全文获取类型
收费全文 | 10483篇 |
免费 | 1543篇 |
国内免费 | 1303篇 |
专业分类
电工技术 | 797篇 |
综合类 | 925篇 |
化学工业 | 258篇 |
金属工艺 | 162篇 |
机械仪表 | 464篇 |
建筑科学 | 147篇 |
矿业工程 | 85篇 |
能源动力 | 163篇 |
轻工业 | 73篇 |
水利工程 | 88篇 |
石油天然气 | 70篇 |
武器工业 | 119篇 |
无线电 | 1324篇 |
一般工业技术 | 868篇 |
冶金工业 | 337篇 |
原子能技术 | 23篇 |
自动化技术 | 7426篇 |
出版年
2024年 | 101篇 |
2023年 | 210篇 |
2022年 | 349篇 |
2021年 | 354篇 |
2020年 | 413篇 |
2019年 | 378篇 |
2018年 | 348篇 |
2017年 | 492篇 |
2016年 | 511篇 |
2015年 | 614篇 |
2014年 | 734篇 |
2013年 | 857篇 |
2012年 | 825篇 |
2011年 | 883篇 |
2010年 | 677篇 |
2009年 | 726篇 |
2008年 | 806篇 |
2007年 | 732篇 |
2006年 | 593篇 |
2005年 | 505篇 |
2004年 | 388篇 |
2003年 | 315篇 |
2002年 | 282篇 |
2001年 | 231篇 |
2000年 | 188篇 |
1999年 | 120篇 |
1998年 | 106篇 |
1997年 | 97篇 |
1996年 | 76篇 |
1995年 | 68篇 |
1994年 | 49篇 |
1993年 | 49篇 |
1992年 | 35篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
将禁忌搜索算法应用于VLSI门阵列的布局问题,建立了以总线长度和通道拥挤度的布局目标函数,用禁忌搜索算法求解目标函数的最小值,通过实验仿真,将本算法和遗传算法进行了比较,结果表明不论在解的质量和收敛速度方面,禁忌搜索算法优于遗传算法。 相似文献
92.
By identifying parameters such as stiffness values of a structural system, the numerical model can be updated to give more accurate response prediction or to monitor the state of the structure. Considerable progress has been made in this subject area, but most research works have considered only small systems. A major challenge lies in obtaining good identification results for systems with many unknown parameters. In this study, a non-classical approach is adopted involving the use of genetic algorithms (GA). Nevertheless, direct application of GA does not necessarily work, particularly with regards to computational efficiency in fine-tuning when the solution approaches the optimal value. A hybrid computational strategy is thus proposed, combining GA with a compatible local search operator. Two hybrid methods are formulated and illustrated by numerical simulation studies to perform significantly better than the GA method without local search. A fairly large structural system with 52 unknown parameters is identified with good results, taking into consideration the effects of incomplete measurement and noisy data. 相似文献
93.
An interactive agent-based system for concept-based web search 总被引:1,自引:0,他引:1
Search engines are useful tools in looking for information from the Internet. However, due to the difficulties of specifying appropriate queries and the problems of keyword-based similarity ranking presently encountered by search engines, general users are still not satisfied with the results retrieved. To remedy the above difficulties and problems, in this paper we present a multi-agent framework in which an interactive approach is proposed to iteratively collect a user's feedback from the pages he has identified. By analyzing the pages gathered, the system can then gradually formulate queries to efficiently describe the content a user is looking for. In our framework, the evolution strategies are employed to evolve critical feature words for concept modeling in query formulation. The experimental results show that the framework developed is efficient and useful to enhance the quality of web search, and the concept-based semantic search can thus be achieved. 相似文献
94.
Dohnal Vlastislav Gennaro Claudio Savino Pasquale Zezula Pavel 《Multimedia Tools and Applications》2003,21(1):9-33
In order to speedup retrieval in large collections of data, index structures partition the data into subsets so that query requests can be evaluated without examining the entire collection. As the complexity of modern data types grows, metric spaces have become a popular paradigm for similarity retrieval. We propose a new index structure, called D-Index, that combines a novel clustering technique and the pivot-based distance searching strategy to speed up execution of similarity range and nearest neighbor queries for large files with objects stored in disk memories. We have qualitatively analyzed D-Index and verified its properties on actual implementation. We have also compared D-Index with other index structures and demonstrated its superiority on several real-life data sets. Contrary to tree organizations, the D-Index structure is suitable for dynamic environments with a high rate of delete/insert operations. 相似文献
95.
