全文获取类型
收费全文 | 38841篇 |
免费 | 4268篇 |
国内免费 | 2160篇 |
专业分类
电工技术 | 3089篇 |
技术理论 | 3篇 |
综合类 | 4836篇 |
化学工业 | 2097篇 |
金属工艺 | 780篇 |
机械仪表 | 2012篇 |
建筑科学 | 4615篇 |
矿业工程 | 1852篇 |
能源动力 | 1136篇 |
轻工业 | 3813篇 |
水利工程 | 2078篇 |
石油天然气 | 4136篇 |
武器工业 | 872篇 |
无线电 | 2577篇 |
一般工业技术 | 2479篇 |
冶金工业 | 1130篇 |
原子能技术 | 292篇 |
自动化技术 | 7472篇 |
出版年
2024年 | 180篇 |
2023年 | 557篇 |
2022年 | 1103篇 |
2021年 | 1336篇 |
2020年 | 1375篇 |
2019年 | 1135篇 |
2018年 | 1112篇 |
2017年 | 1192篇 |
2016年 | 1522篇 |
2015年 | 1593篇 |
2014年 | 2673篇 |
2013年 | 2360篇 |
2012年 | 3077篇 |
2011年 | 3230篇 |
2010年 | 2318篇 |
2009年 | 2430篇 |
2008年 | 2206篇 |
2007年 | 2618篇 |
2006年 | 2337篇 |
2005年 | 2045篇 |
2004年 | 1649篇 |
2003年 | 1379篇 |
2002年 | 1006篇 |
2001年 | 879篇 |
2000年 | 697篇 |
1999年 | 585篇 |
1998年 | 452篇 |
1997年 | 419篇 |
1996年 | 336篇 |
1995年 | 288篇 |
1994年 | 222篇 |
1993年 | 177篇 |
1992年 | 108篇 |
1991年 | 106篇 |
1990年 | 76篇 |
1989年 | 86篇 |
1988年 | 42篇 |
1987年 | 38篇 |
1986年 | 36篇 |
1985年 | 30篇 |
1984年 | 38篇 |
1983年 | 36篇 |
1982年 | 21篇 |
1981年 | 21篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1959年 | 9篇 |
1956年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
71.
本文主要介绍了在动态汽车衡的试验过程中不确定度来源,并以动态试验为例重点介绍了计算各分量的标准不确定度、合成标准不确定度以及扩展不确定度的方法. 相似文献
72.
The Florida Department of Transportation (FDOT) is in the process of implementing Pontis, a Bridge Management System, to provide decision support to engineers in the headquarters and district offices as they make routine policy, programming, and budgeting decisions regarding the preservation and improvement of the state’s bridges. As part of this effort, an ongoing research program is underway to adapt the system to FDOT needs as well as to advance the state of the art in several areas important to the Department. Most of the research results are organized around a new project-level decision support framework that complements and builds on Pontis’ existing network-level analysis. Specific new models include accident risk and user cost due to roadway width and alignment deficiencies; user cost of load capacity and vertical clearance restrictions, and moveable bridge openings; project-level prediction models for bridge element condition and costs; and prediction of economics of scale and scoping possibilities. The new models are built into a highly graphical spreadsheet model for decision support use. 相似文献
73.
Stereotype threat research has demonstrated that stereotypes can harm student performance in the face of public evaluation by peers or an experimenter. The current study examined whether stereotypes can also threaten in private settings. Female students completed a math test in 3-person groups, which consisted of either 2 other women (same gender) or 2 men (minority). In addition, students either believed their performance would be broadcasted to their peers (public) or not (private). Results revealed that minority students performed worse than same-gender students in both public and private environments. This finding supports the concept of threatening intellectual environments and shows how far reaching the effects of stereotypes can be. The authors discuss these findings in relation to research on tokenism and to stereotype threat and its educational implications. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
75.
棉织物手感值的模糊综合评判研究 总被引:4,自引:0,他引:4
利用模糊综合评判数学模型对棉织物的手感值进行了计算与分析,这种方法简单、可靠,与主观评估结果有很好的一致性,为纺织生产的质量判断提供了便利。 相似文献
76.
77.
78.
This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations. 相似文献
79.
文章通过对五口井的现场应用介绍,阐述了快速色谱分析技术在油气层识别和解释方面的准确性,探讨了该技术在薄油气层的发现和评价、快速钻进条件下油气层的发现、对油气层全烃组份变化的统一、水平井的地质导向以及排除钻井液添加荆对油气显示的影响五个方面的优势,从而论证了快速色谱分析技术在油气勘探中的应用价值。 相似文献
80.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献