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   73篇
  免费   0篇
  国内免费   1篇
电工技术   2篇
化学工业   6篇
金属工艺   8篇
机械仪表   2篇
建筑科学   1篇
轻工业   8篇
无线电   3篇
一般工业技术   10篇
冶金工业   29篇
自动化技术   5篇
  2024年   1篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2014年   2篇
  2013年   4篇
  2012年   3篇
  2011年   1篇
  2009年   1篇
  2008年   5篇
  2007年   1篇
  2006年   4篇
  2005年   2篇
  2004年   4篇
  2003年   1篇
  2002年   2篇
  2001年   2篇
  1999年   2篇
  1998年   12篇
  1997年   5篇
  1996年   3篇
  1995年   1篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1989年   1篇
  1982年   1篇
  1979年   1篇
  1976年   2篇
排序方式: 共有74条查询结果,搜索用时 0 毫秒
41.
    
Zinc is an essential trace element for humans and animals, being located, among other places, in the synaptic vesicles of cortical glutamatergic neurons and hippocampal mossy fibers in the brain. Extracellular zinc has the potential to interact with and modulate many different synaptic targets, including glutamate and GABA receptors. Because of the central role of these neurotransmitters in brain activity, we examined in this study the sleep‐promoting activity of zinc by monitoring locomotor activity and electroencephalogram after its administration to mice. Zinc‐containing yeast extract (40 and 80 mg/kg) dose dependently increased the total amount of nonrapid eye movement sleep and decreased the locomotor activity. However, this preparation did not change the amount of rapid eye movement sleep or show any adverse effects such as rebound of insomnia during a period of 24 h following the induction of sleep; whereas the extracts containing other divalent cations (manganese, iron, and copper) did not decrease the locomotor activity. This is the first evidence that zinc can induce sleep. Our data open the way to new types of food supplements designed to improve sleep.  相似文献   
42.
The incidence of thromboembolic complications among 288 patients with atrial fibrillation (AF) who were followed up during an average period of 7.2 years was examined retrospectively. The annual incidence of thromboembolic complications was 1.6% in total, 1.7% in valvular heart disease (n=128), and 2.1% in non-valvular heart disease (n=117). No thromboembolism occurred in lone AF (n=43), defined as the complete absence of any underlying disease. The type of AF before embolic attack was chronic in 26 cases and paroxysmal in 6 cases. The cardiac rhythm at the time of the embolic attack was AF, except in 2 cases in which ECG was not recorded. In all patients with thromboembolic complications who were receiving antithrombotic therapy during the follow-up, the anticoagulant effect just before the embolic attack was found to be insufficient. Major bleeding was not observed in the patients receiving antithrombotic therapy. Thromboembolism in AF in long-term follow-up tends to occur more frequently in patients with underlying heart disease and in those with chronic AF compared rather than paroxysmal AF; it rarely occurs in lone AF. We should not hesitate to administer sufficient anticoagulant therapy in AF patients who are at high risk of developing thromboembolic complications.  相似文献   
43.
To develop a high-rate diamond deposition process using combustion flame method, diamond deposition equipment with twin acetylene/oxygen welding torch was manufactured, and diamond deposition by using this equipment was carried out. 304 Stainless steel plates and molybdenum plates were used as substrates. The diamond deposition was conducted under the following conditions: oxygen flow rate: 1.25 SLM, acetylene/oxygen flow ratio: 1.15, and diamond deposition temperature: around 1473 K. Consequently, diamonds could be deposited even on the stainless steel substrate, and diamond deposition rate was promoted by using twin torch equipment. Besides, the diamond/molybdenum hybrid coating using diamonds deposited by twin torch equipment have the same wear-resistant property as that using diamonds by the single torch equipment. From these results, this technique was thought to have high potential for high-rate diamond deposition in combustion flame method.  相似文献   
44.
    
