首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5800篇
  免费   764篇
  国内免费   360篇
电工技术   72篇
综合类   530篇
化学工业   1666篇
金属工艺   71篇
机械仪表   182篇
建筑科学   310篇
矿业工程   24篇
能源动力   54篇
轻工业   1538篇
水利工程   22篇
石油天然气   37篇
武器工业   14篇
无线电   306篇
一般工业技术   321篇
冶金工业   247篇
原子能技术   36篇
自动化技术   1494篇
  2024年   25篇
  2023年   94篇
  2022年   347篇
  2021年   463篇
  2020年   213篇
  2019年   175篇
  2018年   160篇
  2017年   182篇
  2016年   208篇
  2015年   253篇
  2014年   372篇
  2013年   409篇
  2012年   407篇
  2011年   440篇
  2010年   361篇
  2009年   357篇
  2008年   384篇
  2007年   395篇
  2006年   329篇
  2005年   256篇
  2004年   216篇
  2003年   182篇
  2002年   115篇
  2001年   91篇
  2000年   69篇
  1999年   57篇
  1998年   45篇
  1997年   45篇
  1996年   51篇
  1995年   48篇
  1994年   35篇
  1993年   20篇
  1992年   24篇
  1991年   20篇
  1990年   14篇
  1989年   14篇
  1988年   4篇
  1987年   11篇
  1986年   5篇
  1985年   6篇
  1984年   2篇
  1982年   2篇
  1980年   2篇
  1964年   3篇
  1963年   3篇
  1961年   3篇
  1958年   1篇
  1957年   1篇
  1956年   1篇
  1955年   1篇
排序方式: 共有6924条查询结果,搜索用时 15 毫秒
41.
针对作业车间调度问题的特征,提出一种基于基因表达式的克隆选择算法。在这个方法中,采用基因表达式编程算法中的编码方式来表示调度方案,同时为了提出的方法具有更强的全局搜索能力,运用克隆选择算法作为搜索引擎。最后,验证提出的方法的有效性,对7组Benchmark实例进行测试。实验结果表明,基于基因表达式的克隆选择算法在求解作业车间调度问题中是非常有效的。  相似文献   
42.
面部表情识别广泛应用于各种研究领域,针对面部表情识别使用深度神经网络方法结构复杂、可解释性差和传统机器学习方法特征提取缺乏多样性、识别率低的问题.提出了一种新的深度卷积级联森林(Deep Convolution Cascade Forest,DCCF)方法用于人脸面部表情识别,该方法通过卷积神经网络深度学习人脸面部显著特征,并采用基于随机森林的级联结构森林逐层学习识别出不同的面部表情特征,提高了人脸表情的识别准确率.DCCF在JAFFE、CK+和Fer2013 3个公开面部表情数据集进行了实验,并对面部表情提取的5种特征和7种分类方法进行了比较分析,结果显示DCCF在对比的算法中人脸表情识别性能最好,3个数据集的准确率分别达到91.4%,98.7%,71.6%.  相似文献   
43.
Fault detection and isolation in rotating machinery is very important from an industrial viewpoint as it can help in maintenance activities and significantly reduce the down-time of the machine, resulting in major cost savings. Traditional methods have been found to be not very accurate. Soft computing based methods are now being increasingly employed for the purpose. The proposed method is based on a genetic programming technique which is known as gene expression programming (GEP). GEP is somewhat a new member of the genetic programming family. The main objective of this paper is to compare the classification accuracy of the proposed evolutionary computing based method with other pattern classification approaches such as support vector machine (SVM), Wavelet-GEP, and proximal support vector machine (PSVM). For this purpose, six states viz., normal, bearing fault, impeller fault, seal fault, impeller and bearing fault together, cavitation are simulated on centrifugal pump. Decision tree algorithm is used to select the features. The results obtained using GEP is compared with the performance of Wavelet-GEP, support vector machine (SVM) and proximal support vector machine (PSVM) based classifiers. It is observed that both GEP and SVM equally outperform the other two classifiers (PSVM and Wavelet-GEP) considered in the present study.  相似文献   
44.
研究中医冠心病医案,高效挖掘有益信息规则问题,由于中医医案数据量大、关联性强,针对传统的关联规则挖掘算法处理中医医案数据时存在效率低、收敛速度慢及漏报规则等问题,提出一种小生境技术和基因表达式编程相结合的挖掘关联规则的方法。通过惩罚函数设置支持度阈值,利用小生境技术执行小生境演化、融合算法,结合基因表达式编程算法操作简单、鲁棒性强的优势搜索强关联规则,有效避免了算法早熟,解决了规则冗余。针对治疗冠心病的中医医案进行了验证性实验,实验结果表明,改进算法在提取有效信息的效率上有较大的提高,挖掘结果对冠心病中医临床诊治具有一定的参考价值。  相似文献   
45.
