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   1058篇
  免费   57篇
  国内免费   1篇
电工技术   17篇
化学工业   118篇
金属工艺   5篇
机械仪表   8篇
建筑科学   28篇
矿业工程   2篇
能源动力   14篇
轻工业   220篇
水利工程   5篇
石油天然气   1篇
无线电   135篇
一般工业技术   163篇
冶金工业   336篇
原子能技术   8篇
自动化技术   56篇
  2023年   5篇
  2022年   16篇
  2021年   30篇
  2020年   27篇
  2019年   22篇
  2018年   18篇
  2017年   20篇
  2016年   23篇
  2015年   15篇
  2014年   24篇
  2013年   24篇
  2012年   31篇
  2011年   40篇
  2010年   33篇
  2009年   25篇
  2008年   39篇
  2007年   38篇
  2006年   41篇
  2005年   27篇
  2004年   26篇
  2003年   24篇
  2002年   16篇
  2001年   12篇
  2000年   19篇
  1999年   23篇
  1998年   100篇
  1997年   68篇
  1996年   58篇
  1995年   26篇
  1994年   26篇
  1993年   20篇
  1992年   21篇
  1991年   17篇
  1990年   11篇
  1989年   18篇
  1988年   14篇
  1987年   6篇
  1986年   8篇
  1985年   6篇
  1984年   8篇
  1983年   5篇
  1982年   5篇
  1981年   4篇
  1980年   9篇
  1979年   7篇
  1977年   8篇
  1976年   13篇
  1975年   5篇
  1974年   7篇
  1973年   4篇
排序方式: 共有1116条查询结果,搜索用时 10 毫秒
21.
In this paper, an indirect noninvasive method for measuring input impedance and the variations in the assembly of the interconnect and packaging between antenna and the integrated circuit (IC) effects of passive radio frequency identification (RFID) transponder (tags) antennas is presented. The analysis of different RFID tags is presented together with the experimental data.  相似文献   
22.
23.
This study examined (a) the role of avoidance coping in prospectively generating both chronic and acute life stressors and (b) the stress-generating role of avoidance coping as a prospective link to future depressive symptoms. Participants were 1,211 late-middle-aged individuals (500 women and 711 men) assessed 3 times over a 10-year period. As predicted, baseline avoidance coping was prospectively associated with both more chronic and more acute life stressors 4 years later. Furthermore, as predicted, these intervening life stressors linked baseline avoidance coping and depressive symptoms 10 years later, controlling for the influence of initial depressive symptoms. These findings broaden knowledge about the stress-generation process and elucidate a key mechanism through which avoidance coping is linked to depressive symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
24.
A comparison of two different styles of operator position in a trencher were compared using biomechanical principles and a field survey. A major postural difference between the two styles is the amount of time spent by the operators looking to the rear of their seated position. This was confirmed by a simple experiment. The style of position used in the skid steer type of trencher, facing the working tool, was found to be significantly better than the traditional fore-aft tractor style configuration.  相似文献   
25.
Numerical calculations are presented of the electron and hole ionization rates in GaAs/AlGaAs multiquantum-well APDs (avalanche photodiodes) as a function of the applied electric field and the spatial geometries, i.e., the barrier- and well-layer widths, respectively. The model is calibrated to existing experimental data on bulk GaAs materials and then extrapolated to the multiquantum well structure. It is found that at high electric field strengths the net ionization rate approaches the weighted average of the constituent bulk rates; the potential discontinuity is relatively insignificant. The potential discontinuity most greatly affects the electron ionization rate at low applied electric field strengths within a spatially symmetric structure. It is further determined that the electron-to-hole ionization rate ratio is greatest at low applied electric fields with a spatially symmetric structure with equal well and barrier widths  相似文献   
26.
27.
28.
Nonthermal plasma (NTP) is defined in terms of partly ionised gas which overall temperature is quite low because the stored energy is mostly in free electrons. Applications of NTP have been expanded to new areas of food applications such as the microbial inactivation and also the elimination of pesticide and toxic chemical residues in food such as fruits and vegetables while nutritional content and key characteristics are still preserved. Plasma treatment has successfully decreased the concentrations of pesticides by about 45‐71%. In this article, NTP technologies as well as investigations about applying of NTP for removing pesticide residues and improving microbial safety in fresh produce are described. Potential applications of NTP in food processing together with some of their challenges and limitations are also discussed.  相似文献   
29.
Extracellular mechanical cues have been shown to have a profound effect on osteogenic cell behaviour. However, it is not known precisely how these cues alter intracellular mechanics to initiate changes in cell behaviour. In this study, a combination of in vitro culture of MC3T3-E1 cells and finite-element modelling was used to investigate the effects of passive differences in substrate stiffness on intracellular mechanics. Cells on collagen-based substrates were classified based on the presence of cell processes and the dimensions of various cellular features were quantified. Focal adhesion (FA) density was quantified from immunohistochemical staining, while cell and substrate stiffnesses were measured using a live-cell atomic force microscope. Computational models of cell morphologies were developed using an applied contraction of the cell body to simulate active cell contraction. The results showed that FA density is directly related to cell morphology, while the effect of substrate stiffness on internal cell tension was modulated by both cell morphology and FA density, as investigated by varying the number of adhesion sites present in each morphological model. We propose that the cells desire to achieve a homeostatic stress state may play a role in osteogenic cell differentiation in response to extracellular mechanical cues.  相似文献   
30.
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