This study demonstrates that the luciferin of the firefly squid Watasenia scintillans, which generally reacts with Watasenia luciferase, reacted with human albumin to emit light in proportion to the albumin concentration. The luminescence showed a peak wavelength at 540 nm and was eliminated by heat or protease treatment. We used urine samples collected from patients with diabetes to quantify urinary albumin concentration, which is essential for the early diagnosis of diabetic nephropathy. Consequently, we were able to measure urinary albumin concentrations by precipitating urinary proteins with acetone before the reaction with luciferin. A correlation was found with the result of the immunoturbidimetric method; however, the Watasenia luciferin method tended to produce lower albumin concentrations. This may be because the Watasenia luciferin reacts with only intact albumin. Therefore, the quantification method using Watasenia luciferin is a new principle of urinary albumin measurement that differs from already established methods such as immunoturbidimetry and high-performance liquid chromatography.  相似文献   
45.
46.
Cirrhotic patients with ascites refractory to diuretics also have blunted response to marked elevations of plasma atrial natriuretic factor levels alone or to moderate intravascular volume expansion by head-out water immersion. However, these patients usually undergo natriuresis after peritoneovenous shunting. To dissect the factors responsible for this response, we studied the effects on separate days of moderate intravascular volume expansion and highly elevated plasma atrial natriuretic factor levels (head-out water immersion and atrial natriuretic factor infusion) or marked volume expansion and moderate plasma atrial natriuretic factor level elevation (head-out water immersion and albumin infusion) in 13 alcoholic cirrhotic patients with massive ascites. Three of these patients, who responded to initial head-out water immersion with a negative sodium balance, served as controls. Unresponsiveness to head-out water immersion was confirmed in the remaining 10 patients on both days on the basis of blunted natriuretic response (urinary sodium excretion < 0.8 mmol/hr after 2 hr). In contrast, these 10 refractory patients were able to achieve negative sodium balance with both combinations. Mean urinary sodium excretion increased from a baseline level of 0.13 +/- 0.10 mmol/hr to a peak level of 2.29 +/- 0.61 mmol/hr after head-out water immersion and atrial natriuretic factor infusion and from 0.10 +/- 0.3 mmol/hr to 1.61 +/- 0.62 mmol/hr after head-out water immersion and albumin infusion. Both maneuvers were associated with suppression of plasma renin activity and serum aldosterone levels. With head-out water immersion and atrial natriuretic factor infusion, we noted a significant increase in 5' cyclic GMP levels, a second messenger of atrial natriuretic factor, indicating possible activation of atrial natriuretic factor receptors at the inner medullary collecting ducts. In contrast, with head-out water immersion and albumin infusion no such increase in levels occurred, indicating that the increase in urinary sodium excretion was mainly due to increased delivery of sodium to the cortical distal nephron, as indicated by a disproportionate increase in urinary potassium excretion. In conclusion, massive (as opposed to moderate) volume expansion or greatly elevated levels of plasma atrial natriuretic factor associated with moderate volume expansion can improve blunted atrial natriuretic factor responsiveness in cirrhotic patients with refractory ascites. This appears to be achieved by way of a marked increase in distal delivery of filtrate in the kidney, with or without activation of distal atrial natriuretic factor receptors in the inner medullary collecting ducts.  相似文献   
47.
The emotional reactivity and association ability of the Tsukuba High Emotional (THE), the Tsukuba Low Emotional (TLE), and the Wistar-Imamichi (WI) strains of rats were studied in two experiments. Suppression of licking and lever pressing by unsignaled shocks were used to measure emotionality in Experiments 1 and 2, respectively. Contrary to our expectations, the WI rats which had formed a part of the foundation population of the Tsukuba strains, proved to be the most emotional, and the THE and TLE did not differ in emotionality from each other in either experiment. Association ability was measured by the speed of discriminating dangerous and safe periods under matched levels of emotional arousal. Association ability proved to be best in TLE rats, especially in Experiment 2, in which the procedures were somewhat improved on the basis of the results of Experiment 1. We discuss the results in terms of the motivational system and of the behavioral characteristics established during the course of selective breeding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
48.
    
Culturing three-dimensional (3D) tissues with an appropriate microenvironment is a critical and fundamental technology in broad areas of cutting-edge bioengineering research. In addition, many technologies have engineered tissue functions. However, an effective system for transporting nutrients, waste, or oxygen to affect the functions of cell tissues has not been reported. In this study, we introduce a novel system that employs diffusion and convection to enhance transportation. To demonstrate the concept of the proposed system, three layers of normal human dermal fibroblast cell sheets are used as a model tissue, which is cultured on a general dish or porous collagen scaffold with perfusable channels for three days with and without the perfusion of culture media in the scaffold. The results show that the viability of the cell tissue was improved by the developed system. Furthermore, glucose consumption, lactate production, and oxygen transport to the tissues were increased, which might improve the viability of tissues. However, mechanical stress in the proposed system did not cause damage or unintentional functional changes in the cultured tissue. We believe that the introduced culturing system potentially suggests a novel standard for 3D cell cultures.  相似文献   
49.
A combination of anisotropic shielding effect and temperature dependence of NMR chemical shifts makes it possible to develop a supramolecular method for determination of absolute configuration of chiral compounds. The concept, theoretical derivatization, and first demonstration of this daedal noncovalent method using a host-guest system is described. This noncovalent method requires only three substrate solutions and can in principle be applied to any host-guest systems that follow the van't Hoff relation and have a clear anisotropic shielding effect based on a well-defined complex structure regardless of the extent of enantiomer selectivity.  相似文献   
50.
Tahara K  Tobe Y 《Chemical reviews》2006,106(12):5274-5290
  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