袁锋 《计算机仿真》2012,29(2):204-207,352
研究原发性高血压病靶器官损害准确预测问题,由于原发性高血压病靶器官损害的影响因子之间存在着高度冗余和非线性,导致传统方法预测准确率低,为提高预测精度,构建了一种改进的基因表达式编程算法的原发性高血压病靶器官损害预测模型,首先设计了适合靶器官损害预测的适应度函数,然后为克服早熟现象提出了以平均适应度形式自适应的改变重组算子概率和变异算子概率,通过数据训练得到靶器官损害的2年预测模型。采用对山东中医药大学第二附属医院原发性高血压病历史数据进行验证性仿真,结果表明,方法的预测精度更高,在原发性高血压病靶器官损害的预测中有着广泛的应用前景。  相似文献   
46.
47.
The expression of p16 is a good surrogate of human papillomavirus (HPV) infection in HPV-associated cancers. The significance of p16 expression, HPV genotype and genera in the outcome of patients with HPV-associated cervical cancer (CC) is unclear. Our aim is to ascertain the prognostic significance of these factors. Data from 348 patients (median age: 47.5 years old) with CC, diagnosed in two referral centers, were retrospectively collected. Advanced disease (FIGO2018 IB2-IV) was present in 68% of patients. A single HPV genotype was identified in 82.8% of patients. The most common HPVs were HPV16 (69%) and HPV18 (14%). HPV genera reflected this distribution. HPV16 tumors presented at an earlier stage. P16 was negative in 18 cases (5.2%), 83.3% of which were squamous cell carcinomas. These cases occurred in older patients who tended to have advanced disease. In the univariate analysis, HPV16 (HR: 0.58; p = 0.0198), α-9 genera (HR: 0.37; p = 0.0106) and p16 overexpression (HR: 0.54; p = 0.032) were associated with better survival. HPV16 (HR: 0.63; p = 0.0174) and α-9 genera (HR: 0.57; p = 0.0286) were associated with less relapse. In the multivariate analysis, only the International Federation of Gynecology and Obstetrics (FIGO) stage retained an independent prognostic value. HPV16, α-9 genera and p16 overexpression were associated with better survival, although not as independent prognostic factors. Patients with p16-negative HPV-associated CC were older, presented with advanced disease and had worse prognosis.  相似文献   
48.
49.
陈龙    张水平    王海晖    陈言璞   《武汉工程大学学报》2021,43(6):681-688
针对面部表情分类的模型中参数较复杂、识别准确率较低的问题,提出了一种基于知识图谱辅助识别的多任务学习算法模型(MLAM),该模型由基于深度学习的识别模块与知识图谱嵌入模块两部分构成。首先从输入的数据中提取潜在的人脸局部表情特征,通过知识图谱实现局部表情和个体的复杂交互;然后在MLAM 模型中设计一个交叉压缩单元,关联这两个独立模块,自动学习局部表情和实体特征的高级交互,并在这两个任务之间传递交叉知识转移;最后,在FER2013和CK+的数据集上对比了同类算法,实验结果表明,该模型在上述数据集上分别得到了0.69和0.99的识别率,提高了面部表情识别准确率。  相似文献   
50.
Salt stress is a major increasing threat to global agriculture. Pongamia (Millettia pinnata), a semi-mangrove, is a good model to study the molecular mechanism of plant adaptation to the saline environment. Calcium signaling pathways play critical roles in the model plants such as Arabidopsis in responding to salt stress, but little is known about their function in Pongamia. Here, we have isolated and characterized a salt-responsive MpCML40, a calmodulin-like (CML) gene from Pongamia. MpCML40 protein has 140 amino acids and is homologous with Arabidopsis AtCML40. MpCML40 contains four EF-hand motifs and a bipartite NLS (Nuclear Localization Signal) and localizes both at the plasma membrane and in the nucleus. MpCML40 was highly induced after salt treatment, especially in Pongamia roots. Heterologous expression of MpCML40 in yeast cells improved their salt tolerance. The 35S::MpCML40 transgenic Arabidopsis highly enhanced seed germination rate and root length under salt and osmotic stresses. The transgenic plants had a higher level of proline and a lower level of MDA (malondialdehyde) under normal and stress conditions, which suggested that heterologous expression of MpCML40 contributed to proline accumulation to improve salt tolerance and protect plants from the ROS (reactive oxygen species) destructive effects. Furthermore, we did not observe any measurable discrepancies in the development and growth between the transgenic plants and wild-type plants under normal growth conditions. Our results suggest that MpCML40 is an important positive regulator in response to salt stress and of potential application in producing salt-tolerant crops.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号