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   5270篇
  免费   293篇
  国内免费   7篇
电工技术   79篇
综合类   2篇
化学工业   1355篇
金属工艺   67篇
机械仪表   130篇
建筑科学   198篇
矿业工程   6篇
能源动力   208篇
轻工业   704篇
水利工程   36篇
石油天然气   16篇
无线电   471篇
一般工业技术   928篇
冶金工业   529篇
原子能技术   40篇
自动化技术   801篇
  2024年   8篇
  2023年   48篇
  2022年   235篇
  2021年   277篇
  2020年   144篇
  2019年   164篇
  2018年   175篇
  2017年   131篇
  2016年   196篇
  2015年   164篇
  2014年   226篇
  2013年   370篇
  2012年   321篇
  2011年   384篇
  2010年   312篇
  2009年   263篇
  2008年   282篇
  2007年   210篇
  2006年   174篇
  2005年   165篇
  2004年   120篇
  2003年   131篇
  2002年   121篇
  2001年   71篇
  2000年   62篇
  1999年   77篇
  1998年   148篇
  1997年   90篇
  1996年   74篇
  1995年   60篇
  1994年   49篇
  1993年   41篇
  1992年   25篇
  1991年   21篇
  1990年   16篇
  1989年   22篇
  1988年   20篇
  1987年   16篇
  1986年   14篇
  1985年   13篇
  1984年   14篇
  1983年   9篇
  1982年   15篇
  1981年   13篇
  1980年   10篇
  1979年   8篇
  1978年   8篇
  1977年   7篇
  1976年   10篇
  1975年   6篇
排序方式: 共有5570条查询结果,搜索用时 46 毫秒
11.
正项目地址_中国北京项目面积_8000m~2设计单位_ArkA北京亦庄半岛幼儿园项目是设计团队与半岛教育集团的第二次合作,目标是将蒙特梭利教育理念和建筑设计融为一体,创造出一个更合理的空间和安全的环境,让孩子们能够自由快乐地学习和成长。原有的建筑物是一个开放的空间,整个大空间分作4层。设计团队的首要任务是根据孩子的比例改造空间。在设计时,设计团队加入了许多小房屋的设计,以此让孩子更具有主人感和安全感。对教室的设计是简约的房屋;图书馆则是一个开放空间,在其中央种下一棵树,好似一个乡村小镇的广场;走廊设计成多功能的开放空间,孩子  相似文献   
12.
13.
Linear-viscoelastic characteristics and performance are evaluated throughout the blending process of polyethylene and polypropylene with bitumen. Results indicate that type, form and percentage of polyolefin play a significant role in the time evolution of the composite's mechanical response. Toluene extraction of modified bitumen revealed, for the first time, the formation of a sponge-like polymer network. Visual inspection and Fourier transform infrared analysis of the polyolefins recovered after extraction indicates higher affinity of the polyethylene with bitumen in agreement with the rheological test results. The use of polypropylene is discouraged if rutting performance is a concern, and polyethylene in both pellets and powder form at 4%, and after 210 min of blending produces a modified bitumen with acceptable performance.  相似文献   
14.
The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is also regulated by ANS. In this study, we explored salivary proteome changes produced in thirty-eight University students by a test stress, which simulated an oral exam. Students underwent a relaxation phase followed by the stress test during which an electrocardiogram was recorded. To evaluate the effect of an olfactory stimulus, half of the students were exposed to a pleasant odor diffused in the room throughout the whole session. Saliva samples were collected after the relaxation phase (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis, and patterns at different times were compared. Spots differentially expressed were trypsin digested and identified by mass spectrometry. Western blot analysis was used to validate proteomic results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of α-amylase, polymeric immunoglobulin receptor (PIGR), and immunoglobulin α chain (IGHA) secretion were observed after the stress test was performed in the two conditions. Moreover, the presence of pleasant odor reduced the acute social stress affecting salivary proteome changes. Therefore, saliva proteomic analysis was a useful approach to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers.  相似文献   
15.
Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials.  相似文献   
16.
17.
This paper presents a novel framework for manufacturing and cost-related knowledge formalization. This artefact allows industries to capitalize the knowled  相似文献   
18.
19.
20.
To date, the only effective means to respond to the spreading of the COVID-19 pandemic are non-pharmaceutical interventions (NPIs), which entail policies to reduce social activity and mobility restrictions. Quantifying their effect is difficult, but it is key to reducing their social and economic consequences. Here, we introduce a meta-population model based on temporal networks, calibrated on the COVID-19 outbreak data in Italy and applied to evaluate the outcomes of these two types of NPIs. Our approach combines the advantages of granular spatial modelling of meta-population models with the ability to realistically describe social contacts via activity-driven networks. We focus on disentangling the impact of these two different types of NPIs: those aiming at reducing individuals’ social activity, for instance through lockdowns, and those that enforce mobility restrictions. We provide a valuable framework to assess the effectiveness of different NPIs, varying with respect to their timing and severity. Results suggest that the effects of mobility restrictions largely depend on the possibility of implementing timely NPIs in the early phases of the outbreak, whereas activity reduction policies should be prioritized afterwards.  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