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81.
Tong-Hua Su Author Vitae Tian-Wen Zhang Author Vitae Hu-Jie Huang 《Pattern recognition》2009,42(1):167-182
Great challenges are faced in the off-line recognition of realistic Chinese handwriting. This paper presents a segmentation-free strategy based on Hidden Markov Model (HMM) to handle this problem, where character segmentation stage is avoided prior to recognition. Handwritten textlines are first converted to observation sequence by sliding windows. Then embedded Baum-Welch algorithm is adopted to train character HMMs. Finally, best character string maximizing the a posteriori is located through Viterbi algorithm. Experiments are conducted on the HIT-MW database written by more than 780 writers. The results show the feasibility of such systems and reveal apparent complementary capacities between the segmentation-free systems and the segmentation-based ones. 相似文献
82.
In this paper, we first introduce the use of an interactive hidden Markov model (IHMM) for modeling and analyzing default
data in a sector. Under the IHMM, transitions of the hidden risk states of the sector depend on the observed number of bonds
in the sector that default in the current time period. This incorporates the feedback effect of the number of defaults on
the transitions of the hidden risk states. This feature seems to be more realistic and does not enjoy by the traditional HMMs.
We then develop a “dynamic” version of the binomial expansion technique (BET) modulated by the IHMM for modeling the occurrence
of defaults of bonds issued by firms in the same sector. Under the BET modulated by the IHMM, the number of bonds defaulting
in each time period follows a Markov-modulated binomial distribution with the probability of defaulting of each bond depending
on the states of the IHMM, which represent the hidden risk states of the sector. Efficient method will be presented for estimating
the model parameters in the BET modulated by the IHMM. We shall compare the hidden risk state process extracted from the IHMM-modulated
BET with that extracted from the BET modulated by HMM in order to illustrate the significance of the feedback effect using
real data. We shall also present the estimation results for the BET modulated by the IHMM and compare them with those for
the BET modulated by the HMM. 相似文献
83.
A structured-based neural network (NN) with backpropagation through structure (BPTS) algorithm is conducted for image classification
in organizing a large image database, which is a challenging problem under investigation. Many factors can affect the results
of image classification. One of the most important factors is the architecture of a NN, which consists of input layer, hidden
layer and output layer. In this study, only the numbers of nodes in hidden layer (hidden nodes) of a NN are considered. Other
factors are kept unchanged. Two groups of experiments including 2,940 images in each group are used for the analysis. The
assessment of the effects for the first group is carried out with features described by image intensities, and, the second
group uses features described by wavelet coefficients. Experimental results demonstrate that the effects of the numbers of
hidden nodes on the reliability of classification are significant and non-linear. When the number of hidden nodes is 17, the
classification rate on training set is up to 95%, and arrives at 90% on the testing set. The results indicate that 17 is an
appropriate choice for the number of hidden nodes for the image classification when a structured-based NN with BPTS algorithm
is applied. 相似文献
84.
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86.
集对分析是处理不确定性问题的新方法,它通过联系度展示了研究对象间关系的详细结构。方法原理简单,使用方便,能解决很多实际水文水资源问题。简要介绍了集对分析的基本原理,重点分析了集对分析在水文水资源分析计算、预测和评价中的应用研究进展,展望了集对分析在水文水资源领域的研究目标、内容和拟解决的关键问题。 相似文献
87.
A discrete-time control problem of a finite-state hidden Markov chain partially observed in a fractional Gaussian process is discussed using filtering. The control problem is then recast as a separated problem with information variables given by the unnormalized conditional probabilities of the whole path of the hidden Markov chain. A dynamic programming result and a minimum principle are obtained. 相似文献
88.
A hidden Markov model (HMM) with a special structure that captures the ‘semi’-property of hidden semi-Markov models (HSMMs) is considered. The proposed model allows arbitrary dwell-time distributions in the states of the Markov chain. For dwell-time distributions with finite support the HMM formulation is exact while for those that have infinite support, e.g. the Poisson, the distribution can be approximated with arbitrary accuracy. A benefit of using the HMM formulation is that it is easy to incorporate covariates, trend and seasonal variation particularly in the hidden component of the model. In addition, the formulae and methods for forecasting, state prediction, decoding and model checking that exist for ordinary HMMs are applicable to the proposed class of models. An HMM with explicitly modeled dwell-time distributions involving seasonality is used to model daily rainfall occurrence for sites in Bulgaria. 相似文献
89.
90.
研究隐马尔可夫模型(HMM)的一种有区分力的训练方法.在多层前向神经网络的
框架中实现了HMM的前向概率计算.基于这一框架,利用偏导数的反向传播计算方法,通
过梯度上升的优化过程来实现互信息的最大化,从而对HMM进行有区分力的训练.这一
训练方法被称之为HMM的反向传播训练方法.此外,还设计了一个用以实现这一训练方
法的在数值计算上具有强鲁棒性的算法.语音识别的实验结果证实了这一训练方法的优越
性. 相似文献