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   50134篇
  免费   3162篇
  国内免费   1100篇
电工技术   1585篇
综合类   1644篇
化学工业   8892篇
金属工艺   1590篇
机械仪表   1827篇
建筑科学   3010篇
矿业工程   604篇
能源动力   1417篇
轻工业   4467篇
水利工程   894篇
石油天然气   575篇
武器工业   269篇
无线电   4067篇
一般工业技术   7265篇
冶金工业   7113篇
原子能技术   434篇
自动化技术   8743篇
  2023年   426篇
  2022年   909篇
  2021年   1350篇
  2020年   956篇
  2019年   912篇
  2018年   1114篇
  2017年   1124篇
  2016年   1210篇
  2015年   1385篇
  2014年   1848篇
  2013年   3291篇
  2012年   2872篇
  2011年   3334篇
  2010年   2835篇
  2009年   2721篇
  2008年   2955篇
  2007年   3031篇
  2006年   2550篇
  2005年   2226篇
  2004年   1745篇
  2003年   1486篇
  2002年   1374篇
  2001年   1009篇
  2000年   799篇
  1999年   688篇
  1998年   595篇
  1997年   594篇
  1996年   566篇
  1995年   587篇
  1994年   534篇
  1993年   521篇
  1992年   510篇
  1991年   293篇
  1990年   422篇
  1989年   396篇
  1988年   324篇
  1987年   359篇
  1986年   316篇
  1985年   421篇
  1984年   417篇
  1983年   320篇
  1982年   297篇
  1981年   284篇
  1980年   274篇
  1979年   273篇
  1978年   247篇
  1977年   225篇
  1976年   206篇
  1975年   195篇
  1974年   174篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
There is an analogy between single-chip color cameras and the human visual system in that these two systems acquire only one limited wavelength sensitivity band per spatial location. We have exploited this analogy, defining a model that characterizes a one-color per spatial position image as a coding into luminance and chrominance of the corresponding three colors per spatial position image. Luminance is defined with full spatial resolution while chrominance contains subsampled opponent colors. Moreover, luminance and chrominance follow a particular arrangement in the Fourier domain, allowing for demosaicing by spatial frequency filtering. This model shows that visual artifacts after demosaicing are due to aliasing between luminance and chrominance and could be solved using a preprocessing filter. This approach also gives new insights for the representation of single-color per spatial location images and enables formal and controllable procedures to design demosaicing algorithms that perform well compared to concurrent approaches, as demonstrated by experiments.  相似文献   
93.
94.
Multi-functional biochip for medical diagnostics and pathogen detection   总被引:2,自引:0,他引:2  
We describe a multi-functional biochip (MFB), which uses two different types of bioreceptors, including nucleic acid and antibody probes, on a single platform. The multi-functional capability of the MFB device for biomedical diagnostics is illustrated by measurements of DNA probes specific to gene fragments of Bacillus anthracis and antibody probes targeted to Escherichia coli. Calibration curves for monitoring pathogenic species using antibody probes against E. coli and DNA probes for B. anthracis illustrate the capability of the device for medical diagnostics and for quantitative detection of pathogenic agents.  相似文献   
95.
The authors report 3 experiments in which participants were invited to judge the probability of statements of the form if p then q given frequency information about the cases pq, p?q, ?pq, and ?p?q (where ? = not). Three hypotheses were compared: (a) that people equate the probability with that of the material conditional, 1 - P(p?q); (b) that people assign the conditional probability, P(q/p); and (c) that people assign the conjunctive probability P(pq). The experimental evidence allowed rejection of the 1st hypothesis but provided some support for the 2nd and 3rd hypotheses. Individual difference analyses showed that half of the participants used conditional probability and that most of the remaining participants used conjunctive probability as the basis of their judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
96.
97.
This article reviews the application of a coupled squeeze flow and intermolecular diffusion model, which was used to predict the quality and size of microwelds in plastics. Weld widths predictions were compared with previously presented experimental results using moving heat source models and temperature fields. The motivation for this work was to develop and verify a model based on fundamental principles that could accurately predict weld size and strength for conventional plastic welding techniques as well as novel techniques such as laser microwelding. It is envisioned that the resulting model could be used to predict proper welding parameters, including laser power and travel speed, to produce welds of varying size. Although insight into weld quality can be derived from this model, it was not the goal of this work to accurately predict weld strength for laser microwelding because of the difficulty in measuring weld strength on the micron scale. However, as reported in Part 1, weld strength for impulse welds were accurately predicted. In this model it was found that variable temperature histories, rather than a single value of maximum weld temperature, allows more accurate modeling of the welding process. In this work (Part 2), microwelds as small as 11 μm in width were produced with transmission infrared welding. In addition, welds over 150‐μm wide were also generated and the model was able to predict the range of weld widths that were found experimentally. It was found that the predictions were in very good agreement with the experimental results. There was some deviation between the experimental data and the model at the extreme parameters and it is believed that this was due to the temperature‐dependent material properties as well as optical aberrations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers  相似文献   
98.
A recent paper by Çimen and Banks [2004. Nonlinear optimal tracking control with application to super-tankers for autopilot design. Automatica, 40(11), 1845–1863] on optimal control system design for oil tanker propulsion and heading highlighted the importance of accurately representing the dynamics of such a vessel. Results presented in that paper are based on a simulation model that provides unrealistic results for an oil tanker of the size considered. Therefore, the results obtained from the simulated ship control problem are not representative of the physical system being considered. In this communication an alternative, more realistic model is presented and discussed with reference to the original publications that define the ship model dynamics.  相似文献   
99.
Business publications and the popular press have stressed the importance of creating conditions for meaningful employee expression in work roles, also known as engagement. Few empirical studies, however, have examined how individual or situational factors relate to engagement. Consequently, this study examines the interplay between employee age, perceived coworker age composition, and satisfaction with older (older than 55) and younger (younger than 40) coworkers on engagement using a sample of 901 individuals employed in the United Kingdom. Results indicated that satisfaction with one's coworkers related significantly to engagement. Moreover, perceived age similarity was associated with higher levels of engagement among older workers when they were highly satisfied with their coworkers over 55 and lower levels of engagement when they were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
100.
陶金勇 《煤炭技术》2003,22(1):25-27
针对朱仙庄矿 84 15工作面切眼特殊的地质条件 ,介绍了高强锚杆 (索 )支护技术成功应用于特厚极软煤层的经验 ,并对巷道支护成本进行了分析  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