This two-part paper presents modelling and scheduling approaches of flexible manufacturing systems using Petri nets (PNs) and artificial intelligence (AI)-based heuristic search methods. In Part I, PN-based modelling approaches and basic AI-based heuristic search algorithms were presented. In Part II, a new heuristic function that exploits PN information is proposed. Heuristic information obtained from the PN model is used to dramatically reduce the search space. This heuristic is derived from a new concept, the resource cost reachability matrix, which builds on the properties of B-nets proposed in Part I. Two hybrid search algorithms, (1) an approach to model dispatching rules using analysis information provided by the PN simulation and (2) an approach of the modified stage-search algorithm, are proposed to reduce the complexity of large systems. A random problem generator is developed to test the proposed methods. The experimental results show promising results. 相似文献
96.
Chaotic dynamics in a recurrent neural network model, in which limit cycle memory attractors are stored, is investigated by means of numerical methods. In particular, we focus on quick and sensitive response characteristics of chaotic memory dynamics to external input, which consists of part of an embedded memory attractor. We have calculated the correlation functions between the firing activities of neurons to understand the dynamical mechanisms of rapid responses. The results of the latter calculation show that quite strong correlations occur very quickly between almost all neurons within 1 ~ 2 updating steps after applying a partial input. They suggest that the existence of dynamical correlations or, in other words, transient correlations in chaos, play a very important role in quick and/or sensitive responses. 相似文献
97.
For more than a decade, researchers have actively explored the area of image/video analysis and retrieval. Yet one fundamental
problem remains largely unsolved: how to measure perceptual similarity between two objects. For this purpose, most researchers
employ a Minkowski-type metric. Unfortunately, the Minkowski metric does not reliably find similarities in objects that are
obviously alike. Through mining a large set of visual data, our team has discovered a perceptual distance function. We call
the discovered function the dynamic partial function (DPF). When we empirically compare DPF to Minkowski-type distance functions in image retrieval and in video shot-transition
detection using our image features, DPF performs significantly better. The effectiveness of DPF can be explained by similarity theories in cognitive psychology. 相似文献
98.
Efficient resource search method has significant impact on the scalability and availability of P2P network.Generally there are two search methods,pure Peer-to-Peer method and central index method.Recently,some search methods with super-peer concept are appearing,which are the compromise of those two methods and have favorable scalability and availability.In this paper,we compare the advantage and deficiency of these three kinds of search methods,and based on JX-TA platform design the super-peer search method. 相似文献
99.
Kim L. Blackmore Robert C. Williamson Iven M. Y. Mareels William A. Sethares 《Mathematics of Control, Signals, and Systems (MCSS)》1997,10(4):331-363
We propose and analyse a populational version of stepwise gradient descent suitable for a wide range of learning problems. The algorithm is motivated by genetic algorithms which update a population of solutions rather than just a single representative as is typical for gradient descent. This modification of traditional gradient descent (as used, for example, in the backpropogation algorithm) avoids getting trapped in local minima. We use an averaging analysis of the algorithm to relate its behaviour to an associated ordinary differential equation. We derive a result concerning how long one has to wait in order that, with a given high probability, the algorithm is within a certain neighbourhood of the global minimum. We also analyse the effect of different population sizes. An example is presented which corroborates our theory very well.This work was supported by the Australian Research Council. 相似文献
100.
Approximate similarity retrieval with M-trees 总被引:4,自引:0,他引:4
Pavel Zezula Pasquale Savino Giuseppe Amato Fausto Rabitti 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):275-293
Motivated by the urgent need to improve the efficiency of similarity queries, approximate similarity retrieval is investigated
in the environment of a metric tree index called the M-tree. Three different approximation techniques are proposed, which
show how to forsake query precision for improved performance. Measures are defined that can quantify the improvements in performance
efficiency and the quality of approximations. The proposed approximation techniques are then tested on various synthetic and
real-life files. The evidence obtained from the experiments confirms our hypothesis that a high-quality approximated similarity
search can be performed at a much lower cost than that needed to obtain the exact results. The proposed approximation techniques
are scalable and appear to be independent of the metric used. Extensions of these techniques to the environments of other
similarity search indexes are also discussed.
Received July 7, 1998 / Accepted October 13, 1998 相似文献