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   185篇
  免费   5篇
电工技术   1篇
化学工业   29篇
金属工艺   22篇
机械仪表   4篇
建筑科学   3篇
矿业工程   2篇
能源动力   2篇
轻工业   24篇
无线电   6篇
一般工业技术   21篇
冶金工业   53篇
原子能技术   2篇
自动化技术   21篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   12篇
  2018年   4篇
  2017年   3篇
  2016年   3篇
  2015年   2篇
  2014年   11篇
  2013年   9篇
  2012年   10篇
  2011年   12篇
  2010年   11篇
  2009年   9篇
  2008年   2篇
  2007年   8篇
  2006年   4篇
  2005年   5篇
  2004年   6篇
  2003年   4篇
  2002年   9篇
  2001年   1篇
  2000年   3篇
  1999年   6篇
  1998年   17篇
  1997年   7篇
  1996年   3篇
  1995年   7篇
  1994年   3篇
  1993年   6篇
  1990年   1篇
  1989年   2篇
  1986年   1篇
  1983年   1篇
  1980年   1篇
  1976年   1篇
  1924年   1篇
排序方式: 共有190条查询结果,搜索用时 0 毫秒
21.
We examined serum levels of a CD44 splice variant that contained variant exons 8-10 (CD44v8-10) as a tumor marker in colorectal cancer patients. We performed enzyme-linked immunosorbent assays in 81 sera obtained from 71 colorectal cancer patients and 10 healthy controls. Serum CD44v8-10 levels were significantly higher in the colorectal cancer patients than in the healthy controls (0.209 +/- 0.098 versus 0.114 +/- 0.019 OD; P < 0.01). There was a close correlation between immunohistochemical expression and serum CD44v8-10 levels. Surgical resection of the tumors resulted in a reduction of serum CD44v8-10 levels. There was no significant correlation between serum CD44v8-10 level and serosal invasion or histologic type. However, a significant correlation was observed between serum CD44v8-10 level and lymphatic or venous invasion. In addition, serum CD44v8-10 levels were significantly higher in carcinomas associated with lymph node or liver metastasis than in those without metastasis. These findings suggest the usefulness of serum CD44v8-10 level in the prediction of colorectal cancer metastasis.  相似文献   
22.
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   
23.
24.
The polarizability of gyrotropic spheres is studied in this short article. Gyrotropic media are anisotropic in two respects: the symmetric part of the permittivity dyadic is uniaxial, and furthermore, there is also antisymmetric part in the permittivity. The polarizability is also dyadic with its components depending on the relations of the permittivity components of the material.  相似文献   
25.
BACKGROUND: The two most frequently used options to reduce the occurrence of acute otitis media (AOM) are tympanostomy tubes and prophylactic antibiotics. The goal of this study was to create a decision model to identify which intervention, if any, is preferred from the perspective of parents with young children. METHODS: We developed a decision analysis model based on probabilities obtained from the literature and outcome disutilities obtained by interviewing parents. These parameters were placed into the model along with the anticipated number of episodes of AOM a child was expected to have in the coming year without intervention. Sensitivity analyses were performed on the effectiveness of the interventions, the disutilities (burdens associated with specific outcomes or interventions) associated with the interventions, and the characteristics of AOM episodes that the child would experience without any intervention. RESULTS: Thirty-seven parents with young children were interviewed for this project. The preferred intervention for a child was sensitive to the number of episodes of AOM the child was anticipated to have in the coming year, the percentage of these episodes predicted to be severe, and how parents rated tympanostomy tubes compared with prophylactic antibiotics. In our base case of four episodes of AOM in the coming year (two mild episodes and two severe episodes), we found that tympanostomy tubes resulted in the best average outcome. Under different patient conditions, however, the preferred strategy could be either the use of prophylactic antibiotics or watchful waiting. CONCLUSIONS: In our base case, the model suggested that tympanostomy tubes were preferable to prophylactic antibiotics. However, there is no single preferred preventive intervention for all children with recurrent AOM because of variation in the character of infections and the values parents give to the potential outcomes.  相似文献   
26.
