全文获取类型
收费全文 | 20892篇 |
免费 | 2064篇 |
国内免费 | 1926篇 |
专业分类
电工技术 | 762篇 |
技术理论 | 13篇 |
综合类 | 2574篇 |
化学工业 | 279篇 |
金属工艺 | 168篇 |
机械仪表 | 693篇 |
建筑科学 | 1502篇 |
矿业工程 | 350篇 |
能源动力 | 102篇 |
轻工业 | 235篇 |
水利工程 | 267篇 |
石油天然气 | 89篇 |
武器工业 | 113篇 |
无线电 | 5060篇 |
一般工业技术 | 897篇 |
冶金工业 | 2963篇 |
原子能技术 | 20篇 |
自动化技术 | 8795篇 |
出版年
2024年 | 94篇 |
2023年 | 293篇 |
2022年 | 472篇 |
2021年 | 673篇 |
2020年 | 777篇 |
2019年 | 658篇 |
2018年 | 640篇 |
2017年 | 795篇 |
2016年 | 909篇 |
2015年 | 983篇 |
2014年 | 1576篇 |
2013年 | 1591篇 |
2012年 | 1378篇 |
2011年 | 1494篇 |
2010年 | 1302篇 |
2009年 | 1250篇 |
2008年 | 1315篇 |
2007年 | 1407篇 |
2006年 | 1189篇 |
2005年 | 1135篇 |
2004年 | 971篇 |
2003年 | 882篇 |
2002年 | 683篇 |
2001年 | 634篇 |
2000年 | 292篇 |
1999年 | 196篇 |
1998年 | 132篇 |
1997年 | 116篇 |
1996年 | 93篇 |
1995年 | 98篇 |
1994年 | 60篇 |
1993年 | 37篇 |
1992年 | 34篇 |
1990年 | 34篇 |
1989年 | 23篇 |
1988年 | 29篇 |
1987年 | 22篇 |
1985年 | 20篇 |
1966年 | 26篇 |
1965年 | 28篇 |
1964年 | 56篇 |
1963年 | 46篇 |
1961年 | 43篇 |
1960年 | 22篇 |
1959年 | 30篇 |
1958年 | 22篇 |
1957年 | 33篇 |
1956年 | 24篇 |
1955年 | 45篇 |
1954年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Koenen Karestan C.; Stellman Jeanne Mager; Stellman Steven D.; Sommer John F. Jr. 《Canadian Metallurgical Quarterly》2003,71(6):980
Risk factors affecting the course of posttraumatic stress disorder (PTSD) are poorly understood. As part of a larger study on characterizing exposure to herbicides in Vietnam, the authors investigated this issue in a random sample of 1,377 American Legionnaires who had served in Southeast Asia during the Vietnam War and were followed over a 14-year period. High combat exposure, perceived negative community attitudes at homecoming, minority race, depression symptoms at Time 1, and more anger at Time 1 predicted a more chronic course. Community involvement at Time 1 was protective and associated with decreased risk at Time 2. Discomfort in disclosing Vietnam experiences was associated with an increased risk for developing PTSD but did not predict its course. Combat exposure predicted PTSD course more strongly than any other risk factor. Findings suggest recovery from PTSD is significantly influenced by perceived social support. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
Review of book: Media violence and its effects on aggression: Assessing the scientific evidence, by Jonathan L. Freedman. Toronto: ON: University of Toronto Press, 2002, 227 pp. Hardcover. ISBN 0-8020-3553-1. Reviewed by Claire Crooks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
Richard F. D.; Bond Charles F. Jr.; Stokes-Zoota Juli J. 《Canadian Metallurgical Quarterly》2003,7(4):331
This article compiles results from a century of social psychological research, more than 25,000 studies of 8 million people. A large number of social psychological conclusions are listed alongside meta-analytic information about the magnitude and variability of the corresponding effects. References to 322 meta-analyses of social psychological phenomena are presented, as well as statistical effect-size summaries. Analyses reveal that social psychological effects typically yield a value of r equal to .21 and that, in the typical research literature, effects vary from study to study in ways that produce a standard deviation in r of .15. Uses, limitations, and implications of this large-scale compilation are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
移动式数据挖掘平台模型 总被引:1,自引:0,他引:1
本文提出了一种移动式网络海量数据挖掘平台,给出了数据挖掘任务的形式化描述,详细讨论了平台的体系结构、工作原理与流程。该平台克服了传统网络计算模式的缺陷,支持对异质、分散数据源和知识源的挖掘和检索,具有开放性、可伸缩性、灵活性、可扩展性、健壮性。 相似文献
35.
