sensor on-board of
a vehicle, and then identifies the detected road signs. This paper presents an automatic neural-network-based road sign recognition
system. First, a study of the existing road sign recognition research is presented. In this study, the issues associated with
automatic road sign recognition are described, the existing methods developed to tackle the road sign recognition problem
are reviewed, and a comparison of the features of these methods is given. Second, the developed road sign recognition system
is described. The system is capable of analysing live colour road scene images, detecting multiple road signs within each
image, and classifying the type of road signs detected. The system consists of two modules: detection and classification.
The detection module segments the input image in the hue-saturation-intensity colour space, and then detects road signs using
a Multi-layer Perceptron neural-network. The classification module determines the type of detected road signs using a series
of one to one architectural Multi-layer Perceptron neural networks. Two sets of classifiers are trained using the Resillient-Backpropagation
and Scaled-Conjugate-Gradient algorithms. The two modules of the system are evaluated individually first. Then the system
is tested as a whole. The experimental results demonstrate that the system is capable of achieving an average recognition
hit-rate of 95.96% using the scaled-conjugate-gradient trained classifiers. 相似文献
958.
Michael M. Li Brijesh Verma Xiaolong Fan Kevin Tickle 《Neural computing & applications》2008,17(4):391-397
This paper investigates a new method to solve the inverse problem of Rutherford backscattering (RBS) data. The inverse problem
is to determine the sample structure information from measured spectra, which can be defined as a function approximation problem.
We propose using radial basis function (RBF) neural networks to approximate an inverse function. Each RBS spectrum, which
may contain up to 128 data points, is compressed by the principal component analysis, so that the dimensionality of input
data and complexity of the network are reduced significantly. Our theoretical consideration is tested by numerical experiments
with the example of the SiGe thin film sample and corresponding backscattering spectra. A comparison of the RBF method with
multilayer perceptrons reveals that the former has better performance in extracting structural information from spectra. Furthermore,
the proposed method can handle redundancies properly, which are caused by the constraint of output variables. This study is
the first method based on RBF to deal with the inverse RBS data analysis problem. 相似文献
959.
Specification of communicating processes: temporal logic versus refusals-based refinement 总被引:1,自引:1,他引:0
Gavin Lowe 《Formal Aspects of Computing》2008,20(3):277-294
In this paper we consider the relationship between refinement-oriented specification and specifications using a temporal logic.
We investigate the extent to which one can check whether a program in a process algebra, such as Communicating Sequential
Processes (CSP), satisfies a temporal logic specification using a refinement-based model checker, such as FDR. We consider
what atomic formulae are appropriate in a temporal logic for specifying communicating processes, in particular where one wants
to talk about the availability of events. We then show that, perhaps surprisingly, the standard stable failures model is not
adequate for capturing specifications in such a logic: instead the refusal traces model must be used. We formalise the logic
by giving it a semantics in this model. We show that the temporal operators eventually and until, and negation, cannot, in general, be tested for via simple refinement checks. For the remaining fragment of the logic, we
present a translation into simple refinement checks. Finally, we show that refusal traces equivalence is characterised by
a slightly augmented version of that fragment.
M. J. Butler 相似文献
960.
This work presents a driving system for a peristaltic micropump that is based on piezoelectric actuation. The effects of the
actuation sequence on pump performance are also considered. A valveless peristaltic micropump based on piezoelectric actuation
is designed and fabricated using microelectromechanical system technology. The pump has three parts––silicon, Pyrex glass
and commercially available bulk PZT (lead zirconate titanate) chips. The peristaltic micropump actuated by PZT chips comprises
three chambers that are in series. The driving system consists of an ATmega 8535 microprocessor, a high voltage power supply,
three differential amplifiers, a phase controller, an A/D converter, a 555 oscillator and an LCD module. It is supplied via
a 110 Vrms 60-Hz AC line and is programmable. The system can produce step-function signals with voltages of up to 100 Vpp and frequencies ranging from 10 Hz to 1 kHz, as the inputs for the pump. Fluid pumping with air is successfully demonstrated.
Additionally, 3-, 4- and 6-phase actuation sequences for the pump are designed and used to study the effects on pump performance,
as revealed by the flow rate and the displacement of a pump diaphragm. The experimental results show that the flow rate and
the displacement of the diaphragm actuated by the 4-phase sequence exceed those actuated by the 3- and 6-phase sequences.
A flow rate of 17.6 μl min−1 and a displacement of 2.91 μm (peak-to-peak) in 4-phase peristaltic motion are achieved at 100 Hz and 100 Vpp. The results demonstrate that the pump actuated in the 4-phase sequence is the most efficient. Consequently, the actuation
sequences can affect the pump performance. 相似文献