全文获取类型
收费全文 | 1533101篇 |
免费 | 24650篇 |
国内免费 | 7005篇 |
专业分类
电工技术 | 34556篇 |
综合类 | 6396篇 |
化学工业 | 272281篇 |
金属工艺 | 64733篇 |
机械仪表 | 43466篇 |
建筑科学 | 46618篇 |
矿业工程 | 11549篇 |
能源动力 | 50349篇 |
轻工业 | 114914篇 |
水利工程 | 15631篇 |
石油天然气 | 37688篇 |
武器工业 | 144篇 |
无线电 | 197484篇 |
一般工业技术 | 288585篇 |
冶金工业 | 175697篇 |
原子能技术 | 34085篇 |
自动化技术 | 170580篇 |
出版年
2021年 | 15610篇 |
2020年 | 11886篇 |
2019年 | 14666篇 |
2018年 | 16383篇 |
2017年 | 15901篇 |
2016年 | 21809篇 |
2015年 | 17451篇 |
2014年 | 28737篇 |
2013年 | 88021篇 |
2012年 | 36123篇 |
2011年 | 49143篇 |
2010年 | 43302篇 |
2009年 | 51579篇 |
2008年 | 45665篇 |
2007年 | 43196篇 |
2006年 | 45081篇 |
2005年 | 40100篇 |
2004年 | 42073篇 |
2003年 | 41845篇 |
2002年 | 40781篇 |
2001年 | 37728篇 |
2000年 | 36209篇 |
1999年 | 35317篇 |
1998年 | 48611篇 |
1997年 | 41453篇 |
1996年 | 36847篇 |
1995年 | 31633篇 |
1994年 | 29599篇 |
1993年 | 29412篇 |
1992年 | 26459篇 |
1991年 | 23549篇 |
1990年 | 23831篇 |
1989年 | 22971篇 |
1988年 | 21455篇 |
1987年 | 19706篇 |
1986年 | 19111篇 |
1985年 | 22443篇 |
1984年 | 22415篇 |
1983年 | 20402篇 |
1982年 | 19340篇 |
1981年 | 19467篇 |
1980年 | 18147篇 |
1979年 | 18638篇 |
1978年 | 17825篇 |
1977年 | 17904篇 |
1976年 | 19267篇 |
1975年 | 16094篇 |
1974年 | 15557篇 |
1973年 | 15660篇 |
1972年 | 13111篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
McKinley P.K. Xu H. Esfahanian A.-H. Ni L.M. 《Parallel and Distributed Systems, IEEE Transactions on》1994,5(12):1252-1265
Multicast communication, in which the same message is delivered from a source node to an arbitrary number of destination nodes, is being increasingly demanded in parallel computing. System supported multicast services can potentially offer improved performance, increased functionality, and simplified programming, and may in turn be used to support various higher-level operations for data movement and global process control. This paper presents efficient algorithms to implement multicast communication in wormhole-routed direct networks, in the absence of hardware multicast support, by exploiting the properties of the switching technology. Minimum-time multicast algorithms are presented for n-dimensional meshes and hypercubes that use deterministic, dimension-ordered routing of unicast messages. Both algorithms can deliver a multicast message to m-1 destinations in [log 2 m] message passing steps, while avoiding contention among the constituent unicast messages. Performance results of implementations on a 64-node nCUBE-2 hypercube and a 168-node Symult 2010 2-D mesh are given 相似文献
962.
Weight smoothing to improve network generalization 总被引:2,自引:0,他引:2
A weight smoothing algorithm is proposed in this paper to improve a neural network's generalization capability. The algorithm can be used when the data patterns to be classified are presented on an n-dimensional grid (n>/=1) and there exists some correlations among neighboring data points within a pattern. For a fully-interconnected feedforward net, no such correlation information is embedded into the architecture. Consequently, the correlations can only be extracted through sufficient amount of network training. With the proposed algorithm, a smoothing constraint is incorporated into the objective function of backpropagation to reflect the neighborhood correlations and to seek those solutions that have smooth connection weights. Experiments were performed on problems of waveform classification, multifont alphanumeric character recognition, and handwritten numeral recognition. The results indicate that (1) networks trained with the algorithm do have smooth connection weights, and (2) they generalize better. 相似文献
963.
in the above paper Yu (IEEE Trans. Neural Networks, vol.3, no.6, p.1019-21 (1992)) claims to prove that local minima do not exist in the error surface of backpropagation networks being trained on data with t distinct input patterns when the network is capable of exactly representing arbitrary mappings on t input patterns. The commenter points out that the proof presented is flawed, so that the resulting claims remain unproved. In reply, Yu points out that the undesired phenomenon that was sited can be avoided by simply imposing the arbitrary mapping capacity of the network on lemma 1 in the article. 相似文献
964.