分析了现有移动通信网络存在的问题,阐述了第2代移动通信核心网向第3代移动通信核心网演进的必然性:讨论了第2代移动通信核心网向第3代移动通信核心网演进所采用的演进策略,介绍了两种可供选择的全IP核心网络的参考结构。 相似文献
36.
Thai Binh Wan Rachel Seneviratne Aruna Rakotoarivelo Thierry 《Mobile Networks and Applications》2003,8(1):27-36
The high expectations and demand for users to access the Internet from anywhere at anytime has made user mobility an important part of the design and development of the next generation mobile communications and computing. Traditionally user mobility has been divided into two areas: Terminal Mobility and Personal Mobility. In recent years terminal mobility has focused on the movement of the terminal and developed extensions to IP protocols such as Mobile IP. In contrast, personal mobility has only received limited attention, and is somewhat lagging behind. This research has either focussed on personal mobility in communications or personalisation of operating environments. As a result, to date no framework for providing true personal mobility has emerged. In this paper, we introduce a new personal mobility framework called IPMoA (Integrated Personal Mobility Architecture), which integrates both aspects of personal mobility to provide a complete personal mobility solution, and illustrate the viability of this approach through a proof-of-concept implementation. 相似文献
37.
This study investigated the relationship between self-appraisals of performance, symptom severity and post-event rumination in social phobia, and evaluated the effect of treatment on these variables. A socially phobic group and a nonanxious control group performed an impromptu speech and were told that their performance would be evaluated. Participants appraised their performance immediately after the speech and 1 week later, and the frequency of post-event rumination during the week following the speech was assessed. The socially phobic group maintained the negative appraisals of their speech over the week, whereas the nonclinical group showed increased positivity about their performance The socially phobic group also engaged in more negative rumination than controls. Treatment improved perceptions of performance and reduced negative rumination. These results are discussed in the light of cognitive models of social phobia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
中国3G业务的市场需求有两个方面:一是迅猛增长、规模庞大的用户群对移动语音业务的需求;二是较高收入用户群对移动数据业务的需求。3G运营商的目标市场包括大众用户对移动语音的需求、大众用户对移动数据业务的需求、企业用户对移动数据业务的需求以及批发型用户的需求等。本结合国内外移动运营商的数据业务开展状况,初步探讨了中国3G运营商的移动数据业务模式和3G业务的收入模式。 相似文献
39.
We consider nonholonomic mobile manipulators built from an n
a
joint robotic arm and a nonholonomic mobile platform with two independently driven wheels. Actually, there is no efficient kinematic formalism for these systems which are generally characterized by their high number of actuators. So, kinematic modelling is presented with particular emphasis on redundancy. Whereas kinematic redundancy is well known in the holonomic case, it is pointed out that it is necessary to define velocity redundancy in the case of nonholonomic systems. Reduced velocity kinematics based on quasi-velocities are shown to provide an efficient formalism. Two examples of mobile manipulators are presented. Finally, reduced velocity kinematics and velocity redundancy are shown to be adequate tools in order to realize operational task while optimizing criteria such as manipulability. 相似文献
40.
The State of the Art in Text Filtering 总被引:1,自引:0,他引:1
This paper develops a conceptual framework for text filtering practice and research, and reviews present practice in the field.
Text filtering is an information seeking process in which documents are selected from a dynamic text stream to satisfy a relatively
stable and specific information need. A model of the information seeking process is introduced and specialized to define text
filtering. The historical development of text filtering is then reviewed and case studies of recent work are used to highlight
important design characteristics of modern text filtering systems. User modeling techniques drawn from information retrieval,
recommender systems, machine learning and other fields are described. The paper concludes with observations on the present
state of the art and implications for future research on text filtering.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献