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   2749篇
  免费   106篇
  国内免费   1篇
电工技术   28篇
综合类   3篇
化学工业   733篇
金属工艺   97篇
机械仪表   60篇
建筑科学   182篇
矿业工程   5篇
能源动力   55篇
轻工业   262篇
水利工程   16篇
石油天然气   5篇
无线电   179篇
一般工业技术   477篇
冶金工业   515篇
原子能技术   42篇
自动化技术   197篇
  2022年   26篇
  2021年   43篇
  2019年   36篇
  2018年   44篇
  2017年   39篇
  2016年   59篇
  2015年   56篇
  2014年   68篇
  2013年   97篇
  2012年   89篇
  2011年   109篇
  2010年   74篇
  2009年   88篇
  2008年   92篇
  2007年   84篇
  2006年   76篇
  2005年   78篇
  2004年   87篇
  2003年   63篇
  2002年   65篇
  2001年   56篇
  2000年   41篇
  1999年   53篇
  1998年   128篇
  1997年   97篇
  1996年   72篇
  1995年   49篇
  1994年   55篇
  1993年   44篇
  1992年   35篇
  1991年   47篇
  1990年   35篇
  1989年   38篇
  1988年   31篇
  1987年   25篇
  1986年   30篇
  1985年   42篇
  1984年   48篇
  1983年   42篇
  1982年   32篇
  1981年   38篇
  1980年   37篇
  1979年   24篇
  1978年   35篇
  1977年   28篇
  1976年   36篇
  1975年   27篇
  1974年   33篇
  1973年   21篇
  1970年   21篇
排序方式: 共有2856条查询结果,搜索用时 724 毫秒
1.
Schmitt  M.P. 《Electronics letters》1998,34(18):1725-1726
A new hybrid automatic repeat request scheme employing packet combining based on the Viterbi decoder is presented. It is shown that the proposed form of combining, together with a rearrangement of the signal constellation, can outperform similar forms of packet combining such as average diversity combining  相似文献   
2.
A total of 438 manufacturing firms reported their business relocation activity, their overall attitude toward the business climate in Michigan, and their assessment of 34 business climate dimensions. Using a lens model paradigm, we explored reasons for a lack of relation between actual relocation decisions and overall business climate attitudes. Location decisions were most highly correlated with distance and labor considerations, whereas overall business climate was most highly correlated with tax considerations, and secondarily correlated with labor problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Rationalizing drawings for chemical apparatus . For small and medium-sized manufacturers of apparatus, producing drawings may constitute a disproportionate waste of time and personnel, particularly when no new designs are involved but only modification or improvement of drawings supplied by the customer. One possibility for rationalizing drawing is to simplify the old-fashioned approach by using symbols for frequently drawn or standard items, or by listing alphanumerically. This presumes a kind of systematization permitting determination of those symbols and their reasonable use, as well facilitating rationalization by means of data processing. There are different approaches to computer-aided drawing (from computer controlled drawing-board to interactive screens); here a CAD programme is presented which was especially developed for graphic presentation of chemical apparatus, and which can be used without learning a programming language.  相似文献   
4.
5.
The current study investigated the impact of requiring respondents to elaborate on their answers to a biodata measure on mean scores, the validity of the biodata item composites, subgroup mean differences, and correlations with social desirability. Results of this study indicate that elaborated responses result in scores that are much lower than nonelaborated responses to the same items by an independent sample. Despite the lower mean score on elaborated items, it does not appear that elaboration affects the size of the correlation between social desirability and responses to biodata items or that it affects criterion-related validity or subgroup mean differences in a practically significant way. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
For provenance assignments of wines strontium isotope ratios can be used because soils from different wine-growing regions, and hence the wines grown there, each show specific ratios. Some successful applications are demonstrated.
87Sr/86Sr aus Gestein und Boden in Rebe und Wein
Zusammenfassung Zur Herkunftsbestimmung von Weinen können Strontium-Isotopenverhältnisse herangezogen werden, da die Böden verschiedener Weinbaugebiete, und damit die dort gezogenen Weine, jeweils spezifische Verhältnisse aufweisen. Einige erfolgreiche Anwendungen werden demonstriert.
  相似文献   
7.
PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation.  相似文献   
8.
9.
Metrology of freeform shaped parts   总被引:2,自引:0,他引:2  
E. Savio  R. Schmitt 《CIRP Annals》2007,56(2):810-835
The scope of this keynote paper is to present the state of the art in the metrology of freeform shapes with focus on the freeform capabilities of the most important measuring techniques and on related metrological issues. Some examples of products are presented, for which the metrology of freeform shapes is important to guarantee the desired functional performance of the product. A classification of freeform measuring tasks and the corresponding metrological requirements are presented. A review of the most important measuring techniques is presented along with their capabilities for freeform measuring tasks. Specification and verification of freeform surfaces, including data evaluation and comparison to specifications are discussed, along with the measurement uncertainty and traceability of freeform measurements.  相似文献   
10.
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