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   8250篇
  免费   722篇
  国内免费   173篇
电工技术   209篇
综合类   714篇
化学工业   424篇
金属工艺   57篇
机械仪表   272篇
建筑科学   1091篇
矿业工程   75篇
能源动力   126篇
轻工业   2334篇
水利工程   296篇
石油天然气   59篇
武器工业   25篇
无线电   261篇
一般工业技术   614篇
冶金工业   1606篇
原子能技术   40篇
自动化技术   942篇
  2024年   81篇
  2023年   221篇
  2022年   374篇
  2021年   448篇
  2020年   399篇
  2019年   375篇
  2018年   281篇
  2017年   361篇
  2016年   331篇
  2015年   295篇
  2014年   424篇
  2013年   520篇
  2012年   432篇
  2011年   562篇
  2010年   446篇
  2009年   398篇
  2008年   421篇
  2007年   434篇
  2006年   466篇
  2005年   419篇
  2004年   299篇
  2003年   249篇
  2002年   195篇
  2001年   143篇
  2000年   70篇
  1999年   57篇
  1998年   30篇
  1997年   30篇
  1996年   25篇
  1995年   24篇
  1994年   16篇
  1993年   18篇
  1992年   12篇
  1990年   23篇
  1989年   18篇
  1988年   20篇
  1987年   14篇
  1986年   16篇
  1985年   13篇
  1984年   12篇
  1983年   14篇
  1982年   17篇
  1981年   8篇
  1980年   17篇
  1979年   7篇
  1966年   9篇
  1963年   10篇
  1961年   7篇
  1958年   9篇
  1957年   7篇
排序方式: 共有9145条查询结果,搜索用时 15 毫秒
121.
The Internet is the preferred source of health information followed by healthcare providers, friends and family, print media, and television (Baxter & Egbert, 2008). Yet, previous research about online sexual health resources for LGBTQ (lesbian, gay, bisexual, transgendered, queer) groups, especially lesbian and bisexual (LB) women, primarily consists of introductions and reviews of related websites rather than critique of the quality of the information present (e.g. Clark, 2003; Finlon, 2002; McKay, 2011). Thus, the goals of this study were to examine the LB women’s sexual and relational health content in online sources and identify the degree to which the online sources considered LB women’s identity and standpoint when presenting sexual and relational health messages. The analysis includes a comparison of text-based and video-based online messages related to LB women’s sexual and relational health. We argue that there is an overall lack of quality in the online sexual and relational health messages for LB women, and that websites are not comprehensive enough in their coverage of LB women’s sexual and relational health.  相似文献   
122.
This article offers a new perspective on the boundaries between health and non-health data in the age of ‘Quantified-Self’ apps: the ‘data-sensitiveness-by-computational-distance’ approach-or, more simply, the ‘sensitive-by-distance’ approach. This approach takes into account two variables: the intrinsic sensitiveness (a static variable) of personal data and the computational distance (a dynamic variable) between some kinds of personal data and pure health (or sensitive) data, which depends upon computational capacity. From an objective perspective, computational capacity depends on the level of development of data retrieval technologies at a certain moment, the availability of ‘accessory data’, and the applicable legal restraints on processing data. From a subjective perspective, computational capacity depends on the specific data mining efforts (or the ability to invest in them) taken by a given data controller: economic resources, human resources, and the use of accessory data. A direct consequence of the expansion of augmented humanity in collecting and inferring personal data is the increasing loss of health data processing ‘legibility’ for data subjects. In order to address this issue, we propose exploiting the existing legal tools in the General Data Protection Regulation to empower data subjects (the right to data access, the right to know the logic involved in automated decision-making, data portability, etc.).  相似文献   
123.
本文利用高速数控铣刀铣削中不同侧面方向的切削力和振动信号以及声发射信号均方根值,以数据驱动的形式对刀具磨损进行了拟合评估. 在本次研究中,分别从时域、频域和时频联合域上探索与刀具磨损相关的敏感特征,具体特征提取方法包括时域统计分析、频域上的快速傅里叶变换(FFT)和时频联合分析的小波变换(WT). 本文中,决策树被用于回归问题而非分类问题,用于评估刀具磨损值. 同时,引入AdaBoost算法对回归树模型进行提升,并从模型的准确性、稳定性和适用性三个方面上综合对比了提升的决策树回归模型和原模型的性能. 研究表明,AdaBoost算法提升的回归决策树模型在预测的准确性和稳定性上都有一定程度上提高,并且在面向全新刀具磨损预测的适用性上也取得了不错的提升效果.  相似文献   
124.
为顺应河流生态可持续发展,提出健康河流、生命河流等概念,维持河流生态系统健康已经成为流域综合管理的必然趋势。综合运用水文学、水力学、泥沙地貌学和水生生态学的基本理论和方法研究河流生态健康的表征因子,确定各因子的阈值,建立流域性水体水质可续发展评价体系。以河流可持续发展为基础,引用代表性的相关指标进行筛选,对流域水质指标进行数值化分析,以苏子河流域水质特性为研究对象,选取出评估河流健康状况的环境因子,客观反映出中小河流域健康状况,为河流的可持续管理和生态环境建设提供参考。  相似文献   
125.
