全文获取类型
收费全文 | 243802篇 |
免费 | 2949篇 |
国内免费 | 1244篇 |
专业分类
电工技术 | 4863篇 |
综合类 | 265篇 |
化学工业 | 35468篇 |
金属工艺 | 10880篇 |
机械仪表 | 7071篇 |
建筑科学 | 6241篇 |
矿业工程 | 481篇 |
能源动力 | 6285篇 |
轻工业 | 24188篇 |
水利工程 | 1836篇 |
石油天然气 | 1335篇 |
武器工业 | 3篇 |
无线电 | 31064篇 |
一般工业技术 | 44930篇 |
冶金工业 | 50157篇 |
原子能技术 | 3867篇 |
自动化技术 | 19061篇 |
出版年
2021年 | 1572篇 |
2019年 | 1430篇 |
2018年 | 2322篇 |
2017年 | 2225篇 |
2016年 | 2445篇 |
2015年 | 1909篇 |
2014年 | 3163篇 |
2013年 | 10807篇 |
2012年 | 5454篇 |
2011年 | 7802篇 |
2010年 | 6297篇 |
2009年 | 6970篇 |
2008年 | 7569篇 |
2007年 | 7673篇 |
2006年 | 7039篇 |
2005年 | 6529篇 |
2004年 | 6258篇 |
2003年 | 6275篇 |
2002年 | 6255篇 |
2001年 | 6387篇 |
2000年 | 5809篇 |
1999年 | 6423篇 |
1998年 | 16580篇 |
1997年 | 11617篇 |
1996年 | 8960篇 |
1995年 | 6693篇 |
1994年 | 5912篇 |
1993年 | 5733篇 |
1992年 | 4054篇 |
1991年 | 3997篇 |
1990年 | 3583篇 |
1989年 | 3510篇 |
1988年 | 3446篇 |
1987年 | 2910篇 |
1986年 | 2847篇 |
1985年 | 3415篇 |
1984年 | 3053篇 |
1983年 | 2745篇 |
1982年 | 2549篇 |
1981年 | 2568篇 |
1980年 | 2431篇 |
1979年 | 2276篇 |
1978年 | 2239篇 |
1977年 | 2811篇 |
1976年 | 4173篇 |
1975年 | 1900篇 |
1974年 | 1796篇 |
1973年 | 1787篇 |
1972年 | 1462篇 |
1971年 | 1317篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Two novel configurations for digitally tunable optical filters based on arrayed-waveguide grating (AWG) multiplexers are described in detail with emphasis on the connection of the AWG multiplexer and optical switches. Performance comparisons show that conventional configurations are disadvantaged by the switch size required and loss imbalance among the optical frequency-division-multiplexed (FDM) channels; the proposed configurations require only O(√(N)) switch elements to select one of N FDM channels, and the loss imbalance is lower by up to 75% in decibel 相似文献
42.
Sugawara F. Aoki K. Yamaguchi H. Sasaki K. Sasaki T. Fujisaki H. 《Electron Device Letters, IEEE》1997,18(10):483-485
A new lateral MOS-gated thyristor, called the Base-Current-Controlled Thyristor, is described. This device is designed so that most holes at the on-stage reach the P base through the floating P+ region adjacent to the P base and the on-state MOSFET. At the turn-off stage, the interruption of the hole current to the P base due to switching off the above MOSFET occurs simultaneously with the conventional turn-off operation. The concept of this device is verified experimentally by using the fabricated lateral device with the external MOSFET. This device exhibits a better trade-off relation between the on-state voltage and the turn-off time compared uith the conventional MOS-gated thyristor 相似文献
43.
Watanabe H. Komori J. Higashitani K. Sekine M. Koyama H. 《Semiconductor Manufacturing, IEEE Transactions on》1997,10(2):228-232
A novel monitoring method for plasma-charging damage is proposed. This method performs a quick and accurate evaluation using antenna PMOSFET. It was found that not only hot-carrier (HC) lifetime but transistor parameters such as initial gate current and substrate current were changed according to the degree of plasma-charging damage. However, the present work suggests that monitoring the shift of drain current after a few seconds of HC stress is a more accurate method to indicate plasma-charging damage. The monitoring method using the present test structure is demonstrated to be useful for realizing highly reliable devices 相似文献
44.
A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications 相似文献
45.
A constant-time algorithm for labeling the connected components of an N×N image on a reconfigurable network of N3 processors is presented. The main contribution of the algorithm is a novel constant-time technique for determining the minimum-labeled PE in each component. The number of processors used by the algorithm can be reduced to N/sup 2+(1/d/), for any 1⩽d⩽log N, if O(d) time is allowed 相似文献
46.
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
47.
We have developed a problem-solving framework, called ConClass, that is capable of classifying continuous real-time problems dynamically and concurrently on a distributed system. ConClass provides an efficient development environment for describing and decomposing a classification problem and synthesizing solutions. In ConClass, decomposed concurrent subproblems specified by the application developer effectively correspond to the actual distributed hardware elements. This scheme is useful for designing and implementing efficient distributed processing, making it easier to anticipate and evaluate system behavior. The ConClass system provides an object replication feature that prevents any particular object from being overloaded. In order to deal with an indeterminate amount of problem data, ConClass dynamically creates object networks that justify hypothesized solutions, and thus achieves a dynamic load distribution. A number of efficient execution mechanisms that manage a variety of asynchronous aspects of distributed processing have been implemented without using schedulers or synchronization schemes that are liable to develop bottlenecks. We have confirmed the efficiency of parallel distributed processing and load balancing of ConClass with an experimental application 相似文献
48.
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
49.
This paper is a reply to Laviolette and Seaman's critical discussion of fuzzy set theory. Rather than questioning the interest of the Bayesian approach to uncertainty, some reasons why Bayesian find the idea of a fuzzy set not palatable are laid bare. Some links between fuzzy sets and probability that Laviolette and Seaman seem not to be aware of are pointed out. These links suggest that, contrary to the claim sometimes found in the literature, probability theory is not a special case of fuzzy set theory. The major objection to Laviolette and Seaman is that they found their critique on as very limited view of fuzzy sets, including debatable papers, while they fail to account for significant works pertaining to axiomatic derivation of fuzzy set connectives, possibility theory, fuzzy random variables, among others 相似文献
50.
In the editorial by J.C. Bezdek (ibid., p.1), an example is presented to demonstrate differences between fuzzy membership and probability. The authors argue that probability can be used in a way much more closely analogous to this use of fuzzy membership, weakening the argument for the latter 相似文献