全文获取类型
收费全文 | 31324篇 |
免费 | 5073篇 |
国内免费 | 4181篇 |
专业分类
电工技术 | 3679篇 |
技术理论 | 2篇 |
综合类 | 4304篇 |
化学工业 | 778篇 |
金属工艺 | 579篇 |
机械仪表 | 2345篇 |
建筑科学 | 1567篇 |
矿业工程 | 741篇 |
能源动力 | 995篇 |
轻工业 | 565篇 |
水利工程 | 762篇 |
石油天然气 | 669篇 |
武器工业 | 454篇 |
无线电 | 3520篇 |
一般工业技术 | 2316篇 |
冶金工业 | 1076篇 |
原子能技术 | 90篇 |
自动化技术 | 16136篇 |
出版年
2024年 | 194篇 |
2023年 | 541篇 |
2022年 | 959篇 |
2021年 | 1122篇 |
2020年 | 1288篇 |
2019年 | 1150篇 |
2018年 | 1130篇 |
2017年 | 1308篇 |
2016年 | 1419篇 |
2015年 | 1572篇 |
2014年 | 2006篇 |
2013年 | 2250篇 |
2012年 | 2487篇 |
2011年 | 2716篇 |
2010年 | 2170篇 |
2009年 | 2095篇 |
2008年 | 2238篇 |
2007年 | 2558篇 |
2006年 | 1926篇 |
2005年 | 1656篇 |
2004年 | 1337篇 |
2003年 | 1123篇 |
2002年 | 987篇 |
2001年 | 776篇 |
2000年 | 637篇 |
1999年 | 538篇 |
1998年 | 420篇 |
1997年 | 349篇 |
1996年 | 276篇 |
1995年 | 250篇 |
1994年 | 237篇 |
1993年 | 155篇 |
1992年 | 127篇 |
1991年 | 111篇 |
1990年 | 93篇 |
1989年 | 65篇 |
1988年 | 55篇 |
1987年 | 29篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 26篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1966年 | 10篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
An organization requires performing readiness-relevant activities to ensure successful implementation of an enterprise resource planning (ERP) system. This paper develops a novel approach to managing these interrelated activities to get ready for implementing an ERP system. The approach enables an organization to evaluate its ERP implementation readiness by assessing the degree to which it can achieve the interrelated readiness relevant activities using fuzzy cognitive maps. Based on the interrelationship degrees among the activities, the approach clusters the activities into manageable groups and prioritizes them. To help work out a readiness improvement plan, scenario analysis is conducted. 相似文献
3.
Electrocardiogram is the most commonly used tool for the diagnosis of cardiologic diseases. In order to help cardiologists to diagnose the arrhythmias automatically, new methods for automated, computer aided ECG analysis are being developed. In this paper, a Modified Artificial Bee Colony (MABC) algorithm for ECG heart beat classification is introduced. It is applied to ECG data set which is obtained from MITBIH database and the result of MABC is compared with seventeen other classifier's accuracy.In classification problem, some features have higher distinctiveness than others. In this study, in order to find higher distinctive features, a detailed analysis has been done on time domain features. By using the right features in MABC algorithm, high classification success rate (99.30%) is obtained. Other methods generally have high classification accuracy on examined data set, but they have relatively low or even poor sensitivities for some beat types. Different data sets, unbalanced sample numbers in different classes have effect on classification result. When a balanced data set is used, MABC provided the best result as 97.96% among all classifiers.Not only part of the records from examined MITBIH database, but also all data from selected records are used to be able to use developed algorithm on a real time system in the future by using additional software modules and making adaptation on a specific hardware. 相似文献
4.
At some point in their careers, clinicians who work or consult in forensic and correctional settings will almost certainly encounter individuals who exhibit psychopathic personality features. Because of the widespread use of this disorder to inform legal and clinical decision making, psychologists should be exceedingly familiar with the relevant research literature on this topic before venturing into these settings. This article reviews the empirical bases of several clinically relevant claims and assertions regarding psychopathy and concludes that many areas of research are decidedly more equivocal in their findings than is commonly perceived. Although there is much to be gained by assessing psychopathy in various contexts, clinicians need to be cautious about drawing overzealous and empirically questionable conclusions about an important disorder that also has great potential for abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Ben-Jye Chang 《Telecommunication Systems》2006,33(4):333-352
3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for
achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each
accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic
rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long
handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost
of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher
Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose
herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce
the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed
approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments.
Meanwhile, the optimal number of rake combiners is also analyzed in this paper.
This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018. 相似文献
6.
基于ISO/IEC17799标准建立了一个综合的信息系统风险分析框架,并运用模糊多准则决策(FMCDM)方法计算信息安全风险,根据风险等级矩阵(RLM)对信息资产风险进行级别划分,最终建立评估信息资产相关风险的完整模型。 相似文献
7.
在时变多径衰落信道下,接收到的CDMA信号功率变化较大,此时D-Rake盲自适应多用户检测器性能显著下降,将变步长LMS算法与基于主分量的相干合并引入到D-Rake(DecorrelatingRake)检测器中,构成一种变步长D-Rake,称之为VD-Rake(Variablestep-sizeDecorrelatingRake)检测器。该检测器能克服原D-Rake检测器对信号功率变化较敏感等缺点,有效地改善了D-Rake检测器的性能。 相似文献
8.
Introduces the current issue of the American Psychologist, which examines the ramifications of the Brown vs. Board of Education decision and its sequelae over the last 50 years, with a special focus on the mixed role of psychological research and practice. Despite the great strides toward a more just society since May 17, 1954, inequities remain in schooling, in social relations, and in economic opportunity. How will history judge American psychology 50 years from now vis-a-vis the possibilities it helped create via Brown? The articles in this special issue suggest several important directions of research and action our field will need to take if the verdict of history is to be a positive one. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
用数值方法进行地下水水资源评价时 ,需要给出每个节点上的初始地下水位值。本文着重阐述了区域化变量和变差函数及其计算步骤 ,指出变差函数在分析地下水位的空间变异的重要性 相似文献
10.