Multiple plant stresses can affect the health, esthetic condition, and timber harvest value of conifer forests. To monitor spatial and temporal dynamic forest stress conditions, timely, accurate, and cost-effective information is needed that could be provided by remote sensing. Recently, satellite imagery has become available via the RapidEye satellite constellation to provide spectral information in five broad bands, including the red-edge region (690-730 nm) of the electromagnetic spectrum. We tested the hypothesis that broadband, red-edge satellite information improves early detection of stress (as manifest by shifts in foliar chlorophyll a + b) in a woodland ecosystem relative to other more commonly utilized band combinations of red, green, blue, and near infrared band reflectance spectra. We analyzed a temporally dense time series of 22 RapidEye scenes of a piñon-juniper woodland in central New Mexico acquired before and after stress was induced by girdling. We found that the Normalized Difference Red-Edge index (NDRE) allowed stress to be detected 13 days after girdling — between and 16 days earlier than broadband spectral indices such as the Normalized Difference Vegetation Index (NDVI) and Green NDVI traditionally used for satellite based forest health monitoring. We conclude that red-edge information has the potential to considerably improve forest stress monitoring from satellites and warrants further investigation in other forested ecosystems.  相似文献   
126.
The protection of patients’ health information is a very important issue in the information age. Health Insurance Portability and Accountability Act (HIPAA) of privacy and security regulations are two crucial provisions in the protection of healthcare privacy, especially electronic medical information. For the quality and efficiency of the electronic services, it is necessary to construct better performance for the user and the trusted party. Based on elliptic curve cryptography (ECC) and complying with HIPAA regulations, this article presents an efficient key management scheme to facilitate inter-operations among the applied cryptographic mechanisms. In addition, the proposed scheme can achieve the complete functionality which includes: (1) a dictionary of key tables is not required for users and other units; (2) users can freely choose their own passwords; (3) users can freely update their passwords after the registration phase; (4) the computational cost is very low for users and the trusted center or server; (5) users are able to access their individual medical information through the authorization process; (6) case of consent exceptions intended to facilitate emergency applications or other possible exceptions can also be dealt with easier.  相似文献   
127.
面向P2P特定信息的传播动力学模型研究   总被引:1,自引:1,他引:0  
丁军平  蔡皖东 《计算机科学》2011,38(11):96-99,113
鉴于P2P特定信息传播与传染病传播的相似性,传播动力学是P2P特定信息传播的最新研究方向。针对现有传播动力学模型都不能准确模拟P2P特定信息传播过程的问题,对现有的SEIR传播动力学模型进行改进,建立了SEInR模型。该模型的主要特点包括:将传统的感染者(I)分为n个子类,每个子类赋予不同的模型参数;建立潜伏者(E)与移除者(R)之间的转换关系等。应用现代数学中的矩阵理论,得到SEInR模型的基本再生数计算公式,并对其进行分析。仿真结果表明,所提出的SEInR模型比传统SEIR模型能够更准确地模拟P2P特定信息传播过程,得到的基本再生数计算公式能够准确反映P2P特定信息的传播阂值。  相似文献   
128.
张燕 《计算机与网络》2008,34(17):68-70
现代网络通讯技术的快速发展和应用,使基于Intemet的远程数据监测成为可能。提出了一种基于C/S模式的远程结构健康监测系统,阐述了其体系结构及各部分功能,并开发了基于TCP/IP协议的远程通信程序,最终达到了远程监控的目的。  相似文献   
129.
Chemical mediation of egg capsule deposition by mud snails   总被引:1,自引:0,他引:1  
Mud snails (Ilyanassa obsoleta = Nassarius obsoletus = Nassa obsoleta) deposit eggs in protective capsules on hard substrata in soft bottom environments. We studied sites of egg capsule deposition and snail movement responses to odors to determine if chemoreception plays a role in deposition site selection. From results of field surveys, laboratory experiments, and field experiments, we conclude that mud snails use chemoreception for capsule deposition. Attractive odors originate from mud snail and whelk egg capsules and from living bivalves. Evidence for attractive odors from conspecifics is equivocal. Capsules are deposited on living odor sources and nearby hard substrates. We hypothesize that deposition of capsules on living substrates increases the likelihood that embryos will survive by decreasing the chance of smothering of embryos by sediments.  相似文献   
130.
膜法富氧技术及其应用研究   总被引:12,自引:0,他引:12  
介绍了作者在膜法富氧技术方面的研究进展,并将膜法与其他制氧方法进行了比较,最后讨论了膜法富氧技术目前的有关应用,着重研究了膜法富氧在有色金属冶炼,硅酸盐窑炉,化铁炉,加热炉,医疗保健和柴油机增氧等方面的典型应用。  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