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   49447篇
  免费   1814篇
  国内免费   347篇
电工技术   824篇
综合类   557篇
化学工业   10165篇
金属工艺   1074篇
机械仪表   1248篇
建筑科学   2095篇
矿业工程   511篇
能源动力   1287篇
轻工业   4018篇
水利工程   483篇
石油天然气   424篇
武器工业   27篇
无线电   4262篇
一般工业技术   7188篇
冶金工业   9870篇
原子能技术   450篇
自动化技术   7125篇
  2022年   677篇
  2021年   998篇
  2020年   598篇
  2019年   745篇
  2018年   899篇
  2017年   788篇
  2016年   999篇
  2015年   813篇
  2014年   1245篇
  2013年   2850篇
  2012年   1878篇
  2011年   2363篇
  2010年   1788篇
  2009年   1913篇
  2008年   2069篇
  2007年   1981篇
  2006年   1763篇
  2005年   1552篇
  2004年   1471篇
  2003年   1655篇
  2002年   1927篇
  2001年   1516篇
  2000年   997篇
  1999年   999篇
  1998年   1785篇
  1997年   1293篇
  1996年   1117篇
  1995年   879篇
  1994年   777篇
  1993年   788篇
  1992年   630篇
  1991年   423篇
  1990年   553篇
  1989年   522篇
  1988年   468篇
  1987年   512篇
  1986年   458篇
  1985年   590篇
  1984年   548篇
  1983年   490篇
  1982年   457篇
  1981年   400篇
  1980年   399篇
  1979年   419篇
  1978年   345篇
  1977年   336篇
  1976年   409篇
  1975年   296篇
  1974年   249篇
  1973年   275篇
排序方式: 共有10000条查询结果,搜索用时 837 毫秒
41.
42.
43.
Microsystem Technologies - This paper represents low power and high speed design issues of Hamming code generation and error detection circuit using complementary metal oxide semiconductor (CMOS)...  相似文献   
44.
Some individuals are able to determine the weekday of a given date in a few seconds (finding for instance that June 12, 1900, was a Tuesday). This ability has fascinated scientists for many years because it is predominantly observed in people with limited intelligence and may appear very early in life. Exceptional visual memory, exceptional concentration abilities, or privileged access to lower levels of information not normally available through introspection have been advanced to explain such phenomena. In the present article, the authors show that a simple cognitive model can explain all aspects of the performance of Donny, a young autistic savant who is possibly the fastest and most accurate calendar prodigy ever described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
45.
46.
Up until today extreme rainfall properties are frequently applied in sewer design guidelines. Uncertainty in the estimation of such properties will hence directly influence the dimensions of sewers, structures and pumps. In this paper the issue of potential trend and noise in the estimation is investigated for 6 rain series ranging from 19 to 55 years in duration. Different to recent research that predicts a climate induced-increase in heavy precipitation no clear indication for such trend was found in the investigated historical rain series. Another important aspect is the length of the rain series that is required for the estimation of extreme rainfall properties and the associated uncertainty. The analysis indicates that at least a period of 10 years should be used for the estimation. But even so the possible deviation expressed in terms of the 90 percentile is in the order of 5 to 10% of the 'true value', defined as the value derived when the whole given series is used for the estimation.  相似文献   
47.
48.
The objective of this research was to investigate the feasibility of visible transmission spectroscopy for the non‐destructive assessment of the freshness of an individual egg. A total of 600 intact white‐shelled eggs of the same flock (Lohmann, 40 weeks of age) were measured. To obtain a considerable variation in freshness, groups consisting of 60 eggs were stored (18 °C, 55% RH) for 0, 2, 4, 6, 8, 10, 12, 14, 16 and 18 days. The non‐destructive spectral measurements were compared with the two most widely used destructive freshness parameters, namely Haugh units and albumen pH. A partial least squares (PLS1) model was built in order to predict Haugh units and pH of the albumen based on the transmission spectra. The correlation coefficients between the predicted value and the measured value were 0.842 and 0.867 for Haugh unit and pH of the albumen, respectively. These results show that the light transmission spectrum of an egg provides quantitative information about egg freshness. Relevant information concerning egg freshness is restricted to the interval between 570 and 750 nm. Furthermore, the models obtained for both destructive parameters were strikingly similar, indicating that Haugh unit and pH have the same physico‐chemical background. Copyright © 2006 Society of Chemical Industry  相似文献   
49.
Integrated tests (IT) applied to the Units I and II of the CNAAA Nuclear Power Plants (Angra dos Reis, Rio de Janeiro, Brazil) vara part of a comprehensive test program required to have the commercial operational licence issued. The IT cover operation at zero power and the subsequent power levels (the power escalation) until the nominal power operation.

This paper reports and compares the results of systematic neutron and gamma equivalent dose-rate measurements performed inside and outside the reactor containment of each Unit, during the start-up phase of the operation, for different power levels of the reactors. It also compares the collective-doses measured along the operation of the two units of the CNAAA wich similar data of the Grafenrheinfeld nuclear power plant (Germany) — basic-of-project for the CNAAA — Unit II — and analyses the data under the fight of the state-of-art.  相似文献   

50.
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