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   121篇
  免费   6篇
综合类   2篇
化学工业   16篇
机械仪表   2篇
建筑科学   2篇
矿业工程   1篇
能源动力   5篇
轻工业   4篇
无线电   21篇
一般工业技术   28篇
冶金工业   12篇
自动化技术   34篇
  2023年   1篇
  2022年   1篇
  2020年   5篇
  2019年   6篇
  2018年   4篇
  2017年   7篇
  2016年   3篇
  2015年   6篇
  2014年   5篇
  2013年   6篇
  2012年   6篇
  2011年   8篇
  2010年   5篇
  2009年   8篇
  2008年   8篇
  2007年   9篇
  2006年   13篇
  2005年   6篇
  2004年   4篇
  2003年   3篇
  2002年   3篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1993年   1篇
  1981年   1篇
  1979年   1篇
排序方式: 共有127条查询结果,搜索用时 0 毫秒
21.
Bilateral femurs of 12-week-old female Sprague-Dawley rats were fractured, and the fractured femurs were harvested 36 h, 3, 7, 10, and 14 days after the fracture. Localization of cell proliferation in the fracture calluses was investigated using immunohistochemistry with antiproliferating cell nuclear antigen (PCNA) monoclonal antibodies. Thirty-six hours after the fracture, many PCNA-positive cells were observed in the whole callus. The change was not limited to mesenchymal cells at the fracture site where the inflammatory reaction had occurred, but extended in the periosteum along almost the entire femoral diaphysis where intramembranous ossification was initiated. On day 3, periosteal cells or premature osteoblasts in the newly formed trabecular bone during intramembranous ossification still displayed intense staining. On day 7, many premature chondrocytes and proliferating chondrocytes were PCNA positive. Endochondral ossification appeared on days 10 and 14, and the premature osteoblasts and endothelial cells in the endochondral ossification front were stained with anti-PCNA antibodies. Quantification of PCNA-positive cells was carried out using an image analysis computer system, obtaining a PCNA score for each cellular event. The highest score was observed in the periosteum early after the fracture near the fracture site. Immunohistochemistry using anti-PCNA antibodies showed that the distribution of proliferating cells and the degree of cell proliferation varied according to the time lag after the fracture, suggesting the existence of local regulatory factors such as growth factors, and that significant cell proliferation was observed at the beginning of each cellular event.  相似文献   
22.
We consider equality sets of prefix morphisms, that is, sets E(g1,g2)={w|g1(w)=g2(w)}, where g1 and g2 are prefix morphisms. Recall that a morphism g is prefix if, for all different letters a and b, g(a) is not a prefix of g(b). We prove a rather surprising equality on families of languages, namely, that the family of regular star languages coincides with the family of languages of form πA(E(g1,g2)) for some prefix morphisms g1 and g2, and a projection πA which deletes the letters not in A.  相似文献   
23.
A family of compact CMOS rail-to-rail input stages with constant-g m is presented. To attain a constant-gm over the whole common-mode input range, an electronic zener diode is inserted between the tails of the complementary input pairs. This zener keeps the sum of the gate-source voltages of the input pairs, and therefore the g m of the rail-to-rail input stage, constant. Two possible implementations of the zener have been realized and inserted in a rail-to-rail input stage. These input stages are implemented in two two-stage compact amplifiers. Both amplifiers have been realized in a 1 μm BiCMOS process. They have a unity-gain frequency of 2-MHz, for a capacitive load of 20 pF  相似文献   
24.
We recently described a novel homogeneous assay principle based on upconversion fluorescence resonance energy transfer (UC-FRET), where an upconverting phosphor (UCP) is utilized as a donor. The UC-FRET has now been applied to a competitive homogeneous immunoassay for 17beta-estradiol (E2) in serum, using a small-molecular dye as an acceptor. The assay was constructed by employing an UCP coated with an E2-specific recombinant antibody Fab fragment as a donor and an E2-conjugated small-molecular dye, Oyster-556, as an acceptor. Standard curves for the assay were produced both in buffer and in male serum. Sensitized acceptor emission was measured at 600 nm under continuous laser diode excitation at 980 nm. In buffer, the IC50 value of the assay was 1 nM and in serum 3 nM. The lower limits of detection (mean of zero calibrators, 3 SD) were 0.4 and 0.9 nM, respectively. The measurable concentration range extended up to 3 nM in buffer and 9 nM in serum. Equilibrium in the assay was reached in 30 min. The novel principle of UC-FRET has unique advantages compared to present homogeneous luminescence-based methods and can enable an attractive assay system platform for clinical diagnostics and for high-throughput screening approaches.  相似文献   
25.
A novel atomic layer deposition process for the preparation of fluoride thin films in a temperature range of 225 degrees C-400 degrees C is introduced. The crystallinity, morphology, composition, thicknesses, refractive indices, and transmittance of the films are analyzed. Low impurity levels are obtained at 350 degrees C-400 degrees C with good stoichiometry. Refractive indices of 1.34-1.42 for MgF(2), 1.43 for CaF(2), and 1.57-1.61 for LaF(3) films are obtained.  相似文献   
26.
The effects of the fuel injection pressure on a heavy-duty diesel engine exhaust particle emissions were studied. Nonvolatile particle size distributions and gaseous emissions were measured at steady-state engine conditions while the fuel injection pressure was changed. An increase in the injection pressure resulted in an increase in the nonvolatile nucleation mode (core) emission at medium and at high loads. At low loads, the core was not detected. Simultaneously, a decrease in soot mode number concentration and size and an increase in the soot mode distribution width were detected at all loads. Interestingly, the emission of the core was independent of the soot mode concentration at load conditions below 50%. Depending on engine load conditions, growth of the geometric mean diameter of the core mode was also detected with increasing injection pressure. The core mode emission and also the size of the mode increased with increasing NOx emission while the soot mode size and emission decreased simultaneously.  相似文献   
27.
28.
29.
A low-complexity distributed power allocation algorithm is proposed to reduce the interference and improve the transmitting rate of edge users. Different scenarios are considered and user experience of indoor communication is promoted. The simulation results prove the effectiveness of our algorithm. The proposed power control scheme ensures that more users can achieve their required rate and the fairness of different users is improved. Besides, more than 50% energy can be saved without loss in outage ability, and energy efficiency is also promoted. In addition, the proposed algorithm can be extended to scenarios that the required rates of pico stations can be changed periodically.  相似文献   
30.
This field study evaluated the level of muscular, cardiorespiratory and thermal strain of mast and pole workers. We measured the muscular strain using electromyography (EMG), expressed as a percentage in relation to maximal EMG activity (%MEMG). Oxygen consumption (VO2) was indirectly estimated from HR measured during work and expressed as a percentage of maximum VO2 (%VO2max). Skin and deep body temperatures were measured to quantify thermal strain. The highest average muscular strain was found in the wrist flexor (24 ± 1.5%MEMG) and extensor (21 ± 1.0%MEMG) muscles, exceeding the recommendation of 14%MEMG. Average cardiorespiratory strain was 48 ± 3%VO2max. Nearly half (40%) of the participants exceeded the recommended 50%VO2max level. The core body temperature varied between 36.8°C and 37.6°C and mean skin temperature between 28.6°C and 33.4°C indicating possible occasional superficial cooling. Both muscular and cardiorespiratory strain may pose a risk of local and systemic overloading and thus reduced work efficiency. Thermal strain remained at a tolerable level.  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