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   380095篇
  免费   3858篇
  国内免费   764篇
电工技术   7824篇
综合类   644篇
化学工业   55581篇
金属工艺   16312篇
机械仪表   14392篇
建筑科学   9188篇
矿业工程   1600篇
能源动力   9108篇
轻工业   32141篇
水利工程   3589篇
石油天然气   4940篇
武器工业   8篇
无线电   46393篇
一般工业技术   76757篇
冶金工业   62058篇
原子能技术   6464篇
自动化技术   37718篇
  2021年   2276篇
  2019年   2138篇
  2018年   11641篇
  2017年   12118篇
  2016年   8043篇
  2015年   3073篇
  2014年   4522篇
  2013年   14320篇
  2012年   9888篇
  2011年   18136篇
  2010年   15647篇
  2009年   15680篇
  2008年   15874篇
  2007年   17831篇
  2006年   8573篇
  2005年   11466篇
  2004年   9667篇
  2003年   9049篇
  2002年   7948篇
  2001年   7606篇
  2000年   7337篇
  1999年   7565篇
  1998年   17661篇
  1997年   12833篇
  1996年   10109篇
  1995年   7882篇
  1994年   7228篇
  1993年   6924篇
  1992年   5299篇
  1991年   5084篇
  1990年   4933篇
  1989年   4781篇
  1988年   4679篇
  1987年   3886篇
  1986年   4007篇
  1985年   4718篇
  1984年   4275篇
  1983年   4021篇
  1982年   3601篇
  1981年   3761篇
  1980年   3456篇
  1979年   3418篇
  1978年   3225篇
  1977年   3814篇
  1976年   4847篇
  1975年   2780篇
  1974年   2660篇
  1973年   2675篇
  1972年   2215篇
  1971年   1963篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
This paper focuses on the hydrodynamics of third sound on a superfluid 3 He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range.  相似文献   
112.
Heat transfer of highly consistent shear-thinning fluids flowing in a horizontal cylindrical channel has been investigated numerically and experimentally when the outer channel wall is subjected to a constant convective heat exchange. The case considered being cooling, a possible ice deposit must be taken into account. The variation of the rheological properties with temperature must be considered as well.  相似文献   
113.
114.
115.
The biotransformation of oxazepam by Bifidobacterium bifidum was studied. The major metabolite was purified by chromatographic methods and found to be desmethyldiazepam using NMR, IR and other physicochemical data.  相似文献   
116.
Butyl, hexyl, and 2-ethylhexyl diesters of 1,1-bis(5-carboxyl-2-furyl)-2,2-dichloroethene, hexyl and 2-ethylhexyl diesters of 1,1-bis(5-carboxyl-2-furyl) ketone, and the hexyl diester of 1,1-bis(5-carboxyl-2-furyl)methane were synthesized from furfural and evaluated for their plasticizing abilities toward PVC, by the application of dynamic mechanical thermal analysis and [di(2-ethylhexyl) phthalate] as a standard of reference. © 1995 John Wiley & Sons, Inc.  相似文献   
117.
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre.  相似文献   
118.
119.
120.
This investigation retrospectively examined changes in marital satisfaction following stroke. The relationship between such changes and other pertinent factors were also examined, including severity of aphasia, knowledge of aphasia, number of months after stroke, and length of the marriage. The subjects were 40 spouses of patients with aphasia grouped according to severity of the aphasia (mild, moderate, severe). Spouses completed two different measures of marital satisfaction--the Marital Satisfaction Scale (MSS) and the Marital Comparison Level Index (MCLI). These measures were completed in both a prestroke (retrospective reporting) and a poststroke format to allow for change to be assessed. In addition, a Knowledge of Aphasia questionnaire was completed by the normal spouses to evaluate their understanding of the disorder of aphasia. There was a significant difference between prestroke and poststroke scores on both the MSS and the MCLI, indicating a lower level of satisfaction following the stroke. The amount of change between prestroke and poststroke MSS and MCLI scores was not related to either number of months poststroke or number of years married. Although there was no relationship between changes in prestroke and poststroke scores on the MCLI and Knowledge of Aphasia scores, there was a significant correlation between changes in these scores on the MSS and Knowledge of Aphasia scores. Hence, the more knowledge spouses had regarding aphasia, the less the negative impact the stroke had on marital satisfaction, as measured by the MSS. Results are discussed in terms of the interdisciplinary treatment needs of aphasic patients and the implications for future investigations.  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