全文获取类型
收费全文 | 13092篇 |
免费 | 2031篇 |
国内免费 | 1407篇 |
专业分类
电工技术 | 1281篇 |
综合类 | 1682篇 |
化学工业 | 410篇 |
金属工艺 | 166篇 |
机械仪表 | 801篇 |
建筑科学 | 721篇 |
矿业工程 | 264篇 |
能源动力 | 363篇 |
轻工业 | 250篇 |
水利工程 | 398篇 |
石油天然气 | 212篇 |
武器工业 | 137篇 |
无线电 | 1106篇 |
一般工业技术 | 846篇 |
冶金工业 | 273篇 |
原子能技术 | 40篇 |
自动化技术 | 7580篇 |
出版年
2024年 | 42篇 |
2023年 | 131篇 |
2022年 | 232篇 |
2021年 | 315篇 |
2020年 | 405篇 |
2019年 | 404篇 |
2018年 | 366篇 |
2017年 | 469篇 |
2016年 | 533篇 |
2015年 | 615篇 |
2014年 | 864篇 |
2013年 | 866篇 |
2012年 | 1017篇 |
2011年 | 1117篇 |
2010年 | 936篇 |
2009年 | 955篇 |
2008年 | 1083篇 |
2007年 | 1089篇 |
2006年 | 955篇 |
2005年 | 796篇 |
2004年 | 610篇 |
2003年 | 550篇 |
2002年 | 387篇 |
2001年 | 314篇 |
2000年 | 269篇 |
1999年 | 203篇 |
1998年 | 139篇 |
1997年 | 132篇 |
1996年 | 130篇 |
1995年 | 120篇 |
1994年 | 85篇 |
1993年 | 57篇 |
1992年 | 57篇 |
1991年 | 53篇 |
1990年 | 49篇 |
1989年 | 40篇 |
1988年 | 31篇 |
1987年 | 17篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1976年 | 4篇 |
1963年 | 7篇 |
1961年 | 8篇 |
1960年 | 4篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Xiang Zhou 《Information Processing Letters》2008,108(1):3-9
In this article, with Ehrenfeucht-Fraïssé games we prove that Δ1≠Δ0 on BFR, which implies Δ≠Δ0 on BFR, and thus solve an open problem raised by Albert Atserias in his dissertation (Δ0,Δ1,Δ are fragments of first order logic and BFR is a class of finite sets which in essence is equivalent to a class of finite pure arithmetic structures with built-in BIT predicate). 相似文献
13.
If the production process, production equipment, or material changes, it becomes necessary to execute pilot runs before mass production in manufacturing systems. Using the limited data obtained from pilot runs to shorten the lead time to predict future production is this worthy of study. Although, artificial neural networks are widely utilized to extract management knowledge from acquired data, sufficient training data is the fundamental assumption. Unfortunately, this is often not achievable for pilot runs because there are few data obtained during trial stages and theoretically this means that the knowledge obtained is fragile. The purpose of this research is to utilize bootstrap to generate virtual samples to fill the information gaps of sparse data. The results of this research indicate that the prediction error rate can be significantly decreased by applying the proposed method to a very small data set. 相似文献
14.
DU Jia-li LIU Yuan-yuan YU Ping-fang 《通讯和计算机》2009,6(7):68-78
By means of analysis of artificial intervention in ready-retrieved text, training set used to compare with new texts from large-scale real texts corpus is provided. It is based on the data-originated presentation of training set that a special formula to calculate semantic cohesion between new texts and training set is devised. The semantic cohesion of new text is the average value of semantic evaluation of all elements involved, and semantic evaluation of an element depends on its semantic relevance with the training set and on the semantic ratio of its domain to synonymous domain. In terms of empirical verification a conclusion is drawn that semantic cohesion is the key measurement standard of textual retrieval. Despite the advantages of textual retrieval, limitations of formula-raised condition and analyst's accomplishments make the analysis involved in this paper imperfect. 相似文献
15.
16.
Yao-Tien Chen Author Vitae 《Pattern recognition》2010,43(11):3699-3711
This paper proposes an alternative criterion derived from the Bayesian risk classification error for image segmentation. The proposed model introduces a region-based force determined through the difference of the posterior image densities for the different classes, a term based on the prior probability derived from Kullback-Leibler information number, and a regularity term adopted to avoid the generation of excessively irregular and small segmented regions. Compared with other level set methods, the proposed approach relies on the optimum decision of pixel classification and the estimates of prior probabilities; thus the approach has more reliability in theory and practice. Experiments show that the proposed approach is able to extract the complicated shapes of targets and robust for various types of medical images. Moreover, the algorithm can be easily extendable for multiphase segmentation. 相似文献
17.
在目标检测与提取中,传统的蛇模型和基于活动轮廓的局部区域检测方法受到初始条件或者自身的收敛性约束的影响,不仅时间花费多,而且不具备鲁棒性。本文提出一种基于C V模型的变分水平集的目标检测与提取方法,通过大量实验验证,在花费时间和鲁棒性上得到了显著的改善。 相似文献
18.
Duan Li Xiaoling Sun Jianjun Gao Shenshen Gu Xiaojin ZhengAuthor vitae 《Automatica》2011,47(9):2094-2098
Reachability is one of the most important behavioral properties of Petri nets. We propose in this paper a novel approach for solving the fundamental equation in the reachability analysis of acyclic Petri nets, which has been known to be NP-complete. More specifically, by adopting a revised version of the cell enumeration method for an arrangement of hyperplanes in discrete geometry, we develop an efficient solution scheme to identify firing count vector solution(s) to the fundamental equation on a bounded integer set, with a complexity bound of O((nu)n−m), where n is the number of transitions, m is the number of places and u is the upper bound of the number of firings for all individual transitions. 相似文献
19.
Vidroha Debroy Author VitaeW. Eric WongAuthor Vitae 《Journal of Systems and Software》2011,84(4):587-602
Test set size in terms of the number of test cases is an important consideration when testing software systems. Using too few test cases might result in poor fault detection and using too many might be very expensive and suffer from redundancy. We define the failure rate of a program as the fraction of test cases in an available test pool that result in execution failure on that program. This paper investigates the relationship between failure rates and the number of test cases required to detect the faults. Our experiments based on 11 sets of C programs suggest that an accurate estimation of failure rates of potential fault(s) in a program can provide a reliable estimate of adequate test set size with respect to fault detection and should therefore be one of the factors kept in mind during test set construction. Furthermore, the model proposed herein is fairly robust to incorrect estimations in failure rates and can still provide good predictive quality. Experiments are also performed to observe the relationship between multiple faults present in the same program using the concept of a failure rate. When predicting the effectiveness against a program with multiple faults, results indicate that not knowing the number of faults in the program is not a significant concern, as the predictive quality is typically not affected adversely. 相似文献
20.
We consider the following problem: Given a finite set of straight line segments in the plane, find a set of points of minimum size, so that every segment contains at least one point in the set. This problem can be interpreted as looking for a minimum number of locations of policemen, guards, cameras or other sensors, that can observe a network of streets, corridors, tunnels, tubes, etc. We show that the problem is strongly NP-complete even for a set of segments with a cubic graph structure, but in P for tree structures. 相似文献