Network information criterion-determining the number of hiddenunits for an artificial neural network model 总被引:6,自引:0,他引:6
The problem of model selection, or determination of the number of hidden units, can be approached statistically, by generalizing Akaike's information criterion (AIC) to be applicable to unfaithful (i.e., unrealizable) models with general loss criteria including regularization terms. The relation between the training error and the generalization error is studied in terms of the number of the training examples and the complexity of a network which reduces to the number of parameters in the ordinary statistical theory of AIC. This relation leads to a new network information criterion which is useful for selecting the optimal network model based on a given training set. 相似文献
965.
966.
Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation. 相似文献
967.
Different hierarchical models in pattern analysis and recognition are proposed, based on occurrence probability of patterns. As an important application of recognizing handprinted characters, three typical kinds of hierarchical models such asM
89-89,M
89-36 andM
36-36 have been presented, accompanied by the computer algorithms for computing recognition rates of pattern parts. Moreover, a comparative study of their recognition rates has been conducted theoretically; and numerical experiments have been carried out to verify the analytical conclusions made. Various hierarchical models deliberated in this paper can provide users more or better choices of pattern models in practical application, and lead to a uniform computational scheme (or code). The recognition rates of parts can be improved remarkably by a suitable hierarchical model. For the modelM
89-36 in which case some of the Canadian standard handprinted characters have multiple occurrence probabilities, the total mean recognition rates of the given sample may reach 120% of that by the model proposed by Li et al., and 156% of that obtained from the subjective experiments reported by Suen. 相似文献
968.
Michael D. Vose 《Annals of Mathematics and Artificial Intelligence》1994,10(4):423-434
This paper examines the influence of mutation on the behavior of genetic algorithms through a series of examples and experiments. The results provide an existence proof that mutation is a far more profound operator than has ever been recognized. Implications are discussed which point to the importance of open questions concerning genetic algorithms. The paper also reviews the implementation of the infinite population model of Vose which forms the computational basis of this investigation. 相似文献
969.
The bounded disorder file organization proposed by W. Litwin and D.B. Lomet (1987) uses a combination of hashing and tree indexing. Lomet provided an approximate analysis with the mention of the difficulty involved in exact modeling of data nodes, which motivated this work. In an earlier paper (M.V. Ramakrishna and P. Mukhopadhyay, 1988) we provided an exact model and analysis of the data nodes, which is based on the solution of a classical sequential occupancy problem. After summarizing the analysis of data nodes, an alternate file growth method based on repeated trials using universal hashing is proposed and analyzed. We conclude that the alternate file growth method provides simplicity and significant improvement in storage utilization 相似文献
970.
Volcano-an extensible and parallel query evaluation system 总被引:2,自引:0,他引:2
To investigate the interactions of extensibility and parallelism in database query processing, we have developed a new dataflow query execution system called Volcano. The Volcano effort provides a rich environment for research and education in database systems design, heuristics for query optimization, parallel query execution, and resource allocation. Volcano uses a standard interface between algebra operators, allowing easy addition of new operators and operator implementations. Operations on individual items, e.g., predicates, are imported into the query processing operators using support functions. The semantics of support functions is not prescribed; any data type including complex objects and any operation can be realized. Thus, Volcano is extensible with new operators, algorithms, data types, and type-specific methods. Volcano includes two novel meta-operators. The choose-plan meta-operator supports dynamic query evaluation plans that allow delaying selected optimization decisions until run-time, e.g., for embedded queries with free variables. The exchange meta-operator supports intra-operator parallelism on partitioned datasets and both vertical and horizontal inter-operator parallelism, translating between demand-driven dataflow within processes and data-driven dataflow between processes. All operators, with the exception of the exchange operator, have been designed and implemented in a single-process environment, and parallelized using the exchange operator. Even operators not yet designed can be parallelized using this new operator if they use and provide the interator interface. Thus, the issues of data manipulation and parallelism have become orthogonal, making Volcano the first implemented query execution engine that effectively combines extensibility and parallelism 相似文献