全文获取类型
收费全文 | 469389篇 |
免费 | 4263篇 |
国内免费 | 1082篇 |
专业分类
电工技术 | 8365篇 |
综合类 | 275篇 |
化学工业 | 70948篇 |
金属工艺 | 22910篇 |
机械仪表 | 16194篇 |
建筑科学 | 9759篇 |
矿业工程 | 4288篇 |
能源动力 | 10377篇 |
轻工业 | 29248篇 |
水利工程 | 5866篇 |
石油天然气 | 14751篇 |
武器工业 | 40篇 |
无线电 | 51113篇 |
一般工业技术 | 104444篇 |
冶金工业 | 77070篇 |
原子能技术 | 14599篇 |
自动化技术 | 34487篇 |
出版年
2021年 | 4527篇 |
2019年 | 4277篇 |
2018年 | 7916篇 |
2017年 | 8207篇 |
2016年 | 8621篇 |
2015年 | 4888篇 |
2014年 | 8563篇 |
2013年 | 20076篇 |
2012年 | 12550篇 |
2011年 | 16302篇 |
2010年 | 13210篇 |
2009年 | 14899篇 |
2008年 | 15451篇 |
2007年 | 15076篇 |
2006年 | 12840篇 |
2005年 | 11301篇 |
2004年 | 11030篇 |
2003年 | 11094篇 |
2002年 | 10492篇 |
2001年 | 10792篇 |
2000年 | 10237篇 |
1999年 | 10084篇 |
1998年 | 22905篇 |
1997年 | 16577篇 |
1996年 | 12718篇 |
1995年 | 9803篇 |
1994年 | 8902篇 |
1993年 | 8991篇 |
1992年 | 6942篇 |
1991年 | 6882篇 |
1990年 | 6853篇 |
1989年 | 6536篇 |
1988年 | 6354篇 |
1987年 | 5841篇 |
1986年 | 5697篇 |
1985年 | 6103篇 |
1984年 | 5761篇 |
1983年 | 5537篇 |
1982年 | 5214篇 |
1981年 | 5194篇 |
1980年 | 5139篇 |
1979年 | 5121篇 |
1978年 | 5137篇 |
1977年 | 5635篇 |
1976年 | 7026篇 |
1975年 | 4591篇 |
1974年 | 4638篇 |
1973年 | 4641篇 |
1972年 | 4080篇 |
1971年 | 3625篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
141.
Several variations of cache-based checkpointing for rollback error recovery from transient errors in shared-memory multiprocessors have been recently developed. By modifying the cache replacement policy, these techniques use the inherent redundancy in the memory hierarchy to periodically checkpoint the computation state. Three schemes, different in the manner in which they avoid rollback propagation, are evaluated in this paper. By simulation with address traces from parallel applications running on an Encore Multimax shared-memory multiprocessor, we evaluate the performance effect of integrating the recovery schemes in the cache coherence protocol. Our results indicate that the cache-based schemes can provide checkpointing capability with low performance overhead, but with uncontrollable high variability in the checkpoint interval 相似文献
142.
We present new methods for load balancing of unstructured tree computations on large-scale SIMD machines, and analyze the scalability of these and other existing schemes. An efficient formulation of tree search on an SIMD machine consists of two major components: a triggering mechanism, which determines when the search space redistribution must occur to balance the search space over processors, and a scheme to redistribute the search space. We have devised a new redistribution mechanism and a new triggering mechanism. Either of these can be used in conjunction with triggering and redistribution mechanisms developed by other researchers. We analyze the scalability of these mechanisms and verify the results experimentally. The analysis and experiments show that our new load-balancing methods are highly scalable on SIMD architectures. Their scalability is shown to he no worse than that of the best load-balancing schemes on MIMD architectures. We verify our theoretical results by implementing the 15-puzzle problem on a CM-2 SIMD parallel computer 相似文献
143.
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
144.
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
145.
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
146.
We describe a binding environment for the AND and OR parallel execution of logic programs that is suitable for both shared and nonshared memory multiprocessors. The binding environment was designed with a view of rendering a compiler using this binding environment machine independent. The binding environment is similar to closed environments proposed by J. Conery. However, unlike Conery's scheme, it supports OR and independent AND parallelism on both types of machines. The term representation, the algorithms for unification and the join algorithms for parallel AND branches are presented in this paper. We also detail the differences between our scheme and Conery's scheme. A compiler based on this binding environment has been implemented on a platform for machine independent parallel programming called the Chare Kernel 相似文献
147.
Shrivastava S.K. McCue D.L. 《Parallel and Distributed Systems, IEEE Transactions on》1994,5(4):421-432
The object-oriented approach to system structuring has found widespread acceptance among designers and developers of robust computing systems. The authors propose a system structure for distributed programming systems that support persistent objects and describe how properties such as persistence and recoverability can be implemented. The proposed structure is modular, permitting easy exploitation of any distributed computing facilities provided by the underlying system. An existing system constructed according to the principles espoused here is examined to illustrate the practical utility of the proposed approach to system structuring 相似文献
148.
This paper proposes a system based on a parallel genetic algorithm with enhanced encoding and operational abilities. The system, used to evolve feedforward artificial neural networks, has been applied to two widely different problem areas: Boolean function learning and robot control. It is shown that the good results obtained in both cases are due to two factors: first, the enhanced exploration abilities provided by the search-space reducing evolution of both coding granularity and network topology, and, second, the enhanced exploitational abilities due to a recently proposed cooperative local optimizing genetic operator. 相似文献
149.
What is the implication for business when information technology (IT) changes in the workplace without a commensurate change in the composition of business programs educating tomorrow's employees? A survey of MBA graduates forms the basis of this article on the IT skills needed in the marketplace. 相似文献
150.