27.
ABSTRACT

Behaviour of trace elements in the nickel matte smelting was studied at 1673 K (1400°C) by equilibration-quenching techniques followed by direct phase analyses using electron probe X-ray microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. The matte-slag samples at silica saturation were equilibrated with SO2-CO-CO2-Ar mixtures of fixed pSO2, pS2 and pO2 in order to obtain a pre-determined oxidation degree for the sulphide matte, and thus to generate a targeted iron concentration of the nickel-copper–iron sulphide matte (Ni:Cu = 5, w/w), depending on the slag chemistry. The slag composition was varied from 0 to 2 wt-% K2O and 0–10 wt-% MgO in silica saturation. The studied trace elements were Co, Ge, Pb, Se and Sn, but also the matte-to-slag distributions of the slag forming fluxing components Mg (MgO) and Si (SiO2) were determined experimentally. Selenium was the only trace element studied which strongly enriched in the low-iron nickel mattes, and the deportment became larger when the sulphide matte depleted with iron. All the other trace elements behaved in the opposite way.  相似文献   
28.
Extracellular matrix (ECM) proteins are known to play a role in inflammatory and hyperplastic processes. Our aim in the present study was to study the distribution of tenascin (Tn), cellular fibronectins (cFn) and myofibroblasts around biodegradable poly-L/D-lactide (PLA) implants with monoclonal antibodies (MAb). Ethylene-oxide and gamma-irradiation sterilized PLA plate-type implants were inserted into the dorsal subcutaneous tissue of ten adult rabbits. Follow-up times were 4, 12, 16, 36 and 48 wk. Only some inflammatory cells were observed. In electron microscopy, a close coherence between the implant and the stromal tissue was seen. Immunoreactivity for Tn, cFn and -actin was detected as a distinct layer bordering the implant, regardless of the sterilization method for the first 36 wk. From week 36 onwards, Tn immunoreactivity was downregulated while cFn immunoreactivity still persisted. A moderate upregulation for myofibroblasts was seen on the week 48 specimens, when hydrolysation of PLA implant had started. The persistent content of myofibroblasts, Tn and cFn suggests a prolonged wound healing produced by PLA implants. The absence of Tn at the week 48 specimens suggests that cFn, rather than Tn may be needed for -actin-mediated contraction by myofibroblasts.  相似文献   
29.
This paper formulates a theoretical model of flight deck team performance as a dynamic human‐machine system, later referred to as CRM‐DYMO (Crew Resources Management‐DYnamic MOdel). The model identifies human and machine subsystems. The human subsystem describes the activities taken by the flight crew and the machine subsystem describes the changes in the aircraft's state. The human subsystem's output forms an input for the machine subsystem, and the machine subsystem's output feeds back to the human system creating a closed loop system. Pilots’ performance are described as competencies, which form part of the elements in the human subsystem. This paper concentrates only on CRM competencies as defined by the International Civil Aviation Authority and the International Air Transport Association. In addition to the detailed conceptual model of the human subsystem and associated competencies, the approach is illustrated with reference to two accident case studies. These demonstrate how CRM‐DYMO can assist in analyzing CRM and help in identifying how the different system components interact. Although the case studies demonstrate the benefits of CRM‐DYMO, they merely serve as a starting point to understand how CRM works and will hopefully encourage supporting quantitative simulation modeling and empirical studies.  相似文献   
30.
Elemental Ti-48Al-2Cr-2Nb powders were mechanically alloyed (MA) for 8 h and 45 h. The MA powders were then consolidated by reactive hot isostatic pressing (HIP). The microstructure of the HIPed materials consisted of equiaxed γ-TiAl and α2-Ti3Al phases. During the high-temperature annealing of the HIPed materials, the α2-Ti3-Al phase transformed into a lamellar structure consisting of alternating laths of α2-Ti3Al and γ-TiAl. It is suggested that a high content of interstitial elements together with the microalloying elements of niobium and/or chromium in MA powders raises α/(α + γ) transus to a higher temperature.  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